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对超声波塑料焊接过程进行了分析,发现在焊接接头经历熔化开始,铺展,熔融物挤出及接头凝固不同阶段中,压力的作用也不尽相同。 相似文献
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设计了三维焊接凝固裂纹的数值模拟与预测软件系统,使普通的焊接技术人员可以简便地实现焊接凝固裂纹的数值模拟与预测.系统由三部分组成:前处理,后处理和凝固裂纹预测部分.其中系统的前处理可以帮助用户选择接头类型,对接头进行网格剖分,输入材料性能参数、焊接工艺条件以及力学边界条件等,并自动以MSC.Marc命令流的形式存储成MSC.Marc的过程文件.依据生成的过程文件,自行连接MSC.Marc有限元软件,对焊接凝固裂纹的温度场和应力、应变场进行数值模拟计算,并存储模拟结果,为后处理做准备. 相似文献
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采用BNi68CrWB钎料粉末对K24和GH648异种高温合金进行钎焊连接,分析了接头典型界面组织,提出了钎焊过程反应机理.结果表明,接头由共晶区、等温凝固区和扩散区组成.共晶区由WB,CrB和镍基固溶体组成,等温凝固区为镍基固溶体,GH648侧扩散区由WB,WxBy,CrxBy,以及沿晶界析出的镍基固溶体和少量的Cr2Ni3相组成,K24侧扩散区与母材差异不明显.钎焊过程由元素富集、母材溶解、等温凝固和共晶凝固四个阶段组成.其中等温凝固阶段是钎焊过程中最关键的阶段,等温凝固不完全时,钎缝中央存在共晶组织,影响接头性能.钎焊温度1 150℃,保温120 min时,等温凝固完全,接头组织均匀,力学性能最优,室温拉剪强度可达323 MPa. 相似文献
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为了探明单晶过渡液相(TLP)扩散焊接头组织与性能的关系,采用扫描电镜(SEM)研究接头微观组织,并进行力学性能测试. 结果表明,接头由连接区和基体区所组成. 当等温凝固过程未完成时,连接区由等温凝固区和快速凝固区组成,而等温凝固区主要由γ和γ'相组成,快速凝固区主要是由共晶组织组成. 当等温凝固完成而固态均匀化过程不充分时,连接区由等温凝固区和分布在接头中心的硼化物相组成. 采用低温等温凝固,高温固态均匀化的焊接工艺可以获得高性能的接头. 相似文献
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研究标准热处理对扩散焊IN-738LC高温合金显微组织和力学性能的影响。对连接样品进行全固溶退火、部分固溶退火和时效处理3个不同的热处理。结果表明,在1120℃下焊接5 min,会导致不完全等温凝固,在焊缝处形成富Ni、Cr的硼化物共晶相。当保温时间延长到45 min时,接头中发生完全等温凝固,形成镍的先共晶固溶体γ相。等温凝固和非等温凝固样品的标准热处理能完全消除扩散影响区的硼化物相,并在等温凝固区形成γ’析出相。然而,在非等温凝固样品的接头区观察到不连续的再凝固产物。等温凝固样品经标准热处理后,剪切强度最高(约801 MPa),为基材剪切强度的99%。 相似文献
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综述了焊缝金属对SUPER 304H钢焊接性的影响。结果表明,SUPER 304H钢不同成分GTAW奥氏体焊缝的热裂纹倾向较大;焊缝中凝固裂纹倾向主要是受A凝固模式控制,而HAZ液化裂纹倾向的主要原因则与晶界析出相,以及铜的富集等因素有关。不同成分奥氏体焊缝接头的力学性能各异;合适的焊缝化学成分和优化的焊接工艺是获得满意接头综合力学性能的重要技术手段。不同成分形成的"同质"或"异质"焊缝,其微观组织皆为奥氏体+析出相。熔化焊焊缝为A凝固模式,非熔化焊的摩擦焊焊缝为AF凝固(相转变)模式。 相似文献
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采用Ni-Cr-Fe基钎料对Hastelloy X高温合金进行了活性扩散钎焊。通过扫描电镜、能谱分析、X射线衍射等测试手段分析了接头微观结构和相组成,并且研究不同焊接温度和保温时间对接头微观结构演变的影响。结果表明,焊接接头主要包括凝固区、扩散区和基体区,其中凝固区主要由γ固溶体和复杂硼化物M_3B_2(M=Cr,Mo)组成;而扩散区则由γ固溶体和3种不同形态的Cr,Mo的硼化物组成。随着焊接温度的升高和保温时间的延长,扩散区晶内析出的硼化物逐渐减少,同时在晶间处的析出相增多。在1 170℃,30 min条件下,接头的最大硬度出现在凝固区的析出相位置,约为406 HV1。 相似文献
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When heavy machines and large scaled receiver system of communication equipment are manufactured, it always needs to produce large- sized steel castings, aluminum castings and etc. Some defects of hot cracking by thermal stress often appear during solidification process as these castings are produced, which results in failure of castings.Therefore predicting the effects of technological parameters for production of castings on the thermal stress during solidification process becomes an important means. In this paper, the mathematical models have been established and numerical calculation of temperature fields by using finite difference method (FDM) and then thermal stress fields by using finite element method (FEM) during solidification process of castings have been carried out. The technological parameters of production have been optimized by the results of calculation and the defects of hot cracking have been eliminated. Modeling and simulation of 3D thermal stress during solidification processes of large-sized castings provided a scientific basis, which promoted further development of advanced manufacturing technique. 相似文献
