What does a Level 1 Inspector do? Verifying that the specified base metal and welding materials are used and maintained in proper

conditions. Verifying that joint preparation and fit-up meet the requirements of the welding procedure and

drawings. Examining and evaluating welds according to specified procedure.

Welding Inspector must : Observe

Relevant actions related to weld quality throughout the production Record

Record, log all production, inspection points relevant to quality, including final report Compare

To compare all recorded information with the acceptance criteria and any other relevant clause in the applied application standard

Welding A group of processes used to join metallic and non-metallic materials. Often done using heat but

maybe done using pressure or a combination of heat and pressure.Joint

The junction of members or the edges of members that are to be joined or have been joined(AWS).

A configuration of members(BS 499)Toxic fumes in welding

Aluminum Chromium Brellium Copper

Power The amount of the maximum voltage used in welding is 800 V. High current, low voltage In welding the current always flows from (-) to (+) pole. AC : Alternating Current, 60 Hz in North America DCEN : Direct Current Electrode negative= DCSP : Direct Current Straight Polarity

Electrode is (-). The current flows from the electrode to the work piece. The heat is produced at the surface of the work piece.

DCEP : Direct Current Electrode Positive = DCRP : Direct Current Reverse PolarityThe electrode is (+). The current flows from the work piece to the electrode. The heat is produced at the electrode.

The selection of current depends ono Processo Type of electrodeo Arc atmosphereo The metal being welded

Heat in the arc Change the arc length Change the shielding gas Addition of potassium salts reduces arc voltage

Metal Arc Transfer Metal is transferred across the arc(consumable electrode) Mechanism of transfer

o The molten metal drop touches and transfers by surface tensiono Magnetic Pinch Effecto Gravity(Flat welding)

More heat is transferred than non-consumable electrodes Ionization column must be present to conduct electricity(The arc)

Coalescing Mechanism Fusion via gigh density energy

Efficiency The conversion of electrode to material

Welding Positions

Physics of Welding Variables Electromagnetic Pinch Force Surface Tension Gravity Heat Inputs Electrical Resistance

The Properties of Matter Physical properties

o Coloro Melting Temperatureo Density(weigth per unit volume)

Chemical Properties o How the metal reacts in an environmento Corrosion resistance : The ability to resist corrosion.o Qxidationresistance : The ability to resist combining with oxygen.

Mechanical Properties o Strength : The ability to resist load without failingo Tensile Strength : The ability to resist pulling force.o Compressive Strength : The ability to resist crushing force. o Ductility : The ability to resist deformation without breaking.o Brittleness : The inability to resist fracture.o Toughness : The ability to resist cracking.o Hardness : The ability to resist indentation or scratching.o Grain Size : Important in determining mechanical properties.

Effect of Welding Heat creates stress, affects ductility and toughness Effects of previous heat treating are lost around the weld If done properly usually stronger than base metal Can effect the chemical resistance

Expansion and Contraction Metal expands when heated Metal contracts when cooled Expansion and contraction create stress Welding jigs or fixtures prevent movement but lock in stress(Jigs are temporary, fixtures are

more permanent)Type of welds

Groove Weld Fillet Weld Plug Weld Slot Weld

Reducing Distortion Tack weld Align parts for contraction Use jigs or fixtures Preheating Interpass Heating Post Heating Heat treat welded parts Proper welding procedures Joint Design Welding Sequence Pre-bending using strongbacks and wedges Balanced welding Stiffeners

Basic Weld Joints

Welding Technology Fundamentals

Chapter 2 – Welding and Cutting ProcessesProcess is an operation used to produce a product. Processes in industry :

o Rivettingo Forgingo Castingo Cuttingo Turningo Bendingo Welding

Blacksmiths have used their skills and knowledge to work metal into many desired products. Metal workers are employed today to make prototype parts. Prototype Partsare the first models of parts that later may be mass-produced.Forge Welding(FOW), the parts are heated until they are very hot and in a softened state. The heated ends then placed together on an anvil and struck repeatedly with a hammer by a blacksmith.Welding is a process of joining metallic or non-metallic material in a relatively small area by heating the area to the welding temperature. Most metals and plastics are weldable.Fusion Welding is the process of joining materials by applying heat until the areas of the weld joint reach their melting points, and flow together, forming a single piece after they cool.Most welding processes require heat, but welds are also made with the metal at or near room temperature(Cold welding, explosion welding). Parts joined by welding are known weldments.

