700 MPa热轧板强度不合格原因分析与控制  

CAUSE ANALYSIS AND CONTROL OF UNQUALIFIED 700 MPa HOT ROLLED PLATE

作　　者：杨慧贤 Yang Huixian(HBIS Materials Technology Research Institute,Shijiazhuang 050023,Hebei)

机构地区：[1]河钢材料技术研究院,河北石家庄050023

出　　处：《河北冶金》2024年第6期64-69,共6页Hebei Metallurgy

摘　　要：针对700 MPa级别的高强汽车大梁钢,在其他生产工艺方案相同的情况下,采用Ti微合金化和Nb-Ti复合微合金化两种不同的成分方案,产品的屈服强度相差较大的问题,通过金相显微镜、扫描电镜、透射电镜对汽车大梁钢的金相组织、析出物形貌、析出物成分等进行分析研究,探讨了屈服强度相差大的原因,并提出了相应的工艺控制措施。结果表明:Ti微合金化汽车大梁钢屈服强度低的主要原因是Ti含量较高,TiN、TiC析出相尺寸粗大,恶化钢材性能。加热温度和卷取温度控制不合理,导致Ti析出和铁素体晶粒细化不能很好结合,使得TiN、TiC的析出强化、细晶细化和相变强化作用未充分发挥。Nb-Ti复合微合金化汽车大梁钢轧制过程中形成复合的纳米级析出物(Nb,Ti)C,抑制晶界的长大,阻止奥氏体晶粒长大和粗化,起到细化晶粒的作用,有效改善钢材的性能。为此,在实际生产中,均热温度应控制在1210~1230℃,卷取温度控制在600~620℃,Ti含量应控制在0.05%~0.10%,有效阻止晶粒长大粗化,保证产品的力学性能。For 700 MPa high strength automobile beam steel,in the case of the same production process,the yield strength of the product is very different with two different composition schemes of Ti microalloying and Nb-Ti composite microalloying.The metallographic structure,morphology and composition of precipitates of automobile beam steel were analyzed by metallographic microscope,scanning electron microscope and transmission electron microscope.The reason of the difference in yield strength was discussed,and the corresponding process control measures were put forward.The results show that the main reasons for the low yield strength of Ti microalloyed automobile beam steel are the high Ti content,the coarse size of TiN and TiC precipitates,and the deterioration of steel properties.The unreasonable control of heating temperature and coiling temperature leads to the failure of Ti precipitation and ferrite grain refinement,and the effects of TiN and TiC precipitation enhancement,fine crystal refinement and phase transformation enhancement are not fully played.In the rolling process of NB-Ti composite microalloyed automobile large beam steel,the composite nanoscale precipitates(Nb,Ti)C are formed,which inhibits the growth of grain boundaries,prevents austenite grain growth and coarsening,plays the role of refining grains,and effectively improves the performance of steel.Therefore,in the actual production,the soaking temperature should be controlled at 1210~1230℃,the coiling temperature should be controlled at 600~620℃,and the Ti content should be controlled at 0.05%~0.10%,which effectively prevents the grain growth and coarsening and ensures the mechanical properties of the product.

关 键 词：析出物 屈服强度 汽车大梁钢 微合金化 加热温度 

分 类 号：TG142.1[一般工业技术—材料科学与工程]