【作者】 孙辉；

【导师】 董海； 谭明辉；

【作者基本信息】 大连理工大学 ， 机械工程（专业学位）， 2018， 硕士

【摘要】 近些年来汽车的供需逐年增加,相应的汽车排气系统的需求量也大幅增加。排气系统的制造材料已由过去单一的普通碳钢,逐渐向镀铝不锈钢、高强钢等材料多元化方向发展,其中镀铝不锈钢以优异的抗腐蚀性能开始逐渐的用于汽车排气系统的制造。由于镀铝不锈钢在汽车排气系统中的应用,因此排气系统的焊接方法也需要不断的改进和提高,其中的冷金属过渡焊接技术(CMT焊接技术)是排气系统厂家提高产品焊接质量的重要手段。但目前的实际应用范围较小,对于镀铝不锈钢管件的焊接工艺参数还没有相应的指导资料。因此研究薄壁镀铝不锈钢管件冷金属过渡焊接方法,找出合理的焊接电流及电压等工艺参数对提高企业的生产效率及产品质量都具有非常重要的指导意义。本文是以409Al和439马氏体不锈钢为研究对象,首先运用数值模拟的方法对CMT焊接的工艺参数进行筛选,找到一组适合的电流、电压范围;在此基础上,结合焊接试验,调整了5种焊接电流和5种焊接电压,采用固定电流调整电压的方法进行了25组焊接试验,并通过外观检测筛选、磁粉和渗透相结合的无损检测方法以及气密性试验等方式展开研究,确定出最优的焊接参数值。实验结果:本文建立了CMT焊接有限元模型,针对CMT焊接“冷-热-冷”交替的特点对热源模型进行处理,得到了较为精确的结果。经过大量模拟与实验数据的对比,在焊接电流为75A、焊接电压为20V时,焊接试样接头处无焊接缺陷,质量良好。此外,又通过了外观检测、焊缝无损检测以及工件的气密性检测等环节,测试结果均符合质量标准的要求。对试验结果进行观察和分析,得出的结论为:不锈钢薄管CMT焊接电压和电流的最佳值分别为20V和75A。更多还原

【Abstract】 In recent years,the supply and demand of automobiles have increased year by year,and the requirements for automotive exhaust systems have also increased considerably.The manufacturing materials of the exhaust system have been developed from traditional carbon steels to aluminized stainless steels,high strength steels,and so on.Aluminized stainless steel began to be used in the manufacture of automobile exhaust system with excellent corrosion resistance.Because of the application of aluminized stainless steel in the automotive exhaust system,the welding method of the exhaust system needs constant improvement.In especial,cold metal transition welding technology(CMT welding technology)is an important means for the exhaust system manufacturers to improve the welding quality of products.However,the actual application range of the CMT is smaller,and there is no corresponding guidance data for the welding process parameters of aluminized stainless steel pipe fittings.Therefore,it is very important to study the CMT welding method of thin-walled aluminum stainless steel pipe,find out the welding parameters such as voltage and current reasonable.It has very important guiding significance for improving production efficiency and product quality.In this paper,409 Al and 439 stainless steel are taken as the research object.The numerical simulation method is used to screen the welding parameters of CMT in order to find a set of suitable current and voltage ranges.On this basis,combined with welding test,5 welding current and 5 welding voltage are adjusted(25 sets of welding tests).Finally,the above methods integrate appearance screening,magnetic particle testing,penetrant testing and air tightness test,the optimum welding parameter value are determined.The results indicated that a finite element model of CMT welding was established.In view of the characteristics of CMT welding "cold-hot-cold" alternation,the heat source model is dealt with.More accurate results was obtained.A large amount of simulation were compared with experimental data.Good quality weldments were obtained when the welding current is 75 A and the welding voltage is 20 V.In addition,these weldments passed the test of integrate appearance screening,nondestructive examination and air tightness test.Test results are in line with quality standards.Through a series of experiments and theoretical analysis,the optimum welding current parameter of stainless steel thin tube is 75 A,and the optimum parameter of welding voltage is 20 V by CMT.更多还原