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研究了低碳钢、普通市售Ｘ６５钢和高洁净度Ｘ６５钢三种超细晶粒钢焊接ＨＡＺ的晶粒长大倾向。试验结果表明，这些超细晶粒钢都具有严重的晶粒长大倾向；低碳超细晶粒钢比Ｘ６５＄细晶粒钢有更为严重的晶粒长大，这是因为前者不含有能阻碍晶粒长大的稳定碳、氮化物形成元素Ｎｂ和Ｔｉ，而后者中含有这些元素；高洁净度Ｘ６５超细晶粒钢的ＨＡＺ晶粒长大倾向小于普通市售Ｘ６５超细晶粒钢。这是因为钢中杂质元素含量越多，α→γ转变温度越低，即Ａｃ３点越低，在同样的焊接热循环条件下，普通市售Ｘ６５超细晶粒钢中的γ晶粒在高温停留时间就越长，晶粒长大的程度也就越大。
The grain growth tendency of HAZ welded with three kinds of ultrafine grained steels, mild steel, common commercial X65 steel and high cleanliness X65 steel was studied. The experimental results show that these ultrafine grained steels have a serious tendency of grain growth. Low-carbon and ultrafine grained steels have more severe grain growth than X65 $ fine grain steels because the former does not contain The stable carbides and nitrides, which can hinder the grain growth, form the elements Nb and Ti, which are contained in the latter. The HAZ grains with high cleanliness degree of X65 ultra-fine grain steel tend to grow smaller than the ordinary commercial X65 ultrafine grain steel. This is because the more the content of impurity elements in steel, the lower the α → γ transition temperature, ie, the lower the Ac3 point, under the same welding thermal cycling conditions, The longer the residence time, the greater the degree of grain growth.