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针对国内某钢厂大断面轴承钢棒材连铸连轧后(棒材直径≥60 mm)先共析碳化物网状等级超标问题,通过对前期的研究工作进行归纳总结,在保证连铸连轧的基础上设置新型水冷系统并进行超快速冷却工业化试验,检验冷却到室温后棒材微观组织性能和先共析碳化物网状等级。试验结果表明:通过高温终轧后设定合理的超快速冷却工艺参数可以显著提高棒材表层以及芯部的冷却速率,抑制强碳化物形成元素的晶界处偏析。超快冷后棒材的室温微观组织均为片层珠光体。晶界处先共析碳化物的网状析出得到消除,仅在棒材芯部有少量碳化物呈弥散分布,碳化物网状等级符合行业标准。
Aiming at the problem of excessive eutectoid carbide mesh grade after the continuous casting and rolling of a large section bearing steel bar of a domestic steel mill (bar diameter ≥60 mm), the author summarizes the previous research work, On the basis of rolling and rolling, a new type of water cooling system is set up and the industrialization test of ultra-fast cooling is conducted. The microstructure and properties of the first eutectoid carbide network after cooling to room temperature are examined. The experimental results show that the cooling rate of the bar surface and the core can be significantly increased by setting reasonable super-rapid cooling process parameters after high-temperature finish rolling, and segregation at the grain boundaries of the carbide-forming elements is inhibited. The microstructure of ultra-fast cold bar at room temperature is lamellar pearlite. At the grain boundary, the proeutectoid carbides are eliminated in the form of mesh, and only a small amount of carbides are dispersed in the core of the bar. The carbide mesh grade conforms to the industry standard.