Stainless Steel Flashcards
Why was stainless steel developed?
Excellent corrosion resistance and improved mechanical properties
What is the protective layer in stainless steel called and what is it made of?
Passive layer made of at least 11.5% Chromium
What are the 5 categories of stainless steel?
1) Ferritic
2) Martensitic
3) Austenitic
4) Precipitation hardening
5) Duplex
Describe Ferritic stainless steel
- Classified under the 405, 409, 430, 446 series
- Made of 12-30% Cr, less than 0.2% C
- non-heat treatable but can be cold worked
-low strength with poor ductility, weldability, and notch toughness
-applied in automotive trim, heat exchanger tubes, and furnace combustion chambers
-ferrite microstructure
-good corrosion resistance and immunity to stress cracking
Describe Martensitic stainless steel.
- classified under the 403, 410, 440 series
- made of 12-17% Cr, and up to 1.1% C
- heat treatable
- good toughness, strength, and corrosion resistance
- used in valves, surgical tools, cutlery, nuts and bolts, and vessel lining
Describe Austenitic stainless steel
- classified under 304, 316, 316L, 321, and 347 series
- made of 16-25% Cr, 7-20% Ni, and less than 0.8% C
- non-heat treatable
- susceptible to intergranular corrosion at 435-815 deg Celcius
- a weld can be heat treated to dissolve carbides and cool fast to lower Carbon content
- not ferromagnetic
- used in bolts and rivets, cutlery, food processing, and chemical process equipment
Describe Precipitation Hardening stainless steels
- made of various percentages of Cr, C, Ni, Al, Cu, Ti, or Mo
- low toughness compared to other stainless steels
- used in gears, valves, high strength shafts, and turbines
Describe duplex stainless steel
- classified under 2205, and Ferrilium 225
- made of 21-23% Cr, 4.5-6.6% Ni, 2.5-3.5% Mo, and 0-0.03% C
- combines the properties of austenitic and ferritic stainless steel
- good against pitting
- used in heat exchanger tubes
What types of stainless steels are magnetic?
1) Ferritic
2) Martensitic
Which types of stainless steels are heat-treatable?
1) Martensitic
2) Precipitation hardening