Advantages of Welding and Cutting Processes Most equipment is portable Thanks to modern welding techniques, engineers are able to design strongs parts that are

lightweight, complex, and often less expensive than other joining methods. In general, weldments use less material, take less time, and are cheaper to produce than

machined parts.

Applications of welding and cutting processes are unlimited.(Example : Termal Spraying process is used to add some weldable metal onto the stone surfaces, and then this metal can be welded to join stones together.)

Chapter 3 – The Physics of Welding

Welding Theory

Welding With HeatWelding is often done using heat. A filler material is commonly used when heat is used. Shielded Metal Arc Welding(SMAW) is a process that uses heat and filler material. In this process, heat is created by an arc that is struck between an electrode and base metal(metal to be welded).

Welding with Heat and PressureFiller material is generally not used when both heat and pressure are used. In Resistance Spot Welding, pressure is applied through opposing electrodes. Electrical current flows from one electrode through the base metal to the other electrode. Resistance to the electrical current provides the heat required to join pieces.

Welding with PressureHead and filler material are not required. In Cold Welding Process, very clean pieces of metal are forced together under considerable pressure.

Properties of MetalThe properties of metal are largely determined by the chemical composition of a metal. A metal alloy consist of different elements. Properties are affected by the method of processing such as bending, roling, welding, etc.

Physical Properties Color Melting temperature Density(Density is the weight of a particular material per unit volume.)

Chemical PropertiesChemical properties determine the way a material reacts in a given environment. They are :

Corrosion resistance is the ability of a material to withstand corrosive(acid and saltwater) attack.

Oxidation resistance is the ability of a material to resist the formation of oxides.Metal oxides occur when oxygen combines with the metal.

Mechanical PropertiesMechanical properties determine how a material reacts under applied loads and forces.Strength : resistance to applied loads without failing.Tensile strength : resistance to pulling forces.Compressive strength : resistance to pressing or crushing forces. Note : Tensile and Compressive strength are opposite with respect to the direction of the applied load.Ductility : to stretch or bend without breakingBrittleness : inability of a material to resist fracturing. Opposite of ductility.Toughness : resistance to cracking and a crack from processing. Ductile materials are usually very tough.

Hardness : resistance to indentation or scratching. Hardness of some steels can be improved by quenching and tempering.Grain size plays an important role in determining the mechanical properties. Largeor coarse grained materials are brittle but not ductile. Fine grained materials are ductile but not brittle.

Effects of WeldingHeat produced by welding creates stress in the metal. Ductility and toughness are affected by heat as well. A weld that is made correctly is usually stronger than the base metal. An incorrect welding may cause some serious problems. For example : a corrosion-resistant steel pipe may lose its resistance at an improperly welded joint, or an armor plate may lose its toughness and a crack may develop at the weld.

Expansion and Contraction of MetalWhen heat is applied to metal, it expands. When heat is removed, it cools and contacts. Expansion and contraction cause a stress in the metal. The metal may relieve the stress by changing its shape. Deformation or movement is not acceptable in many welding applications. Welding jigs and fixtures are commonly used to keep parts from moving.When welding a butt joint, the root opening may be reduced in size toward the end of the weld because the weld metal conracts and pulls the pieces together. To prevent this, the pieces should be tack welded. The outer edges of the base metal may also bend toward the weld bead. To prevent this, the pieces may be clamped into a welding fixture or positioned with a reverse angle to compensate for the movement. When welding a T-joint, the vertical piece may be pulled toward the weld bead. To prevent this, place the piece in a welding fixture or tack weld the vertical piece a few degrees from the perpendicular.The 6 Technique used to reduce movement and/or stress

Tack weld Align the parts to allow for contraction Use welding jigs or fixtures Preheat the parts Heat-treat the welded parts Use the porper welding procedure

StraighteningThe priciples of expansion and contraction can be used to straighten bent or warped parts. The part is heated on the correct side to cause it to expand using a oxyfuel .

Heat-Treating

Various heat-treating processes are used in industry such as annealing, stress relieving, and quenching and tempering. Heat treating can be applied before, during or after the welding process.

PreheatingThe entire part is heated before welding. Preheating causes less expansion of the part during welding. When the part cools, less contraction occurs and less stress is developed.

