31 Jan Steels For Quenching and Tempering
Quenched and tempered steels are alloyed or non alloyed steels of which chemical compositions are convenient for hardening especially due to their high carbon content (0,25-0,60 C %) and displays high strenght and toughness at a certain drawing resistance.
The steels in this group gain high strenght and toughness by the application of both quenching and tempering operations. Hardening of steel is achieved by quenching it in a convenient media after heating above the austenitic transformation temperature and holding for the transformation of microstructure to austenite. Main purpose of quenching is to obtain a complete martensitic structure by using minimum cooling speed. Martensitic structure obtained after quenching is so brittle for many applications. To remove the brittleness and residual stresses, material is subjected to tempering for providing a good toughness. Tempering is; heating the steel piece below the temperature A1 and holding it for a sufficient time. To obtain the required microstructure and mechanical properties, austenitizing temperature, cooling speed, tempering time and temperature must be appropriate.
Due to their superior mechanical properties, quenched and tempered steels are used in a wide range of applications such as production of various machine and engine parts, forging parts, various bolts, nuts and pin screws, crank shaft, axles, command and drive parts, piston arms, various shafts and gears.