Spot Welding final year Project of B.Sc Engineering in Metallurgy and Material PU (Jameel_Sarwar)

1. A COMBINE STUDY OF SPOT WELD’S STRENGTH OF
MILD STEEL AND STAINLESS STEEL (304)
Supervisor:
Dr. Muhammad Kamran
Co-Supervisor:
Miss Sehrish Mukhtar
Submitted By
Jameel Sarwar E14-338
Ali Naqi Awan E14-341
Suleman Rafiq E14-343
Session 2013-17
COLLEGE OF ENGINEERING AND EMERGING TECHNOLOGIES
DEPARTMENT OF METALLURGY AND MATERIALS ENGINEERING
UNIVERSITY OF THE PUNJAB,
LAHORE

2. A COMBINE STUDY OF SPOT WELD’S STRENGTH OF
MILD STEEL AND STAINLESS STEEL (304)
Supervisor:
Dr. Muhammad Kamran
Co-Supervisor:
Miss Sehrish Mukhtar
Submitted By
Jameel Sarwar E14-338
Ali Naqi Awan E14-341
Sulaman Rafiq E14-343
Session 2013-17
Department of Metallurgy and Materials Engineering,
Faculty of Engineering and Technology
University of the Punjab, Lahore, Pakistan
Research Project on

3. A COMBINE STUDY OF SPOT WELD’S STRENGTH OF
MILD STEEL AND STAINLESS STEEL (304)
This report is submitted to Department of Metallurgy and Materials
Engineering, College of Engineering and Emerging Technologies,
Faculty of Engineering and Technology, University of the Punjab, Quaid-
e-Azam Campus, Lahore Pakistan in partial fulfillment requirements for
the
Degree
of
Bachelor of Science
in
Metallurgy and Materials Engineering
Approved by
Internal Examiners: _____________________ _____________________
Dr. Muhammad Kamran Mam Sehrish Mukhtar
External Examiner: Dr. Furqan Ahmad
Submitted by:
Jameel Sarwar E14-338
Ali Naqi Awan E14-341
Sulaman Rafiq E14-343
Session 2013-17
Department of Metallurgy and Materials Engineering,
Faculty of Engineering and Technology
University of the Punjab, Lahore, Pakistan

5. READ, IN THE NAME OF YOUR LORD
WITH THE NAME OF ALMIGHTY ALLAH
WHO CREATED, CREATED MAN FROM A CLOT.
READ, AND YOUR LORD IS THE MOST BOUNTEOUS
WHO THOUGHT BY THE PEN
TAUGHT MAN WHICH DID NOT KNOWN
(AL-QURAN)

6. ACKNOWLEDGEMENT
Praise to Allah! May Allah peace and blessing upon Prophet Muhammad, his family
and companions, and those who follow their guidance.
I would like to thank to my supervisor, Dr. Mohammad Kamran for his guidance
throughout the project. I also would like to thank Sir Nauman Siddique for his
guidance, support and helpful tips to complete the experiment and answering any
question regarding the spot welding machine.
A special acknowledgement goes to my parents for their great support and motivation
to accomplish this project. Not forget, the lab assistants and all my friends who
involve in this project.

7. ABSTRACT
Resistance spot welding (RSW) is used in Fabrication and automotive industry
because of their advantages such as high speed, high production, suitability for
automation, easy to process and low operational cost.
In this research, the strength on the tensile-shear and tensile-peel type of welding
joints in spot welding of 2 mm thicknesses mild steel sheets and stainless steel was
investigated. The welding joints were exposed to tensile shear and tensile-peel using
tensile test machine, and the effect of welding time and pressure on tensile-peel
strength and tensile shear strength was researched by using related period diagrams. A
weld pressure and weld time is 70, 75 Psi and 1 – 4 second respectively was selected
during the welding process. In this experiment increasing welding times because high
heat input to weld zone and extending weld nugget, so the strength of joints increases
mine while excessive heat energy input causes void and crack formations, partially
spurt out of molten metal and so, the strength of joint decreases. The optimum
parameter for tensile shear type is 4 second welds time and 75 Psi pressure. Finally,
the result shown the higher strength of orientation using spot welding machine is
tensile shear type.
Key words: Welding, Mild Steel, Stainless Steel 304, Resistance Spot Welding,
Universal Testing Machine, Scanning Electrode Microscope, Stereo-Microscope