Interpass HeatingIt is a method of heating metal while it is being welded or between weld passes. Preheating is applied and interpass heating is used to maintain an elevated temperature. This process is used to reduce expansion, contraction and stress resulting from welding.

Annealing and NormalizingThe metal is heated and allowed to cool slowly, so the hardness decreases and ductility increases. Cracks or distortions become less possible and the part can be bent or machined easier. In normalizing process, a metal is heated to a very high temperature(910°C-Steel) in a furnace for a certain time and removing the metal and allowing it to cool to room temperature. Annealing is similar but requires slower cooling process. Therefore, the metal is kept in an annealing oven ant temperature is slowly lowered.

Stress RelievingThis process is similar to annealing but lower temperatures are used(650°C-Mild Steel). The steel is kept at that temperature for a few hours and then allowed to air cooled.

Quenching and TemperingThese processes are used to harden steel and stell alloys. In quenching, the metal is heated to a fairly high temp. and maintained for a given time at this temperature, then metal is cooled quickly immersing into water, oil or other liquid. The metal becomes very hard and brittle. Then the metal is tempered by reheating to several hudred degrees and cooling. After tempering, the metal becomes less hard and no longer brittle. Tempered metals have good toughness.

Electrical PrinciplesElectricity can measured in terms of voltage and current. Voltage is the force that causes electrons to flow through a circuit and measured in volts. Voltage is always present in an electrical circuit but we cannot see any arc when the circuit is open. This is called open circuit voltage(OCV). The air gap between the electrode and base metal offers resistance to the flow of electrons. Resistance is the opposition to the flow of electrons and measured in ohms. A higher voltage setting allows the arc length to be longer. The arc stops if the arc length is longer than the voltage allows.Current is the flow of electrons in an electrical circuit and measured in ampere. If there is no arc, there is no current flowing. When an arc is struck, current is produced as electrons flow across the arc. In some welding applications, a higher voltage or current is required. In other applications, a lower voltage or current may be required.

Units of MeasurementBasic convertion information between and in SI metric and US conventional system.

Chapter 4 – Weld Joints and Positions

Basic Weld JointsA weld joint refers to how the parts to be joined are assembled prior to welding.Base metal, the metal to be joined.Base material, if the part to be welded is not metal.

Butt JointThis is used when parts are joined edge-to-edge. Common examples are the deck plates on a ship or the pipes of an oil pipeline. Both are assembled end-to-end.The edges of the base metal often require special preparation for quality results. Edge preparation refers to how the edges of the joint are shaped prior to welding. If the base metal is thin, the edges may just be squared without additional machining or cutting or bent to form flare-groove or edge-flange joints. When base metal is over 3/16”(4.8mm) thick, edges are bevelled by machining or flame cutting to allow the weld penetrate to the required depth. Thick base metal may be machined, gouged or flame cut along the upper or lower edges of joint, or both, to form a double bevel, V-, J-, or U-groove; or a flared

groove. A groove weld is made by fusing molten filler metal into a butt joint that has been set up in a groove formation include a single-square groove, a single or double bevel, V-, J-, or U-groove, or a flared groove. Various parts of a groove joint :Groove face : The surface formed on the edge of the base metal after it has been machined or flame cut.Groove angle : The total angle formed between the groove face on one piece and the groove face on the other piece.Bevel angle : The angel between the bevel of the joint and a plane perpendicular to the surface of the base material.Weld root : The point where the weld intersects the base metal surface near the bottom of the joint.Root face : The distance from the weld root to the point where the bevel angle begins.Root opening : The distance between the two pieces at the root of the weld.Weld face : The outer surface of the weld bead on the side the weld was made.Face reinforcement : The distance from the top of the weld face to the surface of the base metal.Root reinforcement : The distance that the penetration projects from the root side of the joint.Weld Toe : The point where the weld bead contacts the base metal surface.Joint Penetration(weld size) : The depth that a weld extends into the joint from the surface.

Lap JointIt is formed by two overlapping pieces of base metal.

Corner Joint It is formed by two pieces of base metal that are at an angle of approximately 90° to one another.

XxxxxxxxxWeld Beads and Weld Passes

Weald Bead : one weld pass of filler metal that is added to a weld joint. Weld Pass : occurs each time a welder lays one weld bead across a weld joint. For thin materials

only one weld pass or bead is required.For thick materials more than one pass or bead is required.

