中文摘要：

冲击试验是衡量金属材料韧性的最有效手段之一。对690 MPa级低合金高强钢熔敷金属进行–50℃示波冲击,分析焊接层间温度在80℃和200℃时试样的冲击性能。应用光学显微镜、扫描电子显微镜、电子背散射衍射等分析手段并采用Lepera腐蚀法,对近断口区的组织、M-A组元及夹杂物进行观察,研究冲击过程中裂纹的形核和扩展规律。结果表明：层温对熔敷金属冲击吸收功影响显著,层温80℃和200℃时,所选冲击试样裂纹形成功和扩展功分别相差6.7 J和34.0 J。进一步研究表明,两种层温下,近断口区组织主要由板条状贝氏体和粒状贝氏体组成。层温80℃时,组织主要以板条状贝氏体为主,粒状贝氏体少量分布,M-A组元以少量的颗粒状存在;层温200℃时,粒状贝氏体数量增多,M-A组元的形态以条状和块状居多,数量增加;M-A组元这种形态和数量上的变化是导致两种层温下启裂功不同的主要原因。而熔敷金属中大角度晶界数量的不同,是造成两种层温下裂纹扩展功不同的主要因素。

英文摘要：

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.