60kg汽车用热轧高扩孔钢生产与应用

Production and application of hot-rolled high hole-expansion steel(60 kg grade) for automobile

针对传统60 kg高强钢无法满足特殊用户使用要求的现状,宝钢采用低碳低硫的成分及特定的精炼方式,结合特殊的热轧工艺,开发出一种新型60 kg高扩孔钢。通过比较分析60 kg高扩孔钢和传统60 kg高强钢的化学成分、生产工艺、金相组织、力学性能,发现高扩孔钢具有更好的综合力学性能。扩孔裂纹传播特征及扩孔裂纹扩展的机理分析表明,由于传统高强钢存在珠光体及带状特征,加速了扩孔裂纹的萌生及快速扩展;而高扩孔钢以多边形铁素体为主,有效阻碍了裂纹的扩展,因此组织均匀性是获得高扩孔率的关键因素之一。最后,以车轮轮辐为例介绍60 kg高扩孔钢的应用,60 kg高扩孔钢冲压轮辐中心孔及螺栓孔等关键部位成形良好,并通过用户成形认证。

As conventional high strength steel can not meet the requirements of some special customers,Baosteel developed a new high hole-expansion steel（60 kg grade） with low carbon and sulphur content in a particular refining way combined with a special hot rolling process.Through comparing and analyzing the chemical compositions,production technology,metallurgical structures and mechanical properties of the high hole-expansion steel and traditional high strength steel,it was found that the former has better comprehensive mechanical properties.The characteristics of crack transmission and the mechanism of crack growth showed that as the latter consisted of pearlite and lamellar structures,it accelerated crack transmission and as the former mainly consisted of a polygonous ferrite structure,it effectively stopped crack growth.Therefore,a conclusion can be drawn that a homogeneous microstructure of steel will be one of the key factors to have a high hole-expansion ratio.Finally,the paper took wheel spoke as an example and described the application of the hole-expansion steel（60 kg grade）.As it can be well-formed when stamping center holes and bolt holes,the steel has been authenticated by consumers.