Multiple pass Root pass : The first weld Filler passes : Intermediate weld passes. Cover Pass : The final weld pass. A weld bead should not be thicker than 6.4 mm. A weld bead may be made as a stringer bead or a weave bead.

o Stringer Bead : Stringer beads are made by moving the troch or electrode holder along the weld without any side-to-side motion. They are used when a standard bead width is acceptable.

o Weave Bead : Used to create a wider weld pool. By moving the torch or electrode holder side-to-side.

Joint GeometryThe shape and dimensions of a joint(weld), in cross section, prior to welding.(AWS)Assembly design depends on

Metal thickness Metal Shape Load requirements of the part

Properly prepared J or U joint decreases the groove dimensions while allowing adequate space for welding

In the Tail Welding Process Welding Procedure “Typical” representative of all welds on the drawing

Fire HazardsFire Classification Class A : Solid material such as paper, wood, or cloth Class B : Combustible liquids such as gasoline, oil, paint tinner Class C : Electrical equipment such as switches, fuse boxes, or motors Class D : Combustible metals such as titanium and magnesiumBurn Hazards First Degree Second Degree Third Degree

Eye Hazards and Arc Rays Flying Sparks, metal chips UV or infrared rays(Arc Flash)

Electrical HazardsMachinery HazardsFumes and Ventilation

Chapter 20 – Oxyfuel Gas CuttingOxyfuel Gas Cutting : A process used to cut metal by rapidly oxidizing it.Oxyfuel Gas Cutting and Oxyfuel Gas Welding are general terms for a group of cutting and welding processes that use heat produced by a gas flame to cut and join various metals. Example : Oxyacetylene and oxyfuel gas weldin processes.Fuel gases : are those that will support combustion(burn) when combined with oxygen.Fuel Gases

Acetylene(3093 C. This is the highest temp.) Propane(Brazing or soldering) Butane( “ “ ) Hydrogen Natural gas( “ “ ) MPS gas(methylacetylene-propadien)in other name MAPP gas.

A cut cut depends on the welder’s skill, cutting tip size and the oxygen pressure. Slag : Hard crust(Kabuk, dıştabaka), Iron oxide Kerf : The slot or opening produced in the metal when cutting. Quality of the kerf depends on :

o Cutting tip sizeo Oxygen pressureo Torch forward speedo Steady torch movement

o Torch tip angleo Distance of preheat flames from the base metal

Bell-mounted kerf : because of too much oxygen pressure Oxygen is stored in cylinders at a pressure of about 2200 psig Acetylene may form explosive compounds when combined with copper, mercury, or silver. Oxy-fuel Connections

o Oxygen – Green and right hand threadso Fuel - Red and left hand threads

Backfire : Flashback

o Check Valveo Flashback Arrestor

Cutting Torch : used to control and mix fuel gas with oxygen and direct the oxyfuel gas flame to the cutting area.

Welding rod : a long, thin rod of a similar type of metal to that being welded. As the rod is melted, it is added to the the weld bead.

MODULE 6 – SMAW

SMAW, is a welding process in which the base metals are heated to fusion or melting temperatureby an electrical arc. The arc is created between a covered metal electrode and the base metal.

The temperature can reach over 5000 C.Polarity

The direction that the electrons flow. Electrons flow from a (-) to (+) body. DCEN : Direct Current Electrode Negative = DCSP : Direct Current Straight Polarity DCEP : Direct Current Electrode Positive = DCRP : Direct Current Reverse Polarity

Cycle : A set of repeating events Frequency : The number of cycles per second, measured in hertz(Hz) SMAW require Constant Current(CC)=Droop Curve Machines=Droopers 25% change in voltage creates 4% change in current. Welding transformer are called step-down transfromers.(Voltage reduced)

Variables Input Power Requirements Rated output current : A nameplate on the machine Duty Cycle : How long a welding machine can be used at its max.current. Based on 10 minutes. Open Circuit Voltage

o The voltage of the welding machine when it is on, but it is not used.o Typically 80 V.

SMAW Electrodes in CSA W 48-01 carbon steel covered electrodes chromium and chromium-nickel covered electrodes low alloy steel covered electrodes

The Functions of the Electrode Coverings Add filler metal

Create protective gas shield Create a flux to remove impurities Create slag to protect bead as it cools Add alloys to improve mechanical and chemical properties Determine the polarity of electrode

The Effect of Current Types DCEP : Deeper Penetration, Low Deposition Rate DCEN : Less Penetration, Faster Deposition AC : Medium Penetration

Two methods to startstrike an arc : Scratch the electrode on the metal then draw it Pecking motion

Arc Length : The distance between the electrode and the base metal. Should be equal to the diameter of the electrode.

