The Effects of Heating Rates on the Tempering of 4140 Steel

Induction and furnace tempering can be used to achieve equivalent mechanical properties in quenched and tempered martensitic steels. Typically induction tempering takes place at higher temperatures for a short time while furnace tempering is conducted at lower temperatures for longer times.  The great difference between these two tempering process is heating rates. This paper presents the experimental results of controlled furnace and induction tempering heat treatments with particular attention to microstructure, mechanical properties for AISI 4140 steel. It was found that the size, morphology, and number density of carbides present determine the mechanical properties and are strongly influenced by the heating rates. These results have widespread impact in several industrial applications relying on both furnace and induction quench and temper processes.