焊接热输入对Q690高强钢热影响区组织和韧性的影响  

Effect of heat input on the microstructure and toughness of heat affect zone of Q690 high strength steel

作　　者：李亚江[1] 蒋庆磊[1] 暴一品[1] 王娟[1] 张蕾[1] 

机构地区：[1]山东大学材料液固结构演变与加工教育部重点实验室,济南250061

出　　处：《中国科技论文在线》2011年第2期98-102,共5页

基　　金：高等学校博士学科点专项科研基金资助项目(200804220020)

摘　　要：采用不同的热输入焊接淬火-回火态低合金高强钢Q690,研究焊接热输入对接头热影响区的显微组织、精细结构及冲击韧性的影响。结果表明,当热输入从14 kJ/cm提高到20 kJ/cm时,热影响区冲击韧性先升高再降低。热输入提高到约16 kJ/cm时,热影响区中下贝氏体的形成可有效限制马氏体的尺寸,细化奥氏体晶粒内的组织并形成许多大角度晶界,有益于提高接头热影响区的冲击韧性;冲击断口纤维区具有韧窝特征,放射区有较大的撕裂台阶。当热输入较大时,上贝氏体铁素体侧形成的与板条平行的脆性Fe3C条损害了热影响区的塑韧性,冲击断口纤维区的断口具有滑移特征,韧窝数量少,放射区形成小的撕裂刻面。High strength low-alloy steel Q690 in quenched and tempered conditions was welded by gas shielded arc welding with different welding heat inputs. The influence of heat input on the microstructure, fine structures and impact toughness of the heat affected zone （HAZ） of the joint was investigated via scanning electron microscope, transmission electron microscopy and Charpy V-notch tests. The results indicated that the optimum impact toughness in HAZ was obtained at the heat input about 16 kJ/cm. The formation of lower bainite effectively restricted the size of martensite laths. The microstructure within austenite grains was refined and many large angle lath boundaries were formed, which contributed to enhancing the impact toughness in HAZ. Fibrous zones in fractured surfaces of impact specimens were characterized by dominant elongated dimples. Large cleavage steps were observed in the radical zone. With the heat input increasing, carbide particles paralleled to the habit planes of bainitic ferrite were formed. These carbide particles are detrimental to the toughness of the joint. Slip bands were shown in the fibrous zone. Coarsen carbides along upper bainitic ferrite held back the formation of dimples. The radical zone was composed of small cleavage facets due to more crack initiation sites provided by carbides.

关 键 词：高强钢 焊接 热影响区 显微组织 韧性 

分 类 号：TG457.11[金属学及工艺—焊接]