关键词: 电磁热, 焊接接头, 埋藏裂纹, 无损检测, 止裂, 编码靶标, 精度, 小视场, 坐标测量

Abstract: Embedding crack is prefabricated in 2Cr13 welding joints which are generated by butt welding method, and its location and size are demarcated by ultrasonic nondestructive testing. Temperature field around crack which is embedding and circular in welded joints at the moment of pulse current discharge is calculated by thermoelectric coupling numerical simulation methods. Meanwhile residual stress field is analyzed after crack arrest. Crack arrest experiments on specimens with welding joints are carried out by ZL-2 equipment. Microstructure of buried crack tip is analyzed and the properties of flexural behavior and tension are tested before and after crack arrest. The study shows that the crack tip is melting and passivated due to the temperature of crack tip over its melting point at the time of discharge. Thus, the further expansion of crack can be prevented. The microstructure near crack tip refined obviously and white layer structure which has a good strength and toughness is produced, further it prevents the crack from the propagation. The flexural strength of welded joints increases by 18.0%, tensile strength increases by 11.7% and fracture elongation increases by 34.6% after crack arrest by electromagnetic heating. The study confirmed that the pulse current discharge achieves the goal of buried crack arrest in 2Cr13 welding joints and improves the mechanical properties of welded joints.

Key words: Crack arrest, Electromagnetic heating, Embedding crack, Nondestructive testing, Welded joints, Coordinate Measurement, Coding Target, Precision, Small Field of View