welder's handbook.pdf

8/20/2019 welder's handbook.pdf

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'T' joint

filletweld

buttweld

Butt joint

air must be excludedfrom heated area

electrode

arc

high currentlo w voltage

supply

blowpipefuel gas flame


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nozzle to platedistance-kept atabout 19-25mm

arc length

shielding gas

gas nozzle

spool of wire

drive rolls keep constantwire feed speed

work

powersupply unitkeeps arclengthconstant


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joints in flat position

overhead

verticalvertical


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voltagehigh

correct

low

7 5 0 - 8

0 0

450 - 550


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cross section of flux cored wires

flux

joint


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tungstenelectrode

weld pool


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w el d i n g c ur r en t

weld surfacesmooth at end ofweld run

current reduced in

steps

arc extinguished

crater of hole atend of weld

time

w el d i n g c ur r en t


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pencil torch

swivel head torch

pencil torch

swivel head torch

torch body

ceramicnozzle

gas lens

tungstenelectrode

gas gas

uniform laminar gas flow


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weldconsistsof overlappingcircular weld pools

pulse duration

waveform for pulsed TIG welding

c u r r e n t a m p

s

t i m e

l o w

l e v e l

p u l s e

m e a n

p u l s e

h i g h l e v e l

p u l s e

p u l s e h e

i g h t

direction of

welding

conventional TIG - welding speedprogressively increased from A-B

pulsed TIG - constant travel speed

B A


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clamp clampjointline

workpiece

copper backingbar with holes at5mm intervals

argon flows throughholes to protectunderside of weld

nozzle placedin contact sheetto give correctarc length

TIG spot welding is notrecommended for aluminium


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plasmagas

work piece

tungstenelectrode

arc plasma jet

shieldinggas

direction of weld

keyhole


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'T' joint

Corner joint

Butt joint

gap notgreater than half sheet thickness

no gap


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7 5 _ 8 0

o

o

7 5 0 - 8

0 0

450 - 550

1 0 m m

5 0 m m

copperbacking bar


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Single 'V'

Double 'V'

t

g

Rf

g

Rf


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root-run supportedby groove inbar

copperbacking bar

filling passes

root run

capping pass

tack weld to hold backing strip

root-runfixed intobacking strip


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roller manipulator

one driven unit and one idler

overhead

flat

vertical

branch

butt

flange


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flange rotated

fillet butt

Unbacked butt joint

uniform root gap

Backed butt joint

backing strip


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A-lack of inter-run fusion

B-lack of side fusion

A

BA

B


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(stainless steel and aluminium)


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better profile

less spatter

stable arc givesuniform width

smooth surface


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700

600

500

400

300

200

100

50 100 150 200 250 300 350 400 450

1718

1516

1314

11

12

109

7

8

5

6

34

2

1

Melting rate of carbon steel filler wires m/min

Welding current A

W i r e

f e e

d s

p e e

d i n

/ m i n

0 . 8

m m

1 . 0

m m

1 . 2 m m

1. 6 m m


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1 2 3

4

mmmmmmmmmm mmmmmmmmmm AAAAA VVVVV


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6 5 o

- 7 5 o

removable backing

up to 3.2mm

1mm 1.6mm

4.8mm and thicker

gap=half sheet thickness

up to 3.2mm

no root gapno root gapno root gapno root gapno root gap

Typical conditions for TIG weldingTypical conditions for TIG weldingTypical conditions for TIG weldingTypical conditions for TIG weldingTypical conditions for TIG welding

Recommended joint preparation


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ensure surface alongjoint line is free ofoxides and grease up to 3.2mm - no gap

over 4.8m - 0.8mm gap

up to 3.2mm - no gapup to 3.2mm - no gapup to 3.2mm - no gapup to 3.2mm - no gapup to 3.2mm - no gap

over 4.8mm - 0.8mm gapover 4.8mm - 0.8mm gapover 4.8mm - 0.8mm gapover 4.8mm - 0.8mm gapover 4.8mm - 0.8mm gap


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no gap

up to 3.2mm thickness

1mm gap

4.8mm and thicker


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nozzle

cutting oxygen jet

preheat

flame

molten slag andmetal ejected from cut

cut face

PrinciplesPrinciplesPrinciplesPrinciplesPrinciples

Oxygen-fuel gas cutting is widelyused to cut:

It can produce a variety of edgeprofiles on plates, pipes and sections

Cutting responseCutting responseCutting responseCutting responseCutting response

Very good

Must use flux inoxygen jet.