Arc Blow : The arc is deflected from its normal path by magnetic field created by current. Change the position of work leads. AC produce less magnetism.

Two types of weld beads : Stringer : along a line, no side-to-side motion. Width should be 2-3 times electrode diameter. Weave : made along a line by side-to-side motion. No wider than 6 times electrode diameter

Angles Travel angle : 20 ° Work angle : 90 °

The following must be kept constant while welding The arc length The electrode angle The weld bead width The forward welding speed

Drag Welding : A welding technique in which the electrode covering is in contact with the base metal. Drag welding ensures a constant arc length.

Reading the weld bead can provide info on the following variables : Amperage setting Arc Length Travel Speed

SMAW ELECTRODES The electrode wires used for most steel electrodes is low carbon steels. Hydrogen in a weld lowers its strength Diameter of a electrode = diameter of the uncoated wire Deposition rate : the amount of filler metal deposited in one minute.

DCEP : Deeper Penetration, Low Deposition Rate, Low HydrogenDCEN : Less Penetration, Faster Deposition

AC : Medium Penetration, Potassium added as a arc stabilizer4, 7, 8 : Iron powder :Fast Fill, heavy slag, easy to remove, Fast deposit rate so less welding time and less cost, 5, 6, 8 : Low Hydrogen Electrodes, DCEP, Basic, convex profile, good toughness, slags hard to remove.0, 1 :Cellulose: deep penetration, Thin layer of slag, Low deposition, high spatter, high hydrogen, fast travelEXX12-13-14 –Titania,- Rutile, AC or DC –Slag easy to detach, smooth profile.Fill or freeze factor :Iron powder makes it fast fill. If it is at overhead position, it has to be fast freeze. However, iron powder and overhead position should be considered together at the same time, they should comprimise. In this case it is going to be fill freeze.

MODULE 7 – GAS METAL ARC WELDING The tungsten electrode is practically Nonconsumable. Before selecting the weld current, these questions must be answered :

o Type of base metalo Thicknesso Type of jointo Position

Type of current used in GTAW o ACo DCEPo DCEN

Voltageo When AC welding, you must use continuous high frequency voltageo When DC welding, you can use high frequency voltage to start arc but you do not have

to. Post flow : After the arc stops, shielding gas will continue to flow. (General rule is 1 second of

gas flow for each 10 amps of current.) Checklist while setting up GTAW Machine :

o Set the type of currento Set the current rangeo Set the desired current amounto Set the high-frequency switch to the desired position.o Set the contactor switch to the desired positiono Set the current switch to the desired positiono Set the post flow timer for the desired post flow

Electrode tipso Point type - for AC currento Ball type – The ball no larger than electrode diameter - for DC current

Precut lengths or rods are usually 36”(914mm) GTAW Variations

o Autogenouso Automatico Hot wire

o Multi-electrode

GMAW(Gas Metal Arc Welding) = MIG(Metal Inert Gas) A welding process in which metals are joined by heating them with a welding arc between a

continuous consumable electrode and the base metal. Only DC is used in this process. Usually,DCEP(DCRP) is used, The use of DCEN(DCSP) is seldom. CV power supply. The electrode is melted and becomes a part of the weld. For this reason, the electrode is called

a consumable electrode. A shielding gas is used to protect the weld from the air. FCAW(Flux Core Arc Welding) and GMAW are very similar processes. The main difference

between these processes is the use of flux. In GMAW process, Flux is not used, but in FCAW process, the electrode contains a flux in the center to add alloying elements to the weld.

Advantages of GMAW and FCAWo Longer weld can be made without stopping. This eliminates many of the stops and starts

that can be major cause of weld defects.o Welding speed is faster than SMAW.o No slag, very little spatter. More of the electrode becomes a part of the weld.o Deeper penetration than SMAW.o Less training and skill are required to weld with GMAW and FCAW than SMAW.

Disadvantages of GMAW and FCAWo The equipment is more costly than SMAW.o Some weld joints are hard to reach with the welding gun.o Sudden air movements can blow shielding gas away, resulting in a weld defect.

