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Basic Welding Terms

Scroll down or Jump straight to a heading below Welding Consumables Welding Equipment Cutting Welding Automation / Robotic Welding

What is Arc Welding? Arc welding is a method of joining two pieces of metal into one solid piece. To do this, the heat of an electric arc is concentrated on the edges of two pieces of metal to be joined. The metal melts, while the edges are still molten, additional melted metal is added. This molten mass then cools and solidifies into one solid piece. Find out more by reading one of the articles below:q q q

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Safe Practices Promote Arc Welding Safety Arc Welding Fundamentals Power Shopping: Choosing the Ideal Welding Power Source by Selecting the Proper Welding Process 20 Frequently Asked Questions AWS Classifications Explained

Welding Consumables

Stick Electrode A short stick of welding filler metal consisting of a core of bare electrode covered by chemical or metallic materials that provide shielding of the welding arc against the surrounding air. It also completes the electrical circuit, thereby creating the arc. (Also known as SMAW, or Stick Metal Arc Welding.)

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Creating High Quality Stick Welds: A Users Guide How To Strike and Establish an Arc 20 Frequently Asked Questions

MIG Wire Like a stick electrode, MIG wire completes the electrical circuit creating the arc, but it is continually fed through a welding gun from a spool or drum. MIG wire is a solid, non-coated wire and receives shielding from a mixture of gases. (Process is also known as GMAW, or Gas Metal Arc Welding.) Learn More:q q q q

Common Problems and Remedies for GMAW 20 Frequently Asked Questions Frequently Asked MIG welding Questions MIG vs. Flux-Cored: Which Welding Process is Right for You?

Cored Wire (Flux-Cored Wire) Cored wire is similar to MIG wire in that it is spooled filler metal for continuous welding. However, Cored wire is not solid, but contains flux internally (chemical & metallic materials) that provides shielding. Gas is often not required for shielding. (Process is also known as FCAW, or Flux-Cored Arc Welding.) Learn More:q q

20 Frequently Asked Questions MIG vs. Flux-Cored: Which Welding Process is Right for You?

Submerged Arc A bare metal wire is used in conjunction with a separate flux. Flux is a granular composition of chemical and metallic materials that shields the arc. The actual point of metal fusion, and the arc, is submerged within the flux. (Process is also known as SAW, or Submerged Arc Welding.)

Stainless Steel Stainless steel electrodes and wire are used for welding applications where corrosion resistance is required. Stainless steel consumables are designed to match the composition of stainless steel base metals. Learn More:q

MIG welding Stainless Steel

Hardfacing A stick of electrode or cored wire that is designed not to fuse two pieces of metal together, but to add a layer of surface metal to a work-piece in order to reduce wear. An example of this is the shovel on an excavator.

Welding Equipment

Stick Welders Heating the coated stick electrode and the base metal with an arc creates fusion of metals. An AC and/or DC electrical current is produced by this machine to create the heat needed. An electrode holder handles stick electrodes and a ground clamp completes the circuit. Learn More:q q q q

Creating High Quality Stick Welds: A Users How To Strike and Establish an Arc 20 Frequently Asked Questions Summer Projects: Weld Your Own Texas Grill!

TIG Welders A less intense current produces a finer, more aesthetically pleasing weld appearance. A tungsten electrode (non-consumable) is used to carry the arc to the workpiece. Filler metals are sometimes supplied with a separate electrode. Gas is used for shielding. (Process is also known as GTAW, or Gas Tungsten Arc Welding.)

MIG Welders and Multi-Process Welders Constant Voltage and Constant Current welders are used for MIG welding and are a semi-automated process when used in conjunction with a wire feeder. Wire is fed through a gun to the weld-joint as long as the trigger is depressed. This process is easier to operate than stick welding and provides higher productivity levels. CC/CV welders operate similarily to CC (MIG) welders except that they possess multiprocess capabilities - meaning that they are capable of performing flux-cored, stick and even TIG processes as well as MIG. Learn More:q q q

Common Problems and Remedies for GMAW 20 Frequently Asked Questions Frequently Asked MIG welding Questions

Engine Driven Welders Large stick or multi-process welders are able to operate independent of input power and are powered by a gasoline, diesel, or LPG engine instead. Ideal for construction sites and places where power is unavailable. Learn More:q

How To Select the Right Engine Driven Welder for the Job

Wire Feeder / Welders For MIG welding or Flux-Cored wire welding, wire feeder welders are usually

complete and portable welding kits. A small built in wire feeder guides wire through the gun to the piece. Learn More:q q q q q q

How To Select a Compact Wire Feeder Welder Using tools Wire-Feeder Welders Common Problems and Remedies for GMAW 20 Frequently Asked Questions Frequently Asked MIG welding Questions MIG Welding Aluminum with Lincoln Compact Wire Feeder Welders

Semiautomatic Wire Feeders For MIG welding or Flux-Cored welding, semiautomatic wire feeders are connected to a welding power source and are used to feed a spool of wire through the welding gun. Wire is only fed when the trigger is depressed. These units are portable.

Automatic Wire Feeders For MIG, Flux-Cored, or submerged arc welding, automatic wire feeders feed a spool of wire at a constant rate to the weld joint. They are usually mounted onto a fixture in a factory/industrial setting and are used in conjunction with a separate power source.

Magnum Guns / Torches MIG welding guns and TIG welding torches are handheld welding application tools connected to both the wire feeder and power source. They direct the welding wire to the weld joint and control the wire feed with the use of a trigger mechanism.

Cutting

Plasma Cutters A constricted cutting arc is created by this machine, which easily slices through metals. A high velocity jet of ionized gas removes molten material from the application. Learn More:q

Plasma cutting: Determining if its Right for You and What to Look for in a Machine

Oxyfuel Gas Cutting Oxyfuel gas cutting process involves preheating the base metal to a bright cherry red, then introducing a stream of cutting oxygen which will ignite and burn the metal. Learn more on Oxyfuel Gas Cutting

Welding Automation / Robotic Welding Robotic Welding Systems The combination of a robotic arm, a welding power source and a wire feeder produces welds automatically using various programs, welding fixtures and accessories. Learn More on Robotic Welding and Welding Automation.

Environmental Systems Also known as fume extraction, these systems are often incorporated into a robotic fixture to remove welding fumes natural to the process from the welding environment. Usually a vacuum unit, they can be portable or mounted onto a wall. View Fume Extraction Packages

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by Ken Brown, Project Research Manager, The Lincoln Electric Company

Safe Practices Promote Arc Welding Safety

Arc welding is a safe process when sufficient measures are taken to protect the welder from potential hazards and when proper operating practices are followed. Major hazards welders can encounter if these dangers are overlooked include fumes and gases, arc rays and sparks, and electric shock. Here are a few of the main precautions that will help welders avoid trouble. For further safety information and details on safe welding, contact the manufacturer of your welding equipment or the American Welding Society. Everyone with welding responsibility should also be familiar with ANSI standard Z49.1, "Safety in Welding and Cutting." Fumes and Gases Are Silent Hazards The fumes and gases that result from the welding process can cause acute or chronic health effects if proper precautions are ignored. The fume plume contains solid particles from the consumables (electrodes), base metal, base metal coating and gases formed in the process, which include oxides of nitrogen and ozone.. The gases used for shielding (argon, helium, and carbon dioxide) are nontoxic, but as they are released, they displace oxygen in breathing air. This can cause dizziness, unconsciousness, and even death with longer exposures. Avoid exposure to fumes and gases whenever possible, and use ventilation equipment or a respirator when necessary.

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Keep your head out of the fumes. Use enough ventilation or exhaust to remove fumes and gases from the work area. Mechanical equipment should exhaust at least 2000 cfm of air for each welder, except where individual exhaust hoods, booths, or air-line respirators

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Natural ventilation may be used under certain conditions. For welding or cutting mild steel, natural ventilation is usually sufficient if a room has at least 10,000 cubic feet per welder, with a ceiling height of at least 16 feet. Cross-ventilation should not be blocked, and welding should not be done in a confined space.

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Don't get too close to the arc ("Avoid the plume"). Use corrective lenses to help you maintain the proper distance if necessary. Read and understand the Material Safety Data Sheets (MSDS) for the product. Read and obey warning labels on all containers of welding materials. Use a smoke extractor-type welding gun for semiautomatic welding processes. Arc Rays and Sparks Can Injure Eyes and Burn Skin These are the most obvious hazards because they are the most visible. However, they should not be taken for granted. While the dangers may be well recognized, consider these factors:q Protect your eyes and face with a properly fitted welding helmet that is equipped with the correct grade of filter plate (See ANSI Z49.1 and Z87.1 standards). Fig. 1 shows suggested shade numbers for various arc welding processes. Infrared radiation can cause retinal burning and cataracts. Even brief exposure to ultraviolet (UV) radiation can cause an eye burn known as "welder's flash," which results in extreme discomfort, swelling, fluid excretion, and possibly temporary blindness.

