Cast Structure Evolution in Pulsed Mode Electroslag Remelting

The results of a study on the characteristics of cast metal structure evolution in pulsed mode electroslag remelting (ESR) with layer-by-layer ingot formation are presented. Experiments were carried out on ingots of 85–220 mm diameter from carbon steels (S235JR, C22E) and a Fe–Ni–Co alloy (54Fe–29Ni–17Co). Remelting was performed in a chamber-type electroslag furnace in an argon atmosphere. Experiments were conducted under various conditions of the layer-by-layer ingot formation process. The resulting ingots were cut along their axis to study solidification patterns. It has been established that conducting ESR in a pulsed mode makes it possible to control the metal structure and produce ingots with a structure significantly finer than that obtained by conventional ESR. It is shown that during layer-by-layer formation, columnar crystals are localized within individual layers of metal and do not cross the boundaries between the deposited layers. A nearly linear relationship between the size of cast grains and the height of the deposited layer has been determined. The optimal structural refinement is achieved when the height of a single layer is maintained within the range of (0.1–0.5) × ingot diameter. For defect-free interlayer bonding the duration of melting pauses must be such that no more than 75–95% of the volume of the molten pool solidifies before the next portion is remelted. The study proposes principles for controlling cast structure in pulsed mode ESR, providing guidelines for producing ingots up to 220 mm in diameter with enhanced homogeneity.