Metal Transfer Filler metal from the electrode must leave the electrode and enter the weld. This is called metal

transfer.

Three ways of metal transfer Short circuiting transfer Globular transfer

The arc melts the end of the electrode and the base metal. A globule increases at the end of the electrode until it is larger than the diameter of the electrode. It continues to grow in size until the globule falls off. Can not be applied overhead position.

Spray transferHundreds of small droplets are formed every second. They travel at a high rate of speed directly into the weld. Good penetration, a little spatter. The weld pool is very fluid. Used in flat and horizontal position.Pulsed spraying transfer is very similar to spray transfer, but two different current are used. Background and peak current.

Pulsed SpraySuitable for out of position

GMAW Equipment Welding machine Wire feeder

Welding gun Electrode wire Shielding gas supply and controlsGMAW Power Supply CV or constant potential power supply is used for GMAW. In SMAW and GTAW processes, CC is

used. CV power supply can be a transformer-rectifier or an inverter(much smaller and lighter) The welding machine for GMAW is considered to be self-adjusting.

Wire feeder Used to feed electrode wire to the welding gun. Wire feed speed is set on the wire feeder by the welder and DC motor controls the speed. Inch switch : cause the electrode to feed out. No welding current during that. Purge switch : to manually control the flow of shielding gas. When the switch is pressed, the

shielding gas flows.

Shielding Gases Argon (Most common). Very deep penetration in the center but with undercut. To eliminate

undercut, oxygen or carbon dioxide is added. Less penetration and a little spatter in this case. Carbon Dioxide. It can be used as a shielding gas alone with only mild steel and low-alloy steel. Mixture of these gases together with Helium or Oxygen may also be used. Argon and Helium are inert gases, and they do not combine with the weld metal. Carbon Dioxide and Oxygen are active gases, and they combine with the weld metal. In this

case, the weld becomes oxidized. Active gases are only used when welding on ferrous metals.The type of Shielding Gas affects : Type of metal transfer Penetration and shape of weld bead Speed of welding Mechanical properties of the weld

HEATING Preheating Just prior to welding Interpass Heating During welding Post Weld Heat Treatmant After welding

How Much Preheat? Depends on : Base metal chemistry Plate thickness Restraint Rigidity of members Heat input of welding process

W59-03 5.7 Preheat, Interpass Temperatures, and Heat Input Control Experience has shown that the minimum temperatures specified in Table 5.3(Pg.56-57) are

adequate to prevent cracking in most cases. However, higher preheat temperatures may be required in situations involving :

o Higher restrainto Higher hydrogeno Lower welding heat inputo Steel composition at the top of the specification

Alternatively, minimum preheat and interpass temperatures can be established on the basis of steel composition. 2 Methods are explained in W59-03 Appendix P.

HAZ Hardness Control : Limited to filled welds Hydrogen control : Based on an assumption that cracking does not occur if the average

hydrogen level remaining does not exceed a critical value after it has cooled to about 50°C. That critical value depends on the composition of the steel and restraint. The necessary preheat to allow enough hydrogen diffuse out of the jointcan be estimated using this method.

EXAMPLE :Given :Thickness 70 mm.Low HydrogenProcess FCAWBasic (H1)High RestraintGrade of Steel : SAE 1020

Step 1 : Go to the Procedure Handbook of Arc Welding – Pg.16.1-62 and 16.1-63Find SAE 1020 steel composition on tables.Step 2 : Put the values which you have found on the tables in this formula.

How much hydrogen is expected to be in this material?You can find only C and MN values on AISI-SAE Standard Carbon Steels table.

Step 3 : Go to the W59-03 Table P1-Susceptibility Index Grouping as Function of Hydrogen Level, H,

and Composition Parameter, , on page 274 and find related Susceptibility Index Grouping

In this case, H1 is a given, 0.26 value corresponds to , so our index grouping is C.Step 4 : Find Table P2(a) Minimum Preheat and Interpass Temperature for Three Levels of Restraint table on Page 275 in W59-03. Find minimum Preheat and Interpass Temperature on this table consideringRestraint(in this case High), Thickness of the material(70mm) and Susceptibility index(C).Restraint High Thickness 40-70mm 149 °C

Methods of preheating Production of small parts maybe best in a furnace Natural gas premixed with air Acetylene or propane torches Electric strip heaters parallel to joint

