Abstract
The effects of cold-rolling on strength and toughness at 4K were investigated for a high manganese steel, 32Mn-7Cr steel. The yield strength at 4K was 1118MPa for the unrolled steel and was increased to 1379MPa and 1786MPa for the 20 and 40% cold-rolled steels, respectively. However, the elongation and the reduction of area were decreased with an increase in reduction ratio. Especially, the elongation was significantly decreased. The Charpy absorbed energy and the fracture toughness were also decreased markedly. The decrease in toughness by cold-rolling was due to the formation of subcrack and "flat brittle facet" in the fractured surface. The subcrack was caused by intergranular failure, and the flat brittle facet is believed to be produced mainly by intergranular failure and partly by twin boundary failure.
