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Zinc

Zinc. 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. Zinc Specific Gravity 7.14, slightly less than iron Low melting temp 787F (419C)

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Zinc

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  1. Zinc

  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. Zinc • Specific Gravity 7.14, slightly less than iron • Low melting temp 787F (419C) • Low boiling temp 1665F (907C) - Fuming, Vapor • Electrical Conductivity 25% of Copper (2 x steel) • Zinc Alloys • Two Alloy Types • Cast Zinc • Rolled Zinc • Zinc Alloys Brittle at RT, elevated temp mechanical working • Zinc Alloys have recrystallization temp at or below RT • Recrystallization reduces strength in rolled alloys • Use low heat input to reduce HAZ Softening (Resistance Weld) • Mechanical Clean & Abraded to clean surface

  4. Uses • Cast forms • Roofing • Chemical Processing Applications

  5. Resistance Welding of Rolled Alloys • Spot & Seam Welding • Equivalent or Slightly Lower Current than steel (lower resistance, lower melting temp) • Lower Force than steel (softer) • Low inertia head, more indentation needs faster follow-up • Disp Strengthened Electrodes, High alloying with copper • Mechanical clean surface • Internal defects or cavities common, low boiling point • Forge force can help • Seam Welding • Increased roll speed requires increased current

  6. Cu Zn

  7. Rolled Alloy Spot & Seam

  8. Cast Alloy Spot & Seam Weld

  9. Electrode: class 2 with 3 in radius dome

  10. Electrode: class 2 with 15 degree bevel and face radius of 3 inches

  11. Resistance Welding of Cast Zinc Alloys • Start with the same recommendation as Rolled Alloys • High Resistance Films (electro-deposited & others) Removed The castings generally have extra coatings

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