TWI TemplateCSWIP 3.1 Welding Inspection
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Welding Terminology and Definitions
Course Reference WIS 5
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Welding Terminology & Definitions
What is a Weld?
A localised coalescence of metals or non-metals produced either by heating the materials to the welding temperature, with or without the application of pressure, or by the application of pressure alone (AWS)
A permanent union between materials caused by heat, and or pressure (BS499)
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Welding Terminology & Definitions
What is a Joint?
The junction of members or the edges of members that are to be joined or have been joined (AWS)
A configuration of members (BS499)
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Joint Terminology
Butt Preparations
Single Sided Butt Preparations
Single-J
Single-U
Single sided preparations are normally made on thinner materials, or when access form both sides is restricted
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Double Sided Butt Preparations
Double sided preparations are normally made on thicker materials, or when access form both sides is unrestricted
-Vee
Double
-Bevel
Double
-J
Double
-U
Double
Joint Preparation Terminology
Single-V Butt
Single-U Butt
Size for size, Typically U prep geometry better suited for materials thicker than 20mm as narrower bevel angle will reduce weld metal volume.
For sizes bellow 20mm the vee butt is better suited as lesser weld metal volume
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Joint Preparation Terminology
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Weld Terminology
Compound weld
Fillet weld
Butt weld
Edge weld
Spot weld
Plug weld
Welded Butt Joints
A_________Welded butt joint
A_________Welded T joint
A_________Welded lap joint
A_________Welded closed corner joint
Joint Types - Weld Types
Weld Zone Terminology
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Weld Zone Terminology
Excess Root Penetration
Welding Technology
tempered zone
Toe Blend
6 mm
20°
This statement is not quantitative and therefore open to individual interpretation
The higher the toe blend angle the greater the amount of stress concentration
The toe blend angle ideally should be between 20o-30o
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Features to Consider
Mitre Fillet
Convex Fillet
Concave Fillet
A concave profile is preferred for joints subjected to fatigue loading
Fillet Weld Profiles
Fillet welds - Shape
Fillet Weld Leg Length
b. = Horizontal leg length
a. = Vertical leg length
b
a
Note: The leg length should be approximately equal to the material thickness
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Fillet Weld Features
Fillet Weld Throat Thickness
Deep Penetration Fillet Weld Features
b
a
Fillet Weld Sizes
Design Throat Thickness = Leg Length x 0.7
Question: The Leg length is 14mm. What is the Design Throat?
Answer: 14mm x 0.7 = 10mm Throat Thickness
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Fillet Weld Sizes
Leg Length = Design Throat Thickness x 1.4
Question: The Design Throat is 10mm. What is the Leg length?
Answer: 10mm x 1.4 = 14mm Leg Length
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Features to Consider
Fillet welds connecting parts with fusion faces with an angle more than 1200 or less than 600 should not use the previous calculations.
1200
600
Features to Consider
The design throat thickness of a flat or convex fillet weld connecting parts with the fusion faces which form an angle between 600 and 1200 may be calculated by multiplying the leg length by the appropriate factors as given below:
0.7
0.65
0.6
0.55
0.5
Features to Consider
Importance of Fillet Weld Leg Length Size
Approximately the same weld volume in both Fillet Welds, but the effective throat thickness has been altered, reducing considerably the strength of weld B
2mm
(b)
4mm
8mm
(a)
4mm
Fillet Weld Sizes
Question: How larger in c.s.a. is (b) comparable to (a)?
4mm
6mm
6mm
4mm
(a)
(b)
Fillet Weld Sizes
Area = 4 x 4 = 8mm2
2
2
The c.s.a. of (b) is over double the area of (a)
without the extra excess weld metal being added
4mm
6mm
(a)
(b)
4mm
6mm
(a)
(b)
EFFECTIVE THROAT THICKNESS
Features to Consider
Terminology
Terminology
?
Questions
QU 1. Sketch a single-U butt joint and indicate the following
a. Root gap b.Root face c.Included angle d. Root radius
QU 2. Sketch a tee joint, fillet welded and indicate the following
a. Leg length b.Throat thickness c. Root d. Weld toes
QU 3. Sketch five joint types in addition to a butt joint
QU 4. Identify the the following features from the sketch
Welding Terms
Joint Design & Weld Preparation
Bevel angle must allow:
manipulation of electrode to ensure sidewall fusion
Bevel Angle
Joint Design & Weld Preparation
allow controlled root fusion
Too small = burn-through
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Joint Design & Weld Preparation
Root Gap
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Weld Preparation
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WELD PREPARATION
for mechanised GMAW of pipework
for MMA welding of pipe joints > ~20mm (compound bevel)
12 to 15°
Weld preparation
Arc welding
Weld preparation
MMA
MAG
high heat input process allow a larger root face, less weld metal required, less distortions, higher productivity
if gap is too big risk of possible burn-through
if gap is too small risk of lack of penetration
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Weld preparation
Requires machining slow and expensive
Tight tolerance easier set-up
Large tolerance set-up can be difficult
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Weld preparation
Variations in cutting line
Root face too small burn-through
Variations in cutting angle
Included angle too large heavy distortions, increase amount of filler metal required
Included angle too small lack of penetration, lack of side wall fusion
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Weld preparation
No root face
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Weld preparation
Too big/too small included angle
Recut groove preparation
susceptible to corrosion
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Weld preparations
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Weld preparations
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Weld preparations
Pipe weld preparation - one side access only!
for wall thickness up to 3 mm
for wall thickness 3 to 20 mm
for wall thickness over 20 mm
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Weld preparations
Pipe weld preparation - one side access only!
self-adjusting items
susceptible to corrosion
lower fatigue life
To ensure minimum root mismatch, the internal bore is sometimes machined with a low angled bevel
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Weld preparations
danger of burn-through
difficult to set-up
Weld preparations
Bevel angle = 30º
Included angle = 60º
lap and square edge butt joints do not require preparation
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Weld preparations
Steel
Aluminium
to reduce distortions on stainless steels welds, reduce included angle and increase root face
to avoid lack of side wall fusion problems aluminium require larger included angles than steel
60º
30º
70-90º
35-45º
Weld preparations
Thickness of parent material impacts upon weld preparation
a single bevel groove requires a volume of weld metal proportional to the square of plate thickness
its lack of symmetry lead to distortions
Reduce shrinkage by:
reduce weld volume
Weld preparations
reduce root gap
Weld preparations
use double bevel weld prep
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Weld preparations
Thickness of parent material impacts upon weld preparation
U prep better than V prep
V prep better than U prep
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Weld preparations
Reduce distortions by using an asymmetric V prep instead of a symmetric V prep
Thickness of parent material impacts upon weld preparation
t/3
t
after welding half of depth, root back gouging
weld completely on backside
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Weld preparation
PC asymmetric preparation
If symmetric preparation is used in the PC position the weld may spill out of the groove
60º
30º
60º
15º
Weld preparation
Static loads - prohibited application of one sided fillet weld
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Weld preparation
Static loads - equal throat T joints
13 mm
Weld preparation
Static loads - equal throat T beams in bending
neutral axis
neutral axis
Lower neutral axis is more advantageous (also helps to reduce residual distortions!)
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Weld preparation
double bevel weld
cyclic load
WELD TYPES