摘要
针对柳钢生产HRB500E钢筋时出现屈服强度R_(eL)、塑性指标A_(gt)分别低至440 MPa、5.0%的性能异常现象,通过对拉伸试样进行断口形貌、拉伸曲线、化学成分及金相组织分析,对工艺执行及取样过程进行排查,对其产生原因进行了分析。结果表明:HRB500E钢筋性能异常为残余元素B含量异常偏高而导致,当B质量分数达(27~48)×10^(-6)时,Nb.V.N复合微合金化HRB500E钢筋中的贝氏体含量明显增加,拉伸试样无屈服效应,屈服强度大幅下降,塑性指标A_(gt)波动大。为此,调整了高硼坯料控轧控冷工艺,采用900℃入K_(2)轧机及920℃上冷床的工艺优化措施,亦即采用轧制过程及轧后冷却强度逐步加强的措施,可以降低B元素高淬透性的影响、抑制贝氏体的生成,使高B钢筋的组织和性能恢复至正常。同时,对合金及入炉废钢从源头上加强管控,制定残余元素含量上限的预警标准,可以极大减少残余元素控制异常或由此引发的钢筋性能波动。
In view of the abnormal performance,such as the yield strength R_(eL) and plasticity index A_(gt) are as low as 440 MPa and 5.0%respectively,of HRB500E reinforced bar produced by Liusteel,the process execution and sampling process were checked,and its causes were analyzed by analyzing the fracture morphology,tensile curve,chemical compositions and microstructure of the tensile sample.The results show that the abnormal performance of HRB500E reinforced bar is caused by the abnormal high residual element B content.When the mass fraction of B reaches(27-48)×10^(-6),the bainite content in Nb-V-N composite microalloyed HRB500E reinforce bar increases significantly,and there is no yield effect in the tensile test,the yield strength decreases significantly as well as the plastic index A_(gt) fluctuates greatly.Therefore,by adjusting the controlled rolling and cooling process of high boron billet,adopting the process optimization measures of biting temperature of 900℃into K_(2) rolling mill and 920℃on cooling bed,that is,the measures to gradually strengthen the cooling intensity during the rolling process and after rolling can reduce the influence of B element on high hardenability,inhibit the formation of bainite,and the microstructure and properties of high B reinforced bar can be restored to normal.At the same time,the control of alloys and charge scrap from the source is strengthened,and the early warning standard for the upper limit of the residual element content is formulated,which can greatly reduce the abnormal control of the residual elements or the fluctuation of reinforcement performance caused by it.
作者
钱学海
何维
温小园
QIAN Xuehai;HE Wei;WEN Xiaoyuan(Technique Center,Guangxi Iron and Steel Group Co.,Ltd.,Liuzhou 545002,China)
出处
《轧钢》
2022年第2期108-112,123,共6页
Steel Rolling
基金
广西创新驱动发展专项资金项目(桂科AA18242013)。
关键词
HRB500E钢筋
无屈服平台
性能异常
化学成分
B元素
贝氏体含量
工艺优化
HRB500E reinforced bar
without yield platform
abnormal property
chemical composition
element B
bainite content
process optimization
