1. Uncoated Plain Carbon Steel Process Variables Continued

2. Uncoated Steel – Process Variables Continued Lesson Objectives When you finish this lesson you will understand: the effect that various welding parameter variables have on the weld quality of uncoated steels (continuation from last module) Learning Activities 1.Look up Keywords 2.View Slides; 3.Read Notes, 4.Listen to lecture 5.View Demo 6.Do on-line workbook 7.Do homework Keywords Electrode Material, Electrode Design, Electrode Coating, Shunting, Post Weld Temper

3. Process Variables Process Parameters: (Manufacturer’s Control) Weld Current Type Weld Time Hold Time Pulsing Electrode Force Electrode Material Electrode Designs Electrode Cooling Postweld Temper Material Parameters: (Steel Company Control) Chemistry Cleanliness Surface Condition Material Processing Thickness

4. Electrode Materials RWMA Class # Electrical Conductivity Composition (%) Ultimate Strength (ksi) Annealing Temperature (°C) Thermal Conductivity (Cal/cm-sec-°C) - 1234512345 Cu 99-Cu, 1-Cd 99.2-Cu, 0.8-Cr 97-Cu, 2.5- Co, 0.5-Be Cu & Be Cu & Al 90 92 80 (C) 82 (F) 48 (C) 52 (F) 20 (C) 23 (F) 18 70 - 0.16 30 - - 60 (F) 30 (C) 62 (F) 95 (C) 105 (F) 110 (C) 170 (F) 660 0.82 710 0.77 (C) 0.75 (F) 0.43 (C) 0.45 (F) 0.18 (C) 0.19 (F) 930 (C) 900 (F) 1020 (C) 900 (F) * C = Cast, F = Forging

5. R B @ 500 C < 30 40 85 % IACS* * Percent Internatinal Annealed Copper Standard 92 80 ~90 Uncoated Steel

6. Turn to the person sitting next to you and discuss (1 min.): Besides alloy content, what other factors might effect the electrical conductivity of copper electrodes? How might this change your decision in the manufacturing technique used to manufacture these electrodes? Would the fact that you are welding steel (as opposed to say aluminum) have any bearing on the manufacturing technique?

7. Process Variables Process Parameters: (Manufacturer’s Control) Weld Current Type Weld Time Hold Time Pulsing Electrode Force Electrode Material Electrode Designs Electrode Cooling Postweld Temper Material Parameters: (Steel Company Control) Chemistry Cleanliness Surface Condition Material Processing Thickness

8. Electrode Geometry “A” 6° 20° 45° 3 1414 1414 1414 1414 20° Pointed Dome Truncated Cone Truncated Cone [Reference: Welding in the Automotive Industry, p.135, D. W. Dickinson]

10. Electrode Face Dia. Vs Welding Current Range 0.028 inch (0.71 mm) 0.05C-0.09P 0.25 inch (6.4 mm) Electrode 0.312 inch (7.9 mm) Electrode 1300A 3300A Weld Time 15 cycles Electrode Pressure 13ksi Hold Time 30 cycles Current, kA 6 7 8 9 10 11 12 13 14 Button Diameter, inch 0.30 0.25 0.20 0.15 0.10 0.05 8 7 6 5 4 3 2 1 mm [Reference: Welding in the Automotive Industry, p.137, D. W. Dickinson]

11. Effect of Electrode Diameter on Current Range 4000 3000 2000 1000 0 0.15 0.2 0.25 0.3 0.35 Electrode Diameter, in. Current Range, Amp Current Range: 0.15 in. Button to Expulsion [Reference: “Spot Weldability of High-Strength Sheet Steels”, Welding Journal 59 (January 1980), Baker & Sawhill]

12. Codes and Equations Used for Electrode Face Selection Ayers & Fisher D = 1.5t + 0.1 (Leng) D = 2t + 0.1 (AWS) Ford BA 13-4

13. Turn to the person sitting next to you and discuss (1 min.): It is surprising that with the many different people who have developed codes governing the electrode face diameter as a function of sheet thickness, they all come to about the same size vs. sheet thickness. Why do you suppose this is the case?

14. Process Variables Process Parameters: (Manufacturer’s Control) Weld Current Type Weld Time Hold Time Pulsing Electrode Force Electrode Material Electrode Designs Electrode Cooling Shunting Material Parameters: (Steel Company Control) Chemistry Cleanliness Surface Condition Material Processing Thickness Upslope/Downslope/ Postweld Temper

15. Hirsch R., Influence of Water Temp& Flow on Electrode Life SMWC VII, AWS, 1996 Poor Cooling Increased Electrode Wear

16. Hirsch R., Influence of Water Temp& Flow on Electrode Life SMWC VII, AWS, 1996 Warm Water Slower Flow

17. Room Temp Refrigerated Dickinson, Welding In Auto AISI, 1981

18. Baysore, J, DCT Inc, Private Communications, July 2000 No Water Cooling

19. Turn to the person sitting next to you and discuss (1 min.): What design criteria did the NOWAT people have to consider when they developed their robots that do not need electrode cooling water?

20. Process Variables Process Parameters: (Manufacturer’s Control) Weld Current Type Weld Time Hold Time Pulsing Electrode Force Electrode Material Electrode Designs Electrode Cooling Shunting Material Parameters: (Steel Company Control) Chemistry Cleanliness Surface Condition Material Processing Thickness Upslope/Downslope/ Postweld Temper

21. Shunting Effect AB IBIB IAIA I total = I A + I B I A R A = I B R B I B /I total = 1 - R B /(R A + R B ) [Reference: Resistance Welding Manual, p.1-7, RWMA]

22. Effect of Shunting Distance (Spot Spacing) AC welding 1/4 in. x 3 in. mild steel Class “8” weld Average shear strength of 24 welds, 17,570 lbs Stock temp 25°C All welds made with one shunt circuit Curve estimated below 2-1/2 in. shunt distance Shunt Distance, in. Shunt Distance, cm Shear Strength of Single Weld, % [Reference: Welding Handbook, Volume 2, p. 551, AWS]

23. Process Variables Process Parameters: (Manufacturer’s Control) Weld Current Type Weld Time Hold Time Pulsing Electrode Force Electrode Material Electrode Designs Electrode Cooling Shunting Material Parameters: (Steel Company Control) Chemistry Cleanliness Surface Condition Material Processing Thickness Upslope/Downslope/ Postweld Temper

24. Upslope/Downslope, Hold Time, & Temper Weld Current Temper Current Electrode Pressure Current Squeeze Time Weld Time Off Time Hold Time Upslope Downslope Temper