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Hardenable Steels

Hardenable Steels. Alloy > 1%. Carbon 0.15-0.8%. Resistance Welding. Learning Activities View Slides; Read Notes, Listen to lecture Do on-line workbook. Lesson Objectives When you finish this lesson you will understand:. Keywords. Finer Grain Cobalt. Mn, Ni, Mo, C, Cr.

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Hardenable Steels

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  1. Hardenable Steels Alloy > 1% Carbon 0.15-0.8%

  2. Resistance Welding • Learning Activities • View Slides; • Read Notes, • Listen to lecture • Do on-line workbook • Lesson Objectives • When you finish this lesson you will understand: Keywords

  3. Finer Grain Cobalt Mn, Ni, Mo, C, Cr Metallurgical Considerations 1.2% C 0.8% C 0.35% C

  4. Factors to be Considered When Welding Hardenable Steels • Surface Cleaning • Weld Force • Weld Current • Weld Time • Upslope • Downslope • Indentation • Preheat • Post Weld Temper

  5. Surface Cleaning Scale usually more tenacious (especially Cr, Cu) Surface Cleaning must be more complete • Pickle (preferred) • Grind / Polish • Shot Blast

  6. Weld Force • Alloy Grades have: • Higher Strength Than Plain Carbon Steels • High Hot Hardness Than Plain Carbon Steels • Therefore: • An increase in weld force (up to 10% greater) is • needed over plain carbon steel at the same gage

  7. Weld Current • Base Metal Resistance is Higher Than Plain • Carbon Steel Because of Higher Alloy Content • Therefore: • Lower Currents are needed (approximately 90% • of that required for Plain Carbon steel)

  8. Weld Time For Lower Alloy Grades: A longer weld time by as much as 2 to 3 times helps. Long Time Lower Current Slower Cooling Short Time Higher Current Rapid Cooling For Higher Alloy Grades: Nose is too far back and longer weld time is not effective

  9. Indentation Long Time Lower Current Slower Cooling

  10. Upslope • Helps Set Electrodes • Helps Bring Parts Together • Some slight enlargement of HAZ but no great • effect on Cooling Rate

  11. Downslope With Downslope Without Downslope

  12. Weld Time Temper Time Temper Heat Quench Time Effect of Quench Time and Temper Heat on Spot Weld

  13. Short Quench Time

  14. Minimum Quench Time Thicker Material 1045 1035 1020 1010 Increase Carbon Moves Range Down

  15. Minimum Temper Heat NiCrMo (86xx) CrMo(4xxx) More Resistant To Tempering Plain Carbon

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