【正文】 大學(xué)本科畢業(yè)設(shè)計(jì)（論文） II Abstract To solve the welding problem in manufacturing 4500mm level bathyscaphe and propel the development of thick titanium alloys structures in industrial, narrowgap TIG welding of thick titanium alloys is proposed as an efficient and economical method. Narrowgap TIG welding of TC4 by using Ti4Al2V filler metal with multilayer welding way, experiments have been done under the different sizes of groove and serials of currents and protecting gasflowrates, to determine the optimum welding parameters after the metallographic analysis and mechanical properties testing of welding joint. Results of welding technology experiment shows that the reliable joint can be obtained under the current of 180A240A, welding lateral contraction is about in 78mm titanium plate, and the joint is narrow with no marked division. Metallographic analysis of narrowgap TIG welding joint shows the rules of grain growth and microstructure characteristics, the changing of currents has little effect on the size of grain and microstructure. The tensile test shows that the tensile strength of joint is higher than the seam metal based on the theory of meshing strengthening in narrowgap welding of titanium alloys, the increase of current leads to the rising of perationratio, that also can contribute to increasing of strength. Results of Welding temperature field measurement show that the titanium alloys welding temperature field has its characteristics in the condition of narrowgap TIG welding. Keywords: thick titanium alloys。 narrowgap TIG。 microstructure。 mechanical property。 welding temperature field 哈爾濱工業(yè)大學(xué)本科畢業(yè)設(shè)計(jì)（論文） III 目 錄 摘 要 ............................................................................................................................... I Abstract ............................................................................................................................. II 第 1 章 緒 論 ................................................................................................................ 1 課題背景及研究的目的和意義 ............................................................................ 1 厚板鈦合金焊接性分析 ........................................................................................ 2 國(guó)內(nèi)外研究現(xiàn)狀及分析 ........................................................................................ 3 MIG 多層多道焊 ............................................................................................. 3 窄間隙 TIG...................................................................................................... 4 電子束焊接 ..................................................................................................... 4 厚板鈦合金窄間隙 TIG 焊接 ................................................................................ 5 第 2 章 焊接工藝試驗(yàn) .................................................................................................... 7 焊槍及保 護(hù)裝置的設(shè)計(jì)及制作 ............................................................................ 7 焊槍的設(shè)計(jì)及制作 ......................................................................................... 7 保護(hù)裝置的設(shè)計(jì) 及 制造 ................................................................................. 8 試驗(yàn)材料和坡口 .................................................................................................. 10 試驗(yàn)設(shè)備及方法 ...................................................................................................11 試驗(yàn)設(shè)備 .......................................................................................................11 窄間隙 TIG 多層焊 .......................................................................................11 微觀組織分析 ...................................................................................................... 13 金相組織觀察 ............................................................................................... 13 SME成分分析 .............................................................................................. 13 力學(xué)性能測(cè)試 ...................................................................................................... 13 硬度測(cè)試 ....................................................................................................... 13 強(qiáng)度測(cè)試 ....................................................................................................... 13 第 3 章 厚板鈦合金窄間隙 TIG 焊接接頭顯微組織分析 .......................................... 15 鈦合金窄間隙 TIG 多層焊焊接接頭宏觀 .......................................................... 16 鈦合金 窄間隙 TIG 多層焊接頭晶粒生長(zhǎng)規(guī)律 .................................................. 17 鈦合金窄間隙 TIG 焊接接頭微觀組織分析 ...................................................... 19 鈦及鈦合金同素異構(gòu)轉(zhuǎn)變 .......................................................................... 19 TC4 鈦合金在不同溫度條件下的相變特點(diǎn) ............................................... 19 哈爾濱工業(yè)大學(xué)本科畢業(yè)設(shè)計(jì)（論文） IV 鈦合金窄間隙 TIG 焊接接頭微觀組織分析 .............................................. 20 焊縫區(qū)域成分分析 .............................................................................................. 22 本章小結(jié) .............................................................................................................. 24 第 4 章 厚板鈦合金窄間隙 TIG 焊接接頭力學(xué)性能測(cè)試 .......................................... 25 厚板鈦合金窄間隙 TIG 焊接接頭的顯微硬度分布 ......................................... 25 厚板鈦合金窄間隙 TIG 焊接接頭強(qiáng)度 ............................................................. 26 厚板鈦合金窄間隙 TIG 焊焊縫斷口分析 .......................................................... 28 本章小結(jié) .............................................................................................................. 28 第 5 章 焊接變形與焊接溫度場(chǎng)的測(cè)定 ...................................................................... 30 78mm厚鈦合金窄間隙 TIG 焊接變形測(cè)量 ....................................................... 30 窄間隙 TIG 焊接坡口尺寸的確定 ......................