厚板转子钢多层多道焊接头不同微区断裂韧度的分析

文中研究了厚板转子钢多层多道窄间隙焊接接头不同微区的断裂韧度，主要包括接头中热影响区粗晶区及细晶区，焊缝中的柱状晶区和等轴晶区.结果表明，焊缝内柱状晶区断裂韧度（J_m）最低，断裂韧度最小值为195 kJ/m2，而热影响区的细晶区断裂韧度最高，J_m为1 265 kJ/m2.热影响区细小的等轴晶粒（1~12 μm）和晶内均匀分布的碳化物是其断裂韧度较好的主要原因.焊缝内组织主要为回火索氏体，以柱状晶形式分布在焊缝中，裂纹容易沿柱状晶晶界扩展，导致焊缝的断裂韧度较低.整个接头柱状晶与等轴晶组织交替分布，提高抗裂纹扩展能力，保证了整个焊接接头的安全可靠.

Research on the fracture toughness of micro zone in the joint based on multi-layer and multi-pass welding of rotor steel

Based on the multi-pass and multi-layer narrow gap submerged arc welding, the fracture toughnesses of different micro zones in the welding joint were studied, mainly including coarse grain and fine grain zones in heat affected zone and column and exquiaxed grain zones in weld seam respectively. The results showed that the column grain zone in the weld seam presented the lower fracture toughness J_m value of 195 kJ/m2, while the fine grain zone of heat affected zone showed the higher J_m value of 1 265 kJ/m2. The reason for the higher fracture toughness value of fine grain was ascribed to finer grain (1~12 μm) and homogeneous carbide distribution which inhibited the crack propagating. Otherwise, the cracks propagated along the coarse grain boundaries in coarse grain zone of heat affected zone which led to the lower Jm value. This complicated joint of interlocked column and exquiaxed grain improved the crack propagating resistance and ensured the safe operation of the welded joint.