weldind Electrode selection.pdf

8/10/2019 weldind Electrode selection.pdf

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Types of welding consumablesTypes of welding consumables

There are many types of materials used when making welds. These weldingmaterials are generally categorized under the term filler metalsfiller metals , defined asthe metal to be added in making a welded, brazed, or soldered joint.

Welding Welding Technology Technology

weld.Specifications of filler metals have been determined by standartorganisations, such as;

AWS (American welding society)AWS (American welding society) and ANSI (The American National StandartInstitute)CSA (Canadian Standart Association)ISO (International Standarts Organisation)ISO (International Standarts Organisation)

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DIN (Germany)EN (European Norm)EN (European Norm)TS (Turkish Standarts)TS (Turkish Standarts)

Dr. O ğ uzhan Yılmaz



Filler MetalsFiller MetalsFiller Metals can be classified intofour basic categories:

Covered electrodes


Fabricated (tubular or cord)electrode wireFluxes for welding

Most specifications includeusability factors showing the;

HORIZONTAL POSITON

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or filler metal is designed f

orthe welding current that shouldbe usedthe type of coating .

Size and packaging information isalso provided.

VERTICAL POSITON

OVERHEAD POSITONDr. O ğ uzhan Yılmaz



Covered ElectrodesCovered Electrodes

The covered electrode is a very popular type of filler metals used in arc welding.The selection of the covered electrode for specific work is based on theelectrode usability, the composition and properties of the deposited weld metal .


n or er o proper y se ec an e ec ro e, s necessary o un ers an efunction of the coating , the basis of specifiying , the usability factors , and thedeposited weld metal properties .

The coating of the electrode provides;The coating of the electrode provides;Gas from the decompositon of certain ingredients of the coating shield the arc fromthe atmosphereThe deoxidizers for purifying the deposited weld metal

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Slag formers to protect the deposited weld metal with a slag from atmosphericoxidationIonizing elements to make the arc more stable and to operate with alternatingcurrentAlloying elements to provide special characteristics to the deposited weld metal

Iron powder to improve productivity of the electrode




An electrode coating is designed to provide as many as possible of thefollowing desirable characteristics:

Specific composition of the deposited weld metalSpecific mechanical properties of the deposited weld metal

Covered electrodesCovered electrodesWelding Welding Technology Technology

Elimination of weld metal porosityElimination of weld metal crackingDesirable weld deposit contourDesirable weld metal surface finish (i.e., smooth)

Elimination of undercut adjacent to the weldMinimum spatter adjacent to the weldEase of manipulation to control slag in all positionsStable arc welding

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High rate of metal depositionElimination of harmful odors and fumesReduced electrode overheating during useStrong, tough, durable coating

Easy slag removal

No single electrode type willmeet all of the requirements.

Instead, there is a variety ofelectrode types, each havingcertain desirable characteristics.




Covered electrodesCovered electrodesThe coatings of electrodes for welding mild and low-alloy steels may havefrom six to twelve ingredients , such as;Cellulose:Cellulose: to provide gaseous shield with reducing agent. The gas shieldsurroundin the arc is roduced b the disinte ration of cellulose.


Metal carbonates: to adjust basicity of the slag and to provide a reducingatmosphere (with the aid of CO gases)Titanium dioxide:Titanium dioxide: to help form a high fluid but quick-freezing slag. It willalso provide ionization for the arc.

Ferromanganese and ferrosilicon:Ferromanganese and ferrosilicon: to help dioxidize the molten weld metaland to supplement the manganese content and silicon content of thedeposited weld metal.Clays and gums:Clays and gums: to provide elasticity for extruding the plastic coating

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ma er a an o e p prov e s reng o e coa ngCalcium fluorideCalcium fluoride : to provide shielding gas to protect the arc, adjust thebasicity of the slag, and provide fluidity and solubility of the metal oxides.Mineral silicates:Mineral silicates: to provide slag and give strength to the electrodecovering

Alloying metals:Alloying metals: include nickel, molybdenum, chromium, and so on, toprovide alloy content to the deposited weld metal.




