共查询到19条相似文献,搜索用时 203 毫秒
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基于热-力耦合的焊接热弹塑性有限元法,建立运动电弧作用下的二维体热源模型.采用"生死单元"技术实现焊缝的顺序生长来完成温度场的计算;选择平面应变模型,计算大厚度多道焊接的残余应力,最终得到钛合金厚板焊接过程温度场和应力场分布以及厚板焊接接头的三维应力的分布规律,并与钛合金厚板应力测试结果进行对比验证,两者很接近.该研究结果为钛合金厚板焊接接头残余应力的研究提供了参考. 相似文献
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采用激光自熔焊、激光填丝焊及激光-电弧复合焊进行高强钢焊接时均会出现热裂纹,且以凝固裂纹为主。针对该问题,文中综合论述了近些年激光及其复合焊高强钢凝固裂纹的研究情况,介绍了凝固裂纹的特点、形成机制及防止措施。从目前的研究结果来看,高强钢激光焊接中凝固裂纹以焊缝纵向裂纹为主,国内外主要从化学成分、熔池几何形状、焊接参数、拘束度4个影响因素研究凝固裂纹的形成,研究侧重于熔池的凸起部分和深宽比对凝固裂纹形成的影响,凸起部分会造成凝固延迟、产生大的拉应力、促进S,P杂质元素的偏析;较大的深宽比会造成局部应力集中从而引发裂纹产生。采用不同工艺方法改变焊缝几何形状是解决激光焊接凝固裂纹的一个重要方向。 相似文献
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采用激光自熔焊、激光填丝焊及激光-电弧复合焊进行高强钢焊接时均会出现热裂纹,且以凝固裂纹为主。针对该问题,文中综合论述了近些年激光及其复合焊高强钢凝固裂纹的研究情况,介绍了凝固裂纹的特点、形成机制及防止措施。从目前的研究结果来看,高强钢激光焊接中凝固裂纹以焊缝纵向裂纹为主,国内外主要从化学成分、熔池几何形状、焊接参数、拘束度4个影响因素研究凝固裂纹的形成,研究侧重于熔池的凸起部分和深宽比对凝固裂纹形成的影响,凸起部分会造成凝固延迟、产生大的拉应力、促进S,P杂质元素的偏析;较大的深宽比会造成局部应力集中从而引发裂纹产生。采用不同工艺方法改变焊缝几何形状是解决激光焊接凝固裂纹的一个重要方向。 相似文献
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针对固定电弧等离子弧焊接过程建立了二维稳态热传导模型 ,在模型中考虑了工件表面与周围环境换热及辐射散热对整个焊接热过程的影响 ,并且将焊接电流在流经工件时产生的焦耳热作为热能方程的源项进行计算。针对所建立的模型 ,采用大型商业软件PHOENICS(Parabolichyperbolicorellipticnumericalintegrationcodeseries)对工件中的温度场以及电流密度的分布进行了计算。采用该软件对焊接热过程进行数值模拟 ,可以很方便地对求解变量和边界条件进行操作 ,显著提高了效率。比较结果显示 ,计算结果与实际测量结果吻合良好 相似文献
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奥氏体不锈钢激光焊接过程中残留液体金属的在线观察 总被引:1,自引:1,他引:0
激光焊接时较快的冷却速度,有可能促进凝固热裂纹的生成,而凝固热裂纹的生成与凝固温度区间内的残留液体金属行为直接相关.采用由高速摄像机和光学显微镜头组成的摄像装置,针对SUS304,SUS316,SUS310S等3种奥氏体不锈钢激光焊接熔池后端残留液体金属的凝固行为进行高速高倍在线观察,对不同焊接速度下的熔池凝固行为进行了分析,并对3种材料凝固前沿残留液体金属的存在范围进行了量化比较.结果表明,在线观察法可辨别的残留液体金属是固液相共存区间的一部分,在线观察得到的残留液体金属的存在范围与热裂纹试验获得的热裂纹敏感性有较好的对应关系. 相似文献
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Numerical simulation of temperature fields for weld metal solidification cracking in stainless steels 总被引:1,自引:1,他引:0
0 IntroductionItisknownthattheweldmetalsolidificationcrackingresultsfromcompetitionbetweenthematerialresistanceandthemechanicaldrivingforceduringthecourseofsolidificationoftheweldmetal[1].Weldmetalsolidificationcrackingoccurswhenthemechanicaldriving… 相似文献
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This paper has analyzed the influences of the he at input of the welding arc, the latent heat of solidification, the fluid flow of liquid metal on the heat conductivity pertaining to the welding solidification crack of stainless steels. As a result, two dimensional heat conduction models with the prescribed heat flux moving along the weld have been developed that can simulate welding arc, convection and radiation heat loss from top and bottom surfaces of the workpiece. Finally, the f inite element model was used to analyze and calculate the temperature fields. 相似文献
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Chen ShujunWang XuanYuan TaoLi Xiaoxu 《金属学报》2018,(12):1735-1744
Magnesium alloys has a wide application prospect due to their good properties, such as high specific strength and specific stiffness, but the susceptibility of liquation cracking is also pretty high. The liquation in partially melted zone of AZ-series magnesium alloys were investigated with circular-patch welding test. The AZ91, AZ31 base alloys were welded with AZ61 and AZ92 filler wires by using the cold metal transter metal inert-gas (CMT-MIG) welding. The results show that, the liquation occurred along the weld edge of AZ91 with the eutectic reaction occurring between gamma(Mg17Al12) phase and Mg-rich phase. The liquation susceptibility of AZ31 was pretty low as gamma(Mg17Al12) was not present in base metal of AZ31. Meanwhile, a new method for predicting liquation cracking based on