论文部分内容阅读
为了研究焊丝中的Mn含量对螺旋焊管焊缝金属的微观组织、力学性能和热裂纹敏感性的影响,选取了3种w(Mn)分别为0.88%,1.05%和1.54%的焊丝,在X70螺旋焊管的生产和试验条件下进行焊接,获得的焊缝金属中w(Mn)分别为1.26%,1.44%和1.67%。通过光学显微镜及扫描电镜的金相学检查分析显示:提高焊缝金属的Mn含量,能降低各相(针状铁素体(AF)、先共析铁素体(PF)和侧板条铁素体(FSP))的晶粒尺寸。而且随着针状铁素体不断增加,先共析铁素体(主要是晶界铁素体)和侧板条铁素体的体积分数会降低。同时力学性能试验结果显示:Mn含量越高,焊缝金属的强度和硬度就越高。冲击韧性和延伸率,观测发现有一个最佳值。Mn含量最大的焊缝金属具有较低的韧性,这归因于淬透性的增加及马奥岛(M/A)及晶界碳化物在针状铁素体位置的形成。对长度超过1 000 m的螺旋焊管焊缝金属的分析显示:当焊缝金属中w(Mn)增加到1.4%时,热裂纹形成的可能性从0.005%减少到0.001%。
In order to study the influence of Mn content in the wire on the microstructure, mechanical properties and hot crack susceptibility of the weld metal, three kinds of welding wire with w (Mn) of 0.88%, 1.05% and 1.54% were selected. Spiral welded pipe production and testing conditions, the weld metal w (Mn) were 1.26%, 1.44% and 1.67%. Metallographic examination by optical microscopy and scanning electron microscopy revealed that increasing the Mn content of the weld metal decreased the strength of each phase (acicular ferrite (AF), pro-eutectoid ferrite (PF) and side-slab ferrite (FSP)) grain size. And with the increasing acicular ferrite, the volume fraction of pro-eutectoid ferrite (mainly grain boundary ferrite) and side lamellar ferrite will be reduced. At the same time mechanical properties test results show that: the higher the Mn content, the higher the strength and hardness of the weld metal. Impact toughness and elongation, observed that there is an optimal value. The weld metal with the highest Mn content has lower toughness due to the increased hardenability and the formation of acicular ferrite at Mau A Island (M / A) and grain boundary carbides. Analysis of weld metal for spiral welded pipe with a length in excess of 1 000 m showed that the hot crack formation potential was reduced from 0.005% to 0.001% as w (Mn) increased to 1.4% in the weld metal.