65号高碳钢小方坯重压下高拉速工艺应用

Application of high casting speed process under heavy reduction of No.65 high carbon steel billet

高拉速条件下生产高碳硬线钢的核心难点是铸坯内部质量控制问题,小方坯重压下技术可以改善其生产硬线钢的铸坯内部质量。为研究高拉速生产过程中高碳钢小方坯重压下的效果,广西钢铁集团有限公司对165 mm×165 mm断面小方坯65号硬线钢进行了单辊重压下研究。基于大量工程实践和模型计算的研究结果表明,单辊重压下的有效压下区间为中心固相率在0.40~0.79范围内,在合适的压下区间,单辊重压下可以同时改善中心疏松、中心缩孔和中心偏析;在中心固相率小于0.30的位置进行单辊重压下会导致压下裂纹和负偏析,同时对缩孔的改善效果也不佳,并且在凝固后压下,单辊15 mm的压下量并未产生理想的“焊合”缩孔效果;在有效的压下区间内执行单辊重压下,压下量越大,铸坯中心偏析、缩孔改善越明显,但压下量受设备能力限制;通过模型指导和生产实践,最终实现165 mm×165 mm断面高碳硬线钢2.5 m/min以上的稳定生产。

The core difficulty in achieving high casting speed in the production of high carbon hard wire steel is the internal quality control of casting billet.The heavy pressing technology of billet is a new technology that can improve the internal quality of hard wire steel produced by billet.In order to study the effect of heavy reduction for high carbon steel billet in the high casting speed production process,Guangxi Iron and Steel Group Co.,Ltd.conducted single roll heavy reduction study on No.65 hard wire steel with 165 mm×165 mm cross-section billet.The research results based on a large number of engineering practices and model calculations indicate that the effective reduction range under single roll heavy reduction is between 0.40 and 0.79 for the center solid phase fraction.In the appropriate reduction range,single roll heavy reduction can simultaneously improve center porosity,center shrinkage,and center segregation.Single roll heavy reduction at position with central solid phase fraction less than 0.30 can lead to cracking and negative segregation during reduction,and the improvement effect on shrinkage is also poor.Moreover,after solidification,no ideal effect of"welding"shrinkage is found with single roll reduction of 15 mm.Within the effective reduction range,single roll heavy reduction is carried out,as the reduction amount increasing,the improvement of center segregation and shrinkage of billet becomes more obvious,but the reduction amount is limited by equipment capacity.Through model guidance and production practice,ultimately achieving stable production of high carbon hard wire steel with a cross-sectional area of 165 mm×165 mm at least 2.5 m/min.