8. TABLE OF CONTENTS
1. Introduction 1
1.1 Introduction 2
1.2 Objectives 2
1.3 Scope of 2
2. Literature Review 4
2.1 Principle of Resistance Welding 5
2.2 Resistance Spot Welding 5
2.3 Seam Welding 7
2.4 Resistance Projection Welding 7
2.5 Flash butt Welding 8
2.6 Parameters for Resistance Spot Welding 9
2.6.1 Electrode Tip Size 10
2.6.2 Electrode’s Pressure 10
2.6.3 Weld Time 11
2.6.4 Water Supply 11
2.6.5 Weld Current 11
2.7 Spot Welding Machine PMC 12
2.8 Specimen’s Materials 14
2.8.1 Stainless Steel 304 14
2.8.2 Mild Steel 14
2.9 Universal Testing Machine (UTS) Test 15
2.9.1 Shear Test 16
2.9.2 Peel Test 17
2.10 Stereo-Microscope 18
2.10.1 Working Procedure 19
2.11Scanning Electron Microscope 19
3. Experimental Work 22
3.1 Material parameters 23
3.1.1 Mild Steel and Stainless Steel 304 23
3.2 Spot Weld parameters 24
3.3 Spot Welding Procedure 25
3.4 Mechanical Test 26

9. 3.4.1 Shear Test of Samples 25
3.4.2 Peel Test of Samples 27
4 Result & Discussion 28
4.1 Shear test 29
4.1.1 Nugget Diameter Vs Pressure 32
4.1.2 Nugget Diameter Vs Time 32
4.1.3 Deformation Vs Load Diagram 33
4.2 Peel test 38
4.2.1 Nugget Diameter Vs Pressure 42
4.2.2 Nugget Diameter Vs Time 43
4.2.3 Deformation Vs Load Diagram 44
4.3 Scanning Electron Microscope Result 49
4.4 Discussion 51
4.4.1 Discussion on shear test 51
4.4.2 Discussion on peel test 52
4.4.3 Discussion on SEM result 52
5 Conclusion 54
5.1 Conclusion 55
5.2 Recommendation 55
References 56

10. List of Tables
Table 2.1 Input Supply of Spot Welding Machine PMC 25 13
Table 2.2 Characteristics of Spot Weld Machine PMC 25 13
Table 2.3 Chemical Composition of Stainless Steel 304 14
Table 2.4 Mechanical Properties of Stainless Steel 304 14
Table 2.5 Chemical Properties of Mild Steel 14
Table 2.6 Mechanical Properties of Mild Steel 15
Table 3.1 Dimension for Shear Specimens (Stainless- steel and mild steel) 23
Table 3.2 Dimension for Peel Specimens (Stainless- steel and mild steel) 24
Table 3.3 Weld Schedule for T and Bar Shape Specimen (Variable Time) 25
Table 3.4 Weld Schedule for T and Bar Shape Specimen (Variable Time) 25
Table 4.1 Difference in nugget size according to the pressure difference
in shear test 32
Table 4.2: Difference in nugget size according to the time difference in Shear test 32
Table 4.3 Maximum Stress beard by the Samples in Shear test 34
Table 4.4 Deformation in Samples according to the Pressure difference
in Shear test 34
Table 4.5 Deformation is Sample according to the Time difference in Shear test 37
Table 4.6 Difference in nugget size according to the pressure difference
in Peel test 42
Table 4.7 Difference in nugget size according to the time difference in Peel test 43
Table 4.8 Maximum Stress beard by the Samples in Peel test 45
Table 4.9 Deformation in Samples according to the pressure difference in Peel test 45
Table 4.10 Deformation in Samples according to the Time difference in Peel test 48

11. List of Figures
Figures 2.1 Sketch of Spot welding 6
Figures 2.2 Copper electrode geometry 6
Figures 2.3 Resistance Seam Welding 7
Figure 2.4 Resistance Projection welding 8
Figure 2.5 Resistance Flash Butt Welding 8
Figure 2.6 Welding current vs thickness of metal sheet 12
Figure2.7 Spot welding machine PMC 25 12
Figure 2.8 varying of current with the increase in metal sheets thickness 13
Figure 2.9 Universal testing machine 16
Figure 2.10 Shear test on Universal testing machine 17
Figure 2.11 Peel test on Universal testing machine 18
Figure 2.12 Stereo-Microscope and their parts 19
Figure 2.13 Scanning Microscope and their Parts 20
Figures 3.1 Welding Sample of Mild Steel and Stainless Steel 304 with
Dimension for Shear test 23
Figures 3.2 Welding Sample of Mild Steel and Stainless Steel 304 with
Dimension or Peel test 24
Figures 3.3 Shear Test of Mild Steel 26
Figures 3.4 (a) Peel Test of Mild Steel (b) Peel Test of Stainless –Steel 27
Figures 4.1 MS shear sample spot welded at 70PSI,(a) Before Test, (b) After Test,
MS shear sample spot welded at 75PSI,(c) Before Test, (d) After Test 29
Figures 4.2 SS shear sample spot welded at 70PSI, (a) Before Test, (b) After Test,
SS shear sample spot welded at 75PSI,(c) Before Test, (d) After Test 29
Figures 4.3 MS shear sample spot welded at 1-SEC, (a) Before Test, (b) After Test
MS shear sample spot welded at 2-SEC, (c) Before Test, (d) After Test,
MS shear sample spot welded at 3-SEC, (e) (Before Test, (f) After Test,
MS shear sample spot welded at 4-SEC, (g) Before Test,(h) After Test 30
Figures 4.4 SS shear sample spot welded at 1-SEC, (a) Before Test, (b) After Test,
SS shear sample spot welded at 2-SEC, (c) Before Test, (d) After Test,

