knowledge of welded joints

1. PARUL INSTITUTE OF ENGINEERING
AND TECHNOLOGY
Project:- Design Of Welded Joints
Group:- PUME_94
Guided By: Purvik Patel
Sr.no Student Name Enrolment No
1 Aakash P Patel 160303109746
2 Akshar K Patel 160303109747
3 Akshesh D Patel 160303109748
4 Alpesh C Patel 160303109749

2.  INTRODUCTION
 The process of permanently joining two or more metal
parts by the fusion of edges of the metals with or
without applying pressure and a filler material is called
welding
 Types of Welding
(1)Pressure or Plastic welding
The piece of metal to be joined are heated to a plastic state
and forced together by external pressure
(Ex) Resistance welding
(2)Fusion welding
The material at the joint is heated to a molten state and
allowed to solidify
(Ex) Gas welding, Arc welding

3.  Classification of welding processes
(i). Arc welding
• Carbon arc
• Metal arc
• Metal inert gas
• Tungsten inert gas
• Plasma arc
• Submerged arc
• Electro-slag
(ii). Gas Welding
• Oxy-acetylene
• Air-acetylene
• Oxy-hydrogen
(iii). Resistance Welding
• Butt
• Spot
• Seam
• Projection
• Percussion
(iv)Thermit Welding
(v)Solid State Welding
• Friction
• Ultrasonic
• Diffusion
• Explosive

4. (vi)Newer Welding
• Electron-beam
• Laser
(vii)Related Process
• Oxy-acetylene cutting
• Arc cutting
• Hard facing
Brazing
• Soldering

5.  Standard Location of Elements of a Welding Symbol
According to Indian Standards, IS: 813 – 1961 (Reaffirmed
1991), the elements of a welding symbol shall have standard
locations with respect to each other.

6.  Basic Weld Symbol

9.  Supplementary weld symbols

10.  Workpiece thickness limits per joint type
Joint type Thickness
Square joint Up to 1⁄4 in (6.35 mm)
Single-bevel joint 3⁄16–3⁄8 in (4.76–9.53 mm)
Double-bevel joint Over 3⁄8 in (9.53 mm)
Single-V joint Up to 3⁄4 in (19.05 mm)
Double-V joint Over 3⁄4 in (19.05 mm)
Single-J joint 1⁄2–3⁄4 in (12.70–19.05 mm)
Double-J joint Over 3⁄4 in (19.05 mm)
Single-U joint Up to 3⁄4 in (19.05 mm)
Double-U joint Over 3⁄4 in (19.05 mm)
Flange (edge of corner)
Sheet metal less than 12
gauge (0.1046 in or 2.657 mm)
Flare groove All thickness

11.  Weldability Factors: Base Metal
1. Some metals melt too easily; e.g., aluminum
2. Metals with high thermal conductivity transfer heat away
from weld, which causes problems; e.g., copper
3. High thermal expansion and contraction in metal causes
distortion problems
4. Dissimilar metals pose problems in welding when their
physical and/or mechanical properties are substantially
different

12.  Inspection and Testing Methods:
 Nondestructive Evaluation (NDE) Tests
1. Ultrasonic testing - high frequency sound waves through
specimen to detect cracks and inclusions
2. Radiographic testing - x-rays or gamma radiation provide
photographs of internal flaws
3. Dye-penetrant and fluorescent-penetrant tests - to detect
small cracks and cavities at part surface
4. Magnetic particle testing – iron filings sprinkled on surface
reveal subsurface defects that distort the magnetic field

13.  Destructive Testing - Mechanical Tests
1. Tension-shear test,
2. fillet break test,
3. tension-shear of spot weld, and
4. peel test for spot weld

14.  Welding defects
 Porous welds
 Poor penetration
 Warping
 Undercut & Underfill
 Distortion
 Cracked welds
 Poor appearance
 Poor fusion
 Brittle welds
 Spatter
 Magnetic blow
 Weld stress

15.  Advantages and Disadvantages of
Welded Joints over Riveted Joints
 Advantages
(1) The welded structures are usually lighter than riveted
structures. This is due to the reason, that in welding,
gussets or other connecting components are not used.
(2) The welded joints provide maximum efficiency (may be
100%) which is not possible in
case of riveted joints.
(3) Alterations and additions can be easily made in the
existing structures.
(4) As the welded structure is smooth in appearance,
therefore it looks pleasing.
(5) In welded connections, the tension members are not
weakened as in the case of riveted joints.

16. (6) A welded joint has a great strength. Often a welded
joint has the strength of the parent
metal itself.
(7) Sometimes, the members are of such a shape (i.e.
circular steel pipes) that they afford
difficulty for riveting. But they can be easily welded.
(8) The welding provides very rigid joints. This is in line
with the modern trend of providing
rigid frames.
(9) It is possible to weld any part of a structure at any
point. But riveting requires enough
clearance.
(10) The process of welding takes less time than the
riveting.

17.  Dis-Advantages
(1) Since there is an uneven heating and cooling during
fabrication, therefore the members
may get distorted or additional stresses may develop.
(2) It requires a highly skilled labour and supervision.
(3) Since no provision is kept for expansion and contraction
in the frame, therefore there is a
possibility of cracks developing in it.
(4) The inspection of welding work is more difficult than
riveting work.