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Protect your body from welding spatter and arc flash with clothing made from durable, flame-resistant material, such as woolen fabrics, and gear that includes flame-proof apron and gloves, leather leggings, and high boots. Avoid clothing made of synthetic materials, which can melt when exposed to extreme heat or sparks, or cotton unless it is specially treated for fire protection. Keep your clothes free of grease and oil, which may ignite. Protect others from spatter, flash, and glare with non-flammable protective screens or curtains. Be sure to wear safety glasses with side shields when in a welding area.

Electric Shock Can Kill

The hazards of electric shock are one of the most serious risks facing a welder. Contact with equipment or metal parts that are electrically "hot' can cause injury or death from the shock or from a fall that results from reaction to the shock. Primary voltage shock (i.e., 230, 460 volts) is the most serious danger because it is much greater than secondary voltage shock (i.e, 60 - 100 volts). Primary voltage shock comes from touching a lead inside the welding power source while you have your body or hand in contact with the welder case or other grounded metal. Turning the equipment's power switch "off" does not turn power off inside the case. Never remove panels without unplugging the input power cord or turning the power disconnect switch off. Secondary voltage shock comes from touching part of the welding circuit, such as a bare spot on the electrode cable, while also touching the grounded metal workpiece. Avoid touching both parts of a circuit at the same time.q

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Be sure you are insulated from the workpiece and ground, as well as other live electrical parts. Don't lean on the workpiece. Use plywood, rubber mats or other dry insulation to stand on, and wear dry, hole-free gloves. Stay dry, and do not weld when you are wet. Never dip the electrode in water to cool it. Check equipment to be sure it is properly grounded, in good repair, and installed according to prevailing codes. Be sure equipment is turned off when not in use. Electric current flowing through a conductor causes Electric and Magnetic Fields (EMF), which can interfere with pacemakers and may effect health in other ways. Consult your physician before arc welding if you have a pacemaker. To avoid excessive exposure to EMF, keep the electrode and work cables together, never place your body between the two cables or coil the electrode lead around your body, and do not work directly next to the welding power source. Other Hazards to Watch Welding sparks can cause fire or explosion and can easily go through small cracks and openings or spray up to 35 feet to adjacent areas. Remove fire hazards from the welding area or cover them with a fire-resistant shield if necessary. Do not weld near unshielded fuel or hydraulic lines.

Cylinders used for shielding gas in some processes can explode if handled improperly. Always store and handle them safely, keep them upright, and protect them from mechanical shocks or falling. Maintain all hoses, fittings and regulators in good condition. Never allow the electrode or any electrically "hot" parts of the welding equipment to touch a cylinder.

Do not weld near fumes from other processes, such as cleaning, degreasing or painting. Some fumes may cause an explosion, and others can form highly toxic gases when exposed to welding arcs and heat. Ear plugs or muffs will help prevent hearing loss from working around noisy arc welding equipment or some processes. They also will keep flying sparks out of your ears, especially when welding overhead or in close quarters. Hearing loss can be gradual and will add up over time, so ear protection is always a good idea.

Welding is indispensable to numerous industrial and consumer products, as it plays a key role in building and maintaining the equipment, tools and infrastructure that make our abundant lifestyle possible. Done properly, it is safe, productive and efficient. Poor safety techniques often translate into poor quality as well as posing a hazard to operators and other people in the area. Insistence on strict safety requirements for welding operations will pay off in employee health and productivity. Supplement 1 Guide for Shade Numbers Electrode Size 1/32 in. (mm) Less than 3 (2.5) 3-5 (2.5-4) 5-8 (4.-6.4) More than 8 (6.4) .. Arc Current (A) Less than 60 60-160 160-250 250-550 Less than 60 60-160 260-250 250-500 Less than 50 50-150 150-500 (Light) (Heavy) Less than 500 500-1000 Minimum Suggested(1) Protective Shade No. Shade (Comfort) 7 8 10 11 7 10 10 10 8 8 10 10 11 10 12 14 11 12 14 10 12 14 12 14

Operation Shielded metal arc welding

Gas metal arc welding and flux cored arc welding

Gas tungsten arc welding

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Air carbon arc cutting

Plasma arc welding .. Plasma arc cutting (Light)2 (Medium)2 (Heavy)2 .. .. ..

Less than 20 20-100 100-400 400-800 Less than 300 300-400 400-800 mm Under 3.2 3.2 to 12.7 Over 12.7 Under 25 25 to 150 Over 150

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6 to 8 10 12 14 9 12 14 3 or 4 2 14 .. 4 or 5 5 or 6 6 or 8 3 or 4 4 or 5 5 or 6

Torch brazing Torch soldering Carbon arc welding .. Gas welding Light Medium Heavy Oxygen cutting Light Medium Heavy in.

Plate thickness

Under 1/8 1/8 to 1/2 Over 1/2 Under 1 1 to 6 Over 6

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(1) As a rule of thumb, start with a shade that is too dark to see the weld zone. Then go to a lighter shade which gives sufficient view of the weld zone without going below the minimum. In oxyfeul gas welding or cutting where the torch produces a high yellow light, it is desirable to use a filter lens that absorbs the yellow or sodium line in the visible light of the (spectrum) operation. (2) These values apply where the actual arc is clearly seen. Experience has shown that lighter filters may be used when the arc is hidden by the workpiece. Data from ANSI/ASC Z49.1-88 Welding Safety

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The Lincoln Electric Company, 1994.

Arc-Welding Fundamentals

Arc welding is one of several fusion processes for joining metals. By applying intense heat, metal at the joint between two parts is melted and caused to intermix - directly, or more commonly, with an intermediate molten filler metal. Upon cooling and solidification, a metallurgical bond is created. Since the joining is an intermixture of metals, the final weldment potentially has the same strength properties as the metal of the parts. This is in sharp contrast to non-fusion processes of joining (i.e. soldering, brazing etc.) in which the mechanical and physical properties of the base materials cannot be duplicated at the joint. In arc welding, the intense heat needed to melt metal is produced by an electric arc. The arc is formed between the actual work and an electrode (stick or wire) that is manually or mechanically guided along the joint. The electrode can either be a rod with the purpose of simply carrying the current between the tip and the work. Or, it may be a specially prepared rod or wire that not only conducts the current but also melts and supplies filler metal to the joint. Most welding in the manufacture of steel products uses the second type of electrode. Basic Welding Circuit Fig. 1 The basic arc-welding circuit

The basic arc-welding circuit is illustrated in Fig. 1. An AC or DC power source, fitted with whatever controls may be needed, is connected by a work cable to the workpiece and by a "hot" cable to an electrode holder of some type, which makes an electrical contact with the welding electrode. An arc is created across the gap when the energized circuit and the electrode tip touches the workpiece and is withdrawn, yet still with in close contact. The arc produces a temperature of about 6500F at the tip. This heat melts both the base metal and the electrode, producing a pool of molten metal sometimes called a "crater." The crater solidifies behind the electrode as it is moved along the joint. The result is a fusion bond.

Arc Shielding However, joining metals requires more than moving an electrode along a joint. Metals at high temperatures tend to react chemically with elements in the air - oxygen and nitrogen. When metal in the molten pool comes into contact with air, oxides and nitrides form which destroy the strength and toughness of the weld joint. Therefore, many arc-welding processes provide some means of covering the arc and the molten pool with a protective shield of gas, vapor, or slag. This is called arc shielding. This shielding prevents or minimizes contact of the molten metal with air. Shielding also may improve the weld. An example is a granular flux, which actually adds deoxidizers to the weld. Figure 2 illustrates the shielding of the welding arc and molten pool with a Stick electrode. The extruded covering on the filler metal rod, provides a shielding gas at the point of contact while the slag protects the fresh weld from the air. The arc itself is a very complex phenomenon. Indepth understanding of the physics of the arc is of little value to the welder, but some knowledge of its general characteristics can be useful. Nature of the Arc An arc is an electric current flowing between two electrodes through an ionized column of gas. A negatively charged cathode and a positively charged anode create the intense heat of the welding arc. Negative and positive ions are bounced off of each other in the plasma column at an accelerated rate. Fig. 2 This shows how the coating on a coated (stick) electrode provides a gaseous shield around the arc and a slag covering on the hot weld deposit.

In welding, the arc not only provides the heat needed to melt the electrode and the base metal, but under certain conditions must also supply the means to transport the molten metal from the tip of the electrode to the work. Several mechanisms for metal transfer exist. Two (of many) examples include: 1. Surface Tension Transfer - a drop of molten metal touches the molten metal pool and is drawn into it by surface tension. 2. Spray Arc - the drop is ejected from the molten metal at the electrode tip by an electric pinch propelling it to the molten pool. (great for overhead welding!) If an electrode is consumable, the tip melts under the heat of the arc and molten droplets are detached and transported to the work through the arc column. Any arc welding system in which the electrode is melted off to become part of the weld is described as metal-arc. In carbon or tungsten (TIG) welding there are no molten droplets to be forced across the gap and onto the work. Filler metal is melted into the joint from a separate rod or wire. More of the heat developed by the arc is transferred to the weld pool with consumable

electrodes. This produces higher thermal efficiencies and narrower heat-affected zones. Since there must be an ionized path to conduct electricity across a gap, the mere switching on of the welding current with an electrically cold electrode posed over it will not start the arc. The arc must be ignited. This is caused by either supplying an initial voltage high enough to cause a discharge or by touching the electrode to the work and then withdrawing it as the contact area becomes heated. Arc welding may be done with direct current (DC) with the electrode either positive or negative or alternating current (AC). The choice of current and polarity depends on the process, the type of electrode, the arc atmosphere, and the metal being welded.

