高强钢焊接氢致裂纹断口微观形貌的研究及模式化

FRACTOGRAPHIC STUDY AND MODELLING OF WELDING HYDROGEN-INDUCED CRACKING IN A HIGH STRENGTH STEEL

采用插销实验和扫描电镜观察方法详细研究了焊缝扩散氢含量和非金属夹杂物对10Ni5CrMoV低碳中合金高强钢焊接热影响区氢致裂纹断口微观形貌的影响。结果得出,扩散氢含量是影响氢致裂纹断口微观形貌的主要因素,在插销净截面应力300～800MPa的范围内,加载应力对延迟扩展区断口形貌无明显影响。钢中硫化物夹杂的增加使扩展区形貌从IG_(HE)向MVC_(HE)转变,而含氧化物夹杂钢则转为QC_(HE)。作者提出了一个新的适于解释氢致裂纹扩展第Ⅱ阶段断口微观形貌的竞争开裂模式,从而从氢致裂纹本质机制上圆满说明了上述实验结果。

The effects of diffusible hydrogen content and nonmetallic inclusions on fractographic morphology of welding hydrogen-induced cracking (HIC) in HAZ of 10N15CrMoV high strergth steel were intensively investigated by implant test and SEM observation. The experimental results showed that the diffusible hydyogen content was the main factor influencing the fra-ctographic appearance of welding HIC, while the obvious influence of implant net stress ranging from 300 to 800 MPa was not observed. It is also found that the addition of sulfide inclusions into 10N15CrMoV steel could alter the fractographic appearance of delayed propagation zone from IGHE to MVCHE, while oxide-bearing steels turned to QCHE. A qualitative hydrogen-induced competition cracking model is suggested for the second stage of HIC propagation, which can satisfactorily explain the experimental results.