夹杂物对无缝钢管裂纹形核和长大的力学影响

内外折是无缝钢管生产过程中常见的缺陷,管坯中的夹杂物对上述缺陷的形成具有重要影响。采用有限元方法,分析含条形MnS夹杂物的16Mn钢受力后的应力、应变分布情况,以期得出夹杂物对钢管内折的影响。分析认为:MnS夹杂物与基体的边界处存在应力、应变集中,而且夹杂物与基体的结合力又比较弱,导致裂纹形核在此处开始;裂纹尺寸越大,应力、应变越严重,裂纹扩展越快,越易达到扩展失稳的临界尺寸,从而形成内折缺陷;长条形夹杂物的端部存在较高的应力、应变集中,应严格控制长条形夹杂物的产生。

Mechanical Effect by Inclusions on Nucleation and Extension of Crack of Seamless Steel Tube

Both inner and outer folds are the common defects of the seamless steel tube as developed during the manufacturing process. And formation of such defects are remarkably affected by the inclusions in the billet for pipe-making.With the FEA method,the stress/strain distribution of the 16 Mn steel containing stripe MnS inclusion which is under load are analyzed to identify the influence by the inclusion on the inner fold of the pipe. The analysis reveals that stress and strain concentrations exist on the boundary between the MnS inclusion and the base metal,and the combining power by the inclusion with the base metal is rather weak,which leads to the nucleation of the crack at such a location. The larger the size of the crack is,the more serious the stress/strain concentration will be,and the faster the crack extends,the more possible for it to get to the critical size for unstability to form the defective inner fold. Since at the end of the stripe inclusion,there exists rather high stress/strain concentration,development of the stripe inclusion should be strictly controlled.