【正文】 摘 要 太陽能熱水系統(tǒng)中用到薄壁不銹鋼與薄壁紫銅氬弧焊 焊接 。不銹鋼與紫銅的焊接屬于異種金屬焊接，兩者的物理性質(zhì)差異很大，因而兩者的焊接難度較大，在氬弧焊過程中易產(chǎn)生各種缺陷。 本文通過 ANSYS 軟件 對(duì)其 焊接過程進(jìn)行 了 模擬， 得到了薄壁不銹鋼與薄壁紫銅 焊接過程中的溫度場(chǎng)、應(yīng)力 場(chǎng)分布，并依據(jù)模擬結(jié)果對(duì)焊接過程中可能出現(xiàn)的缺陷進(jìn)行了分析 。 ANSYS 模擬步驟如下： 首先， 確定薄壁不銹鋼和薄壁紫銅氬弧焊工藝參數(shù)以及焊縫、坡口形狀，為后文的模擬奠定基礎(chǔ)； 然后，建立焊接有限元模型，使用 APDL 語言 編寫熱源施加程序，采用生死單元技術(shù) 模擬焊接焊縫的依次生成 ，應(yīng)用“ *DO— *ENDDO”循環(huán)語句實(shí)現(xiàn)熱源的移動(dòng)，完成對(duì)焊接溫度場(chǎng)的模擬和分析； 最后，利用溫度場(chǎng)與應(yīng)力場(chǎng)間接耦合法，將溫度場(chǎng)分析的結(jié)果溫度作為載荷施加在模型上，模擬出焊接應(yīng)力場(chǎng)，并對(duì)應(yīng)力場(chǎng)模擬結(jié)果進(jìn)行分析。 根據(jù)焊接溫度場(chǎng)、應(yīng)力場(chǎng)模擬結(jié)果，本文分析了薄壁不銹鋼與薄壁紫銅氬弧焊 焊接過程中以及冷卻后可能出現(xiàn)的質(zhì)量缺陷，并提出了一些建議。具體結(jié)論和建議如下： 一、 由于紫銅散熱比不銹鋼快，因此 薄壁不銹鋼和薄壁紫銅 焊接過程中兩管的溫度場(chǎng)分布極不均衡。這使得焊縫兩側(cè)基體金屬熔化程度不一致，可能導(dǎo)致焊縫成形不良。建議在焊接時(shí)電弧稍微偏向紫銅管一側(cè)，防止不銹鋼一側(cè)受熱過多。 二、冷卻結(jié)束后，始焊位置和終焊位置結(jié)合處留有較大的殘余應(yīng)力，為 253MPa，接近這一溫度材料的屈服極限。因此，在焊接結(jié)合處會(huì)有較大的變形，其內(nèi)部可能會(huì)出現(xiàn)較多的裂紋。建議在焊接時(shí)嚴(yán)格控制熔池溫度、電弧大小以及氬氣流量。 三、由 于在焊接過程中不銹鋼管和紫銅管應(yīng)力分布有很大的不同，因此在冷卻結(jié)束后兩管會(huì)產(chǎn)生不同的體積變化。這對(duì)于焊縫是不利的，同時(shí)也會(huì)使焊件不符合焊接前的尺寸公差，導(dǎo)致零件報(bào)廢。建議焊前對(duì)焊件采取反應(yīng)力、反變形措施。 根據(jù)對(duì)焊件焊后應(yīng)力場(chǎng)、焊件焊后變形的分析，本文對(duì)焊件進(jìn)行了強(qiáng)度和變形校核，校核結(jié)果為：焊件合格，焊接可行。 關(guān)鍵詞： 薄壁不銹鋼 和 紫銅 管；氬弧焊； ANSYS APDL；溫度場(chǎng)；應(yīng)力場(chǎng)；數(shù)值模擬 Abstract TIG welding of thinwalled stainless steel and copper tubes is used in solar hot water system. As the welding of stainless steel and copper is dissimilar metal welding and their physical properties are very different, thus the welding of them is difficult and it is easy to produce a variety of defects in the TIG process. In this paper, the welding process of stainless steel with copper is simulated by using ANSYS software, and the temperature field, stress field distribution in the welding process is obtained afterwards, so that the defects that may occur during the welding process are analyzed based on the simulation results. ANSYS simulation steps are as follows: First, the TIG welding process parameters of thinwalled stainless steel and copper are determined with the shape of welding seam and groove, which lays foundation for later simulation。 Then, the simulation and analysis of welding temperature field is pleted by building a finite element model of welding, using APDL to make programs of heat source, applying element birth and death technology to simulate the successive generating of welding seams and adopting * DO— *ENDDO language to realize the movement of heat source。 Finally, the temperature and stress field indirect coupling method is used to simulate the welding stress field by applying the results of temperature field analysis as temperature loads on the model. After that, the results of stress field simulation are analyzed. Based on the simulation results of welding temperature and stress field, the quality defects of thinwalled stainless steel with copper that may occur during the TIG welding and cooling process are analyzed and some remendations are made accordingly. Specific conclusions and remendations are as follows: Firstly, because the heat transferring of copper is faster than stainless steel, so temperature field distribution of thinwalled stainless steel and copper tubes during the welding process is extremely uneven. This may leads to molten inconsistency of base metal on both sides and may cause poor weld seam. It is remended that the welding arc is slightly partial to copper, in case of the excessive heating of stainless steel. Secondly, at the end of cooling, large residual stress that is 253MPa is remained in the junction area among starting and ending position of welding, close to the yield strength of material at the same temperature. Therefore, there will be greater deformation in the junction area and more cracks inside. It is remend that the temperature of molten pool, the size of welding arc and the gas flow of argon should be under strict control. Thirdly, due to the large difference of stress distribution between stainless steel tube and copper tube during the welding process, different volume changes are produced in two tubes at the end of cooling. This is detrimental to the welding seam and also leads to unfitness of dimensional tolerances of welding parts, resulting in scrapping of welding parts. It is remended that antistress and antidistortion measures should be adopted before welding. Based on the analysis of stress field and deformation of welding parts after welding, the strength and deformation checking of welding parts is conducted in this paper. The checking results are: the welding parts are qualified and the welding is feasible. Keywords: Thinwalled stainless steel and copper tubes。 TIG welding。 ANSYS APDL。 Temperature field。 Stress field。 Numerical simulation 目 錄 摘 要 ......................................................................................................................................... I Abstract.......................................................................................................................................II 第 1 章 緒 論 ........................................................................................................................ 1 本課題研究背景 .......................................................................................................... 1 文獻(xiàn)綜述 ...................................................................................................................... 2 焊接溫度場(chǎng)有限元分析的國(guó)內(nèi)外 現(xiàn)狀 ............................................................ 2 焊接應(yīng)力場(chǎng)有限元分析的國(guó)內(nèi)外現(xiàn)狀 ............................................................ 4 ANSYS 在焊接有限元分析中的應(yīng)用 .............................................................. 6 本課題研究?jī)?nèi)容及意義 .............................................................................................. 7 第 2 章 太陽能熱水系統(tǒng)中不銹鋼和紫銅焊接工藝 .............................................................. 9 太陽能熱水系統(tǒng)工作原理及其連接管成型工藝 ...................................................... 9 太陽能熱水系統(tǒng)工作原理 ................................................................................ 9 太陽能熱水系統(tǒng)用連接管成型工藝 ................................................