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利用华铸CAE/Inte-CAST8.0软件对大型铸钢件进行了温度场的凝固模拟,预测了缩孔、缩松缺陷产生的部位,并且分析了缺陷产生的原因,在此基础上对其铸造工艺进行了优化。优化后的模拟结果表明:合理设置保温冒口、冷铁的大小和位置,可以保证铸件顺序凝固,并且延长金属液的有效补缩距离,获得符合国际标准的大型铸钢件。 相似文献
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在粘土砂湿型、手工造型条件下,通过厚壁大型G-AlSi10Mg铸件的工艺试验与改进,对浇注系统进行了工艺优化。实践表明,运用大孔出流底注式浇注系统、冒口与冷铁配合的工艺,可以实现厚大件的均衡凝固,消除缩孔(松)缺陷,提高工艺出品率,浇出合格铸件。 相似文献
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3-D velocity and temperature fields of mold filling and solidification processes of large-sized castings were calculated, and the efficiency and accuracy of numerical calculation were studied. The mold filling and solidification processes of large-sized stainless steel, iron and aluminum alloy castings were simulated by using of new scheme; their casting processes were optimized, and then applied to produce castings. 相似文献
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Modeling characteristics for solidification in single-crystal,investment-cast superalloys 总被引:1,自引:0,他引:1
Andrew L. Purvis Ph.D. Christopher R. Hanslits B.S. Randall S. Diehm M.S. 《JOM Journal of the Minerals, Metals and Materials Society》1994,46(1):38-41
Macroscopic traits of solidification such as thermal gradient, solidification rate, and other criteria functions were extracted from computer modeling data of a single-crystal, investment-cast superalloy. The thermal histories were used to predict the presence or absence of grain defects in the shaped castings. Freckle defects were found on castings with various processing parameters, even though the traditional microstructural defect map predicted no freckles and a consistent microstructure. The findings suggest that the traditional defect map criteria are insufficient to accurately describe the formation of these and other single-crystal grain defects. Hence, additional criteria for porosity formation and other phenomena were investigated and found to be sensitive to changes in solidification conditions and grain defect formation. The additional functions were found to be necessary to fully capture the total energy of all solidification phenomena. When these functions are used in conjunction with the traits of the microstructural defect map, the prediction of defects in single-crystal castings can more accurately describe solidification under the stringent requirements of single-crystal turbine components. 相似文献
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高锰钢铸件裂纹的产生机理探讨 总被引:1,自引:0,他引:1
分析了高锰钢铸件在实际生产中产生裂纹的原因及铸件凝固过程中各种因素的影响,从结构设计、化学成分控制、浇铸工艺和热处理工艺等方面提出了预防措施。 相似文献
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测试了在100~500℃温度下,碱酚醛树脂砂与硅砂混合配比的溃散性,找出了型砂全部溃散时的最低温度为400℃。运用Procast软件模拟了不同壁厚的圆筒形铸钢件的凝固过程及铸型和型芯的温度场;研究了圆筒形铸钢件壁厚(模数)与碱酚醛树脂砂临界吃砂量的关系,给出了两者之间的回归方程。 相似文献