Table of Contents
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What is Stainless Steel , Properties of Stainless Steel ? Types of Stainless Steel ?
What is Stainless Steel ?
A steel with a minimum chromium content of 10.5% or more, and a maximum carbon content of less than 1.20%
Properties of Stainless Steel ?
- Stainless steel has excellent resistant to corrosion.
- Stainless steel becomes corrosion resistant because of formation of un-reactive chromium oxide (Cr203) film which adheres tightly to the surface of metal. this film acts as a barrier protecting metal against corrosion.
- There are different types of SS used in industries.
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Types of Stainless Steel ?
- Austenitic Stainless Steel
- Ferritic Stainless Steel
- Martensitic Stainless Steel
- Precipitation Hardened Stainless Steel
- Duplex / Super Duplex Stainless Steel
1. Austenitic Stainless Steel
- Alloy of Cr, Ni, Fe
- Non-Magnetic
- High Corrosion resistance at temperature up to 1500F
- Hardened by cold working
- Face Centered Cubic – FCC ( Fine grain structure)
- Process high impact strength at low temperature – Ex: Type 304, 304L, 316, 316L
- Widely used in process industry, cookware and a variety of industrial application.
2. Ferritic Stainless Steel :
- Alloy of Cr, Fe
- Magnetic
- Non Harden-able by heat treatment
- Body Centered Cubic – BCC (coarse grain structure)
- Contains high carbon , therefore brittle and relatively poor corrosion resistance
- Has resistance to chloride stress corrosion cracking
- Ex: Type 409, 430, 439
- for marine application, petrochemical, automotive exhaust system, heat exchanger, furnaces.
3. Martensitic Stainless Steel :
- High hardness (carbon added to the alloy)
- Poor Corrosion Resistance
- Heat treatable to high hardness level
- Crystallographic form-distorted structure type 410, 420
- Used extensively in cutlery , Sport knives and multi-purpose tools.
4. Precipitation Hardened Stainless Steel :
- Magnetic
- Heat treatment to high strength
- Very high strength to weight ratio
- Weldable and corrosion resistance similar to type 304
- Ex : 17-7PH, 17-4PH
- Used in making aerospace components, spring etc.
Read this..What is Alloy Steel
5. Duplex Stainless Steel :
- Contain both Austenite and ferrite in microstructure.
- Offer benefits of both Austenite and ferrite stainless steel
- Good resistance to pitting and crevice corrosion
- High strength and high resistance to stress corrosion cracking
- Ex- UNS S32205, S31803, S32760
- Used in sea water system, heat exchanger, structural application etc.
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