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根据低温钢筋穿水冷却工艺特点,利用现场实测数据并结合理论分析得到不同规格低温钢筋穿水冷却过程中的对流换热系数。采用MSC Marc有限元软件与现场试制结果对低温钢筋穿水冷却过程进行了研究。研究了冷却水流量、终轧温度、穿水时间等工艺参数对低温钢筋温度场和组织演变的影响。模拟结果表明:当冷却水流量为120 m3/h时,钢筋芯部开始有珠光体转变;当冷却水流量为400 m3/h时,钢筋芯部无铁素体转变;冷却水流量为160~200 m3/h时,所获得的组织为针状铁素体与贝氏体。终轧温度增加50℃,出水冷装置后钢筋表面温度约增加10℃,返红温度约增加30℃;在200 m3/h水流量下冷却1.2 s,终轧温度为1 050℃时,其芯部组织为针状铁素体与细小的贝氏体。在相同水压与水流量条件下,随着穿水速度的增加,淬透层深度减小,返红温度增加。
According to the characteristics of low temperature steel penetration water cooling process, the convective heat transfer coefficient of different specifications of low temperature steel bars through water cooling process is obtained by field measured data and theoretical analysis. MSC Marc finite element software and on-site trial results were used to study the cooling process of low temperature steel bars. The effects of cooling water flow rate, finishing temperature and water penetration time on the temperature field and microstructure evolution of low temperature steel bars were studied. The simulation results show that when the flow rate of cooling water is 120 m3 / h, the core of the rebar starts to undergo pearlite transformation. When the flow rate of cooling water is 400 m3 / h, the core of the rebar has no ferrite transformation and the cooling water flow rate is 160 ~ 200 m3 / h, the obtained microstructure is acicular ferrite and bainite. The finishing temperature increases by 50 ℃, the surface temperature of steel increases about 10 ℃ and the temperature of red return increases by about 30 ℃ after cooling water is discharged. When the temperature is 200 ℃ / h, the cooling time is 1.2 s and the finishing temperature is 1 050 ℃. Department organized acicular ferrite and fine bainite. With the same water pressure and water flow rate, with the increase of water penetration velocity, the depth of hardened layer decreases and the temperature of red return increases.