Other grades of stainless steel except the austenitic stainless steel

Except the normally used austenitic stainless steel, there're other grades of stainless steel used for the different usage.
For example, there's Duplex Stainless Steel (DSS), means the austenite and ferrite seperately takes 50% of the total
composition, and this kind of stainless steel has both the properties of the austenitic stainless steel and ferritic stainless
steel.





Meanwhile, there's ferritic stainless steel and martensitic stainless steel.  
The strength and the corrosion resistence is not so good for the ferritic stainless steel, and it is mainly used for the decoration parts.
But it has better thermal expansion and thermal conductivity, and it is not easily to be deformed when be heated.

The mechanical properties of the martensitic stainless steel can be adjusted per the heat treatment. 
The standard grades are: 403、410、414、416、416(Se)、420、431、440A、440B and 440C, and they are magnetic.
The martensitic stainless steel has high strength and good corrosion resistence, and it can be used to make the machine parts,
like turbine blade for the steam machine(1Cr13), Shaft and pull rod of steam equipment(2Cr13), and the spare parts applied in the
corrosion medium, like the relief valve, bolt (4Cr13), etc.  And the material with high C, like 4Cr13, 9Cr18 is suitable to 
manufacture the medical instruments, measuring appliances, knife, spring, etc.