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Power Shopping: Choosing the Ideal Welding Power Source by Selecting the Proper Welding Process

The process of choosing a welding power source is much like that of buying a car. It involves searching for a product that is efficient, powerful, easy to handle and, most importantly, suited to the customer's particular needs. But with such a wide selection of power sources on the market, how do welders select the right one for them? The first step is to understand their shop's internal needs. To determine this, examine some commonly used welding processes and for which materials they are best suited. Gas Metal Arc Welding (GMAW)/Flux-Cored Arc Welding (FCAW) GMAW/FCAW (most commonly referred to as MIG or Flux-Cored Welding) uses a spool of wire that is either housed inside the power source or fed from an external wire feeder. This wire or filler material is fed through a welding gun. The power source is used to start and maintain the arc between the wire and the base metal. GMAW or MIG welding utilizes solid metal wire, which requires the use of a shielding gas to protect the weld puddle from the atmosphere. FCAW uses a hollow wire filled with a flux powder that may or may not need an external shielding gas, because the gas may be produced from the flux within the wire as it burns in the arc. The flux in the wire serves many of the same purposes as the electrode coating in SMAW.

GMAW requires the least operator skill, because the machine feeds the wire. The welding operator holds the gun in one hand, squeezes the trigger, and welds. It's that easy! The shielding gas makes for a very smooth arc that remains stable. Since other processes

typically require very specific electrode positioning and manipulation, GMAW is the fastest growing process. With compact units now retailing for less than $500 and the ability to easily weld on much thinner material than stick electrode, this type of unit has become very popular. Welding speeds are also higher because of the continuously fed electrode, absence of slag (with GMAW) and higher filler metal deposition rates. Its operating factor is typically 30-50 percent so 3-5 minutes out of every 10 can be spent creating an arc. In addition, GMAW/ FCAW does not require the degree of operator skill that TIG or stick welding does. GMAW can be used on all of the major commercial metals. FCAW is currently used primarily on steels and stainless steels. These two processes also can be used over a wide range of material thickness and operate in all positions. For these reasons, they are usually the welding processes of choice for most fabrication and production shops. On the downside, equipment for GMAW and FCAW is more complex, more costly and traditionally less portable than stick welding processes (although some new portable models do exist). Welding is typically done within a 10 to 12 foot radius of the wire feeder and the work is usually brought to the weld station. Shielded Metal Arc Welding (SMAW) SMAW, or stick welding, is the most common form of arc welding. In the process, a stick or electrode is placed at the end of a holder. Using electricity from the power source, an arc is struck between the tip of the electrode and the metal welding surface. The heat of the arc melts the tip of the electrode creating the filler material that is deposited as the electrode is consumed. A coated material on the electrode burns and protects the arc from the atmosphere. The burning of the coating produces CO2, which becomes the shielding gas. A slag is also formed which helps refine the weld metal and protect it as it freezes. SMAW is one of the easiest and most versatile ways to weld, since filler material can be easily changed to match different metals just by switching stick electrodes. Whether it is steel, stainless steel, cast iron or high alloy metals, users can clamp in a new rod to be ready for the next project. In addition, stick is versatile because it takes the least equipment, which makes it easy to setup or move to a new location.

When compared to other types of power sources, SMAW welders are generally the least expensive. As a result, they are utilized most often by novice welders, farmers, smaller fabricating shops, maintenance shops and large field construction contractors that weld on a variety of jobs over a large physical area.

The main disadvantage to SMAW is the amount of downtime associated with the process. An electrode is only so many inches in length and must be changed once it is consumed. This requires the operator to stop welding to change the electrode. Frequently, the amount of skill required by the operator is greater than that required for wire fed processes. In addition, it takes time to chip or grind the slag or impurities from the weld. The operating factor or time that the welder is actually "creating sparks" is typically two to three minutes per 10-minute interval. In general, stick welders sacrifice productivity for versatility. Gas Tungsten Arc Welding (GTAW) In GTAW, an electric arc is established between a non-consumable tungsten electrode and the base metal. The arc zone is filled with an inert gas, typically argon, which protects the tungsten and molten metal from oxidation and provides an easily ionized path for the arc current. GTAW produces high quality welds on almost all metals and alloys. Because it can be controlled at very low amperages, it is ideally suited for welding on thin metal sheets and foils. The biggest advantage of GTAW is that high quality welds can be made on almost any weldable metal or alloy. Another major advantage is that filler metal can be added to the weld pool independently of the arc current. With other arc welding processes, the rate of filler metal addition controls the arc current. Other advantages include low spatter, no slag and relatively easy clean up.

The main disadvantage of GTAW is that it produces the slowest metal deposition rate of all the processes. The emphasis is on making welds that are perfect in appearance, which means lower welding current and more welding time. The operator needs to learn to coordinate precise movements of the torch in one hand with adding filler metal from the other hand and controlling current with a foot pedal. The operator also needs to learn how to properly setup the GTAW machine. Tungsten preparation, spark intensity, upslope, downslope, pulsing rate, peak intensity, background current, high frequency and proper grounding can all be very important issues for a GTAW welder. Combined with lower deposit rates, it's easy to see how the GTAW process has a great following in industries such as aerospace, where quality is much more important than cost. Submerged Arc Welding (SAW) SAW uses a continuously fed wire with a granular material called flux to cover the weld area.

This type of welding is used primarily on heavier plate applications such as structural steel and on specialized high speed welding of light sections. The flux plays a central role in achieving high speed and a quality weld. Very little welding fume is produced, leaving the shop air much cleaner. Since the flux covers the whole arc, a welding helmet is not required, leading to a higher operating factor. On long, large welds, multipass and overlay applications, the process can approach a 100 percent operating factor. Productivity can be very high with welding currents over 1000 amps common on automatic applications.

Disadvantages include limited welding positions, because flux comes in granular form. Operators must weld on flat surfaces to assure the flux covers the weld puddle. Another disadvantage is that hot flux can burn shoes and cause handling problems that must be addressed. With some knowledge of the types of welding processes that are available, you should now be able to make a decision as to which process best suits your needs. The next step is to start looking for a power source. Your ideal power source should accommodate your welding process, meet your size requirements, fit within your budget and offer the technology features that are needed in your shop. In the end, a reliable power source-like a reliable carwill continue to serve you for many years to come. Lincoln Electric Products

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20 Frequently Asked Questions

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The E7018 welding rods I've been buying are now marked E7018 H4R. What does the H4R mean? Are these rods different than the E7018 rods I've used before? Why is hydrogen a concern in welding? What is the maximum plate thickness which can be welded with Innershield NR211MP (E71T-11) wire? What electrode can I use to join mild steel to stainless steel? What consumable should be used to weld cast iron? What consumable can be used to weld on SAE 4130 steel tubing? What consumable should be used for weathering steel? What are you recommendations for welding AR400 plate? What consumables are better for welding over rusty, dirty steel? What flux-cored wires are better for welding on high sulfur steel? What precautions should I take when welding T-1 steels? Why are the Charpy impact values from my test welds lower than that printed on your Certificate of Conformance? I'm using Outershield 71M (E71T-1) flux-cored wire with 75Ar/25CO2. Why am I getting gas marks on the weld surface? I'm welding with an Innershield FCAW-SS wire and occasionally get porosity. How can I eliminate this? Can I use flux-cored wires (FCAW-GS or FCAW-SS) on a constant current (CC) stick welding power source? Why is preheat sometimes required before welding? How should preheat be measured? What is interpass temperature? Do I need an oven to store low hydrogen electrodes?

