07MnNiCrMoVDR钢焊接粗晶热影响区的韧化机理

Toughnes mechanism of CGHAZ of 07MnNiCrMoVDR steel

选用垂直于07MnNiCrMoVDR钢板轧制方向的模拟试样,在Gleeble-3500热模拟试验机上对该钢焊接粗晶热影响区的组织转变和韧性进行了研究。结果表明,粗晶区的组织类型主要是贝氏体和低碳板条马氏体的混合组织,粗晶区的低温韧性最差,随着冷却速度的减小,贝氏体由下贝氏体向上贝氏体和粒状贝氏体转变。在高温回火热处理后,粗晶区有再热脆化的倾向,易产生再热脆化,存在再热裂纹的可能性较大。再热脆化的主要原因是晶界析出粗大的碳化物,冷却速度越大,再热脆化现象越严重。

The translation of microstructure and the toughness of coarse grain heat affect zone (CGHAZ) of 07MnNiCrMoVDR steel were investigated by thermal simulation testing machine which type of Gleeble-3500. The simulation samples were picked up from the perpendicular to the rolling direction of 07MnNiCrMoVDR steel. The experimental results indicate that the bainite and low carbon martensite is the dominate microstructure in the CGHAZ. With the cooling rate decreases, the bainite transformed from upper-bainite to low-bainite. The impact absorbing energy of the CGHAZ is worse through the heat treatment. The brittleness of reheat will probably induce the crack of reheat because of coarse grain boundary carbide precipitation. The greater the cooling rate,the more serious of the reheat embrittlement.