T & D Powerpoint

Copyright © 2002 TWI Ltd

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A Joint:* A configuration of members

A Weld:* A union between materials caused by heat, and or pressure


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Butt welds:*

Fillet welds:*

Spot/Seam welds:*

Plug/Slot welds:*

Edge welds:*


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Closed corner

Open corner*

T joints: *

Lap joints: *

Corner joints:*

Butt joints: *


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Angle of bevel*

Included angle*

Root gap*

Root face*

Root radius*

Root landing*


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Single V

Single bevel

Single J

Single U*


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Double bevel

Double V

Double J

Double U*


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This has major effects on economics and distortion control etc

The root face, root gap and angle of bevel values, the choice of single, or double sided preparations, are dictated only by the type of welding process, the position and accessibility of the joint*

The basic rule is this:The basic rule is this:

The more you take out, then the more you must put back in*

Remember, the purposes of a weld preparation is to allow access for the welding process, penetration and fusion through the area of the joint and its faces*


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A butt welded butt joint*

A fillet welded butt joint*

A compound welded butt joint*


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A butt welded T joint*

A fillet welded T joint*

A compound welded T joint*


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A compound welded Lap joint*

A spot welded Lap joint*

A fillet welded Lap joint*


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A butt welded Closed Corner joint*

A fillet welded Closed Corner joint*

A compound welded Closed Corner joint*


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An outside fillet welded Open Corner joint*

An An inside filletinside fillet welded Open C welded Open Corner jointrner joint**

A double fillet welded Open Corner joint*


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1 2

43

A

B

A + B = Excess Weld Metal

Weld FaceWeld Width

Design Throat Thickness1.2.3.4. Weld Toes

Fusion Boundary

Fusion ZoneWeld RootHAZ

Actual Throat Thickness


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Weld face*

Vertical Leg Length*

Horizontal Leg Length*

Design throat*Actual throat*

Excess weld metal *


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“s” = Effective throat thickness

sa

“a” = Nominal throat thickness

Deep throat fillet welds from FCAW & SAW etc*


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*


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80°

20°

6 mm

3 mm*

Very Poor Weld Toe Blend Angle

Improved Weld Toe Blend Angle


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It is also possible that the height of excess weld metal is within within the acceptedthe accepted limitlimit of an applied standard, but the toe blend is unacceptableunacceptable, as shown below*

3 mm90°

Extremely poor toe blend, but excess weld metal is within limits*


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Weld Sizing (Fillets): DTT. ATT. Excess weld metal. Leg length *

Weld Sizing (Butts): DTT. ATT. Excess weld metal.

Weldment Terms: Weld face & root. Fusion zone & boundary. HAZ. Weld toes.Weld width

Preparation Terms: Bevel/included angle. Root face/gap. Land/RadiusTypes of Preparation: Bevel’s. V’s. J’s. U’s. Single & Double.

Types of Joint: Butt. T. Lap. Corner (Open & Closed)

Types of Weld: Butt. Fillet. Spot. Seam Plug. Slot. Edge.

Weld Preparation: Preparing a joint to allow access and fusion.

Joint: A Configuration of members

Weld: A Union of materials


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Welding imperfections can be categorized into groups:

3) Solid Inclusions

4) Lack of fusion

1) Cracks

6) Mechanical or Surface damage

5) Profile & Lack of Filling

2) Gas Pores & Porosity

7) Misalignment*


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A HAZ hydrogen crack, initiated at the weld toe

Most cracks are initiated from stress concentrations *


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Surface breaking porosity

Fine cluster porosity Blow hole > 1.6 mm Ø

Hollow root bead

An isolated internal pore

Coarse cluster porosityShrinkage cavity*


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Internal solid inclusion causing a lack of sidewall fusion

Surface breaking solid inclusionInternal solid inclusion causinga lack of inter-run fusion*

Solid inclusions caused by undercut in the previous weld run

Internal solid inclusion


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Lack of root fusion

Overlap

Lack of inter-run fusion Lack of sidewall fusion

Lack of sidewall fusion & incompletely filled groove*


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An Incompletely filled groove

Lack of root fusion

Spatter

A

Poor toe blendBulbous, or irregular contour

Arc Strikes

Incomplete root penetration

B

*


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Root concavity

Excess penetration, and burn throughRoot oxidation in Stainless Steel

Crater pipe

Shrinkage grooves

*


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Root Run or “Hot pass” undercut

Parent metal, surface undercut

Weld metal, surface undercut*


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Weld metal, surface undercut Parent metal, “top toe” undercut*


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Any surface damage caused by:Grinding

Hammering/chisel marks

Slag chipping hammer marks

Torn cleats (Hammered off attachments)

Arc strikes

All of the above may cause serious weakness to the weld area*


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Linear misalignment measured in mm 3 mm

Angular misalignment measured in degrees*

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Excess weld metal heightLowest plate to highest point

Linear

Angular

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