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1. The E7018 welding rods I've been buying are now marked E7018 H4R. What does the H4R mean? Are these rods different than the E7018 rods I've used before? H4R is an optional supplementary designator, as defined in AWS A5.1-91 (Specification for shielded metal arc welding electrodes). Basically, the number after the "H" tells you the hydrogen level and the "R" means it's moisture resistant. "H4" identifies electrodes meeting the requirements of 4ml average diffusible hydrogen content in 100g of deposited weld metal when tested in the "asreceived" condition. "R" identifies electrodes passing the absorbed moisture test after exposure to an environment of 80F(26.7C) and 80% relative humidity for a period of not less than 9 hours. The H4R suffix is basically just additional information printed on the rod, and does not necessarily mean a change in an electrode previously marked E7018. Back to Top 2. Why is hydrogen a concern in welding? Hydrogen contributes to delayed weld and/or heat affected zone cracking. Hydrogen combined with high residual stresses and crack-sensitive steel may result in cracking hours or days after the welding has been completed. High strength steels, thick sections, and heavily restrained parts are more susceptible to hydrogen cracking. On these materials, we recommend using a low hydrogen process and consumable, and following proper preheat, interpass, and postheat procedures. Also, it is important to keep the weld joint free of oil, rust, paint, and moisture as they are sources of hydrogen. Back to Top 3. What is the maximum plate thickness which can be welded with Innershield NR-211-MP (E71T-11) wire? NR-211-MP is restricted to welding these maximum plate thicknesses: Wire diameter .035"(0.9mm) .045"(1.1mm) .068"(1.7mm) 5/64"(2.0mm) 3/32"(2.4mm) Maximum plate thickness 5/16"(8mm) 5/16"(8mm) 1/2"(13mm) 1/2"(13mm) 1/2"(13mm)

For thicker steels, look to NR-212. It has similar welding characteristics to NR211-MP but is designed for use on materials up to 3/4" (19.0mm) thick. Back to Top 4. What electrode can I use to join mild steel to stainless steel? Electrode selection is determined from the base metal chemistries and the percent weld admixture. The electrode should produce a weld deposit with a small amount of ferrite (3-5 FN) needed to prevent cracking. When the chemistries are not known, our Blue Max 2100 electrode, which produces a high ferrite number, is commonly used. Back to Top 5. What consumable should be used to weld cast iron? Cast irons are alloys which typically have over 2% carbon plus 1-3% silicon and are difficult to weld. Electrodes with a high percentage of nickel are commonly used to repair cast iron. Nickel is very ductile, making it a good choice to weld on cast iron, which is very brittle. Softweld 99Ni and Softweld 55Ni are the Lincoln Electric electrodes designed for welding cast iron. Back to Top 6. What consumable can be used to weld on SAE 4130 steel tubing? On light chrome-moly tubing, mild steel electrodes are commonly used. There is enough pickup of alloy from the base material to give the required tensile strength in the as-welded condition. On multiple pass welds, Cro-Mo alloy electrodes are usually specified. Back to Top 7. What consumable should be used for weathering steel? Core Ten (A242 & A588) steels are weathering steels commonly used for outdoor structures. These steels have a higher resistance to atmospheric corrosion than typical mild steels. Often, welds on these steels are specified for similar corrosion resistance and color match. On single pass welds, mild steel electrodes are commonly used. There is usually enough pickup from the base metal to obtain a good color match. On multiple pass welds, low-alloy electrodes are commonly used to obtain a good color match and similar corrosion resistance. The electrodes commonly specified include those with the suffixes -B1, -B2, -C1, -C2, and -C3.

Back to Top 8. What are you recommendations for welding AR400 plate? AR400 is a quench and tempered steel and may be difficult to weld due its high strength and hardenability. The base steel around the weld rapidly heats and cools during welding, resulting in a heat affected zone (HAZ) with high hardness. Any hydrogen in the weld metal may diffuse into HAZ and may cause hydrogen embrittlement, resulting in delayed underbead or toe cracks outside of the weld. To minimize heat affected zone cracking: 1. Use a low hydrogen consumable with an -H4 or -H2 designation. 2. Preheat to slow the cooling rate. Note that excessive preheat may anneal the base material. 3. Slow cool. More time at elevated temperatures allows the dissolved hydrogen to escape. 4. Peen the weld beads to minimize residual weld stresses. 5. Use the lowest strength filler metal meeting design requirements. If making fillet welds, the weld can be oversized to give the specified strength 6. Minimize weld restraint. Back to Top 9. What consumables are better for welding over rusty, dirty steel? Steel should be cleaned of any oil, grease, paint, and rust before using any arc welding process. However, if complete cleaning cannot be performed, consumables that form a slag, have deeper penetration, are slower freezing, or have higher Silicon and Manganese are recommended for dirty steels. These consumables include: SMAW: Fleetweld 5P+ GMAW: SuperArc L-56, MC-710 FCAW-GS: Outershield 75 FCAW-SS: Innershield NR-311 SAW: Lincolnweld 761 and 780 fluxes Back to Top 10. What flux-cored wires are better for welding on high sulfur steel? AWS D5.20-95 FCAW Specification states that E70T-4 and E70T-7 flux-cored wires are designed with a slag system to produce welds very low in sulfur and resistant to hot cracking. Corresponding Lincoln products are Innershield NS3M and NR-311 self-shielded flux-cored wires. Also our E70T-5, Outershield 75-H gas-shielded flux-cored wire is also a better choice for welding on high sulfur steels.

Back to Top 11. What precautions should I take when welding T-1 steels? T-1 is a quenched and tempered steel. Welding quenched & tempered steels may be difficult due its high strength and hardenability. The base steel around the weld is rapidly being heated and cooled during welding, resulting in a heat affected zone (HAZ) with high hardness. Hydrogen in the weld metal may diffuse into HAZ and cause hydrogen embrittlement, resulting in delayed underbead or toe cracking outside of the weld. To minimize heat affected zone cracking: 1. Use a low hydrogen consumable, like a -H4 or -H2. 2. Preheat. This slows the cooling rate. Note that excessive preheat may anneal the base material. 3. Slow cool. More time at elevated temperatures allows the dissolved hydrogen to escape. 4. Peen the weld beads to minimize residual weld stresses. 5. Use the lowest strength filler metal meeting design requirements. If making fillet welds, the weld can be oversized to give the specified strength 6. Minimize weld restraint. Back to Top 12. Why are the Charpy impact values from my test welds lower than that printed on your Certificate of Conformance? The test results on our Certificate of Conformance were obtained from welding an AWS filler metal test plate. Any change in welding procedure will affect Charpy impact values. Below are common practices for welding test plates when Charpy impact specimens are required: 1. 2. 3. 4. Controlled heat input Controlled preheat and interpass temperature Even number of passes per layer Build-up cap pass to maximum allowed in specification

Back to Top 13. I'm using Outershield 71M (E71T-1) flux-cored wire with 75Ar/25CO2. Why am I getting gas marks on the weld surface? The fast freezing rutile slag on an E71T-1 Outershield wire gives it excellent out-of-position characteristics, but can also trap gases under the slag as the weld solidifies, resulting in gas marks. Gas marks are more commonly observed welding at high procedures under a high Argon blend shielding gas. Gas marking and/or can be minimized by:

1. Switching to 100% CO2 shielding gas 2. 3. 4. 5. 6. Lowering the welding procedure Cleaning the weld joint of paint, rust, and moisture Minimize any wind disturbance Cleaning spatter from inside gas nozzle Increasing the shielding gas flow rate

Back to Top 15. I'm welding with an Innershield FCAW-SS wire and occasionally get porosity. How can I eliminate this? First, make sure the steel is clean. Vaporization of contaminants on the base metal such as moisture, rust, oil, and paint may cause porosity. Second, this can be commonly caused by excessive voltage or too short a stickout (the length of wire from the end of the contact tip to the workpiece). Make sure these are within our recommended parameters. Also, reducing the travel speed also helps minimize porosity. Back to Top 16. Can I use flux-cored wires (FCAW-GS or FCAW-SS) on a constant current (CC) stick welding power source? Our flux-cored wires are designed to operate on constant voltage (CV) DC machines. If used on a constant current (CC) machine, any small changes in electrical stickout (length of the wire from the end of the contact tip to workpiece) will produce large voltage fluctuations, resulting in stubbing and porosity. Therefore, using flux-cored wires on CC is not recommended. Back to Top 17. Why is preheat sometimes required before welding? Preheating the steel to be welded slows the cooling rate in the weld area. This may be necessary to avoid cracking of the weld metal or heat affected zone. The need for preheat increases with steel thickness, weld restraint, the carbon/ alloy content of the steel, and the diffusible hydrogen of the weld metal. Preheat is commonly applied with fuel gas torches or electrical resistance heaters. Back to Top 18. How should preheat be measured? AWS D1.1 Structural Steel Welding Code, Section 5.6 states: Preheat and all

subsequent minimum interpass temperatures shall be maintained during the welding operation for a distance at least equal to the thickness of the thickest welded part, but not less than 3 in. [75mm] in all directions from the point of welding. In general, when preheat is specified, the entire part should be thoroughly heated so the minimum temperature found anywhere on that part will meet or exceed the specified preheat temperature. Back to Top 19. What is interpass temperature? Interpass temperature refers to the temperature of the steel just prior to the depositing of an additional weld pass. It is identical to preheat, except that preheating is performed prior to any welding. When a minimum interpass temperature is specified, welding should not be performed when the base plate is below this temperature. The steel must be heated back up before welding continues. A maximum interpass temperature may be specified to prevent deterioration of the weld metal and heat affected zone properties. In this case, the steel must be below this temperature before welding continues. Back to Top 20. Do I need an oven to store low hydrogen electrodes? All low-hydrogen consumables must be dry to perform properly. Unopened Lincoln hermetically sealed containers provide excellent protection in good storage conditions. Once cans are opened, they should be stored in a cabinet at 250-300F (121-149C). When the electrodes are exposed to the air, they will pickup moisture and should be redried. Electrodes exposed to the air for less than 1 week with no direct contact with water should be redried as follows: E7018: E8018, E9018, E10018, E11018: 1 hour at 650-750F 1 hour at 700-800F

If the electrodes come in direct contact with water or have been exposed to high humidity, they should be predried for 1-2 hours at 180-220F first before following the above redrying procedure. Standard EXX18 electrodes should be supplied to welders twice per shift. Low hydrogen electrodes with the suffix "MR" have a moisture resistant coating and may be left out up to 9 hours or as specified by code requirements.

