Stainless

These are high alloyed steels possessing unusual resistance to attack by corrosive media and atmospheric and elevated temperatures and cover a wide range of Mechanical and Physical properties for particular applications.

Stainless Steel is another corrosion-resistant steel containing 18% chromium and 8% nickel and called 18-8 or stainless steel. It is one of a group of austenitic stainless steels which contain from 16 - 26% chromium, 6 - 22 % Nickel & 1 % silicon and 2% Manganese.

This type of stainless steel are essentially non-magnetic and are hardenable only by cold working. They are highly corrosion resistant. These steels may be polished to a mirror finish and combine attractive appearance with good corrosion resistance. However, they are expensive. The carbon content is usually less than 0.10 %. Small amount of titanium or columbium may also be added.

Properties of 18-8 are good when cold worked.

When water quenched, properties are

1) Tensile:  90,000 psi

2) Yield: 38,000 psi

3) Elongation in 2": 68%

When cold rolled 15%, these properties become

1) Tensile : 140,000 psi

2) Yield: 117,000 psi

3) Elongation in 2" : 11%

These Austenitic stainless steels are fairly easily fabricated and welded and have high strength, excellent appearance , corrosion resistant and high modules of elasticity.

Ferrite Stainless steel contain from 11-27% chromium and are always low carbon steels. The carbon content is about 0.1% but can run as high as 0.35%. Good corrosion resistance are used in application not requiring high strength. Automotive trim and even jewellery are sometimes made of ferrite stainless steels. These steels are soft because of low carbon content. It is used where environment is strongly oxidizing. They contain no nickel.

Martensite Stainless steel: It can be high carbon steels with less chromium and nickel. Carbon content as low as 0.15% or high as 1.2%. Chromium will vary from 4 - 18%. Most of this steel do not have any nickel but a few may have upto 2% nickel. These steels can hardened by heat treatment. It is suitable environments such as atmosphere, fresh water, steam and weak acids. They have hardness upto to 65 HRC. This property, plus their corrosion resistance makes them ideal for knives and other cutlery. High hardness prevent them from very machinable. They are magnetic and not easily welded.

An alloy steel containing 0.5% carbon, 7 - 10% chromium and 1 - 3.75% silicon is known as silchrome. It is used in Internal Combustion Engine valves since it is resistant to hot exhaust gases and maintains its strengths at dull red heats.