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Stainless Steel

Stainless Steel. High Ni & Cr Content Low (Controlled) Interstitials. Nitrogen Strengthened Austenitic. Austenitic. Martensitic. Ferritic. Super Austenitic. Precipitation Hardened. Duplex. Super Ferritic. AOD Furnace. Argon & Oxygen. Today, more than 1/2 of the high chromium steels

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Stainless Steel

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  1. Stainless Steel High Ni & Cr Content Low (Controlled) Interstitials Nitrogen Strengthened Austenitic Austenitic Martensitic Ferritic Super Austenitic Precipitation Hardened Duplex Super Ferritic

  2. AOD Furnace Argon & Oxygen Today, more than 1/2 of the high chromium steels are produced in the AOD Furnace Linnert, Welding Metallurgy AWS, 1994

  3. A=Martensitic Alloys B=Semi-Ferritic C=Ferritic Castro & Cadenet, Welding Metallurgy of Stainless and Heat-resisting Steels Cambridge University Press, 1974

  4. We will look at these properties in next slide! AWS Welding Handbook

  5. Electrical Resistivity Surface & bulk resistance is higher than that for plain-carbon steels Thermal Conductivity About 40 to 50 percent that of plain-carbon steel Melting Temperature Plain-carbon:1480-1540 °C Martensitic: 1400-1530 °C Ferritic: 1400-1530 °C Austenitic: 1370-1450 °C Coefficient of Thermal Expansion Greater coefficient than plain-carbon steels High Strength Exhibit high strength at room and elevated temperatures Surface Preparation Surface films must be removed prior to welding Spot Spacing Less shunting is observed than plain-carbon steels General Properties of Stainless Steels

  6. Static Resistance Comparison Plain-carbon Steel Electrode Electrode Stainless Steel Higher Bulk Resistance Alloy Effect Workpieces Higher Surface Resistance Chromium Oxide Class 3 Electrode Higher Resistance Resistance Higher Resistances = Lower Currents Required

  7. Electrical Resistivity Surface & bulk resistance is higher than that for plain-carbon steels Thermal Conductivity About 40 to 50 percent that of plain-carbon steel Melting Temperature Plain-carbon:1480-1540 °C Martensitic: 1400-1530 °C Ferritic: 1400-1530 °C Austenitic: 1370-1450 °C Coefficient of Thermal Expansion Greater coefficient than plain-carbon steels High Strength Exhibit high strength at room and elevated temperatures Surface Preparation Surface films must be removed prior to welding Spot Spacing Less shunting is observed than plain-carbon steels General Properties of Stainless Steels

  8. Conduction in Plain Carbon Conduction in SS Base Metal Base Metal Weld Nugget Only 40 - 50% Heat conduction in SS Less Heat Conducted Away Therefore Lower Current Required Less Time Required (in some cases less than 1/3)

  9. Electrical Resistivity Surface & bulk resistance is higher than that for plain-carbon steels Thermal Conductivity About 40 to 50 percent that of plain-carbon steel Melting Temperature Plain-carbon:1480-1540 °C Martensitic: 1400-1530 °C Ferritic: 1400-1530 °C Austenitic: 1370-1450 °C Coefficient of Thermal Expansion Greater coefficient than plain-carbon steels High Strength Exhibit high strength at room and elevated temperatures Surface Preparation Surface films must be removed prior to welding Spot Spacing Less shunting is observed than plain-carbon steels General Properties of Stainless Steels

  10. Melting Temp of Plain Carbon Base Metal Base Metal Weld Nugget Melting Temp of SS Melting Temp of SS is lower Nugget Penetrates More Therefore Less Current and Shorter Time Required

  11. Electrical Resistivity Surface & bulk resistance is higher than that for plain-carbon steels Thermal Conductivity About 40 to 50 percent that of plain-carbon steel Melting Temperature Plain-carbon:1480-1540 °C Martensitic: 1400-1530 °C Ferritic: 1400-1530 °C Austenitic: 1370-1450 °C Coefficient of Thermal Expansion Greater coefficient than plain-carbon steels High Strength Exhibit high strength at room and elevated temperatures Surface Preparation Surface films must be removed prior to welding Spot Spacing Less shunting is observed than plain-carbon steels General Properties of Stainless Steels

  12. Ferritic, Martensitic, Ppt. = 6 - 11% greater expansion Austenitic = 15% greater expansion than Plain Carbon Steel Therefore Warpage occurs especially in Seam Welding Hot Cracking can Occur Dong et al, Finite Element Modeling of Electrode Wear Mechanisms, Auto Steel Partnership, April 10, 1995

  13. Electrical Resistivity Surface & bulk resistance is higher than that for plain-carbon steels Thermal Conductivity About 40 to 50 percent that of plain-carbon steel Melting Temperature Plain-carbon:1480-1540 °C Martensitic: 1400-1530 °C Ferritic: 1400-1530 °C Austenitic: 1370-1450 °C Coefficient of Thermal Expansion Greater coefficient than plain-carbon steels High Strength Exhibit high strength at room and elevated temperatures Surface Preparation Surface films must be removed prior to welding Spot Spacing Less shunting is observed than plain-carbon steels General Properties of Stainless Steels

  14. Force High Strength High Hot Strength • Need Higher Electrode Forces • Need Stronger Electrodes (Class 3, 10 & 14 Sometimes Used)

  15. Electrical Resistivity Surface & bulk resistance is higher than that for plain-carbon steels Thermal Conductivity About 40 to 50 percent that of plain-carbon steel Melting Temperature Plain-carbon:1480-1540 °C Martensitic: 1400-1530 °C Ferritic: 1400-1530 °C Austenitic: 1370-1450 °C Coefficient of Thermal Expansion Greater coefficient than plain-carbon steels High Strength Exhibit high strength at room and elevated temperatures Surface Preparation Surface films must be removed prior to welding Spot Spacing Less shunting is observed than plain-carbon steels General Properties of Stainless Steels

  16. Oxide from Hot Rolling Oxide Protective Film • Chromium Oxide from Hot Rolling must be removed by Pickle • Ordinary Oxide Protective Film is not a Problem

  17. Electrical Resistivity Surface & bulk resistance is higher than that for plain-carbon steels Thermal Conductivity About 40 to 50 percent that of plain-carbon steel Melting Temperature Plain-carbon:1480-1540 °C Martensitic: 1400-1530 °C Ferritic: 1400-1530 °C Austenitic: 1370-1450 °C Coefficient of Thermal Expansion Greater coefficient than plain-carbon steels High Strength Exhibit high strength at room and elevated temperatures Surface Preparation Surface films must be removed prior to welding Spot Spacing Less shunting is observed than plain-carbon steels General Properties of Stainless Steels

  18. Look at Each Grade & Its Weldability Austenitic Super Austenitic Nitrogen Strengthened Austenitic Martensitic Ferritic Super Ferritic Precipitation Hardened Duplex

  19. Austenitic • Contain between 16 and 25 percent chromium, plus sufficient amount of nickel, manganese and/or nitrogen • Have a face-centered-cubic (fcc) structure • Nonmagnetic • Good toughness • Spot weldable • Strengthening can be accomplished by cold work or by solid-solution strengthening Applications: Fire Extinguishers, pots & pans, etc.

  20. AWS Welding Handbook

  21. AWS Welding Handbook

  22. Pseudobinary Phase Diagram @ 70% Iron AWS Welding Handbook

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