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AWS Classifications Explained

The American Welding Society (AWS) numbering system can tell a welder quite a bit about a specific stick electrode including what application it works best in and how it should be used to maximize performance. With that in mind, let's take a look at the system and how it works. The prefix "E" designates an arc welding electrode. The first two digits of a 4-digit number and the first three digits of 5-digit number indicate tensile strength. For example, E6010 is a 60,000 psi tensile strength electrode while E10018 designates a 100,000 psi tensile strength electrode. E Electrode 60 Tensile strength 1 Position "10" Type of Coating and Current

The next to last digit indicates position. The "1" designates an all position electrode, "2" is for flat and horizontal positions only; while "3" indicates an electrode that can be used for flat, horizontal, vertical down and overhead. The last 2 digits taken together indicate the type of coating and the correct polarity or current to use. See chart below: Digit 10 11 12 13 14 15 16 27 18 20 22 24 Type of Coating High cellulose sodium High cellulose potassium High titania sodium High titania potassium iron powder titania low hydrogen sodium low hydrogen potassium iron powder iron oxide iron powder low hydrogen High iron oxide High iron oxide iron powder titania Welding Current DC+ AC or DC+ or DCAC or DCAC or DC+ AC or DC- or DC+ DC+ AC or DC+ AC or DC+ or DCAC or DC+ AC or DC+ or DCAC or DCAC or DC- or DC+

28

Low hydrogen potassium iron powder

AC or DC+

As a welder, there are certain electrodes that you will most likely see and use time and time again as you go about your daily operations. A DC machine produces a smoother arc. DC rated electrodes will only run on a DC welding machine. Electrodes which are rated for AC welding are more forgiving and can also be used with a DC machine. Here are some of the most common electrodes and how they are typically used: E6010 DC only and designed for putting the root bead on the inside of a piece of pipe, this is the most penetrating arc of all. It is tops to dig through rust, oil, paint or dirt. It is an allposition electrode that beginning welders usually find extremely difficult, but is loved by pipeline welders world-wide. Lincoln 5P+ sets the standard in this category. E6011 This electrode is used for all-position AC welding or for welding on rusty, dirty, less-thannew metal. It has a deep, penetrating arc and is often the first choice for repair or maintenance work when DC is unavailable. The most common Lincoln product is Fleetweld 180 for hobby and novice users. Industrial users typically prefer Fleetweld 35. E6013 This all-position, AC electrode is used for welding clean, new sheet metal. Its soft arc has minimal spatter, moderate penetration and an easy-to-clean slag. Lincoln Fleetweld 37 is most common of this type. E7018 A low-hydrogen, usually DC, all-position electrode used when quality is an issue or for hardto-weld metals. It has the capability of producing more uniform weld metal, which has better impact properties at temperatures below zero. The Lincoln products are typically Jetweld LH-78 or our new Excalibur 7018. E7024 Typically used to make a large weld downhand with AC in plate that is at least " thick, but more commonly used for plate that is " and up. Lincoln has several electrodes in this category that are called Jetweld 1, 2, or 3. Other Electrodes Although not nearly as common, an electrode may have additional numbers after it such as E8018-B2H4R. In this case, the "B2" indicates chemical composition of the weld metal deposit. The "H4" is the diffusible hydrogen designator, which indicates the maximum diffusible hydrogen level obtained with the product. And "R" stands for the moisture resistant designator to indicate the electrode's ability to meet specific low moisture pickup limits under controlled humidification tests.

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Creating High Quality Stick Welds: A User's Guide

by Harry Sadler, Applications Engineering, The Lincoln Electric Company

Stick welding is the most common form of arc welding, but creating a good weld may not be easy for the beginner. Unlike wire welding where you basically "point and shoot," stick welding has a higher skill level and requires mastery of certain techniques. This article will offer tips that you can follow to increase your chances of creating a high quality stick weld - right from the start. It will also discuss how to troubleshoot problems and correct them. Tips 1. Select Steel in the Normal Range Whenever possible, select steel within the "normal range," these include AISI-SAE 1015 to 1025 steels with 0.1 percent maximum silicon and sulfur content under .035 percent. Selecting these steels will make the stick welding process easier since they can be welded at fast speeds with minimum cracking tendencies. If you are welding with low-alloy steels and carbon steels with chemistry compositions above the "normal range", they will have a tendency to crack, particularly when welding on heavy plate and rigid structures. Because of this, you should use special precautions. In addition, steels with high sulphur and phosphorus contents are not recommended for production welding. If they must be welded, use small diameter, low hydrogen electrodes. Welding with a slow travel speed will further keep the puddle molten allowing gas bubbles time to boil out, creating a better-finished weld. 2. Choose a Joint Position and Electrode that is Conducive to the Metal Joint position can have a great affect on finished weld quality. When welding on 10 to 18 gauge sheet steel, the fastest travel speeds are obtained with the work positioned at a 45 to 75 degrees downhill angle. Also, don't overweld or make a weld that is larger than needed for joint strength - this may lead to burnthrough. For welding mild steel plate with a thickness greater than or equal to 3/16", it is best to have the work positioned flat, because this will make operator manipulation of the electrode the easiest. Lastly, high carbon and low-alloy steel plate can

best be welded with the work in the level position. 3. Follow Simple Principles for Joint Geometry and Fitup Joint dimensions are chosen for fast welding speeds and good weld quality. Proper joint geometry is based upon some simple principles: 1) Fitup must be consistent for the entire joint. Since sheet metal and most fillet and lap joints are tightly clamped for their entire length, gaps or bevels must accurately be controlled over the entire joint. Any variations in a given joint will force the operator to slow his or her welding speed to avoid burnthrough and manipulate the electrode to adjust for the fitup variation. 2) Sufficient bevel is required for good bead shape and penetration; insufficient bevel prevents the electrode from getting into the joint. For example, a deep, narrow bead may lack penetration and has a strong tendency to crack. 3) Sufficient root opening is needed for full penetration, while excessive root opening wastes weld metal and slows welding speed. It is important to note that the root opening must be consistent with the diameter of the electrode being used. 4) A root face or a backup strip is required for fast welding and good quality. Feather edge preparations require a slow costly seal bead. However, double V butt joints without a land are practical when the seal bead cost is offset by easier edge preparation and the root opening can be limited to approximately 3/32". In general, weld seal beads on flat work with 3/16" E6010 at approximately 150 amps DC+. Use 1/8" at approximately 90 amps DC+ for vertical, overhead, and horizontal butt welds. For low hydrogen and seal beads, weld with an EXX18 electrode at approximately 170 amps. 4. Avoid Buildup and Overwelding Fillets should have equal legs and a nearly flat bead surface. Buildup rarely should exceed 1/16". Extra buildup is costly in material and time, adds little to weld strength and increases distortion. For example, doubling the size of a fillet requires four times as much weld metal. Also, it costs 2/3 more to butt weld a " plate (single-V with 1/8" land and 1/32" root opening) when the excess buildup approaches 1/8". 5. Clean the Joint Before Welding To avoid porosity and attain the ideal weld travel speeds, it is important to remove excessive scale, rust, moisture, paint, oil and grease from the surface of joints. If such elements cannot be removed, use E6010 (5P+) or E6011 (35 or 180) electrodes to penetrate through the contaminants and deeply into the base metal. Slow the travel speed to allow time for gas bubbles to boil out of the molten weld before it freezes. 6. Choose the Right Electrode Size Large electrodes weld at high currents for high deposit rates. Therefore, use the largest electrode practical to be consistent with good weld quality. But, electrode size may be limited especially on sheet metal and root passes, where burnthrough can occur. As a general rule, 3/16" is the maximum electrode size practical for vertical and overhead welding, while 5/32" is the maximum size practical for low hydrogen. In addition, joint dimensions sometimes limit the electrode diameter that will fit into the joint.

