Stainless Steels

Silverware is what we think of when discussing this metal because it does not rust, has luster, and does not stain thanks to the Cr (chromium content). We generally do not think of stainless steel in other ways. Stainless steel can be categorized as either:

• Ferritic Stainless Steel

• Austenitic Stainless Steel

• Martensitic Stainless Steel

These three categories can be grouped in to two-classes:

• Straight Chromium Alloys

• Chromium Nickel Alloys

The straight chromium alloys are numbered as 400-series and 500-series. These are the ferritic and martensitic stainless steels. 500-series stainless steels are martensitic. The 400-series stainless steels are both ferritic and martensitic (overlaps into the 400-series).

400-series stainless steels have a Cr content range of 10.5% to 30%.

500-series stainless steels have a low Cr content range of 4% to 6%.

Ferritic stainless steels have a notable property of good to excellent corrosion resistance when combined with heat such as automobile exhaust. This is weldable and has good mechanical properties.

Martensitic stainless steels are notable in steam turbines and mild corrosion resistance with increased toughness and other mechanical properties.

The most recognizable form of stainless steel is the 300-series or the Cr-Ni (Chromium Nickel Alloy). This the austenitic stainless steels and have Ni contents of >6% to over 24% and a Cr contents of 16% to 30%. Austenitic have excellent corrosion resistance but should not be exposed to temperatures above 800F.

A lesser known austenitic stainless is the 200-series with Cr content in the range of 16% to 19%. the second chief constituent element is Mn that substitutes for Ni.

<< Alloy Steels | Non-Ferrous Metals >>