binary phase diagram was proposed. When the initial solidification temperature of weld is higher and the solidification temperature range of weld is shorter than those of base metal, the liquation crack susceptibility of weld is mostly higher. When the initial solidification temperature of weld is close to or below that of base metal, and the solidification temperature range of weld is close to or longer than that of base metal, the liquation cracking susceptibility of weld is lower. This method worked well on predicting the effect of composition of base metal and filler wires on liquation cracking, and the predicting results are consistent with the experimental results. That is, the liquation cracking susceptibility is higher with AZ91 base metal used than that with AZ31 base metal. And, the liquation cracking susceptibility is lower with AZ92 filler wire than that with AZ61 filler wire. 相似文献
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《Science & Technology of Welding & Joining》2013,18(4):471-479
AbstractThe effect of addition of La to a filler metal on microcracking (ductility dip cracking) in the multipass weld metal of alloy 690 was investigated with the aim of improving its microcracking susceptibility. The susceptibility to ductility dip cracking in the reheated weld metal could be greatly improved by adding 0·01–0·02 wt-%La to the weld metal. Conversely, excessive La addition to the weld metal led to liquation and solidification cracking in the weld metal. Hot ductility of the weld metal at the cracking temperature was greatly improved by adding 0·01–0·02 wt-%La to the weld metal, implying that the ductility dip cracking susceptibility was decreased as a result of the desegregation of impurity elements of P and S to grain boundaries due to the scavenging effect of La. The liquation and solidification cracking resulting from excessive addition of La to the weld metal is attributed to the formation of liquefiable Ni–La intermetallic compound. A multipass welding test confirmed that microcracks in the multipass weldment were completely prevented by using a filler metal containing an addition of 0·01 wt-%La. 相似文献
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《Science & Technology of Welding & Joining》2013,18(1):58-67
AbstractExperimental observation and numerical modelling were employed to investigate the solidification cracking behaviour during fibre laser welding of 6013 aluminium alloy. The solidification cracking initiation location and propagation path were studied using a high speed camera system and via metallurgical analysis. A three-dimensional thermomechanical finite element model of fibre laser welding of aluminium alloys was developed, which considered cylindrical volumetric heat source, temperature dependent material properties, solidification shrinkage and stress relaxation in the weld molten pool. The transient evolution and distribution of mechanical strain in the brittle temperature range (BTR) were analysed in detail to find the factors which drove the crack initiation and propagation. The results showed that the solidification cracking initiated near the fusion line and then propagated along the centreline of the weld, which was the result of the strain distribution characteristic in BTR. 相似文献
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使用扫描电镜、能谱、温度场实时采集等测试方法,研究了焊丝中Si含量对AA6063铝合金GMAW焊接头热裂纹敏感性的影响规律及机理. 结果表明,当焊丝为纯铝时,鱼骨试样的焊缝中心会出现细长的焊接裂纹;当焊丝中的Si含量为4.5% ~ 6%时,裂纹的长度变短,但是开裂距离明显增加;当焊丝中的Si含量达到11% ~ 13%时,试样焊缝无裂纹出现. 随着Si含量的不断提高,合金易出现裂纹的凝固温度区间先增大后减小;焊丝中Si含量的不同还会影响凝固后期金属液的流动性,使得焊缝晶界处的物相成分和形态都有明显的区别;同时,Si含量的提高会使得接头的冷却速度先增加后减小,从而导致应力状态改变,热裂纹敏感性先升高后降低. 相似文献