jj104 workshop technology chapter9_ arc welding
Post on 20-Dec-2015
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INTRODUCTION TO ARC INTRODUCTION TO ARC WELDINGWELDING(SMAW)(SMAW)
Terms & DefinitionsTerms & DefinitionsWelding - Joining of two or more Welding - Joining of two or more pieces of metal together by the pieces of metal together by the fusion processfusion process
NOTE: In arc welding, heat is produced by NOTE: In arc welding, heat is produced by the electric arc created.the electric arc created.
SMAW - Shielded Metal Arc WeldingSMAW - Shielded Metal Arc WeldingElectrode - Metal rod which conducts Electrode - Metal rod which conducts a current from the electrode holder a current from the electrode holder to the base metalto the base metalBase Metal - Metal to be weldedBase Metal - Metal to be welded
ContinuedContinued
Bead Weld - Made by one pass of Bead Weld - Made by one pass of the electrodethe electrode
Bevel – Type of edge preparation Bevel – Type of edge preparation containing an anglecontaining an angle
Butt Joint - Weld located between Butt Joint - Weld located between the two edges of metal.the two edges of metal.
Crater - Depression at the end of a Crater - Depression at the end of a weld weld
Safety precautions in SMAW Safety precautions in SMAW weldingwelding
Never look at the arc with the naked Never look at the arc with the naked eye.eye.
Use a welding hood that is in good Use a welding hood that is in good condition and has a #12 shade.condition and has a #12 shade.Wear suitable clothing to protect all Wear suitable clothing to protect all parts of the body. (PPE) parts of the body. (PPE) personal protective personal protective equipmentequipment
Long sleeved shirtLong sleeved shirt
Leather glovesLeather gloves
Collar buttonedCollar buttoned
ContinuedContinuedCuffs turned downCuffs turned down
High topped shoes or bootsHigh topped shoes or boots
Do not strike an arc or weld until Do not strike an arc or weld until you are sure those in the vicinity you are sure those in the vicinity have protective equipment or have protective equipment or will look in the other direction.will look in the other direction.
(Note) Yell “cover” before striking an arc.(Note) Yell “cover” before striking an arc.
ContinuedContinued
Do not weld around combustible Do not weld around combustible or flammable materials.or flammable materials.
Do not pick up hot metal with the Do not pick up hot metal with the hands.hands.
(NOTE) Use a pair of pliers(NOTE) Use a pair of pliers
Do not weld in confined places Do not weld in confined places without ventilationwithout ventilation
ContinuedContinued
Always turn off main switch or Always turn off main switch or disconnect plug when checking over disconnect plug when checking over a welder.a welder.
Do not leave electrode holder on the Do not leave electrode holder on the welding table or in contact with welding table or in contact with grounded metal.grounded metal.
Do not use worn or frayed cables.Do not use worn or frayed cables.
ContinuedContinued
Stand on dry footing when welding.Stand on dry footing when welding.
Keep area around welder clean.Keep area around welder clean.
Keep tools and metals in proper Keep tools and metals in proper location.location.
Types of Arc WeldersTypes of Arc WeldersA.C. – (Alternating current) Welder A.C. – (Alternating current) Welder current alternates direction 120 current alternates direction 120 times per second.times per second.D.C. – (Direct current) Welder D.C. – (Direct current) Welder current flows in the same direction.current flows in the same direction.TIG – (Tungsten Inert Gas) Welder TIG – (Tungsten Inert Gas) Welder may use either A.C. or D.C. with a may use either A.C. or D.C. with a non-consumable tungsten electrode non-consumable tungsten electrode and an inert shielding gas.and an inert shielding gas.
ContinuedContinued
MIG – (Metal Inert Gas) May use A.C. MIG – (Metal Inert Gas) May use A.C. or D.C. with a base wire filler or D.C. with a base wire filler material that is fed automatically material that is fed automatically into weld; also has an inert shielding into weld; also has an inert shielding gas.gas.
Common SMAW ToolsCommon SMAW ToolsWelderWelderElectrode HolderElectrode HolderGround clampGround clampShield or helmetShield or helmetGlovesGlovesChipping hammerChipping hammerSafety goggles or glassesSafety goggles or glassesWire brushWire brushElectrodesElectrodes
Types of ElectrodesTypes of Electrodes
Mild SteelMild Steel
High Carbon SteelHigh Carbon Steel
Hard SurfacingHard Surfacing
Alloys – special purposeAlloys – special purpose
AWS CurrentClass Covering Requirements Position Characteristics
EXX 10 Cellulose DCEP All Deep Penetration,Sodium With Ripples
EXX 11 Cellulose AC, DCEP All Deep Penetration,Potassium Flat Decking With Ripples
EXX22 Rutile DCEN, AC Flat, Horiz. Fillet Deep Penetration,Sodium With Ripples
EXX 24 Rutile AC, DCEP, DCEN Flat, Horiz. Fillet High Deposition50% Iron Shallow PenetrationPowder
EXX 27 Mineral AC,DCEP, DCEN Flat, Horiz. Fillet High Deposition50% Iron Shallow PenetrationPowder
Electrode CharacteristicsElectrode Characteristics
AWS CurrentClass Covering Requirements Position Characteristics
EXX 12 Rutile DCEN, AC All Mild to Medium PenetrationSodium
EXX 13 Rutile AC, DCEP, DCEN All Mild PenetrationSodium
EXX 14 Rutile AC, DCEN All Medium Penetration30% IronPowder
EXX 18 Low-Hydrogen DCEP, AC All Medium Penetration30% IronPowder
EXX 28 Low-Hydrogen AC, DCEP Flat, Horiz. Fillet High Deposition50% IronPowder
Electrode Characteristics Electrode Characteristics continuedcontinued
Common Sizes of ElectrodesCommon Sizes of Electrodes
1/8”1/8”
5/32”5/32”
Sizes of electrodes range from 1/16” Sizes of electrodes range from 1/16” to 3/8”.to 3/8”.
