Basics of welding.pptx

7/29/2019 Basics of welding.pptx

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Welding

Welding is a fabrication orsculptural process that joins

materials (usually metals) by

causing coalescence. This is

often done by melting the workpieces and adding a filler

material to form a pool of molten

material (the weld pool) that

cools to become a strong joint,

with pressure sometimes used in

conjunction with heat, or by

itself, to produce the weld.


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A Brief History of Welding

Late 19th Century

Scientists/engineers apply advances in electricity to heat and/or

join metals (Le Chatelier, Joule, etc.)

Early 20th Century

Prior to World War I welding was not trusted as a method to jointwo metals due to crack issues

1930s and 40s

Industrial welding gains acceptance and is used extensively in the

war effort to build tanks, ships, etc.

Modern Weldingthe nuclear/space age helps bring welding from an art to a

science


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Welding Processes


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Types of Welding

Fusion Welding

Oxyacetylene Gas Welding

Shielded Metal Arc (SMAW)

Metal Inert Gas (MIG)

Tungsten Inert Gas (TIG)

Submerged Arc Welding (SAW)


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Oxyacetylene Gas Welding

Coalescence is produced by oxyacetylene flame.

It can yield temperature up to 3200 deg C.

Filler metal may or may not be used.


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Shielded Metal Arc Welding


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G


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Metal Inert Gas Welding(MIG Welding)

Coalescence is produced by heating the work piece withan electric arc between a continuously fed metal electrodeand the work piece.

No flux is required.

Shielded by inert gas (Argon, CO2,

Helium or mixture).

GMAW torch nozzle cutaway image.

(1) Torch handle,

(2) Molded phenolic dielectric (white)

and threaded metal nut insert (yellow),

(3) Shielding gas diffuser,(4) Contact tip,

(5) Nozzle output face

M l I G W ldi


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M l I G W ldi


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G T A W ldi


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Gas Tungsten Arc Welding(TIG Welding)

TIG welding is an arc welding process in whichthe heat is produced between a non-consumabletungsten electrode and the work metal.

The arc and adjacent heated areas of the work

piece are protected from atmosphericcontamination by a shield of inert gas.

A filler metal may or may not be used dependingupon the requirement. Because the electrode is

non-consumable, a weld can be made by fusionof the base metal without the addition of fillermetal.

G T A W ldi


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G T t A W ldi


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Selection of Inert Gas Shield :Helium and argon gases are mostly used. These do not react

with tungsten or tungsten alloy electrodes and have no

adverse effect on the quality of the weld metal. Argon is more

widely preferred, because it provides a softer arc, which is

smooth and stable. Argon provides greater coverage of theweld puddle at low flow rates. With argon, the flow rate may be

12 to 20 cubic feet per hour.


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SAFETY DURING WELDING

Wear approved safety glasses with side

shields under your welding helmet or face

shield and at all times in the work area.

Wear dry, hole-free insulating gloves

and body protection. Do not touch

electrode with bare hand. Do not wear

wet or damaged gloves.

Do not touch live electrical parts.


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Arc rays can burn eyes and skin.

Use welding helmet with correct shade

of filter.

Wear welders cap and safety glasses

with side shields. Wear complete body protection.


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Confined spaces can be hazardous.

Cylinders can explode if damaged.

Magnetic fields can affect Implanted

Medical Devices.

Hot parts can cause severe burns.


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Weldability

Common Name CarbonContent (%)

Weldability

Ingot Iron 0.03 max Excellent

Low Carbon Steel 0.15 max Excellent

Mild Steel 0.15-0.3 Good

Med. Carbon Steel 0.3-0.6 Fair

High Carbon Steel 0.6-2.0 Poor (Difficult to Weld)


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Carbon Equivalent (CE)

Weldability of steel in terms of its susceptibilityto cracking can be roughly estimated by use of acarbon equivalent (CE).

CE= % C + %Mn + % Ni + % Cr + % Cu - % Mo - % V

4 20 10 40 50 10


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Post Weld Heat Treatment

Throughout the cycle of Heat treatment, the portionoutside the heated band shall be suitably wrapped

under insulation to avoid any harmful temperature

gradient at the exposed surface of pipe.

The temperature attained by the portion under heattreatment shall be recorded by means of

thermocouple, pyrometers.

Standard Joint Design For


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Standard Joint Design ForButt Welding


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Welding Electrode


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Welding Electrode

An electrode is a piece of wire or rod (of metal oralloy) with or without flux covering which carriescurrent and also acts as filler material forwelding.

At one end it is gripped in a holder and arc isgenerated at the other end.

Different types of electrodes are available in themarket for different welding processes.


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Welding Electrode

Welding Electrodes for Alloy & Stainless Steel:Sl.No.

Base Metal P.No.

Welding Electrodes Preheat 0C(see note)

Postweld heattreatment 0C (see

note)A.S.M.E.A.W.S

Classification

1 C-1/2 Mo P 3 S.F.A.5.5 E7018 A1 100C Min. 800Cmin for

thickness 1/2or base metalT.S.>71Ksi

None6500C, 1 hr/in, for

thickness >3/4 orbase metal T.S. > 71Ksi

2 1.1/4 Cr-1/2 Mo

P4 S.F.A.5.5 E8016 B2,E8018 B2

1500C Minimum 7200C, 1hr/in, with 2hrs. min., none forthickness


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Welding Electrode

Sl.No.

Base Metal P.No.



note)A.S.M.E.A.W.S

Classification

4 5 Cr-1/2 Mo

P5 S.F.A.5.4 E505-16or -15

1800C Minimum 7200C, 1 hr/in. with 2hrs. min.

