关键词: M-A组元, 层间温度, 冲击韧度, 大角度晶界

Abstract: Impact test is the most effective method in evaluating toughness of metal materials. The impact properties of deposited metal of 690 MPa level high strength low alloy(HSLA) steel at interpass temperature 80 ℃ and 200 ℃ is analysed by impact test at –50 ℃. The M-A constituents are etched by Lepera reagent. Inclusion, microstructure and M-A constituents near fracture zones are observed and crack initiation and crack propagation are studied in optical microscope(OM), scanning electron microscope(SEM) and electron back-scattered diffraction(EBSD). The results indicate that impact properties of deposited metal are greatly influenced by interpass temperature. The microstructure is composed of lath bainite, and granular bainite at the two interpass temperatures. When interpass temperature is 80 ℃ microstructure is lath bainite and a small number granular bainite, the M-A constituents in the granular bainite is a few and granular; When interpass temperature is 200 ℃ the number of granular bainite increase and the shape of M-A constituents in the granular bainite is bacillary and small bulk. The difference of crack initiation energy results from difference of M-A constituents in shape and number. The number of large angle boundary result in difference of crack propagation at the two interpass temperatures.

Key words: Impact properties, Interpass temperature, Large angle boundary, M-A constituents