發(fā)布時(shí)間：2018-07-25 07:43

【摘要】：熔化極氣體保護(hù)焊是利用電弧作為熱源,氣體作為保護(hù)介質(zhì)的熔化焊,其中保護(hù)氣用量的成本約占焊接工藝成本的10%左右。因此,在保證焊接質(zhì)量基礎(chǔ)上,如何減小保護(hù)氣用量,對降低企業(yè)制造成本和節(jié)省資源具有重要的意義。本研究采用了理論分析、數(shù)值計(jì)算和實(shí)驗(yàn)驗(yàn)證的方法,對保護(hù)氣的用量進(jìn)行了分析和探討,主要研究內(nèi)容如下:(1)根據(jù)氣體保護(hù)焊的相關(guān)理論,分析了焊接過程中影響保護(hù)氣用量參數(shù)之間的相關(guān)關(guān)系,提出了最小量保護(hù)氣的概念,構(gòu)建了保護(hù)氣最小量的數(shù)學(xué)模型。(2)依據(jù)保護(hù)氣最小量數(shù)學(xué)模型,設(shè)計(jì)出普通噴嘴、螺旋噴嘴、縮徑噴嘴和擴(kuò)散噴嘴四種結(jié)構(gòu)的噴嘴,通過FLUENT軟件對四種噴嘴的保護(hù)氣流場進(jìn)行分析計(jì)算。結(jié)果表明,相對于普通噴嘴,縮徑噴嘴和擴(kuò)散噴嘴可以直接減少保護(hù)氣用量,而雙螺旋噴嘴通過增加熔池駐留時(shí)間來減少保護(hù)氣用量。(3)利用FLUENT軟件中的UDF和UDS模塊進(jìn)行二次開發(fā),將電弧導(dǎo)入到流場中進(jìn)行耦合仿真,結(jié)果表明電弧區(qū)的等離子保護(hù)氣的流場形態(tài)發(fā)生很大的變化,受到電弧影響位于工件表面的工件上保護(hù)氣體包裹效果更好,而在焊絲和工件表面之間出現(xiàn)保護(hù)氣縮徑現(xiàn)象。加載電弧的保護(hù)氣流場跟未加載電弧的流場進(jìn)行比較,除了普通噴嘴外所得其余噴嘴各自最小氣體的用量結(jié)論基本一致。(4)構(gòu)建了焊接保護(hù)氣混合配比系統(tǒng),采用氬氣80%+二氧化碳20%混合保護(hù)氣,四種噴嘴、不同流量進(jìn)行了焊接實(shí)驗(yàn)。測試了樣件母材、熱影響區(qū)和焊接區(qū)的硬度,在熱影響區(qū)和母材區(qū)交界處,三種較小保護(hù)氣流量的焊縫的硬度要高于傳統(tǒng)大量的焊縫;通過觀察焊縫的金相組織,發(fā)現(xiàn)雙螺旋噴嘴的晶粒更加均與和細(xì)小。拉伸試驗(yàn)時(shí),樣件均在母材位置斷裂。總體結(jié)果表明,減小保護(hù)氣用量的焊縫能夠滿足甚至優(yōu)于普通大量保護(hù)氣焊縫的力學(xué)性能。本研究得到了江蘇省科技創(chuàng)新基金“船用高效氣體保護(hù)焊微量動(dòng)態(tài)配氣系統(tǒng)”(BC2014202)的支持。本論文對氣體保護(hù)焊保護(hù)氣用量的研究和探討,對焊接領(lǐng)域的機(jī)理研究和工程應(yīng)用具有一定的指導(dǎo)意義和參考價(jià)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.
【學(xué)位授予單位】：江蘇大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TG444.72

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