熔焊保护气体最小用量的研究

发布时间：2018-07-25 07:43

【摘要】：熔化极气体保护焊是利用电弧作为热源,气体作为保护介质的熔化焊,其中保护气用量的成本约占焊接工艺成本的10%左右。因此,在保证焊接质量基础上,如何减小保护气用量,对降低企业制造成本和节省资源具有重要的意义。本研究采用了理论分析、数值计算和实验验证的方法,对保护气的用量进行了分析和探讨,主要研究内容如下:(1)根据气体保护焊的相关理论,分析了焊接过程中影响保护气用量参数之间的相关关系,提出了最小量保护气的概念,构建了保护气最小量的数学模型。(2)依据保护气最小量数学模型,设计出普通喷嘴、螺旋喷嘴、缩径喷嘴和扩散喷嘴四种结构的喷嘴,通过FLUENT软件对四种喷嘴的保护气流场进行分析计算。结果表明,相对于普通喷嘴,缩径喷嘴和扩散喷嘴可以直接减少保护气用量,而双螺旋喷嘴通过增加熔池驻留时间来减少保护气用量。(3)利用FLUENT软件中的UDF和UDS模块进行二次开发,将电弧导入到流场中进行耦合仿真,结果表明电弧区的等离子保护气的流场形态发生很大的变化,受到电弧影响位于工件表面的工件上保护气体包裹效果更好,而在焊丝和工件表面之间出现保护气缩径现象。加载电弧的保护气流场跟未加载电弧的流场进行比较,除了普通喷嘴外所得其余喷嘴各自最小气体的用量结论基本一致。(4)构建了焊接保护气混合配比系统,采用氩气80%+二氧化碳20%混合保护气,四种喷嘴、不同流量进行了焊接实验。测试了样件母材、热影响区和焊接区的硬度,在热影响区和母材区交界处,三种较小保护气流量的焊缝的硬度要高于传统大量的焊缝;通过观察焊缝的金相组织,发现双螺旋喷嘴的晶粒更加均与和细小。拉伸试验时,样件均在母材位置断裂。总体结果表明,减小保护气用量的焊缝能够满足甚至优于普通大量保护气焊缝的力学性能。本研究得到了江苏省科技创新基金“船用高效气体保护焊微量动态配气系统”(BC2014202)的支持。本论文对气体保护焊保护气用量的研究和探讨,对焊接领域的机理研究和工程应用具有一定的指导意义和参考价值。
[Abstract]:Arc is used as heat source and gas as protective medium. The cost of protective gas is about 10% of the cost of welding process. Therefore, on the basis of ensuring welding quality, how to reduce the amount of protective gas is of great significance to reduce the manufacturing cost and save resources. In this study, theoretical analysis, numerical calculation and experimental verification are used to analyze and discuss the amount of shielding gas. The main contents are as follows: (1) according to the related theory of gas shielded welding, In this paper, the correlation relationship between the parameters of protective gas dosage in welding process is analyzed, the concept of minimum protective gas is put forward, and the mathematical model of minimum amount of protective gas is constructed. (2) according to the mathematical model of minimum quantity of protective gas, the common nozzle is designed. The protected airflow field of four kinds of nozzles are analyzed and calculated by FLUENT software for spiral nozzles, diametral nozzles and diffusive nozzles. The results show that, compared with ordinary nozzles, diameter reduction nozzles and diffusion nozzles can directly reduce the amount of protective gas. The double helix nozzle reduces the amount of protective gas by increasing the residence time of the molten pool. (3) using the UDF and UDS modules in the FLUENT software for secondary development, the arc is imported into the flow field for coupling simulation. The results show that the flow pattern of the plasma shielded gas in the arc region changes greatly, and the shielding gas encapsulation effect is better on the workpiece which is affected by the arc, but there is the phenomenon of shielding gas shrinkage between the welding wire and the surface of the workpiece. Compared with the flow field of the unloaded arc, the results of the minimum gas consumption of the other nozzles except the ordinary nozzles are basically the same. (4) A welding protective gas mixing and matching system is constructed. The welding experiments were carried out with argon 80% carbon dioxide 20% mixed protective gas, four nozzles and different flow rates. The hardness of the base metal, heat affected zone and welding zone of the sample was tested. At the junction of the heat affected zone and the base metal area, the hardness of the weld with three kinds of smaller flux of protective gas was higher than that of the traditional mass weld, and the metallographic structure of the weld was observed. It is found that the grains of double helix nozzle are more uniform and fine. During the tensile test, the samples were broken at the base metal position. The overall results show that the welds with reduced amount of protective gas can meet or even outperform the mechanical properties of the conventional large amount of shielded gas welds. The research is supported by Jiangsu Provincial Science and Technology Innovation Fund, Marine High efficiency Gas shielded Welding Micro dynamic Valve Distribution system (BC2014202). This paper has some guiding significance and reference value for mechanism research and engineering application in welding field.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG444.72

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