Covered electordesCovered electordes

Iron or manganese oxide:Iron or manganese oxide: to adjust the fluidity and properties of the slag. Insmall amounts, iron oxide helps to stabilize the arc.Iron powder:Iron powder: to increase the productivity by providing additional metal to be


.

The binder used for most electrode coatings is sodium silicate , which willchemically combine and harden to provide a tough and strong coating .

Covered electrodes can be easily damaged . Therefore they need special careElectrodes may become unusable if they are exposed to moisture for anextended lenght of time .The coatin s of some t es of electrodes absorb moisture when ex osed to

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humid atmosphere.Cellulose, rutile and acid electrodes are fairly insensitive to moisture and cantolerate quite high moisture content without the risk of porosity in the weld.




Covered electrodesCovered electrodes

The coatings of low-hydrogen electrodes pick up moisture quickly whenexposed to a high humidity atmosphere .Electrodes should be stored in a special storeroom with controlled


.Electrodes can be damaged by aging . Very old electrodes of most types willhave a furry surface on the coating , usually white. This is from thecrystallization of the sodium silicate.

8Dr. O ğ uzhan Yılmaz



Electrode selection forElectrode selection for steelssteels

Covered electrodes are mostly used for by welding processes inconstruction and fabrication industries due to cheapness, basicity, flexibility,weldability of different materials etc.


there is no single electrode type for general purpose.Selection of the best electrode type mainly depends on the type of steel andits mechanical properties .In catalogues which are prepared by manufacturers, each type of electrodeis classified as follows:

Manufacturing standartsMaterials to be used for

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Chemical and mechanical propertiesWelding positions to be used




The role of coverings:The role of coverings:

There are five groups of coverings:Acid covering: They contain oxides, silicates and high content ofoxygen. Slag is in porous and honeycomb shape. It can be easily


. ,are not used in general purpose.Cellulose covering: mainly contain celluloses such as, vegetals. Thesesubstances decomposes and produce hydrogen gases . Hydrogenimproves the arc voltage and arc penetration. Due to high hydrogencontent, these types of electrodes are not preferred for the welding ofhigh strength steels.Rutile covering: Main composition is titanium oxide. The titanium oxide

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eas y orms s ag an s a ze e arc. ese e ec ro es can e usefor all positions. Hydrogen content is high which is above the acceptedlimits for high strength steels.Basic covering: The cover mainly consists of calcium-flouride andcalcium carbonate. These electrodes are used for high strength steels.

Weld metal has good mechanical properties. Slag cannot be easilyremoved.




The role of coveringsThe role of coverings

Iron-powder covering: In order to increase the efficiency of the electrodes,iron powders are added to the covers. This process increases the efficiencymore than %100. It also increases the deposition rate and fairly good weld


.




Electrode StandartsElectrode Standarts

Although electrode manufacturers have their own brand-name, electrodesare produced based on specific standarts and designated according to theused standart.


,TS 563 EN 499 Turkish StandartAWS A5.1/ ASTM-233EN 499 European Standarts




TS 563 EN 499 Designation of the elctrodes for nonTS 563 EN 499 Designation of the elctrodes for non- -alloy and lowalloy and low- -alloy steelsalloy steels





Electrode selection for carbon steelsElectrode selection for carbon steelsWelding Welding Technology Technology






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SAMPLE ELECTRODES (1): Rutile E 42 0 RR 12SAMPLE ELECTRODES (1): Rutile E 42 0 RR 12Welding Welding Technology Technology





SAMPLE ELECTRODES (2): Basic E 42 3 B 42 H10SAMPLE ELECTRODES (2): Basic E 42 3 B 42 H10gg gygy





SAMPLE ELECTRODES (3): Alcord 12 SiSAMPLE ELECTRODES (3): Alcord 12 Sigg gygy





SAMPLE ELECTRODES (4): Citodur 600SAMPLE ELECTRODES (4): Citodur 600gg gygy





SAMPLE ELECTRODES (5): INOXSAMPLE ELECTRODES (5): INOX- - Special electrodeSpecial electrode





SAMPLE ELECTRODES (6): CitochromaxSAMPLE ELECTRODES (6): Citochromax




….

Thank you

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weldind Electrode selection.pdf