非金属夹杂物对焊接氢致裂纹敏感性的影响及机理研究

INFLUENCE AND ITS MECHANISM OF NON-METALLIC INCLUSIONS ON WELDING HYDROGEN-INDUCED CRACKING SUSCEPTIBILITY

本文详细研究了硫化物、氧化物等非金属夹杂物对10Ni5CrMoV低碳中合金高强度钢焊接氢致裂纹敏感性的影响及其机理。插销实验结果表明:细小弥散的非金属夹杂物明显提高焊接氢致裂纹抗力。对充氢试样的扩散氢及残余氢的测量结果得出:非金属夹杂物能作为氢的有效陷井而降低氢的表观扩散系数,提高残余氢含量。对HAZ相变行为的研究发现:细小弥散的非金属夹杂物能明显阻碍HAZ奥氏体晶粒长大,使M_s点提高,促进马氏体充分自回火,降低HAZ最高硬度。对实验结果的综合分析认为:细小弥散非金属夹杂物对低碳中合金高强度钢焊接氢致裂纹抗力的改善主要是由于这些夹杂物对HAZ相变行为产生影响的结果,而对HAZ中氢扩敌行为的影响则是次要因素。

An overall study has been made of the influence and its mechanism of non-metallic inclusions, such as sulfides and oxides, on welding hydrogen-induced cracking susceptibility of 10Ni5CrMoV low carbon high strength medium alloy steel. The results obtained from the implant test show that the hydrogen-induced cracking resistance of the steel can be significantly increased by the addition of dispersed fine non-metallic inclusions. The reduction of apparent hydrogen diffusion coefficient and the increase of non-diffusible hydrogen trapped on various inclusion, i.e. traps, as a result of the addition of theseinclusions, are verified by the measurement of diffusible and residual hydrogen contents in hydrogen-charged specimens. The investigation of phase transformation in HAZ shows that the austenite grain growth is effectively inhibitatedby the dispersed fine inclusions so that the martensite phase transformation temperature rises. Therefore, the HAZ hardenability can be greatly reduced in consequence of the self-tempering effect of martensite. It is concluded that the change of HAZ martensite phase transformation behavior is chiefly responsible for the improvement of welding hydrogen-induced cracking resistance of 10Ni5CrMoV steel containing various dispersed fine inclusions. The effect of these inclusions on the HAZ hydrogen diffusion behavior is less important in reducing the welding hydrogen-induced cracking susceptibility.