连铸方坯免加热直接轧制技术的研究与应用

Research and application of direct rolling of free-heating technology of continuous casting billet

连铸方坯免加热直接轧制技术由于坯料不经过加热炉加热,故比传统的经加热炉加热轧制生产工艺节能减排且降低成本。但由于直轧开轧温度低于常规轧制温度,轧件的变形抗力会有所增加,轧制力也增加,最终使棒线区粗、中轧机组电机超负荷运行,影响设备使用寿命;同时,由于直轧坯料头、中、尾温度相差较大(最大温差可达100℃),不利于棒线区轧制工艺以及成品负偏差率、力学性能以及金相组织的稳定;再有,连铸区流与流之间拉速相差较大,导致不同铸坯之间温度相差较大,不利于棒线区轧制工艺的稳定。针对以上问题,介绍了棒线材免加热直接轧制的关键技术,即在连铸区提高拉坯速度,优化连铸出坯节奏(阶梯出坯)、优化二冷区水量;在棒线区增设温度不合坯料剔除程序,优化无间隔轧制技术,优化粗、中轧压下量,采用预穿水分段控冷等措施,保证了直轧工艺的顺利进行,实现了批量生产。

Since billet is not heated by the heating furnace,the technology of direct rolling of free-heating of continuous casting billet is more conducive to energy saving and emission reduction as well as cost reduction than the traditional heating furnace rolling production process.However,because the direct rolling temperature is lower than the conventional rolling temperature,the deformation resistance of the rolled piece will increase,and the rolling force will also increase,eventually causing the motor of the roughing and intermediate rolling units in the rod and wire zone to overload and affecting the service life of the equipment.At the same time,large temperature difference occurs among the head,middle and tail parts of the direct rolling billet(the maximum temperature difference reached 100℃),which is not conducive to the stability of the negative deviation rolling,mechanical properties and microstructure of products.Moreover,the casting speed difference between flows in the continuous casting zone is large,leading to a large temperature difference between different billets,which is not conducive to the stability of the rolling process in the rod and wire zone.In view of the above problems,the key technologies of direct rolling of free-heating for rod and wire were introduced,for example,accelerating the casting speed,optimizing the continuous casting and ejection rhythm(stepped ejection),and optimizing the water volume of secondary cooling zone in the continuous casting zone;adding billet removal procedure for billets with temperature difference,optimizing the non-spaced rolling technology,and optimizing theroughing and intermediate rolling reduction,adopting pre-piercing moisture section and controlled cooling measures in the rod and wire zone.The smooth progress of direct rolling process was ensured and the batch production was realized.