摘要
采用3种药皮成分不同焊条对LNG储罐用9Ni钢进行焊接,利用多元热动力学相图计算软件JMat Pro的Scheil模型配合镍基合金材料数据库对相应焊缝熔敷金属进行偏析计算,通过光学显微镜(OM)分析熔敷金属的组织,并利用IPP软件观测枝晶间距.此外,通过硬度、拉伸和低温冲击等试验评定熔敷金属的力学性能.结果表明,Nb为正偏析元素,3种焊条的熔敷金属组织均由奥氏体树枝晶和析出相组成.OK92.55型焊条的熔敷金属具有更小的枝晶宽度和枝晶间距,这是由于Nb元素的偏析作用,形成的碳化物有抑制枝晶长大的作用,这促使其熔敷金属具有更大的断后延伸率和断面收缩率,具有良好的塑性.3种焊缝在热影响区的硬度最大,这是因为焊接热循环的作用.3种焊条熔敷金属的拉伸断口形貌均为韧窝和解理两种断裂方式相结合的形貌,说明它们既有塑性断裂,还有脆性断裂,但OK92.55型焊条熔敷金属的韧窝占比更高,证明其拉伸塑性较好.3种焊条的熔敷金属的低温冲击断口均为韧窝形貌,OK92.55型焊条熔敷金属的韧窝更深更小,表现出更好的低温韧性.
9 Ni steel was welded with three electrodes to produce a LNG storage tank with different coating compositions.The Scheil model in a multiple thermodynamic phase diagram calculation software,JMatPro,and a nickel-based alloy material database were used to perform a segregation calculation of the cladding metal of corresponding welds.The microstructure of the deposited metal was analyzed by optical microscopy(OM)and the dendrite spacing was observed.In addition,the mechanical properties of the deposited metals were evaluated by hardness,tensile and low temperature impact tests.The results show that Nb is a positive segregation element,and the microstructure of the deposited metal of the three electrodes is composed of austenite dendrites and precipitates.The deposited metal of the OK92.55-type electrode has a smaller dendrite width and dendrite spacing due to the segregation of the Nb element and the formed carbide can inhibit the growth of dendrite,which promotes greater elongation of the deposited metal after fracture and shrinkage of the section due to the good plasticity.The hardness of the three welds is highest in the heat-affected zone due to the effect of the welding heat cycle.The tensile fracture morphology of the deposited metals of the three electrodes is a combination of dimple and fracture modes,indicating both plastic and brittle fracture characteristics.However,the proportion of dimples in the deposited metals of the three electrodes is higher,which proves that the tensile plasticity is good.The low-temperature impact fracture of the deposited metals of the three electrodes is a dimpled morphology,and the dimpled metal of the OK92.55 electrode is deeper and smaller,showing better lowtemperature toughness.
作者
罗震
武钰栋
马成勇
齐彦昌
张禹
Luo Zhen;Wu Yudong;Ma Chengyong;Qi Yanchang;Zhang Yu(School of Materials Science and Engineering,Tianjin University,Tianjin 300350,China;Tianjin Key Laboratory of Advanced Joining Technology,Tianjin 300350,China;General Iron and Steel Research Institute,Beijing 100081,China;Department of Mechanical Engineering,Tsinghua University,Beijing 100084,China)
出处
《天津大学学报（自然科学与工程技术版）》
EI
CSCD
北大核心
2020年第8期771-776,共6页
Journal of Tianjin University：Science and Technology
基金
国家重点研发计划资助项目(2017YFB0305005)
中国博士后科学基金资助项目(2018M641340).
关键词
LNG储罐用钢
镍基焊条
枝晶间距
塑性
韧性
LNG storage tank steel
nickel-based electrode
dendrite spacing
plasticity
toughness
