Stainless Steel

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

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• Lesson Objectives
• When you finish this lesson you will understand

Keywords
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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
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AMartensitic Alloys BSemi-Ferritic CFerritic
Castro Cadenet, Welding Metallurgy of
Stainless and Heat-resisting Steels Cambridge
University Press, 1974
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(No Transcript)
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We will look at these properties in next slide!
AWS Welding Handbook
7
General Properties of Stainless Steels

• 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

• 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-carbon1480-1540 C
• Martensitic 1400-1530 C
• Ferritic 1400-1530 C
• Austenitic 1370-1450 C

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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
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General Properties of Stainless Steels

• 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

• 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-carbon1480-1540 C
• Martensitic 1400-1530 C
• Ferritic 1400-1530 C
• Austenitic 1370-1450 C

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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)
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General Properties of Stainless Steels

• 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

• 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-carbon1480-1540 C
• Martensitic 1400-1530 C
• Ferritic 1400-1530 C
• Austenitic 1370-1450 C

12
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
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General Properties of Stainless Steels

• 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

• 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-carbon1480-1540 C
• Martensitic 1400-1530 C
• Ferritic 1400-1530 C
• Austenitic 1370-1450 C

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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
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General Properties of Stainless Steels

• 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

• 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-carbon1480-1540 C
• Martensitic 1400-1530 C
• Ferritic 1400-1530 C
• Austenitic 1370-1450 C

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Force
High Strength High Hot Strength

• Need Higher Electrode Forces
• Need Stronger Electrodes (Class 3, 10 14
  Sometimes Used)

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General Properties of Stainless Steels

• 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

• 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-carbon1480-1540 C
• Martensitic 1400-1530 C
• Ferritic 1400-1530 C
• Austenitic 1370-1450 C

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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

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General Properties of Stainless Steels

• 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

• 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-carbon1480-1540 C
• Martensitic 1400-1530 C
• Ferritic 1400-1530 C
• Austenitic 1370-1450 C

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Look at Each Grade Its Weldability
Austenitic
Super Austenitic
Nitrogen Strengthened Austenitic
Martensitic
Ferritic
Super Ferritic
Precipitation Hardened
Duplex
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• 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.
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AWS Welding Handbook
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AWS Welding Handbook
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Pseudobinary Phase Diagram _at_ 70 Iron
AWS Welding Handbook