Application of electrical contact heating in grain refining of ultra-pure 42CrMoVNb steel

In this paper the electrical contact heating (ECH) technology was applied to refine the austenitic grain size of medium carbon alloy steel. The ECH equipment was designed to reach uniform heating of uniform heat transfer in the sample. After the heat treatment of the ultra-pure 42CrMoVNb steel using the ECH equipment, a uniform ultrafine microstructure with an average austenite grain size of 1.4 μm was obtained. The mechanical properties of the ultrafine 42CrMoVNb steel were also studied. A high strength (1538 MPa) and high impact toughness (81 J/cm2) was obtained for the ultrafine 42CrMoVNb steel. For the same austenitic grain size, the strength and toughness of the steel subjected to the ECH treatment were improved compared to the steel subjected to a cyclic salt bath quenching treatment.