Macro- and Microstructure Evolution of 5CrNiMo Steel Ingots during Electroslag Remelting Process

Abstract

Acomprehensive mathematical model was established and used to simulate the macroG and microstructure evolution during the production process of 5CrNiMo steel ingot by electroslag remelting (ESR) method. Along the ingot height, the macrostructure distribution characteristics changed from vertical, fine columnar grains to tilted, coarse columnar grains, and this transformation process occurred at the very beginning of ESR. In the cross section of the ingot, there were three grain morphology regions and two grain type transition regions from the outside to the center of the ingot. These regions were the fine columnar grain region, columnar competitive growth transition region, coarse columnar grain region, columnar to equiaxed grain transition (CET) region, and coarse equiaxed grain region. The influence of the remelting rate on the macrostructure and microstructure was investigated using a series of experiments and simulations. The results showed that a low remelting rate could produce a smal grain growth anG gle (GGA); the average secondary dendrite arm spacing (SDAS) firstly decreased and then increased as the remeltG ing rate increased. An excessively high or low remelting rate can increase the GGA and averageSDAS in ingots. Thus, the remelting rate should be controled within a suitable range to reduce composition microsegregation and miG croshrinkage in the ingot to produce anESR ingot with satisfactory hot forging performance.