Measuring Preheat Temperature

Temperature indicating Crayons

Pyrometers Thermocouples Infrared sensorsPost Weld Heat Treatment Annealing

o To make steel soft and ductileo 100°F above critical temperatureo Hold 1 hour per inch of thicknesso Slow cooling usually in furnace

Normalizing

o To get greater hardness&tensile strengtho Reduce stresses, usually after weldingo The same process as Annealing except coolingo Cool in still air

Stress Reliefo To get dimensional stabilityo Softens martensitic areaso Improves fracture resistanceo Slowly heated to about 625°Co Held a period of timeo Slowly cool

Welding ProceduresCWB

Prequalified Joints Not prequalified Joints

ASME No Prequalified Joints

Prequalification: It is tested that if you follow the described variables(prequalified variables) the weld quality is guaranteed.

CWB Prequalified Joints

CSA W59-03 Section 10 cover only 3 process) :o SMAWo FCAWo SAW

All companies applying or certified to CSA Standards W47.1, W47.2 or W186 are required to prepare and submit welding procedure specifications to the CWP for acceptance.

o Thecompanyshallhaveweldingprocedurespecificationsforeachweldingprocess in use.o Submit WPS to CWB for acceptanceo Qualify welders

CWB Not Prequalified Joints

Welding Procedure Specification Procedure Qualification CWB Approval Qualify welders

ASME Weld Procedures No pre-approved joints Each Welding Procedure will have a Procedure Qualification Record(PQR) Three types of variables

o Essential : If these variables are changed, the mechanical characteristics of the product will change(Process, electrode etc.)

o Supplementary : You can change these variables without changing mechanical characteristics(change of the steel grouping)

o Non-essential (Welder qualification)What is included in a welding procedure?

One WPS One or more data sheets(WPDS)

Welding Procedure Specification Scope

Welding Procedure Base Metal Base Metal Thickness Preparation of Base Material Filler Material Shielding Gas Position Minimum Preheat and Interpass Temperatures Electrical Characteristics Welding Technique Treatment of Underside of Groove Weld Metal Cleaning Quality of Welds Storage of Electrodes

CWB Welder Qualification Classification

o S With Backingo T Without Backingo FW Fillet&tack weldso ASW Arc Spot Weldingo WT Tack Welds

Processo SMAWo FCAWo GMAWo SAWo ESWo EGW

Mode of Applicationo Manual SMAW, GTAWo Semi-automatic FCAWo Machine Weldingo Automatic SAW, EBW,ESW, LMW

Positiono Class F Flat Position&Horizontal Filletso Class H Flat and Horizontal positionso Class V Flat, Horizontal&Vertical Positionso Class O Flat, Horizontal, Vertical&Overhead Positions

Electrode Designation

Roughness Requirements 25µm for 100 mm thick material 50µm for 100-200 mm “ “ Surface Finish Comparator is used

Assembly Fillet Welds The parts shall be brought into as close a contact as practical The separation shall not exceed 5mm for the thicknesses less than 75mm For the thicknesses 75 and more than 75mm maximum 8mm separation acceptable If the separation 2mm or greater, the leg shall be increasedby the amount of separation In lap joints, separation between faying surfaces shall not exceed 2mm. Filler materials are

prohibited except as specified on the drawings or asa approved by the contractor’s engineer and made in accordance with Clause 4.6

For partial penetration groove welds are the same as fillet welds with the exception of bearing joints. The bearing joints(Loaded joints) shall be in accordance with the applicable contract specification.

Abutting parts-grrove welds shall be carefully aligned. However, an offset not exceeding 10% of the thickness- no case more than 3mm.

Workmanship TolerancesTack Welds

Preheat is not mandatory for single-pass welds if the tack weld is totally remelted into the weld. If the quality of the final weld is acceptable, defects such as undercut, unfilled crates, and

porosity need not be removedBacking

Backing for groove welds shall be continuous for the full length of the joint. The separation between faying surfaces of butt joints on steel backing shall not exceed 2mm. The use of filler is prohibited unless some conditions are met.

Control of Distortion and Shrinkage Stresses Build-up members shall be such as will minimize distortion and shrinkage. All welds shall be deposited in a sequence balancing the applied heat while the weld progresses. Before start of welding on a structure which shrinkage stresses or distortion are likely to affect

the adequacy of the structure, a program for welding sequence and distortion control shall be developed.