氏体钢TIG焊微观组织与力学性能的研究.pdf

江苏大学硕士学位论文中国低活化马氏体钢TIG焊微观组织与力学性能的研究姓名：邵奇栋申请学位级别：硕士专业：材料加工工程指导教师：雷玉成20091220江苏大学硕士学位论文摘 要低活化铁素体／马氏体钢具有优良的力学性能和热物理性能(较低的辐照肿胀与热膨胀系数、较高的热导率)，以及相对成熟的技术基础，被普遍认为是未来聚变示范堆和聚变动力堆的首选结构材料中国低活化马氏体钢(C㈨钢)是具有中国自主知识产权的、成分及性能优化的低活化铁素体／马氏体钢CLAM钢被定为中国设计研究的ITER试验包层模块的首选结构材料由于低活化的要求，CLAM钢和其他低活化钢一样，采用W、Ta和V等合金元素来取代常规铁素体／马氏体钢中的Mo、Nb和Ni等本文针对5mm的CLAM钢板，采用TIG焊接方法，进行平板对接焊和T型焊实验，焊接完成后对焊件进行不同温度的焊后热处理使用金相显微镜和扫描电镜观察CLAM钢焊接接头微观组织；使用维氏硬度计、拉伸试验机和冲击试验仪对焊接接头进行硬度及力学性能测试根据观察和测试结果，运用冶金学原理和相关理论，对焊接热循环、金相组织、焊接接头的力学性能和硬度以及它们之间的相互关系进行研究分析。

研究结果表明，5mm厚平板对接实验中，单层焊和双层焊焊接接头中晶粒尺寸存在不同，但微观组织都为回火马氏体随着焊后热处理温度的升高，焊缝中马氏体板条束分布逐渐均匀，同时焊缝中板条束也存在增大的趋势两种焊接接头中都有微量M23C6碳化物析出焊后热处理使双层焊焊接接头各区域硬度明显下降，并随热处理温度的升高而降低，实验表明810℃时焊缝金属的硬度下降幅度最大，降至与母材硬度相当焊接接头抗拉强度也随焊后热处理温度的升高而降低，经760℃保温30min热处理的焊接接头抗拉强度为740MPa经810℃热处理的接头抗拉强度降到700MPa以下810℃的单层焊接头断裂在焊缝上，其余试样都断裂在远离焊缝与热影响区的母材上热处理使接头冲击性能得到大幅提升，接头由脆性断裂转变成韧性断裂，未热处理的接头焊缝冲击功为9J，经760℃保温30min热处理的接头焊缝冲击功达108J，断口以韧窝为主CLAM钢T型焊接头焊缝成型良好，但接头翼板存在明显的角变形半V型坡口的T型接头中，由于翼板与腹板的散热环境不同，翼板热影响区晶粒比腹板区精细江苏大学硕士学位论文对比不同接头形式的三板T型焊接头，w型的三板T型焊接头具有填充金属少，晶粒尺寸小、腹板热影响区窄等优点。

关键词： CLAM；TIG；微观组织；力学性能Ⅱ江苏大学硕士学位论文ABSTRACTAs is well—known，reduced activation ferritic／martensitic steels(RAFM)are commonly considered as the primary structural materials for the DEMOfusion plant and the first fusion power reactors because of their excellentthermophysical properties and mechanical properties，for example the lowirradiation swelling and thermal expansion coefficient，high thermalconductivity etc．，and their relative mature technical foundation．China LowActivation Martensitic steel(CLAM)is the RAFM which have independentintellectual property rights with Chinese and optimized chemical compositionand properties．CLAM is considered as the primary structural materials for theChina designed ITER test blanket module．As others RAFMs，W，Ta and V etcin CLAM replaced Mo，Nb and Ni etc．in common ferritic／martensitic steels，because of the low activation requirement．Welding technology and process isone of the key technologies for CLAM using in project．In this paper，5mm CLAM plates were welded by Flat butt welding andT-welding using TIG welding method，and then they were post-weld heattreated at different temperatures．Microstructure and carbide distribution ofweld joint were observed by metalloscope and SEM．Hardness andmechanical properties were tested respectively in hardness test，tensile testand impact test experiments．According to the results of observed and test，metallurgical principles and related theories were used to research andanalysis welding thermal cycle，microstructure，carbide precipitation，themechanical properties and hardness of welded joints．The results show that in the experiments of Flat butt welded on 5mmCLAM plates，both Single—layer and double—layer welded joints appeareddifferent sizes of grain．However,all of the microstructure were temperedⅢ江苏大学硕士学位论文martensite．With the increase of post—weld heat treatment temperature，the lathbeams of martensite gradually uniformed distribution in welding seams，whilethey also had the trend of increasing．Two kinds of welded joints hadmicro—M23C6 carbide precipitate．After post—weld heat treatment the hardnessof double-welded joints decreased in every region，and decreased with theincreases of heat treatment temperature．The experiments showed that at 810℃the hardness of weld metal had the largest decline to the hardness of thebase material．Tensile strength of welded joints also decreased with post—weldheat treatment temperature increased．After heat—treated at 760℃in 30minthe tensile strength of welded joints were740MPa，and the tensile strengthdecreased below 700MPa at 810℃．Single—layer welded joints fractureed inthe weld on the 810℃，the rest of the specimen were broken at the basematerial away from the weld and heat affected zone．Heat treatment made theimpact properties of joints significantly enhanced，turned the brittle fractureinto a ductile fracture．Impact energy of unheat—treated Weld joints were 9J upto 108J after heat—treated at 760。

C in 30min．The fracture Was mainly dimplefracture．Weld of CLAM plates T-welded joints was good shape，but there existedan obvious angle distortion in joint flange．In half V-groove and T-joints thegrain in flange heat-affected zone was finer than web zone due to the differentthermal environments of flange and web zone．Compared to three-panelT-welded joints of different joint forms，W-shaped three—panel T-welded jointshad advantage with less filling metal，small grain size and narrow．webheat．affected zone．Keywords：CLAM；TIG；microstructure；mechanical propertiesIV学位论文版权使用授权书本学位论文作者完全了解学校有关保留、使用学位论文的规定，同意学校保留并向国家有关部门或机构送交论文的复印件和电子版，允许论文被查阅和借阅。

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