本文選題：電子束焊 + 厚板鈦及鈦合金�。� 參考：《山東大學》2017年碩士論文

【摘要】：鈦及鈦合金因其密度小、比強度高、耐腐蝕性好及焊接性好等優(yōu)異的綜合性能,被廣泛用于核潛艇耐壓殼體、管路系統(tǒng)件等船用結(jié)構(gòu)件的制造中。船用結(jié)構(gòu)件多為大厚度焊接件,隨著我國海洋強國戰(zhàn)略規(guī)劃的提出,船用大厚度焊接件的需求量不斷增加,厚板鈦合金的焊接問題引起了廣泛關(guān)注。真空電子束焊具有熱源功率密度高、能量集中、變形小及可焊厚度范圍寬等一系列優(yōu)點,可以避免傳統(tǒng)的焊接方法在焊接厚板鈦合金時所產(chǎn)生的缺陷,獲得性能良好的接頭。本課題分別對厚度30mm純鈦(TA1)及100mmTC4鈦合金大厚板進行了電子束焊(EBW),并對接頭進行了不同工藝的焊后熱處理試驗。研究了熱處理前后厚度30mmTA1及100mmTC4電子束焊接接頭橫截面不同深度處顯微組織、顯微硬度的變化特點,測試了接頭橫截面不同深度處室溫下的拉伸性能、沖擊性能。采用掃描電子顯微鏡(SEM)對接頭斷口形貌進行了觀察并分析顯微組織對斷裂機制的影響。厚度30mmTA1電子束焊接接頭組織由母材區(qū)等軸α到焊縫區(qū)粗大α柱狀晶+鋸齒狀α+針狀α'組織過渡。焊縫區(qū)針狀位α'使得接頭硬度、強度變高,強度最高增幅為5.2%;韌塑性變差,降低幅度在10.7%～19.3%,接頭上部和底部的強度優(yōu)于中部。接頭經(jīng)過750℃×2h FC熱處理焊縫區(qū)域α'馬氏體數(shù)量增多;850℃×2h FC熱處理焊縫的馬氏體α'發(fā)生碎化生成大量無序、短小的針狀組織。650℃×2h FC熱處理后整體硬度降低,850℃×2h FC熱處理后整體硬度升高,熱影響區(qū)存在軟化現(xiàn)象。TA1接頭經(jīng)過熱處理后接頭橫截面不同深度處的組織性能更加均勻。厚度100mmTC4電子束焊接接頭組織由母材區(qū)的等軸(α+β)相連續(xù)過渡到焊縫區(qū)的針狀α'馬氏體。接頭橫截面不同深度處的硬度和強度均高于母材、伸長率低于母材,接頭伸長率最大降低幅度為30.2%,焊縫的沖擊功低于母材的沖擊功。TC4接頭經(jīng)600℃×2h FC處理焊縫α相得到粗化;850℃×2h FC熱處理焊縫針狀α'馬氏體含量增多。(920℃×2h WC)+(500℃C×4h AC)熱處理后焊縫組織為針狀α'馬氏體+原始β晶界;相比于焊件,接頭最大平均抗拉強度增大141MPa,伸長率最多降低了 56.5%,焊縫硬度增大60HV,母材硬度增加40HV。不同熱處理后100mm TC4電子束焊接接頭各層性能更加均勻。TA1焊接件、650℃×2h FC及750℃ ×2hFC熱處理后接頭的拉伸、沖擊斷裂機制均為韌窩斷裂。850℃×2hFC熱處理后拉伸斷裂機制為韌窩和準解離的混合型斷裂,沖擊斷裂機制為準解離斷裂。TC4焊件、600℃×2h FC和850℃×2h FC熱處理后接頭拉伸斷裂機制均為韌窩斷裂,(92℃×2h WC)+(500℃×4h AC)熱處理態(tài)下拉伸試樣斷裂機制為解離斷裂。TC4焊件焊縫沖擊斷裂機制為準解離斷裂,60℃×2h FC和850℃×2h FC熱處理后焊縫斷裂機制為韌窩斷裂;(920℃×2h WC)+(500℃×4h AC)熱處理后焊縫沖擊試樣斷裂機制為解離和韌窩的混合型斷裂,解離斷裂為主。
[Abstract]:Because of its low density, high specific strength, good corrosion resistance and good weldability, titanium and titanium alloys are widely used in the manufacture of marine structural parts such as nuclear submarine pressure shell, pipe system parts and so on.Marine structural parts are mostly welded parts with large thickness. With the strategic planning of our country, the demand for large thickness welded parts is increasing, and the welding problem of thick plate titanium alloy has attracted wide attention.Vacuum electron beam welding (VEBW) has a series of advantages such as high heat source power density, energy concentration, small deformation and wide weldable thickness range. It can avoid the defects of traditional welding method in welding thick plate titanium alloy and obtain good performance joint.In this paper, electron beam welding (EBW) was carried out on thick 30mm pure titanium (TA1) and 100mmTC4 titanium alloy thick plates, and different post-welding heat treatment tests were carried out on the joints.The microstructure and microhardness of 30mmTA1 and 100mmTC4 electron beam welded joints with thickness at different depths before and after heat treatment were studied. The tensile and impact properties at room temperature at different depths of cross section were tested.The fracture morphology of the joint was observed by scanning electron microscope (SEM) and the effect of microstructure on fracture mechanism was analyzed.The microstructure of thick 30mmTA1 electron beam welded joints is from the equiaxed 偽 in the base metal region to the coarse 偽 columnar zigzag 偽 'structure in the weld zone.The needle position 偽'in the weld zone makes the joint hardness, strength is higher, the maximum increase of strength is 5.2, the toughness and plasticity become worse, the decrease range is 10.7 and 19.3.The strength of the upper and bottom joint is better than that of the middle part.After 750 鈩，

本文編號：1731913