12. SS shear sample spot welded at 3-SEC, (e) Before Test, (f) After Test,
SS shear sample spot welded at 4-SEC, (g) Before Test, (h) After Test 31
Figures 4.5 Graph of mild steel and stainless steel's weld nugget diameter Vs pressure
difference 32
Figures 4.6 Graph of mild steel and stainless steel's weld nugget diameter Vs pressure
difference 33
Figure 4.7 Graph of Mild Steel with Pressure variation 33
Figure 4.8 Graph of Stainless-Steel 304 with pressure variation 34
Figure 4.9 Graph of Shear test on Mild Steel & Stainless Steel with pressure
Variation 35
Figure 4.10 Graph of Shear test on Mild Steel with pressure variation 36
Figure 4.11 Graph of Shear test on Stainless-Steel 304 with time variation 36
Figure 4.12 Graph of Shear test on Mild Steel & Stainless Steel with Time
Variation 37
Figures 4.13 MS Peel sample spot welded at 70PSI, (a) Before Test, (b) After Test,
MS Peel sample spot welded at 75PSI, (c) Before Test,(d) After Test 38
Figures 4.14 SS Peel sample spot welded at 70PSI, (a) Before Test, (b) After Test,
SS Peel sample spot welded at 75PSI, (c) Before Test,(d) After Test 39
Figures 4.15 MS Peel sample spot welded at 1-SEC, (a) Before Test, (b) After Test,
MS Peel sample spot welded at 2-SEC, (c) Before Test, (d) After Test,
MS Peel sample spot welded at 3-SEC, (e) Before Test, (f) After Test,
MS Peel sample spot welded at 4-SEC, (g) Before Test,(h) After Test 40
Figures 4.16 SS Peel sample spot welded at 1-SEC, (a) Before Test, (b) After Test,
SS Peel sample spot welded at 2-SEC, (c) Before Test, (d) After Test,
SS Peel sample spot welded at 3-SEC, (e) Before Test, (f) After Test,
SS Peel sample spot welded at 4-SEC, (g) Before Test,(h) After Test 41
Figure 4.17 Graph of mild steel and stainless steel's weld nugget diameter Vs
pressure difference 42
Figure 4.18 Graph of mild steel and stainless steel's weld nugget diameter Vs time
difference 43
Figure 4.19 Graph of Peel Test Mild Steel with pressure variation 44
Figure 4.20 Graph of Peel Test Stainless-Steel 304 with pressure variation 44
Figure 4.21: Graph of Peel test on Mild Steel & Stainless Steel with pressure
Variation 46
Figure 4.22 Graph of Peel Test Mild-Steel with pressure variation 47

13. Figure 4.23 Graph of Peel Test Stainless-Steel 304 with pressure variation 47
Figure 4.24 Graph of Peel test on Mild Steel & Stainless Steel with Time variation 48
Figures 4.25 Figure 4.22: Result of Stainless Steel 304 at 70 (Psi) after shear test by
SEM 49
Figures 4.26 Result of Stainless Steel 304 at 75 (Psi) after Peel test by SEM 50
Figures 4.27 Result of Mild Steel at 70 (Psi) after Peel test by SEM 50
Figures 4.28 Result of Mild Steel at 75 (Psi) after Shear test by SEM 51

14. ABBREVIATION
RSW Resistance Spot Welding
PSI Pound per Square Inch
UTM Universal Testing Machine
HAZ Heat Effected Zone
MS Mild Steel
SS Stainless Steel
SEM Scanning Electron Microscope
SE Stereo-Microscope
KN Kilo-Newton
MM Millimeters
SED Secondary electron detector
DBSD Diffracted backscatter detector