Troubleshooting Weld Defects Here are some of the most common stick welding problems and how to correct them. Spatter Although spatter does not affect weld strength, it does create a poor appearance and increases cleaning costs. There are several ways to control excessive spatter. First, try lowering the current. Make sure it is within the range for the type and size electrode you are welding with and that the polarity is correct. Another way to control spatter is to try a shorter arc length. If the molten metal is running in front of the arc, change the electrode angle. Finally, look for arc blow conditions (commonly referred to as a wandering arc), and be sure the electrode is not wet. Undercutting Undercutting is frequently just an appearance problem, but it can impair weld strength when the weld is loaded in tension or subjected to fatigue. To eliminate undercut, reduce current and slow travel speed, or simply reduce size until you have a puddle size you can handle. Then change the electrode angle so the arc force holds the metal in the corners. Use a uniform travel speed and avoid excessive weaving. Wet electrodes If polarity and current are within the electrode manufacturer's recommendations but the arc action is rough and erratic, the electrodes may be wet. Try dry electrodes from a fresh container. If the problem recurs frequently, store open containers of electrodes in a heated cabinet. Wandering arc With DC welding, stray magnetic fields cause the arc to wander from its aimed course. This is a greater problem at high currents and in complex joints. To control a wandering arc, the best option is to change to AC welding. If that doesn't work, try using lower currents and smaller electrodes or reduce the arc length. In addition, you can change the electrical path by shifting the work connection to the other end of the piece or by making connections in several locations. You may also do this by welding toward heavy tacks or finished welds, using run-out tabs; adding steel blocks to change work current path or tacking small plates across the seam at the weld ends. Porosity Most porosity is not visible. However, since severe porosity can weaken the weld, you should know when it tends to occur and how to combat it. Begin by removing scale, rust, paint, moisture and dirt from the joint. Be sure to keep the puddle molten for a longer time to allow gases to boil out before it freezes. If the steel has a low carbon or manganese content, or a high sulfur (free machining steel) or phosphorus content, it should be welded with a lowhydrogen electrode. Sometimes the sulfur content of free machining steels can be high enough to prevent successful welding. Minimize admixture of base metal into weld metal by using low current and fast travel speeds for less penetration. Or, try using a shorter arc length. A light drag technique is recommended for low hydrogen electrodes. For surface holes, use the same solutions that are used for porosity. If you are using E6010 or 11 electrodes, make sure that they are not too dry. Poor Fusion Proper fusion means the weld must physically bond strongly to both

walls of the joint and form a solid bead across the joint. Lack of fusion is often visible and must be eliminated for a sound weld. To correct poor fusion, try a higher current and a stringer bead technique. Be sure the edges of the joint are clean, or use an E6010 or 11 electrode to dig through the dirt. If the gap is excessive, provide better fitup or use a weave technique to fill the gap. Shallow Penetration Penetration refers to the depth the weld enters into the base metal, and usually is not visible. For full- strength welds, penetration to the bottom of the joint is required. To overcome shallow penetration, try higher currents or slower travel. Use small electrodes to reach down into deep narrow grooves. Remember to allow some gap at the bottom of the joint. Cracking Cracking is a complex subject because there are many different types of cracks that occur in different locations throughout a weld. All cracks are potentially serious, as they can lead to complete failure of the weld. Most cracking is attributed to high carbon or alloy content, or high sulfur content in the base metal. To control this cracking, try these tips: 1. Weld with low hydrogen electrodes 2. Use high preheats for heavier plate and rigid joints 3. Reduce penetration by using low currents and small electrodes. This reduces the amount of alloy added to the weld from melted base metal. 4. Fill each crater before breaking the arc 5. On multiple pass or fillet welds, be sure the first bead is of sufficient size and of flat or convex shape to resist cracking until the later beads can be added for support. To increase bead size, use slower travel speed and a short arc technique or weld 5 degrees uphill. Always continue welding while the plate is hot. 6. Rigid parts are more prone to cracking. If possible, weld toward the unrestrained end. Leave a 1/32" gap between plates for free shrinkage movement as the weld cools. Peen each bead while it is still hot to relieve stresses. Conclusion By following the tips offered here, even a beginner can create a high quality weld. And, if you are experiencing problems, being able to troubleshoot and make corrections will also turn a beginning stick welder into a professional in no time. Stick Electrodes Stainless Steel Consumables Hardfacing Consumables

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How to Strike and Establish an Arc

Source: adapted from New Lessons in Arc Welding, The Lincoln Electric Company, 1990

A welding arc is maintained when the welding current is forced across a gap between the electrode tip and the base metal. A welder must be able to strike and establish the correct arc easily and quickly. There are two general methods of striking the arc: 1. Scratching 2. Tapping The scratching method is easier for beginners and when using an AC machine. The electrode is moved across the plate inclined at an angle, as you would strike a match. As the electrode scratches the plate an arc is struck. When the arc has formed, withdraw the electrode momentarily to form an excessively long arc, then return to normal arc length. (See Figure 1) In the tapping method, the electrode is moved downward to the base metal in a vertical direction. As soon as it touches the metal it is withdrawn momentarily to form an excessively long arc, then returned to normal arc length. (See Figure 2) The principal difficulty encountered in striking the arc is "freezing," or when the electrode sticks or fuses to the work. This is caused by the current melting the electrode tip and sticking it to the cold base metal before it is withdrawn from contact. The extra high current drawn by the Figure 2 "Tapping" method of arc starting "short circuit" will soon overheat an electrode and melt it or the flux, unless the circuit is broken. Giving the electrode holder a quick snap backward from the direction of travel will generally free the electrode. If it does not, It will be necessary to open the circuit by releasing the electrode from the holder. Warning: Never remove your face shield from your face if the electrode is frozen. Free the electrode with the shield in front of your eyes, as it will "flash" when it comes loose.

Tip: Brush your work free of dirt and scale before you strike an arc. To view Lincoln's outstanding line of stick welders click here To view Lincoln's complete line of stick electrodes click here

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Reprinted with permission from the September/October, 1997 issue of Practical Welding Today magazine, copyright 1997 by The Croydon Group, Ltd., Rockford, IL

Common Problems and Remedies for GMAW

In much the same way that the automatic transmission has simplified the process of driving, Gas Metal Arc Welding (GMAW) has simplified the process of welding. Of all welding methods, GMAW is said to be one of the easiest to learn and perform. The main reason is because the power source does virtually all the work as it adjusts welding parameters to handle differing conditions; much like the sophisticated electronics of an automatic transmission. Because less skill is required, many operators are able to GMA weld at an acceptable level with limited training. These same operators run into trouble, however, when they begin creating inferior welds and are unable to diagnose and correct their own problems. The guidelines listed below will help even inexperienced operators create high quality welds as well as offering tips for those who have been using the GMAW process for a number of years. Most common welding problems fall into four categories: I. Weld porosity, II. Improper weld bead profile, III. Lack of fusion, and IV. Faulty wire delivery related to equipment set-up and maintenance. I. Weld Metal Porosity Porosity Problem #1: Improper Surface Conditions The most common cause of weld porosity is an improper surface condition of the metal. For example, oil, rust, paint or grease on the base metal may prevent proper weld penetration and hence lead to porosity. Welding processes that generate a slag such as Shielded Metal Arc Welding (SMAW) or Flux-Cored Arc Welding (FCAW) tend to tolerate surface contaminates better than GMAW since components found within the slag help to clean the metals surface. In GMAW, the only contamination protection is provided by the elements which are alloyed into the wire. Remedies To control porosity, use a deoxidizer within the wire such as silicon, manganese or trace amounts of aluminum, zirconium or titanium. Wire chemistry can be determined by referring

to the American Welding Society (AWS) wire classification system. Test the various types of wire available to find the right chemistry for a given application. To start, try the most common wire type, ER70S-3 (Lincoln L50) which contains 0.9-1.4 percent manganese and 0.45-0.75 percent silicon. If porosity is still present in the finished weld, increase the amount of silicon and manganese found in the wire by switching to an ER70S-4 (Lincoln L54) or an ER70S-6 which has the highest levels of silicon (0.8 -1.15 percent) and manganese (1.4-1.8 percent). Some operators prefer to use a triple deoxidizer such as ER70S-2 (Lincoln L52) which contains aluminum, zirconium or titanium in addition to the silicon and manganese. In addition to changing the wire, further prevent porosity by cleaning the surface of the metal with a grinder or chemical solvents (such as a degreaser.) A word of caution though if using solvents, be certain not to use a chlorinated degreaser such as trichlorethylene near the welding arc -- the fume may react with the arc and produce toxic gases. Porosity Problem #2: Gas Coverage The second leading cause of porosity in welds is a problem with the shielding gas coverage. The GMAW process relies on the shielding gas to physically protect the weld puddle from the air and to act as an arc stabilizer. If the shielding gas is disturbed, there is a potential that air could contaminate the weld puddle and lead to porosity. Remedies Shielding gas flow varies depending on wire size, amperage, transfer mode and wind speed. Typical gas flow should be approximately 30-40 cubic feet per hour. Using a flow meter, check that the shielding gas flow is set properly. There are a variety of flow meters on the market today ranging from simple dial gauges to ball flows all the way up to sophisticated, computerized models. Some operators mistakenly think that a pressure regulator is all that is needed, but the pressure meter will not set flow. A pure carbon dioxide shielding gas requires the use of special flow meters designed specifically for carbon dioxide. These special flow meters are not affected by the frosting that may occur as the carbon dioxide changes from liquid form to a gas. If high winds are blowing the shielding gas away from the puddle, it may be necessary to erect wind screens. According to the AWS Structural Welding Code, it is advisable not to GMA weld when wind speeds are greater than 5 mph. Indoors, ventilation systems may hamper gas coverage. In this case, redirect air flow away from the puddle. If fume extraction is necessary, use equipment designed specifically for this purpose such as MAGNUM Extraction Guns from Lincoln Electric -- they will remove the fume, but not disturb the shielding gas. A turbulent flow of gas as it exits the gun may also lead to porosity problems. Ideally, the gas will lay over the weld puddle much like a blanket. Turbulent gas flow can be caused by too high a flow, an excessive amount of spatter inside the gun nozzle, or spatter build-up in the gas diffuser. Other possible causes of insufficient gas flow may be damaged guns, cables, gas lines, hoses or loose gas fittings. These damaged accessories may create what is referred to as a venturi effect where air is sucked in through these openings and flow is reduced. Lastly, welding with a drag or backhand technique can lead to gas coverage problems. Try to weld with a push or forehand technique which lays the gas blanket out ahead of the arc and lets the gas settle into the joint.