5 9 Cr-

1 Mo

P5 S.F.A.5.4 E505-16

or -15

1800C Minimum 7300C, I hr/in. with

two hrs. min.

6 12 CrType 410

P6 S.F.A.5.4S.F.A.5.4

E410-16or15E309-16or -15

2050C Minimum2050C Minimum

7600C, 1 hr/in. with 2hrs. min None

7 12 CrType 405

P7 S.F.A.5.4S.F.A.5.4S.F.A.5.11S.F.A.5.4

E309-16or15ENi CrFe-3E410-16or15

100C Minimum100C Minimum1500C Minimum

NoneNone7300C 1 hr/in. with 2hrs. min.


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Welding Electrode

Sl.No.

Base Metal P.No.



note)A.S.M.E.A.W.S

Classification

8 3.1/2 Ni P 9B S.F.A.5.5S.F.A.5.5S.F.A.5.11

E8016-C2E8018-C2E Ni Cr Fe-3

950C Minimum 6200C hr/in. 1 hr

minimum

9 18 Cr-8NiSS Type 304SS Type304L

P8 S.F.A.5.4 E308-16or15E308L-16or -15

100

C min. None

10 18 Cr-8NiStabilisedSS Type 347,321

P8 S.F.A.5.4 E347-16or15

100C min. None

11 18 Cr-10Ni-MoSS Type 316SS Type316L

P8 S.F.A.5.4 E316-16or15E316L-16or15

100C min. None


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Inspection Of Welding

Inspection After Welding:

Destructive Tests (for mechanical properties /chemical analysis / spectro etc).

Non Destructive Tests (NDT).

Checking of distortion.


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Welding Procedure Qualifications

This shall be done as per ASME Section IX Article 2

Welding Procedure Specification (WPS).

A WPS is a written qualified welding procedure prepared to

provide direction for making production welds to Code

requirements. The WPS or other documents may be used to

provide direction to the welder or welding operator to assure

compliance with the Code requirements.

Procedure Qualification Record (PQR).

A PQR is a record of the welding data used to weld a testcoupon.


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Welding Procedure Qualifications


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El d Q lifi i T


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Electrode Qualification Test

FIG. 3 FILLET WELD TEST ASSEMBLY

FIG. 4 TEST ASSEMBLY FOR TRANSVERSE TENSIONAND LONGITUDINAL GUIDED BEND TESTS FORWELDS MADE WITH E6022 ELECTRODES

El d Q lifi i T


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Electrode Qualification Test

FIG. 5 GROOVE WELD TEST ASSEMBLY FORMECHANICAL PROPERTIES AND SOUNDNESS OFWELD METAL MADE WITH E7018M ELECTRODES


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W ld Q lifi ti


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Welder Qualification

This shall be done as per ASME Section IX

The performance qualification is done in accordance

with one of any of the qualified Welding Procedure

Specifications (WPS).

When performance qualification is done in

accordance with a WPS that requires Post weld

heat treatment (PWHT), this PWHT may be omitted.

The welded test joints for qualification may be

examined by mechanical tests or by radiography.

W ld Q lifi ti


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Welder Qualification

W ldi D f t


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Welding Defects


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Welding Defects


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Welding Defects

Defect-

Causes-

Remedies

Crack - Insufficient weld size.- Excessive joint

restraint.

- Poor joint design and/or

preparation.

- Filler metal does notmatch base metal.

- Rapid cooling rate.

- Base metal surface

covered with oil,

grease, moisture, rust,and dirt or mill scale.

- Adjust weld size to part

thickness.

- Reduce joint restraint

through proper design.

- Select the proper joint

design.- Use more ductile filler.

- Reduce cooling rate

through preheat.

- Clean properly base metal

prior to welding.

Welding Defects


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Welding Defects

Defect - Causes - Remedies

Lack of

penetration- Travel speed too fast.

- Welding current too

low.

- Poor joint design

and/or preparation.

- Electrode diameter toolarge.

- Wrong type of

electrode.

- Excessively long arc

length.

- Decrease travels

speed.

- Increase welding

current.

- Increase root

opening ordecrease root face.

- Use smaller

electrode.

- Use electrode with

deeper penetrationcharacteristics.

- Reduce arc length.

Welding Defects


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Welding Defects

Defect - Causes - Remedies

Inclusion - Incomplete slag

removal between

passes.

- Erratic travel

speed.

- Too wide aweaving motion.

- Too large an

electrode.

- Letting slag run

ahead of arc.- Tungsten spitting

or sticking.

- Completely remove slag

between passes.

- Use a uniform travel speed.

- Reduce width of weaving

technique.

- Use a smaller electrodesize for better access to

joint.

- Increase travel speed or

change electrodes angle or

reduce arc length.- Properly prepare tungsten

and use proper current.

Testing of Weld joint


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Testing of Weld joint

Several Techniques are available for testing qualityof a weld:

Visual Inspection

Dye Penetrant Testing

Magnetic Particles Testing

Radiography Testing

Ultrasonic Testing

Destructive Testing


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Radiography Test


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Radiography Test

DISCONTINUITY

METAL

RADIATION SOURCE

FILM

Principle :


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Radiography Test


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Radiography Test

Sample Films :

Tungsten

Inclusion

Transverse

Crack

AUTOMATIC WELDING


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AUTOMATIC WELDING


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CASE STUDIES


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CASE STUDIES

CRACK IN WELD OVERLAY OF RTJ GROOVE IN REACTOR


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CASE STUDIES


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CASE STUDIES

WELD FAILURE OF STUB IN REACTOR INLET LINE

Standard Joint

Improper Fit Up

& Welding

Poor Penetration

& Under cut

Crack


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Basics of welding.pptx

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