HRB 400热轧钢筋的断裂失效分析

Analysis on Fracture Failure of HRB 400 Hot-Rolled Ribbed Bar

某批次HRB 400钢筋在进行6%载荷测试时发生了断裂。为了寻找其开裂原因,评比使用风险,对其进行了理化检测。结果表明:其化学成分和金相组织合格;断口扫描电镜分析显示,断口呈脆性断裂,裂纹起源于钢筋表面的夹杂物,微观形貌是沿晶+准解理断裂且有较多的孔洞;导致开裂的原因是材料中有夹杂物且冶金质量较差、氢脆弱化晶界以及表面存在马氏体组织。针对开裂原因采取钢水精炼、用高压水代替酸洗及提高轧制后的温度等工艺措施,彻底解决了HRB 400热轧钢筋的早期断裂问题。

Physical and chemical tests were carried out on the cracked HRB 400 reinforcement bar.Results showed that the chemical composition and metallographic structure of the fracture were qualified,and the fracture surface was brittle fracture by SEM analysis.The crack was originated from the inclusions on the surface of the steel bar,and the micro morphology was intergranular+quasi cleavage fracture with more holes.The causes of cracking were inclusions in the material,poor metallurgical quality,hydrogen embrittlement weakening grain boundary and martensite structure on the surface.The early fracture of HRB 400 hot-rolled steel bar was completely solved by means of steel refining,replacing pickling with high-pressure water and increasing the temperature after rolling.