基于显微组织的多层焊接接头断裂韧性试验研究

EXPERIMENTAL STUDY ON FRACTURE TOUGHNESS OF MULTILAYER WELD JOINT BASED ON MICROSTRUCTURE

对NiCrMoV钢多层焊接接头进行了准静态断裂性能试验,试验中发现埋弧焊焊缝断裂韧性J值分散性较大。根据焊接试样韧性断裂和脆性断裂的情况,分组拟合J-R阻力曲线和计算有pop-in效应的尺寸敏感断裂韧度Jc(25)值。分别对呈现韧断和脆断的多层焊接试样断口的启裂部分进行扫描电镜分析,发现多层焊接焊缝的断裂韧性与试样预制裂纹尖端在焊缝接头中的位置有很大关系。对多层焊接接头各组织的成因以及对断裂韧性的影响进行了分析和研究,可知多层焊缝的粗大柱状晶、再结晶粗晶和再结晶细晶区交替存在的复杂组织是焊接接头断裂韧性分散性大的根本原因。

Quasistatie fracture toughness tests have done on SAW multilayer weld joint of NiCrMoV scaled steel. The test result shows that the dispersion of fracture toughness J of SAW muhilayer weld joint was large. J-R fracture resistance curve was fit and critical Je（25）with pop-in behavior were calculated according to the different of brittle and ductile fracture phenomenon. The crack initiation parts of brittle and ductile fracture of muhilayer welding specimens were analyzed respectively by scanning electron microscopy. There is a great relation between the multilayer weld fracture toughness and the position of pre-crack tip in the weld joints. Analysis and research have been done about the cause of formation of different microstructures of multilayer and effects on fracture toughness properties. It is known that the complex organization of bold columnar crystals, incomplete recrystallized coarse grain and incomplete recrystallized fine grain alternating exists is the essential cause of the large dispersion of fracture toughness.