Comparing fast inductive tempering and conventional tempering: Effects on microstructure and mechanical properties

Abstract

Induction heating processes are of rising interest within the heat treating industry. Using inductive tempering, a lot of production time can be saved compared to a conventional tempering treatment. However, it is not completely understood how fast inductive processes influence the quenched and tempered microstructure and the corresponding mechanical properties. The aim of this work is to highlight differences between inductive and conventional tempering processes and to suggest a possible processing route which results in optimized microstructures, as well as desirable mechanical properties. Therefore, the present work evaluates the influencing factors of high heating rates to tempering temperatures on the microstructure as well as hardness and Charpy impact energy. To this end, after quenching a 50CrMo4 steel three different induction tempering processes are carried out and the resulting properties are subsequently compared to a conventional tempering process. The results indicate that notch impact energy raises with increasing heating rates to tempering when realizing the same hardness of the samples. The positive effect of high heating rate on toughness is traced back to smaller carbide sizes, as well as smaller carbide spacing and more uniform carbide distribution over the sample.

Effects of Rapid Induction Heating on Transformations in 0.6% C Steels

“…It is anticipated that the higher heating rates would reduce the austenite grain size, but this needs to be verified. The higher heating rates have been shown to reduce the size of the cementite precipitates observed during induction tempering [10]. With the smaller cementite precipitate size, it is anticipated that the cementite would dissolve more readily in the austenite during rapid heating and lead to lower Ms temperatures.…”

Localized heat treatment to improve the formability of steel pipes for hydraulic applications: process design and mechanical characterization

“…Several studies demonstrated how microstructure and mechanical properties can be significantly modified by induction heat treatments applied to a wide range of iron-based materials and applications. Different research papers investigated the influence of operating parameters on the mechanical properties, with the focus on bulk materials [5][6][7], superficial aspects [8,9] and welded parts [10,11]. Guo et al [12] showed how the combination of the induction heat and surface peening treatments improved the yield strength without significantly impacting the ductility of pure iron.…”

Localized Heat Treatment to Improve the Formability of Steel Pipes for Hydraulic Applications: Process Design and Mechanical Characterization

“…Several studies demonstrated how microstructure and mechanical properties can be significantly modified by induction heat treatments applied to a wide range of iron-based materials and applications. Different research papers investigated the influence of operating parameters on the mechanical properties, with the focus on bulk materials [5][6][7], superficial aspects [8,9] and welded parts [10,11]. Guo et al [12] showed how the combination of the induction heat and surface peening treatments improved the yield strength without significantly impacting the ductility of pure iron.…”