【摘要】 采用伍德（Wood）液态金属对GTAW制作的平板堆焊试件淬火，以及光学金相、电子背散射衍射等测试手段，研究了焊缝金属对奥氏体不锈钢失延裂纹（Ductility-dip cracking,DDC）敏感性的影响。结果表明，伍德金属淬火在焊缝熔化区中捕获了高温显微组织细节形貌，揭示了310的淬火诱发DDC敏感性比304、316和321严重得多。304和316均凝固为柱状δ晶粒，沿δ柱状晶粒之间的边界形成了几乎连续的γ；由于γ深入δ生长，δ晶粒被γ牢固地结合在一起，阻碍沿δ晶界的DDC。321凝固为等轴δ晶粒，等轴晶粒的弯曲边界阻碍DDC。310凝固为粗直的、沿晶界几乎没有δ的γ柱状晶粒，并且晶界迁移变成为局部直的；由此产生的又长又直的裸晶界成为DDC的理想通道。归纳了奥氏体不锈钢焊缝抗DDC的两种新机制：(1)沿δ柱状晶的边界形成几乎连续的、非平直的γ；(2)凝固为等轴δ晶粒。更多还原

【Abstract】 The effects of weld metal on the sensitivity of austenitic stainless steel to ductility-dip cracking(DDC) were investigated by means of liquid Wood’s metal quenching the plate surfacing specimen made of GTAW, optical metallography and electron backscatter diffraction(EBSD) and other test means. The results show that wood’s metal quenching captures the detailed morphology of elevated-temperature microstructure in weld fusion zone,and reveals that the susceptibility to DDC induced by quenching is much more severe in 310 than in 304、 316 and 321. 304 and 316 both solidifies as columnar grains, and resulting in the formation of a nearly continuous γ along the boundaries between columnar δ grains; Since γgrows deep into δ, δ grains are bonded together firmly by γ to resist DDC along δ grain boundaries. 321 solidifies as equiaxed δ grains, and the tortuous boundaries of equiaxed δ grains resist DDC. 310 solidifies as coarse, straight, columnar grains of γ with little δ along grain boundaries,and the grain boundaries migrate to become locally straight. The resulting long, straight, and naked grain boundaries become ideal paths for DDC. Two new mechanisms for resisting DDC in austenitic stainless steel welds are summarized, formation of nearly continuous,non-straight γ along boundaries of columnar δ grains and solidification as equiaxed δ grains.更多还原