低温钢筋穿水冷却工艺

 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。

Water cooling process for cryogenic rebars

According to the characteristics of water cooling process of cryogenic rebars， convective heat transfer coefficients of cryogenic rebar with different sizes were achieved by means of measured data and theoretical analysis. Based on the industrial trial results， the water cooling process of cryogenic rebar was investigated using MSC. marc finite element software. The effect of parameters， such as water flow， finishing rolling temperature， water cooling time on temperature field and microstructure transformation of cryogenic rebar were studied. The results show that when the cooling water flow is 120 m3/h， pearlitic transformation doesn’t occur in the center of steel rebar； when the cooling water flow is 400 m3/h， there is no ferrite transformation in the center of steel rebar； when the cooling water flow is 160-200 m3/h， the center of steel rebar has composite microstructure consisting of acicular ferrite and bainite. When the finishing rolling temperature rises by about 50 ℃， the surface temperature of steel rebar rises by about 10 ℃ and self-tempering temperature of steel rebar rises by about 30 ℃. When cooling water flow is 200 m3/h and cooling time is 1.2 s， the microstructure of steel rebar consists of acicular ferrite and fine bainite in the 1 050 ℃ finishing rolling. Under the condition of same water pressure and water flow， with the increase of finishing rolling velocity， the hardening layer depth decreases， and self-tempering temperature increases.