Formation mechanism and practical control of surface crack for 09CrCuSb steel billet
SHI Weining1, YE Mingzai1, XU Jiyou1, WANG Jun1, WANG Liu1, YUAN Yuan2
1. Steelmaking Plant, Xiangtan Iron & Steel Group Co., Ltd., Xiangtan 411101, Hunan, China; 2. Technology and Quality Department, Xiangtan Iron & Steel Group Co., Ltd., Xiangtan 411101, Hunan, China
Abstract：09CrCuSb steel is widely used in the manufacturing industry of economizer, heat exchanger and other equipment due to its excellent sulfuric acid dew point corrosion resistance. However, 09CrCuSb steel is prone to surface cracks during continuous casting, which seriously affects the yield, so it becomes an urgent problem to be solved. Through the analysis of metallographic microscope and scanning electron microscope, it was clear that the cause of crack defects under the original process parameters was the precipitation of Cu and proeutectoid ferrite on the grain boundary of the billet surface. By increasing the mold water flow rate from 2 166.67 L/min to 2 666.67 L/min, the mold electromagnetic stirring current from 400 A to 450 A, the specific water volume of the secondary cooling system from 1.10 L/kg to 1.20 L/kg, the casting speed from 2.5 m/min to 3.2 m/min, and applying the thermal insulation device within the range of in and out tension leveler, the precipitation of Cu and proeutectoid ferrite on the grain boundary of the billet surface layer is effectively inhibited. As a result, the excellent surface quality of the billet is obtained, and the qualified rate of magnetic particle flaw detection of rolled round steel is increased from 19.19% to 99.07%. The idea and development practice of 09CrCuSb steel billet crack control provide a new idea for the billet crack control of the same series of low carbon steel containing Cu.
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2023, Vol. 42 