Electrode size is determined by the Electrode size is determined by the diameter of the wire core.diameter of the wire core.
E70XX-H4RE70XX-H4R•ElectrodeElectrodeTensile in KsiTensile in Ksi
Welding Position:Welding Position: 1 = All Position, 2 = Flat & Horizontal1 = All Position, 2 = Flat & Horizontal
Type of Current and CoatingType of Current and Coating*Hydrogen:*Hydrogen: H4 = Less than 4ml/100g weld metal, H8 = Less than 8ml/100g Weld MetalH4 = Less than 4ml/100g weld metal, H8 = Less than 8ml/100g Weld Metal or H16 = Less than 16ml/100g weld metal or H16 = Less than 16ml/100g weld metal
*Meets Requirements of Absorbed Moisture Test*Meets Requirements of Absorbed Moisture Test *Optional Designators*Optional Designators
AWS ClassificationAWS Classification
Electrode Coating FunctionsElectrode Coating Functions
To Provide Deoxidizers & Scavengers To Provide Deoxidizers & Scavengers
To Produce Shielding GasesTo Produce Shielding Gases
To Produce a Slag CoveringTo Produce a Slag Covering
To Provide Mechanical and Physical To Provide Mechanical and Physical PropertiesProperties
To Increase Deposit RatesTo Increase Deposit Rates
Effects of Raising & Lowering Effects of Raising & Lowering CurrentCurrent
Raising currentRaising currentProduces more heatProduces more heat
Lowering currentLowering currentProduces less heatProduces less heat
(Note: On thicker metals more heat is (Note: On thicker metals more heat is necessary in order to get penetration necessary in order to get penetration of the weld.)of the weld.)
Methods of Establishing an ArcMethods of Establishing an Arc
ScratchingScratching
Similar to striking a matchSimilar to striking a match
TappingTappingStraight down and up Straight down and up
Characteristics of Proper Arc Characteristics of Proper Arc LengthLength
End of electrode is the same distance End of electrode is the same distance from the base metal as the diameter from the base metal as the diameter of electrode.of electrode.
1/8” electrode = arc length 1/8”1/8” electrode = arc length 1/8”
Correct arc length makes a steady Correct arc length makes a steady hum of the welder.hum of the welder.Correct arc length makes a “frying” Correct arc length makes a “frying” sound at the arcsound at the arc
Like bacon frying in a panLike bacon frying in a pan
Parts of the welding processParts of the welding process
ElectrodeElectrode
Wire coreWire core
Coating (flux)Coating (flux)
ArcArc
Gaseous shieldGaseous shield
WeldWeld
SlagSlag
Parts ContinuedParts Continued
Heat linesHeat lines
Base metalBase metal
PenetrationPenetration
CraterCrater
15 – 30 degree angle15 – 30 degree angle
Direction of travelDirection of travel
Principles of the SMAW Principles of the SMAW ProcessProcess
Kinds of WeldsKinds of Welds
Fillet Fillet
GrooveGroove
BeadBead
Fillet WeldFillet Weld
Groove WeldsGroove Welds
ContinuedContinued
Types of Weld JointsTypes of Weld JointsButt JointButt Joint
Lap JointLap Joint
Tee JointTee Joint
Corner JointCorner Joint
Edge JointEdge Joint
Square Butt JointSquare Butt Joint
Tee JointsTee JointsA- plain teeA- plain tee
B- single beveledB- single beveled
C- double beveledC- double beveled
D- single JD- single J
E- double JE- double J
Lap JointsLap JointsA- single lap joint, A- single lap joint, one weld.one weld.
B- single lap joint, B- single lap joint, two welds.two welds.
C- offset lap joint.C- offset lap joint.
Corner JointsCorner Joints
Edge JointsEdge Joints
Weld PositionsWeld PositionsFlat - 1F&1GFlat - 1F&1G
Horizontal – 2F&2GHorizontal – 2F&2G
Vertical-3F&3GVertical-3F&3G
Overhead_4F&4GOverhead_4F&4G
Reason for Poor WeldsReason for Poor Welds
Machine adjustment too hot or too Machine adjustment too hot or too coldcold
Electrode size too large or too smallElectrode size too large or too small
Improper movement of electrodeImproper movement of electrode
Improper angle of holding electrodeImproper angle of holding electrode
Improper base metal preparationImproper base metal preparation
Arc length too long or too shortArc length too long or too short
Equipment Arc WeldingEquipment Arc Welding
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