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Uncoated Plain Carbon Steel Process Variables Continued

Uncoated Plain Carbon Steel Process Variables Continued. Uncoated Steel – Process Variables Continued. Lesson Objectives When you finish this lesson you will understand:

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Uncoated Plain Carbon Steel Process Variables Continued

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  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 • Look up Keywords • View Slides; • Read Notes, • Listen to lecture • View Demo • Do on-line workbook • Do homework Keywords Electrode Material, Electrode Design, Electrode Coating, Shunting, Post Weld Temper

  3. 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 Process Variables

  4. Electrode Materials Ultimate Strength (ksi) Annealing Temperature (°C) Thermal Conductivity (Cal/cm-sec-°C) Composition (%) RWMA Class # Electrical Conductivity Cu 90 30 - - - 99-Cu, 1-Cd 60 (F) 660 0.82 1 2 3 4 5 92 80 (C) 82 (F) 30 (C) 62 (F) 930 (C) 900 (F) 99.2-Cu, 0.8-Cr 0.77 (C) 0.75 (F) 97-Cu, 2.5- Co, 0.5-Be 48 (C) 52 (F) 1020 (C) 900 (F) 95 (C) 105 (F) 0.43 (C) 0.45 (F) 20 (C) 23 (F) 110 (C) 170 (F) 0.18 (C) 0.19 (F) Cu & Be 710 Cu & Al 18 70 - 0.16 * C = Cast, F = Forging

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

  6. Questions? • 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 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 Process Variables

  8. Electrode Geometry 1 4 1 4 1 4 1 4 “A” “A” “A” “A” 45° 6° 20° 3 20° 45° Dome Truncated Cone Truncated Cone Pointed [Reference: Welding in the Automotive Industry, p.135, D. W. Dickinson]

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

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

  11. 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

  12. Questions? • 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?

  13. 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 Process Variables • Upslope/Downslope/ Postweld Temper

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

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

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

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

  18. Questions? • 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?

  19. 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 Process Variables • Upslope/Downslope/ Postweld Temper

  20. Shunting Effect IB IA B A Itotal = IA + IB IARA = IBRB IB/Itotal = 1 - RB/(RA + RB) [Reference: Resistance Welding Manual, p.1-7, RWMA]

  21. Effect of Shunting Distance (Spot Spacing) Shunt Distance, cm 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 Shear Strength of Single Weld, % Shunt Distance, in. [Reference: Welding Handbook, Volume 2, p. 551, AWS]

  22. 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 Process Variables • Upslope/Downslope/ Postweld Temper

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

  24. Link to Web Page Demonstration

  25. Homework

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