AISI 300 series properties

This family of stainless accounts for the widest usage of all the stainless steels. These materials are nonmagnetic, have face-centered cubic structures, and possess mechanical properties similar to the mild steels, but with better formability. The AISI designation system identified the most common of these alloys with numbers beginning with 300 and resulted in the term 300 series stainless. Table 3 lists the chemical analyses of some standard austenitic stainless steels and compares them to a few materials from other families of materials. 

Martensitic chromium steels (AISI 400 series) contain no (or very little) nickel, and the chromium content is typically about 12%. These steels can undergo the a-Fe/7-Fe transition at about 1050 °C and so can be heat-treated for improved mechanical properties, much as can ordinary carbon steels. Since they have the a-Fe structure at ambient temperatures, they are ferromagnetic in ordinary service. Examples are type 410 (11.5-13.5% Cr), which is used for turbine blades, and type 416 (12-14% Cr with minor amounts of Se, Mo or Zr), which has good machinability. 

Stainless Steel. Austenitic stainless steels of the AISI 300 series are well suited for low temperature service by their strength and impact resistance properties. They are easy to weld, have a low heat conductivity and require no stress relief. Partially offsetting these factors is their higher cost. The commonly-used analyses of stainless steel are available in thin wall piping schedules 5S and lOS as well as in the normal schedules. Thinner walls are allowable for stainless steel because it is not subject to corrosion. All of its thickness is available for strength. 

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