Ferrous Materials and Non-Ferrous Metals and Alloys 1 introduction

(2) Martensitic stainless steel:

 These steels contain 12–18% chromium and 0.1 to 1.8%

carbon. These steels can be hardened by heat treatment but their corrosion resistance

is decreased. Steels with 12 to 14% chromium and 0.3% carbon are widely used for

table cutlery, tools and equipment. Steel with little less carbon percentage and higher

percentage of chromium are used as springs, ball bearings and instruments under

high temperature and corrective conditions.

(3) Austentic stainless steels:

 These are the most costliest among all stainless steels. In

these steels besides chromium, nickel is also added. Nickel is a very strong austenitic

stabilizer and therefore the microstructure of these steels is austentic at room

temperature. These steels contain 12 to 21% chromium and 8 to 15% nickel and carbon

less than 0.2%. The most familiar alloy of this group is known as 18:8 stainless steel

i.e. 18% chromium and 8% nickel plus other. Other elements like carbon, manganese

and silicon in very small quantities.

2.8 TOOL STEELS

Tool steels are specially alloyed steels designed for high strength, impact toughness and

wear resistance at room and elevated temperatures. They are normally used in forming

and machining of metals. So the requirements in a tool steel are that it should be capable

of becoming very hard and further that it should be able to retain its hardness at high

temperatures normally developed during cutting of materials. This property is known

as “red hardness”. Further, tool steel should not be brittle for smooth working.