Source and control of large-size inclusions in 42CrMo steel
YIN Chuan-lei1,2, ZHAI Wan-li1,2, JANG Dong-chu3, HUI Zeng-jie4, MA Qing-feng3, ZHANG Yi-min3
1. Technology Center, Huaigang Special Steel Co., Ltd., Jiangsu Shagang Group, Huai'an 223002,Jiangsu, China; 2. Key Laboratory of Special Steel New Materials for Rail Traffic of Jiangsu Province, Huai'an 223002, Jiangsu, China; 3. Steelmaking Works, Huaigang Special Steel Co., Ltd., Jiangsu Shagang Group, Huai'an 223002, Jiangsu, China; 4. School of Materials and Engineering, Jiangsu University of Technology, Changzhou 213001, Jiangsu, China
Abstract：For the problem of low pass rate of ultrasonic flaw detection of 42CrMo bonded steel rolling materials, the unqualified sample for flaw detection was analyzed by SEM, etc. It was found that there were spherical inclusions with a diameter of about 100 μm or long bar inclusions with a size of about 1 000 μm in the unqualified samples. By comparing and analyzing the composition of small particle inclusions, subsidiary materials and the refractory materials, it was believed that large-size inclusions came from caused by exogenous inclusions entering in molten steel, which eventually resulted in the low pass rate of flaw detection of rolled products. By increasing the amount of calcium silicate wire, avoiding the slag of the ladle in casting process, using high quality submerged nozzle with erosion rate less than 1.5 mm/h, controlling the mold liquid level fluctuation no more than ±3 mm and applying constant casting speed, etc, it can effectively reduce large inclusions in steel, improve the cleanliness of molten steel, and increase the qualified rate of flaw detection to above 97.5%.
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2021, Vol. 31 
