焊接工艺参数对9％Ni钢热影响区低温韧性的影响

Effects of welding parameters on cryogenic toughness in heat-affected zones for 9% Ni steel

采用热模拟技术研究了热输入和层间温度对9%Ni钢焊接热影响区中四个亚区域低温韧性的影响,并利用光学显微镜、X射线衍射仪对各亚区域的组织形态和数量分布进行了观察分析。结果表明,临界热影响区低温韧性对热输入和层间温度的变化不敏感;层间温度是影响粗晶区低温韧性的主要工艺参数;热输入则是影响过临界粗晶区和临界粗晶区低温韧性的主要工艺参数。热输入越大,晶粒和组织越粗大,低温韧性恶化;层间温度提高,马氏体的自回火作用越显著,低温韧性改善。因此,焊接9%Ni钢时,应采用较小的焊接热输入,配合较高的层间温度。

Effects of heat input and interpass temperature on cryogenic toughness of four sub-zones in heat affected zones(HAZ) were investigated for 9% Ni steel welding.Optical microscope and X-ray diffractometer were used to analyze types and quantitative distribution of microstructures in the sub-zones.Results showed that cryogenic toughness of inter-critical HAZ(ICHAZ) was not sensitive to the change of heat input and interpass temperature.The main technique parameter influencing cryogenic toughness of coarse-grained HAZ(CGHAZ) was interpass temperature,whereas the main technique parameter influencing cryogenic toughness of super-critically reheated coarse-grained HAZ(SRCGHAZ) and inter-critically reheated coarse-grained HAZ(IRCGHAZ) was the heat input.Higher heat input and longer remaining time at high temperature resulted in much coarser grain size and much lower toughness.Higher interpass temperature and stronger self-tempering effect of martensite resulted in higher cryogenic toughness.A match of low heat input and high interpass temperature is recommended to achieve high cryogenic toughness.