20Mn2车桥用无缝钢管外折缺陷分析  

Analysis of External Fold Defect of 20Mn2 Seamless Steel Tube for Automobile Axle Service

作　　者：郭志强 GUO Zhiqiang(Henan Fengbao Special Steel Co.,Ltd.,Linzhou 456500,China)

机构地区：[1]河南凤宝特钢有限公司,河南林州456500

出　　处：《钢管》2021年第4期51-55,共5页Steel Pipe

摘　　要：分析了车桥用20Mn2连铸圆坯在穿孔时出现外折缺陷的原因。通过观察外折缺陷的形貌,认为外折缺陷来源于坯料表面及皮下裂纹。检测了钢管夹杂物、连铸坯化学成分、钢中Als和[N]含量及连铸中间包内的钢液温度,观察了连铸坯裂纹的金相形貌,分析了皮下裂纹试样裂纹断口上的颗粒状夹杂物。检测显示:钢中的Als∧0.025%,[N]≥0.0075%,连铸钢液过热度∧33℃,Als、[N]与连铸钢液的过热度均过高,这是引起钢坯出现裂纹的主要原因;裂纹缺陷处主要夹杂物是MnS+TiN+BN+AlN。当Als和N的含量高及连铸钢液的过热度高同时出现在同一炉钢液,易造成连铸圆坯裂纹缺陷。Analyzed in the article are the causes for the external fold defect as occurring during the piercing of the CC round to be used for making the automobile axle tube.It is regarded via the morphology of the external fold as observed that the fold is originated from the cracks as existing on the surface and sub-surface of the billet.Also checked are the inclusions of the steel tube,the chemical composition of the CC billet,the Als and[N]contents of the steel,and the temperature of the liquid steel in the tundish.The metallographic morphology of the CC billet is observed,and the particle inclusions on the fracture of the specimen of sub-surface cracking part of the billet is analyzed.Thanks to the above mentioned inspections,such data as follows are obtained:in the steel:Als>0.025%,[N]≥0.0075%;the superheat degree of the liquid steel:>33℃ which means that both the Als and[N]contents,and the said superheat degree are too high,and this is just the major cause for the cracking of the billet.The main inclusions as identified at the location of the crack defect include MnS+TiN+BN+AlN.The conclusion is that in case that both very high Als and[N]contents and high super heat degree of the CC liquid steel occur simultaneously in one heat of the steel,it will become very possible to lead the said CC billet crack.

关 键 词：车桥用无缝钢管 20Mn2 外折缺陷 圆坯裂纹 ALS N 过热度 

分 类 号：U465[一般工业技术—材料科学与工程] TF777[机械工程—车辆工程]