焊接热循环峰值温度对1000 MPa级超高强钢热影响区组织性能的影响  

Effect of peak temperature of welding thermal cycle on microstructure property of heat affected zone of 1000 MPa grade ultra-high strength steel

作　　者：孙琦 李太江[1] 李巍[1] 李生文[1] 余阳 李聚涛 娄正计 许博炜 程晔锋 SUN Qi;LI Taijiang;LI Wei;LI Shengwen;YU Yang;LI Jutao;LOU Zhengji;XU Bowei;CHENG Yefeng(Xi’an Thermal Power Research Institute Co.,Ltd.,Xi’an 710054,China)

机构地区：[1]西安热工研究院有限公司,陕西西安710054

出　　处：《热力发电》2024年第4期165-173,共9页Thermal Power Generation

基　　金：西安热工研究院研究开发基金(TQ-23-TYK13)。

摘　　要：为研究1 000 MPa级超高强钢焊接热影响区(HAZ)不同区域的组织性能,采用焊接热模拟技术制备了试验钢在不同热循环峰值温度下的试样,通过夏比冲击试验研究了HAZ不同区域的冲击韧性。结果表明:在亚临界区(SCHAZ)、临界区(ICHAZ)和细晶区(FGHAZ),样品冲击吸收能量、裂纹扩展能量和动态冲击韧度较大,断口上形成较大面积的脚跟形纤维区和剪切唇,微观可看到大小不一的韧窝,样品冲击韧性较好;在粗晶区(CGHAZ),样品各项冲击数据均急剧下降,断口呈宏观脆性断裂,几乎全为放射区,微观下显示准解理断裂特征,表明裂纹扩展时受到的阻力减小,裂纹萌生后稳定扩展的时间减少,失稳扩展较快,样品的冲击韧性恶化,CGHAZ为HAZ中的韧性谷区;组织分析表明,粗大的晶粒和粗大的马氏体板条是导致CGHAZ脆化的主要原因。该结论为探究1 000 MPa级超高强钢在水电工程中的优选研制及工程应用奠定了理论基础。In order to study the microstructure properties of different regions of welding heat affected zone(HAZ)of 1000 MPa grade ultra-high strength steel,the samples of test steel at different peak temperatures of thermal cycle were prepared by welding thermal simulation technique,and the impact toughness of different regions of HAZ was studied through Charpy impact tests.The results showed that,in the subcritical region of HAZ(SCHAZ),the intercritical region of HAZ(ICHAZ)and the fine-grained region of HAZ(FGHAZ),the samples had relatively high impact absorption energy,crack propagation energy and dynamic impact toughness,and a large area of fiber region and shear lip formed on the fracture surface.Toughness dimples of different sizes can be seen at the microscopic level.The samples had good impact toughness.In the coarse-grained region of HAZ(CGHAZ),all impact data of the samples sharply decreased,and the fracture showed a macroscopic brittle fracture,almost all of which are radiological regions.At the microscopic level,it showed quasi cleavage fracture characteristics,indicating that the resistance to crack propagation decreased,and the time for stable propagation decreased after crack initiation,and the instability propagation was fast.The impact toughness of the samples deteriorated,and the CGHAZ region was a ductile valley region in HAZ.The results showed that the coarse grains and the coarse M-A island were the main causes of embrittlement in the CGHAZ region.The conclusion lays a theoretical foundation for the selection,development and engineering application of 1000 MPa grade ultra-high strength steel in hydropower projects.

关 键 词：超高强钢 焊接热模拟 焊接热影响区 冲击吸收能量 断裂韧度 

分 类 号：TG457.11[金属学及工艺—焊接]