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通过Gleeble-3500热模拟机对钒(V)含量分别为0.06%和0.02%的X80管线钢进行了峰值温度为1350℃和750℃的焊接热模拟试验,利用硬度计和光学显微镜(OM)分别分析了焊接热模拟试样硬度和试样中马氏体-奥氏体岛状组织(M-A)的数量、尺寸和形貌。利用透射电镜(TEM)对母材、粗晶区和部分相变区中粒子析出进行了表征。结果表明,与0.02%含V量X80管线钢相比,0.06%含V量的X80管线钢由于V含量较高,在受到多道次焊接热循环影响时,部分相变区有较大量碳化钒(VC)粒子析出,明显阻碍位错运动,使其强度明显提高的同时脆性增大、塑性变形难以进行,导致其焊接热影响区韧性下降。
The thermal simulations of X80 pipeline steels with 0.08% vanadium (V) and 0.02% vanadium (V) were carried out by Gleeble-3500 thermal simulator. The thermal simulations were conducted at 1350 ℃ and 750 ℃ respectively. The hardness of welding heat simulation specimen and the number, size and morphology of martensite-austenitic island structure (MA) in the sample were analyzed. Transmission electron microscopy (TEM) was used to characterize the particle precipitation in the base metal, coarse grain and some of the phase transition regions. The results show that compared with X80 pipeline steel with 0.02% V content, X80 pipeline steel with 0.06% V content has higher V content. Due to the influence of multi-pass welding thermal cycles, a large amount of vanadium carbide (VC) particles precipitated, obviously impeding the dislocation movement, so that the strength was significantly improved at the same time brittleness increases, plastic deformation is difficult to carry out, resulting in the toughness of the heat affected zone decreased.