defects of welding & welding joints

8/13/2019 Defects of Welding & Welding Joints

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By:- Zanjbeel 1


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Course:

Manufacturing Process

Topic:

Defects of Welding & Welding joints

By:- Zanjbeel 2


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By:- Zanjbeel 3

Welding:In engineering, any process in which two or more pieces

of metal are joined together by the application of heat,

pressure, or a combination of both


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By:- Zanjbeel 4


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By:- Zanjbeel 5

Welding Defects:

Welding defects may classify into following four classes:

Shape Defects (fig. 1)

Cracks & Cavities (fig. 2)

Lack of fusion, insufficient through weld (fig. 3)

Solid inclusions (fig. 4)


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By:- Zanjbeel 6(fig. 1)

(fig. 2)


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(fig. 3)


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(fig. 4)


9/25By:- Zanjbeel 9

Common weld defects include:

i. Lack of fusion

ii. Lack of penetration or excess penetration

iii. Porosity

iv. Inclusions

v. Cracking

vi. Undercutvii. Lamellar tearing


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Lack of fusion & Lack of penetration or excess

penetration:

Lack of fusion results from too little heat input an or too rapid

traverse of the welding torch (gas or electric)

Excess penetration arises from too high a heat input or too

slows transverse of the welding torch (gas or electric)



Porosity:

This occurs when gases are trapped in the solidifying weld metal

May arise, from dirt, particularly oil or grease, on the metal in

the vicinity of the weld

Avoided by ensuring all consumables are stored in dry conditions

and work is carefully cleaned


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By:- Zanjbeel 13


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By:- Zanjbeel 14

Inclusions:Can occur when several runs are made along a V join


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By:- Zanjbeel 15

Cracking:

This can occur due to thermal shrinkage or due to a

combination of strain accompanying phase change and thermal

shrinkage


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By:- Zanjbeel 16

Undercutting:

In this case the thickness of one (or both) of the sheets is reduced

at the toe of the weld

There is already a stress concentration at the toe of the weld and

any undercut will reduce the strength of the join.


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By:- Zanjbeel 17

Lamellar tearing:

This is mainly a problem with low quality steels. It occurs in

plate that has a low ductility

These problems can be overcome by using better quality steel,

'buttering' the weld area with a ductile material and possibly by

redesigning the joint


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By:- Zanjbeel 18

Welding Joints:

the manner in which materials fit together. As shown in

Figure,

There are five basic types of weld joints:

Butt joint.

T-joint.

Lap joint.

Corner joint.

Edge joint.


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By:- Zanjbeel 19


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Joint types:

There are various types of welds that can be made in

each of the basic joints. They include:Butt joint: (Shown in fig. a)

Square-groove

Bevel-groove

V-groove

J-groove

U-groove

Flare-V-groove

Flare-bevel-groove


21/25B :- Zan beel

21fig. a

j i ( i fi )


22/25By:- Zanjbeel

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T-joint: (as shown in fig. b)

Fillet weld

Plug weld

Slot weld

Bevel-groove weld

J-groove weld

Flare-bevel-groove weld

fig. b


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Lap joint : (as shown in fig. c)

Fillet weld

Plug weld

Slot weld

Spot weld

Bevel-groove weld

J-groove weld

fig. c


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Corner joint : (in fig. d)

Fillet weld

Spot weld

V-groove weld

J-groove weld

Flare-V-groove weld

Edge weld

Corner-flange weld

fig. d


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By: Zanjbeel 25

Edge joint: (in fig. e)

Square-groove weld

Bevel-groove weld

V-groove weld

J-groove weld

U-groove weld

Edge-flange weld

Corner-flange weldfig. e

defects of welding & welding joints

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