31) Which one of the following is the purpose of tempering a hardened steel component ?

32) While normalizing the steel should be cooled

33) The process of increasing carbon percentage on the surface of Low-carbon steel is known as

34) The process of producing a component with tough and ductile core and a hard outer surface is known as

35) The process of heating steel to about 40 Degree Centigrade above the upper critical temperature and cooling it in still air to room temperature is known as