Abstract: The hydrogen content of the steel to free flake is an important basic datum to make heat treatment of the large forging. The flake sensitivity of Cr-Mo cold roll steel with middle-high carbon contents were studied by means of slow tensile of specimens with various hydrogen contents. The results of experiments show that the hydrogen contents of 70Cr3Mo steel and 9Cr2Mo steel to free flake are limited to 2.7ppm and 2.7ppm repectively.

Key words: 白点, 冷轧辊钢, 慢拉伸试验