论文部分内容阅读
采用热丝TIG半自动焊及手工电弧焊SMAW,用ENi Cr Mo-3型焊丝对Q235B钢板进行对接焊试验。利用光学显微镜、扫描电镜对产生裂纹处的焊缝微观组织进行观察和元素成分分析。结果表明,采用SMAW进行拘束焊接时,焊接电流增至140 A出现裂纹且160 A时裂纹变长;同样条件下采用TIG时电流增至180 A仍无裂纹产生;保持电流180 A不变,将板厚增至20 mm时出现裂纹,表明热输入及板厚引起的拘束度均会增加热裂纹敏感性,TIG焊更利于控制热裂纹。宏观热裂纹为沿晶开裂型,断面形貌为等轴晶且富含Nb,熔敷金属中的显微裂纹多存在于柱状晶晶界或生长末端,裂纹为结晶裂纹。在裂纹起裂位置有富Nb碳化物析出,增加了热裂纹敏感性。
Hot wire TIG semi-automatic welding and manual arc welding SMAW, with ENi Cr Mo-3-type welding wire Q235B steel butt welding test. The microstructure of the weld where cracks were generated was observed by optical microscopy and scanning electron microscopy and the elemental composition was analyzed. The results show that when SMAW is used for restrained welding, the welding current increases to 140 A and the crack grows at 160 A; under the same conditions, the current increases to 180 A with TIG and no crack occurs; Cracks appear when the plate thickness increases to 20 mm, which indicates that the heat input and the restraint caused by the plate thickness increase the susceptibility to hot cracking. TIG welding is more conducive to controlling the hot cracking. The macroscopic hot crack is intergranular cracking type. The cross-sectional morphology is equiaxed and Nb-rich. The micro-cracks in the deposited metal mostly exist at the columnar grain boundary or the growth end, and the crack is a crystal crack. Nb-rich carbide precipitates at crack initiation sites, increasing the susceptibility to hot cracking.