Poor quality cut

Unsuitable

The cutting action depends on a

chemical reaction between oxygenand hot iron or steel.

A preheat-flame is used to raise thesurface of the metal to the tempera-ture at which the reaction takesplace.

The heat from the reaction melts the

metal which is blown from the cut bythe oxygen jet.MetalMetalMetalMetalMetal

MetalMetalMetalMetalMetal

Mild and lowcarbon steels

Stainless steel

Aluminium,copper etc


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The essential equipment for cuttingcomprises:

Oxygen and fuel gas for the preheatflame are mixed in the nozzle.

The type of nozzle is matched to thefuel gas.

For safety, hoses must be fitted withhose protectors at the torch.

nut to connect to torch

flow

disk valve closedwhen gas flowreverses

headassembly

nut

cutting oxygen

pre-heat oxygen

pre-heat fuel

nozzle

seatings

Witt Super 78 and Air ProductsFlashback arrestors.


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The preheat flame:The preheat flame:The preheat flame:The preheat flame:The preheat flame:

Fuel gas can be:Fuel gas can be:Fuel gas can be:Fuel gas can be:Fuel gas can be:

Apachi+™Apachi+™Apachi+™Apachi+™Apachi+™ — propylene based gas,exclusive to Air Products PLC.

AcetyleneAcetyleneAcetyleneAcetyleneAcetylene — colourless unsaturatedhydrocarbon.

PropanePropanePropanePropanePropane — liquified petroleum based

gas.

Choice of fuel gas depends on:Choice of fuel gas depends on:Choice of fuel gas depends on:Choice of fuel gas depends on:Choice of fuel gas depends on:

Factor for choiceFactor for choiceFactor for choiceFactor for choiceFactor for choice Apachi+Apachi+Apachi+Apachi+Apachi+ AcetyleneAcetyleneAcetyleneAcetyleneAcetylene PropanePropanePropanePropanePropane

Time to start cut

Cutting speed

Fuel gas cost

Heating oxygen cost

Ease of handling

= best choice = worst choice


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The aim is to produce a cut with:

The quality of a cut surface depends on a number of variablesThe quality of a cut surface depends on a number of variablesThe quality of a cut surface depends on a number of variablesThe quality of a cut surface depends on a number of variablesThe quality of a cut surface depends on a number of variables

VariableVariableVariableVariableVariable ConditionConditionConditionConditionCondition EffectEffectEffectEffectEffect

too low top edge rounded

too high undercutting

too low cutting stops

too high irregular face variable width

too low excessive melting; slag adheres to face

too high undercut; slag bridges bottom

too small cutting stops

too big top edge very rounded

Nozzle-to-platedistance

Cutting oxygen

pressure

Cutting speed

Preheat flame

kerf width

sharp edge

smooth face

no slag bridge

edge rounded

undercut slag adhering to face slag adhering to bottom edge


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Manual cuttingManual cuttingManual cuttingManual cuttingManual cutting is used for short cutsand the removal of defective parts.

It is difficult to achieve a uniform cutwith manual techniques. Variations intravel speed and nozzle-to-platedistance give irregular cut faces.

Improved results can be obtained bythe use of guides for straight lines . . .

. . . and radius bars for circles.

fixed template

constantdistance


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Mechanised cutting produces asuperior finish to manual operation.

A variety of mechanised traversingsystems are available or the torchcan be moved along a straight line or

by hand to produce a complex shape.

More than one cut can be made atthe same time.

Mechanised systems can be used toprepare the edges of plate prior towelding.

leadingnozzle

trailingnozzle


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ceramic shroud

tungsten electrode

plasma gas

shielding gas

plasma (arc) stream


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Aluminium

Stainless

Steel


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Documents

welder's handbook.pdf