热输入对F460钢焊接粗晶热影响区拉伸性能的影响

Effect of Heat Inputs on Tensile Properties of Coarse Grain Heat Affected Zone for F460 Steel

使用Gleeble3800热模拟试验机对F460钢进行单道次焊接热模拟,得到四种不同热输入下的热模拟试样,并对其进行低温拉伸试验,通过SEM观察粗晶热影响区(CGHAZ)的显微组织、微观断口形貌,分析了CGHAZ的拉伸性能随热输入的变化规律。结果表明:随着热输入的增加,原始奥氏体晶粒与贝氏体团(即有效晶粒)逐渐粗化,相变产物由细密的板条马氏体转变为板条贝氏体与粒状贝氏体的混合组织,其中粒状贝氏体随着热输入的进一步增加而逐渐增加;随着热输入的增加,拉伸屈服强度、抗拉强度以及断面收缩率在20、-95及-196℃试验温度下均逐渐降低;根据拉伸断口微观观察结果表明,起裂源处的解理面尺寸逐渐增大。

The single welding thermal cycle of F460 steel was simulated by Gleeble3800 thermal simulation machine. The tensile properties at different heat input were measured. The corresponded microstructure and fracture surfaces were observed. The results indicated that： with the increase of heat inputs, the original austenite grain and bainite packet （effective grain） size gradually become coarser, and the fine lath martensite gradually transforms into the mixture of lath bainite and granular bainite, and the content of granular bainite becomes higher with the further increasing heat input. With increasing heat input, the yield strength, tensile strength and reduction of area decreases at 20℃, -95℃ and -196℃. The fracture surface shows that the size of cleavage plane increases with the increase of heat input.