Stainless steel - Edwards @ Wiki

1 Types and properties of stainless steel

1.1 Basic knowledge of stainless steel
1.1.1 Stainless steel overview

• Example of stainless steel
  • SUS304: Addition Cr 18 [\%] + Ni 8 [\%]
  • SUS430: Addition Cr 18
  • SUS410: Addition Cr 13
    Note: SUS: Steel special Use Stainless

1.1.2 Improvement of steel properties accompanying addition of Cr and Ni

• Improvement of steel performance with Cr addition
  • Almost eliminating corrosion by adding Cr 10 [\%] or more
  • Chromium oxide is formed against contact with the atmosphere, and a passive film is formed.
  • Corrosion against passive film breakage accompanying chemical reaction.

• Improvement of steel performance with Ni addition
  The addition of Ni is extremely expensive
  Addition
  • High temperature strength
  • Low temperature toughness
  • Good processing characteristics
  • Good weld characteristics

• Magnetism
  • Cr steel + Ni 8 [\%]: Nonmagnetic

1.1.3 Classification of stainless steel

• Stainless steel general classification
  
  
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1.1.3.1 Martensitic stainless steel

• Representative example: SUS 410: Fe + Cr:13 [\%]
  Note: Martens: Adolf Martens .de

• Characteristic
  • Increases to hardening and brittleness to high temperatures,
  • Proper tempering increases strength and toughness.
  • Difficulty in welding
  • Multiple fusion weld cracks

• Measures against fusion welding cracks
  • Prevention by preheating: generally 200 to 400 [^{\circ}C]
  • Countermeasures by post heat treatment process: 700 to 760 [^ {\circ}C]
    Note: PWHT(in JP): Post Weld Heat Treatment

• Example of use
  • Turbine blade
  • valve
  • shaft

1.1.3.2 Ferritic stainless steel

• Magnetism & nikkel
  • Representative example: SUS 430: Fe + Cr:18 [\%]
    Note: EX: Ferrite is an organization of iron(Fe) below 911 [^{\circ}C]
              steel structure
              

• Characteristic
  • High Cr content
  • High corrosion resistance
  • High processing characteristics, Molding processing dominates
  • Easy welding

• Example of use
  • Building interior and exteriors
  • Kitchen appliance
  • Vehicles
  • Household goods

• Notes on heating / cooling transition
  • steel weakness to 475 [^{\circ} C] accompanying slow cooling
    Long time heating: 450 to 500 [^{\circ} C]
  • \sigma Brittleness
    Long time heating: 600 to 800 [^{\circ} C] Steel compound between Fe & Cr
  • Embrittlement characteristics due to high temperature
    900 to 1000 [^{\ circ}C] Coarse crystal grains against high temperature
  • Countermeasures by preheating treatment with 100 to 200 [^{\circ}C]

1.1.3.3 Austenitic stainless steel

• Representative example: SUS 304: Fe + Cr:13 + Ni:8 [\%]
  Note: Roberts-Austen .de

• Characteristic
  • Good ductility
  • Good molding process
  • Good low temperature toughness
  • High temperature strength at 600 [^ {circ} C] or higher is good
  • Sporadic occurrence of cracks on welded joints accompanying fixation
  • Omit preheating
    As the cooling time increases due to preheating,
    precipitation of chromium carbide is promoted and corrosion resistance deteriorates

• Example of use
  • Architecture
  • Chemical Plant
  • Vehicles
  • Household goods

1.1.3.4 Austenitic ferritic stainless steel(2 phase stainless steel)

• Steel structure
  • Mixed ferritic and austenitic stainless steels

• Representative example
  • SUS 329J1: Fe + Cr: 25 + Ni: 4.5 + Mo: 2 [\%]
  • SUS 329J3L: Fe + Cr: 22 + Ni: 5 + Mo: 3 + C: low [\%]
  • SUS 329J4L: Fe + Cr: 25 + Ni: 6 + Mo: 3 + N + C: low [\%]

• Characteristic
  • High seawater corrosion resistance due to high Cr content
  • High Strength

• Example of use
  • Chemical Plant
  • Seawater heat exchanger

1.1.3.5 Precipitation hardening type stainless steel

• Steel structure
  • Produced by precipitation hardening heat treatment
    based on martensite phase and austenite phase

• Representative example
  • SUS 630: Fe + Cr: 17 + Ni: 4 + Cu: 4 + Cu & Nb: Addition [\%]
  • SUS 631: Fe + Cr: 17 + Ni: 7 + Cu: 4 + : Addition Al [\%]

• Precipitation hardening element
  Increase in strength by precipitation hardening heat treatment
  accompanied alone or mixed addition
  • Cu
  • Nb
  • Ti

• Characteristic
  • Hardness increases by heat treatment
  • Hardness is inferior to austenitic stainless steel
  • Concomitant property
    • Corrosion resistance and good processing characteristics in austenitic stainless steel
    • High strength in martensitic stainless steel