shielded metal arc welding. safe practices when arc welding don’t stand in water don’t stand in...
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Shielded Metal Arc Welding
Safe practices when Arc Welding
Don’t stand in waterDon’t stand in water Discard frayed cords and wiresDiscard frayed cords and wires Keep flammable liquids away from heatKeep flammable liquids away from heat
Don’t look at the arc with out a number 10 Don’t look at the arc with out a number 10 lens.lens.
Dress Code
Wear properly fitted clothes.Wear properly fitted clothes. When welding, sleeves should be buttoned and When welding, sleeves should be buttoned and
gloves should be worn.gloves should be worn. Wear boots or high top; Tightly laced shoes.Wear boots or high top; Tightly laced shoes. Do not wear loose clothing, shirt tails, and Do not wear loose clothing, shirt tails, and
unbuttoned sleeves around power equipment.unbuttoned sleeves around power equipment. Do not wear clothes that you do not want to get Do not wear clothes that you do not want to get
dirty. dirty.
The Arc
When electrons jump through the airWhen electrons jump through the air
When the pressure overcomes resistance When the pressure overcomes resistance
V=A X RV=A X R
Parts of the Arc
Arc streamArc stream Vaporized metalVaporized metal
Appears yellowAppears yellow Liquid metalLiquid metal
Appears greenAppears green Arc flameArc flame
Natural gases surrounding arc streamNatural gases surrounding arc streamPale redPale red
Arc Control
LengthLength
AngleAngle
Reverse Polarity(DCEP)
Electrode positiveElectrode positive
Better penetrated welds Better penetrated welds
Straight Polarity (DCEN) Electrode NegativeElectrode Negative
Used when a high rate of filler metal is Used when a high rate of filler metal is required.required.
EXX2X Electrodes EXX2X Electrodes
Alternating Current
Stops and starts Stops and starts Must have enough voltage restart arcMust have enough voltage restart arc
Good penetration Good penetration
Less expensive Less expensive
Classification of Steel Electrodes
Electrode designated by “E” followed by a Electrode designated by “E” followed by a 4- or 5- digit number4- or 5- digit number
First two or three digits - minimum tensile First two or three digits - minimum tensile strength as-welded deposited weld metal strength as-welded deposited weld metal expressed in thousands of pounds per expressed in thousands of pounds per square inch (1000psi)square inch (1000psi) E-60xx - 60,000psi TSE-60xx - 60,000psi TS E-120xx - 120,000 psi TSE-120xx - 120,000 psi TS
Classification of Steel Electrodes
Third or fourth digit refers to the welding Third or fourth digit refers to the welding position.position. E-xx1x - all positionsE-xx1x - all positions E-xx2x - flat and horizontal fillet E-xx2x - flat and horizontal fillet
positionspositions E-xx3x - flat position onlyE-xx3x - flat position only
Classification cont.
The fourth or fifth and last digit indicates the type The fourth or fifth and last digit indicates the type of welding current and the type of flux coveringof welding current and the type of flux covering E-xx10 - DC reverse polarity (electrode E-xx10 - DC reverse polarity (electrode
positive) only (cellulose sodium).positive) only (cellulose sodium). E-xx11 - AC or DC reverse polarity (cellulose E-xx11 - AC or DC reverse polarity (cellulose
potassium ) Fast freeze, cuttingpotassium ) Fast freeze, cutting E-xx13 - AC or DC straight polarity (titania E-xx13 - AC or DC straight polarity (titania
potassium) potassium)
Factors of Electrode Selection
Type of metal to be weldedType of metal to be welded Thickness of metalThickness of metal Position of weldPosition of weld Type of power (DC or AC)Type of power (DC or AC) Cleanliness of metalCleanliness of metal Weld bead appearance desiredWeld bead appearance desired
Flux
Improves the performance in handling, storage Improves the performance in handling, storage and operation of the electrodeand operation of the electrode
Floats out impuritiesFloats out impurities Directs arc stream (stabilizer)Directs arc stream (stabilizer) InsulatorInsulator Prevents oxidation (slag or gas)Prevents oxidation (slag or gas) Holds in heatHolds in heat Iron-powder improves striking ability and Iron-powder improves striking ability and
increases metal deposition rateincreases metal deposition rate
Striking the Arc
Pecking Pecking Touching electrode to Touching electrode to
the base metal and the base metal and moving away to proper moving away to proper arc distance. Moving arc distance. Moving electrode in a vertical electrode in a vertical motion. motion.
Can start precisely Can start precisely where the weld is to where the weld is to be.be.
ScratchingScratching Moving electrode Moving electrode
across base metal across base metal then moving then moving electrode away to electrode away to the proper arc the proper arc distance.distance.
Dose not work Dose not work good in tight placesgood in tight places
Common Striking Problems
Sticking Sticking Lift electrode and Lift electrode and
metalmetal Break electrode Break electrode
from metalfrom metal Remove electrode Remove electrode
from clamp from clamp
Arc is extinguishedArc is extinguished The electrode is The electrode is
moved to far away moved to far away from the base metal from the base metal after the arc is after the arc is struck.struck.
Arc Length
Longer arc Longer arc Increases Increases
Resistance Resistance Increases Voltage Increases Voltage Decreases Current Decreases Current Decreases filler Decreases filler
consumptionconsumption
Shorter arcShorter arc Decreases Decreases
Resistance Resistance Decreases Voltage Decreases Voltage Increases CurrentIncreases Current Increases filler Increases filler
consumption consumption
Arc Length
Should be no more then ¼ inch Should be no more then ¼ inch
The sound of the arc should sound like eggs The sound of the arc should sound like eggs fryingfrying
Bead Width
Stringer beadStringer bead Only motion is in the Only motion is in the
direction of travel direction of travel About 3 times the About 3 times the
width of the electrodewidth of the electrode With 1/8 inch electrode With 1/8 inch electrode
should be 3/8 inchshould be 3/8 inch
Weaving beadWeaving bead Motion side to side Motion side to side
as well as forwardas well as forward About 6 times the About 6 times the
width of the width of the electrode electrode
With 1/8 inch With 1/8 inch electrode should be electrode should be 3/4 inch3/4 inch
Stringer Bead
Weaving Bead
Electrode Angle
Should be 15Should be 15° to 20° tipped forward in the ° to 20° tipped forward in the direction of travel direction of travel
Stringer bead should be at 90° from the Stringer bead should be at 90° from the base metalbase metal
Travel Speed
Bead widthBead width
Bullet-nose-shaped ripplesBullet-nose-shaped ripples
Restarting
Strike ark 3/8 inch in front of previous weld Strike ark 3/8 inch in front of previous weld
Move back to craterMove back to crater
Move forward to finish weldMove forward to finish weld
Restarting
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