Porosity Problem#3: Base Metal Properties Another cause of weld porosity may be attributed simply to the chemistry of the base metal. For instance, the base metal may be extremely high in sulfur content. Remedy Unfortunately, if the problem with porosity lies within the base metal properties, there is not much that can be done. The best solution is to use a different grade of steel or switch to a slaggenerating welding process. II. Improper Weld Bead Profile If operators are experiencing a convex-shaped or concave-shaped bead, this may indicate a problem with heat input or technique. Improper Bead Problem #1: Insufficient Heat Input A convex or ropy bead indicates that the settings being used are too cold for the thickness of the material being welded. In other words, there is insufficient heat in the weld to enable it to penetrate into the base metal. Remedies To correct a problem with running too cold, an operator must first determine if the amperage is proper for the thickness of the material. Charts are available from the major manufacturers, including Lincoln Electric, that provide guidelines on amperage use under varying conditions. If the amperage is determined to be high enough, check the voltage. Voltage that is too low usually is accompanied by another telltale sign of a problem: a high amount of spatter. On the other hand, if voltage is too high, the operator will have problems controlling the process and the weld will have a tendency to undercut. One way to check if the voltage is set properly is to test it by listening. A properly running arc will have a certain sound. For instance, in short arc transfer at low amperages, an arc should have a steady buzz. At high amperages using spray arc transfer, the arc will make a crackling sound. The arc sound can also indicate problems -- a steady hiss will indicate that voltage is too high and the operator is prone to undercut; while a loud, raspy sound may indicate voltage that is too low. Improper Bead Problem #2: Technique A concave or convex-shaped bead may also be caused by using an improper welding technique. For example, a push or forehand technique tends to create a flatter bead shape than a pull or backhand technique. Remedy For best bead shapes, it is recommended to use a push angle of 5-10 degrees. Improper Bead Problem #3: Inadequate Work Cable Problems with the work cable can result in inadequate voltage available at the arc. Evidence of a work cable problem would be improper bead shape or a hot work cable. Remedy Work cables have a tendency to overheat if they are too small or excessively worn. In replacing the cable, consult a chart to determine size based on length and current being

used. The higher the current and longer the distance, the larger the cable needed. III. Lack of Fusion If the consumable has improperly adhered to the base metal, a lack of fusion may occur. Improper fusion creates a weak, low quality weld and may ultimately lead to structural problems in the finished product. Lack of Fusion Problem: Cold Lapping in the Short Arc Transfer Process In short arc transfer, the wire directly touches the weld pool and a short circuit in the system causes the end of the wire to melt and detach a droplet. This shorting happens 40 to 200 times per second. Fusion problems may occur when the metal in the weld pool is melted, but there is not enough energy left to fuse it to the base plate. In these cases, the weld will have a good appearance, but none of the metal has actually been joined together. Since lack of fusion is difficult to detect visually, it must be checked by dye-penetrant, ultrasonic or bend testing. Remedies: To guarantee correct fusion, ensure that voltage and amperage are set correctly. If the operator is still having problems after making those adjustments, it may require a change in the welding technique. For example, changing to a flux-cored wire or using the spray arc transfer method instead. In spray arc transfer, the arc never goes out so cold lapping and lack of fusion are not issues. Spray arc welding takes place at amperages high enough to melt the end of the wire and propel the droplet across the arc into the weld puddle. IV. Faulty Wire Delivery If the wire is not feeding smoothly or if the operator is experiencing a chattering sound within the gun cable, there may be a problem with the wire delivery system. Most of the problems related to wire delivery are attributed to equipment set-up and maintenance. Faulty Wire Delivery Problem #1: Contact Tip There is a tendency among operators to use oversized tips, which can lead to contact problems, inconsistencies in the arc, porosity and poor bead shape. Remedies: First, make sure that the contact tip in the gun is in working order and sized appropriately to the wire being used. Visually inspect the tip and if it is wearing out (becoming egg-shaped), it will need to be replaced. Faulty Wire Delivery Problem #2: Gun Liner A gun liner, like the contact tip, must be sized to the wire being fed through it. It also needs to be cleaned or replaced when wire is not being fed smoothly. Remedy: To clean the liner, blow it out with low-pressure compressed air from the contact tip end, or replace the liner. Faulty Wire Delivery Problem #3: Worn Out Gun Inside the gun are very fine strands of copper wire that will eventually break and wear out with time.

Remedy: If the gun becomes extremely hot during use in one particular area, that is an indication that there is internal damage and it will need to be replaced. In addition, be certain that the gun is large enough for the application. Operators like to use small guns since they are easy on the hand, but if the gun is too small for the application, it will overheat. Faulty Wire Delivery Problem #4: Drive Roll Drive rolls on the wire feeder periodically wear out and need to be replaced. Remedies: There are usually visual indications of wear on the grooves of the rolls if replacement is necessary. Also, make sure that the drive roll tension is set properly. To check tension, disconnect the welding input cable from the feeder or switch to the cold feed option. Feed the wire and pinch it as it exits the gun with the thumb and forefinger. If the wire can be stopped by pinching, more drive roll tension is needed. The optimum tension will be indicated by feeding that is not stopped while pinching the wire. If the drive roll tension is too high, it may deform the wire leading to birdnesting (tangling) and a burn back (when the arc climbs the wire and fuses the wire to the contact tip.) Make sure that the drive rolls and the guide tube are as close together as possible. Next, check the path from where the wire leaves the reel to where it enters the drive rolls. The wire must line up with the incoming guide tubes so there is no scrapping of the wire as it goes through the tube. On some wire feeders, the wire spool position is adjustable -- align it so that it makes a straight path into the tube. Faulty Wire Delivery Problem #5: Wire Coming Off Reel and Tangling Some wire feeding problems occur because the inertia from the wire reel causes it to coast after the gun trigger is released. Remedy: If the reel continues to coast, the wire on the reel will loosen and the wire may come off or become tangled. Most wire feeding systems have an adjustable brake on the wire reel. The brake tension should be set so that the reel does not coast. By following these four guidelines, a GMAW operator new to the world of welding or even someone more experienced should have an easier time diagnosing problems before they affect the quality of the work.

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Developed by The Lincoln Electric Company

Frequently Asked MIG Welding Questions

Here are some of the most frequently asked questions that The Lincoln Electric Company receives regarding general MIG welding issues.q q q q q

Does my choice of MIG welding wire really affect the quality of the weld? Does shielding gas affect the quality of the finished weld? Are there any other tips you can provide for higher quality MIG welding? How important is a good electrical ground in MIG welding? How important is the Contact Tip in MIG welding?

Q: Does my choice of MIG welding wire really affect the quality of the weld? A: While there are many options on the market today for mild steel welding wire, we will concentrate on the two most popular for small shops or hobbyists. Lincoln Electric offers several types of its copper-coated SuperArc MIG wire - including the popular L-50 and L-56. Although both are 70,000 lb. tensile strength wires designed for welding mild or carbon steels, it is the amount of deoxidizers found in the wires that sets them apart. SuperArc L-50 (AWS classification ER70S-3) is a great general fabrication MIG wire and it usually allows you to make quality welds on clean steel. For production work, .035, and .045 are the most common diameters. However, you may want consider SuperArc L-56 when you need to weld steels that have less than perfect surface conditions. In the same way you can upgrade gasoline for your automobile from regular to premium for enhanced performance, you can do the same for welding wire. For this reason, SuperArc L-56 wire (AWS classification of ER70S-6) carries more deoxidizers in its chemistry. This means that it has more built-in cleaning action to handle contaminants of welding such as surface rust, oil, paint and dirt. With L-56, you may not be required to do as much cleaning of the steel before welding. This higher quality of cleaning offered by the deoxidizers usually translates into a higher quality weld materials with less than stellar surface conditions. Most automotive manufacturers now mandate this type of

wire for any automotive repairs. In addition, this wire is available in diameters ranging from .025 to 1/16 which meet the welding performance demands of thin sheet metal (24 gage) to heavy plate welding. TRY SUPER ARC L-56! For more information on SuperArc Products Click Here SuperArc/SuperArc MIG Wire -- Order Bulletin C4.10 Q: Does shielding gas affect the quality of the finished weld? A: For most mild steel applications, CO2 will provide adequate shielding, but when you must have a flatter bead profile, less spatter or better wetting action, you may want to consider adding 75 to 90% argon to your CO2 shielding gas mix. Why? Argon is essentially inert to the molten weld metal and therefore will not react with the molten weld metal. When CO2 is mixed with Argon, the reactivity of the gas is reduced and the arc becomes more stable. But, Argon is more expensive. In production welding, selecting the perfect shielding gas can be a science of its own. Attributes such as material thickness, welding position, electrode diameter, surface condition, welding procedures and others can affect results. Common gas mixes for the home hobbyist and small fabricator would be:q

100% CO2 -Lowest price, generally greatest penetration, and higher levels of spatter. Limited to short circuit and globular transfer. 75% Argon - 25% CO2 -Higher price, most commonly used by home hobbyist and light fabricator, lower levels of spatter and flatter weld bead than 100% CO2. Limited to short circuit and globular transfer. 85% Argon - 15% CO2-Higher price, most commonly used by fabricators, with a good combination of lower spatter levels and excellent penetration for heavier plate applications and with steels that have more mill scale. Can be used in short circuit, globular, pulse and spray transfer. 90% Argon - 10% CO2- Higher price, most commonly used by fabricators, with a good combination of lower spatter levels and good penetration for a wide variety of steel plate applications. Can be used in short circuit, globular, pulse and spray transfer.

