CAJ | 학술논문

为研究大热输入条件下埋弧自动焊（ submerged arc welding ，SAW）对海洋平台用550 MPa钢焊接接头组织与低温韧性的影响，采用50 kJ· cm-1的焊接热输入，测定接头各区域冲击吸收功，并观测各区断口形貌及显微组织．结果表明：焊接接头韧性从焊缝到母材，呈现先降低后升高的趋势，最低处在熔合线及熔合线2 mm处．焊缝处组织为针状铁素体加细小弥散的碳化物，断口形貌为韧窝和解理台阶，-60℃冲击吸收功为110 J．熔合线及熔合线2 mm处断口形貌基本相同，只由放射区组成，无纤维区，微观特征为大面积的解理面，没有韧窝；微观组织为粗大粒状贝氏体，冲击吸收功非常低只有25 J．熔合线5 mm处断口纤维区面积较大，微观形貌含有大量的韧窝，微观组织为细小的铁素体、碳化物及粒状贝氏体，该区为焊接接头的正火区，具有优异的低温韧性，-60℃冲击吸收功为202 J．
위연구대열수입조건하매호자동한（ submerged arc welding ，SAW）대해양평태용550 MPa강한접접두조직여저온인성적영향，채용50 kJ· cm-1적한접열수입，측정접두각구역충격흡수공，병관측각구단구형모급현미조직．결과표명：한접접두인성종한봉도모재，정현선강저후승고적추세，최저처재용합선급용합선2 mm처．한봉처조직위침상철소체가세소미산적탄화물，단구형모위인와화해리태계，-60℃충격흡수공위110 J．용합선급용합선2 mm처단구형모기본상동，지유방사구조성，무섬유구，미관특정위대면적적해리면，몰유인와；미관조직위조대립상패씨체，충격흡수공비상저지유25 J．용합선5 mm처단구섬유구면적교대，미관형모함유대량적인와，미관조직위세소적철소체、탄화물급립상패씨체，해구위한접접두적정화구，구유우이적저온인성，-60℃충격흡수공위202 J．
In this work,low-temperature toughness and microstructure of 550 MPa offshore platform steel SAW welded joint is researched .The heat input is 50 kJ· cm -1 .Optical and scanning election microscopy has been used to investigate the microstructure and the fracture morphology of different regions of welding joints .Charpy impact tests are evaluated to measure the charpy absorbed energy of different regions in detail .The result shows that the toughness of welded joints from the weld seam to the base metal decreases first and then increases .The microstructures of weld seam are acicular ferrite and fine dispersed carbide .The fracture is characterized by dim-ple and cleavage step, and the charpy absorbed energy in weld seam at -60℃is 110 J.The fracture morphology of fusion line and the zone 2 mm away from fusion line consists of radioactive zone and non -fiber zone , and its microcosmic morphology is characterized by large cleavage plane without dimple;the microstructure of the two re-gions is coarse granular bainite , the charpy absorbed energy in this zone at -60℃is only 25 J.A large area of fi-brous zone with lots of dimples is observed in the fracture 5mm away from the fusion line.The fracture is located in normalized zone whose microstructure consists of fine ferrite , carbide and granular bainite .Normalized zone shows excellent low-temperature toughness and its charpy absorbed energy at -60℃is 202 J.