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TRY C-25 SHIELDING GAS (75% Argon, 25% CO2 ) Q: Are there any other tips you can provide for higher quality MIG welding? A: Try a smaller diameter wire. Although the most common diameters of welding wire are .035 and .045, a smaller diameter wire usually will make it easier to create a good weld. Try an .025 wire diameter, which is especially useful on thin materials of 1/8 or less. The reason? Most welders tend to make a weld that is too big - leading to potential

burnthrough problems. A smaller diameter wire welds more stable at a lower current which gives less arc force and less tendency to burn through. If you keep your weld current lower, you will have a greater chance of success on thinner materials. This is a good recommendation for thinner materials; but be careful using this approach on thicker materials (>3/16) because there may be a risk of lack of fusion. Whenever a change like this is made, always verify the quality of the weld meets its intended application. TRY SuperArc .025" L-56! For more information on SuperArc Products Click Here SuperArc/SuperArc MIG Wire -- Order Bulletin C4.10 Q: How important is a good electrical ground in MIG welding? A: In arc welding, an arc is established from the electrode to the workpiece. To do this properly, the arc requires a smooth flow of electricity through the complete electrical circuit, with minimum resistance. If you crimp a garden hose while watering the lawn, the flow at the sprinkler head is much reduced. Beginning welders often make the mistake of attaching the work clamp (or electrical ground) to a painted panel or a rusty surface. Both of these surfaces are electrical insulators and do not allow the welding current to flow properly. The resulting welding arc will be difficult to establish and not very stable. Other telltale signs of an improper electrical connection are a work clamp that is hot to the touch or cables that generate heat. Another key point to consider when attaching the welding ground is to place the welding ground on the piece being welded. Welding current will seek the path of least resistance so if care is not taken to place the welding ground close to the arc, the welding current may find a path unknown to the operator and destroy components unintended to be in the welding circuit. SO . . . FIRMLY ATTACH WORK CABLES TO CLEAN BARE METAL AND CLOSE TO THE WELDING ARC. To receive additional safety information Click Here Q: How important is the Contact Tip in MIG welding? A: Very important. Make sure the gun tip isnt worn out or that weld spatter is not on the tip near the exit hole. The contact tip in the gun should be perfectly round and just a few thousandths larger than the wire itself. Worn tips are typically oval and can cause an erratic arc from the random electrical connection and physical movement of the wire inside the worn tip. Genuine Lincoln contact tips are precisely made from a wear-resistant copper alloy for superior welding performance. If the contact tip enters the molten weld pool, it should be immediately replaced. For most casual welders, a good rule of thumb to assure high quality welding is to change the tip after ever 100 lbs. of wire. Another point to remember about contact tips is that they should always be threaded completely into the gas diffuser and tightened prior to welding to give a smooth flow of welding current. IF THE CONTACT TIP LOOKS QUESTIONABLE, GET A NEW LINCOLN TIP, THREAD IT COMPLETELY INTO THE GAS DIFFUSER AND TIGHTEN.

To view or order our MIG / MAG Welding Guide -- Order Bulletin C4.200 Conclusion: The Lincoln Electric Company offers a full range of MIG solutions Take a look at our equipment like the mid-sized PowerMIG 255, the Waveform Control TechnologyTM tour de force named the PowerWave 455, and rugged, adaptive Series 10 wire feeders capable of MIG pulsing. Even more importantly, try for yourself the consistent quality and feedability of our SuperArc copper-coated and SuperGlide bare mild steel wires, the carefully crafted Blue Max Stainless MIG wires and the wide range of aluminum SuperGlaze MIG wires now available. In addition to products, we at Lincoln take pride in our MIG welding expertise and application assistance. If you have a question regarding our MIG solutions for your application, please contact us via phone at 1.888.921.9353 or via e-mail.

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MIG vs. Flux-Cored: Which Welding Process Is Right for You?

You are about to make the plunge and buy your first wirefeed welder. Being a toolguy (or gal), you don't want to waste your money on a toy that goes out with the trash in a few weeks. You most likely are very comfortable building things from wood, but you always wanted to step up to steel. You probably want to run it off of 115 volt input, so that it is very portable, but maybe stepping up to the 230 volt input machines with the option of welding thicker material(more than ") is a valid point. You think the decisionmaking process is over when you are hit with yet another question - which welding process will you use? . . . GMAW (MIG) or FCAW (fluxcored)? If you are like most novice welding operators, you may be confused as to the differences of these two choices. The best answer depends on 3 things. First, what you are welding. Second, where are you welding it. And Third, the surface finish of what you are welding. We will help you to decipher between the two processes, then describe advantages and disadvantages of each and wrap up by giving you usage tips. Ultimately, we hope to help you decide on a solution that will give you the best results for your application. The suggestions here are conservative and should be attainable by a beginner. Welding is a skill and an art about 95% can learn to do. Very few baseball players are able to hit over .350 in the majors. Very few welders have the skills to make picture perfect welds. It is critical to have good eye/hand coordination and a steady hand. Arc practice time is the only instructor that will teach you to truly set the machine properly. With basic motor skills, practice and patience, you should attain success at making sound welds. The Definitions Gas Metal-Arc Welding: (GMAW) as identified by the American Welding Society, is also popularly known as MIG (Metal Inert Gas) and uses a continuous solid wire electrode for filler metal and an externally supplied gas(typically from a high-pressure cylinder) for shielding. The wire is usually mild steel, typically copper colored because it is electroplated with a thin layer of

copper to protect it from rusting, improve electrical conductivity, increase contact tip life and generally improve arc performance. The welder must be setup for DC positive polarity. The shielding gas, which is usually carbon dioxide or mixtures of carbon dioxide and argon, protects the molten metal from reacting with the atmosphere. Shielding gas flows through the gun and cable assembly and out the gun nozzle with the welding wire to shield and protect the molten weld pool. Molten metal is very reactive to oxygen, nitrogen and hydrogen from the atmosphere, if exposed to it. The inert gas usually continues to flow for some time after welding to keep protecting the metal as it cools. A slight breeze can blow the shielding away and cause porosity, therefore welding outdoors is usually avoided unless special windscreens are erected. However, if done properly, operator appeal and weld appearance are excellent with MIG and it is most welders' favorite process to use. Good technique will yield excellent results. The properly made finished weld has no slag and virtually no spatter. A "push" gun angle is normally used to enhance gas coverage and get the best results. If the material you are welding is dirty, rusty, or painted it must be cleaned by grinding until you see shiny bare metal. MIG welding may be used with all of the major commercial metals, including low carbon steel, low alloy steel, and stainless steel and aluminum with potential for excellent success by a novice. Aluminum MIG Welding aluminum requires much more than just changing to aluminum wire. Get comfortable welding steel first. Since aluminum is very soft, it requires aluminum drive rolls that have a U-groove and no teeth to bite or cause wire flaking. Cleanliness of the wire and base metal are critical. Wipe the material with acetone on a clean shop rag. Use stainless steel wire brushes that have only been used on aluminum. Drive roll tension and gun length must be minimized. A Teflon, nylon or similar gun liner is needed to minimize friction in feeding the wire and 100% pure Argon gas is required for shielding. Special contact tips are often recommended. Special gun movement techniques are often highly desirable. It is a challenge, but it can be done. Self-shielded Flux-Cored Arc-Welding process (FCAW per the American Welding Society), or flux-cored for short, is different in that it uses a wire which contains materials in its core that, when burned by the heat of the arc, produce shielding gases and fluxing agents to help produce a sound weld, without need for the external shielding gas. We achieve a sound weld, but in a very different way. We have internal shielding instead of external shielding. The shielding is very positive and can endure a strong breeze. The arc is forceful, but has spatter. When finished, the weld is covered with a slag that usually needs to be removed. A "drag" angle for the gun is specified which improves operator visibility. The settings on the wirefeeder / power source are slightly more critical for this process. Improper technique will have results that are magnified. This type of welding is primarily performed on mild steel applications outdoors. The Innershield .035" NR-211MP is often used for the 115 volt machines and the .045" Innershield NR-211MP is typically used in the 230 volt machines. Farmers have found that these products can save a planting or harvest by repairing a broken machine out in the middle of the field in record time. General Usage Rules

MIG As a rule of thumb, it is recommended to use a compact 115volt input (or 230 volt) MIG wirefeeder/welder indoors on clean new steel that is 24 to 12 gauge thick. 12 gauge is a little less than 1/8" thick.