發(fā)布時(shí)間：2018-03-27 21:58

  本文選題：7N01鋁合金　切入點(diǎn)：空心型材　出處：《山東大學(xué)》2017年碩士論文

【摘要】：隨著全球大氣污染問(wèn)題不斷突出,節(jié)能減排的重要性日益凸顯。在高速列車領(lǐng)域,車體輕量化是實(shí)現(xiàn)節(jié)能減排的重要途徑之一。鋁合金具有質(zhì)量輕、比強(qiáng)度高、可焊性好、導(dǎo)電導(dǎo)熱性好、耐腐蝕、回收再生性高等優(yōu)點(diǎn),是目前高速列車實(shí)現(xiàn)車體輕量化的最理想材料之一。目前高速列車的承載結(jié)構(gòu)主要采用7×××系鋁合金擠壓型材。在鋁型材連續(xù)擠壓生產(chǎn)過(guò)程中,兩根相鄰擠壓坯料間的界面會(huì)在型材內(nèi)部形成橫向焊縫,而橫向焊縫將導(dǎo)致型材性能下降,需要對(duì)包含橫向焊縫區(qū)域的型材進(jìn)行切除,顯著降低了產(chǎn)品的成品率。由于7×××系鋁合金硬度較高,材料流動(dòng)性能較差,所以型材中橫向焊縫的延伸長(zhǎng)度會(huì)大大增加,特別是空心型材中橫向焊縫延伸長(zhǎng)度增加更為明顯,嚴(yán)重影響了產(chǎn)品成品率。因此,開(kāi)展對(duì)7×××系空心鋁型材擠壓橫向焊縫的相關(guān)研究具有非常重要的工程意義。本文以高速列車用7N01空心鋁型材為研究對(duì)象,采用實(shí)驗(yàn)研究和數(shù)值模擬相結(jié)合的方法開(kāi)展對(duì)橫向焊縫演變規(guī)律和微觀組織的系統(tǒng)研究。本文所做的主要工作和所獲得主要結(jié)論如下:(1)進(jìn)行了 7N01空心鋁型材擠壓實(shí)驗(yàn),研究獲得了空心型材中橫向焊縫的宏觀形貌和演變規(guī)律。同時(shí)利用SEM和EBSD測(cè)試技術(shù)對(duì)橫向焊縫區(qū)域的微觀組織、織構(gòu)組成及含量和拉伸斷口形貌等進(jìn)行了觀察和分析,研究結(jié)果表明,橫向焊縫區(qū)域新坯料和舊坯料的晶粒尺寸、織構(gòu)含量和拉伸斷口形貌等均存在明顯差異。(2)實(shí)驗(yàn)測(cè)試了 7N01鋁合金鑄錠的力學(xué)性能參數(shù)及熱物理性能參數(shù)。通過(guò)熱壓縮實(shí)驗(yàn)獲得了不同應(yīng)變速率和不同變形溫度下7N01鋁合金的應(yīng)力-應(yīng)變數(shù)據(jù),并且對(duì)實(shí)驗(yàn)數(shù)據(jù)進(jìn)行了摩擦和溫度的雙重修正,基于修正后的數(shù)據(jù)建立了7N01鋁合金應(yīng)變補(bǔ)償型Arrhenius本構(gòu)模型和熱加工圖。(3)根據(jù)所獲得的力學(xué)-熱物性參數(shù)及本構(gòu)模型參數(shù),利用HyperXtrude軟件建立了 7N01空心鋁型材橫向焊縫演變過(guò)程模擬模型。通過(guò)與擠壓實(shí)驗(yàn)中所獲得的料頭形狀、擠壓壓力曲線、橫向焊縫形貌及橫向焊縫延伸長(zhǎng)度等結(jié)果進(jìn)行對(duì)比,驗(yàn)證了本文所采用的力學(xué)-熱物性參數(shù)、本構(gòu)模型及橫向焊縫數(shù)值模型的準(zhǔn)確性。(4)利用所建立的橫向焊縫模擬模型,研究了擠壓工藝參數(shù)和模具結(jié)構(gòu)參數(shù)對(duì)橫向焊縫延伸長(zhǎng)度的影響規(guī)律。研究發(fā)現(xiàn),除擠壓溫度外,適當(dāng)調(diào)整擠壓速度、擠壓比以及阻流塊高度、焊合室圓角半徑和分流橋下沉深度等均可有效減小橫向焊縫的延伸長(zhǎng)度。
[Abstract]:The importance of energy saving and emission reduction is becoming more and more prominent along with the global air pollution problem. In the field of high-speed trains, the lightweight of the car body is one of the important ways to achieve energy saving and emission reduction. Aluminum alloy has light quality, high specific strength, good weldability. Good thermal conductivity, corrosion resistance, high recovery and regeneration, etc. At present, it is one of the most ideal materials for the high-speed train to realize the lightweight of the car body. At present, the bearing structure of the high-speed train mainly adopts the 7 脳 脳 脳 series aluminum alloy extruded section. In the process of continuous extrusion of aluminum profile, The interface between the two adjacent extruded billets will form a transverse weld inside the profile, and the transverse weld will lead to the deterioration of the profile properties. Because the hardness of 7 脳 脳 脳 series aluminum alloy is higher and the material flow property is poor, the extension length of transverse weld in the profile will increase greatly, especially in the hollow section. Therefore, it is very important to study the extrusion transverse weld of 7 脳 脳 脳 series hollow aluminum profile. In this paper, the 7N01 hollow aluminum profile used in high-speed train is taken as the research object. A systematic study on the evolution and microstructure of transverse weld was carried out by means of experimental study and numerical simulation. The main work and main conclusions obtained in this paper are as follows: (1) the extrusion experiment of 7N01 hollow aluminum profile is carried out. The macroscopic morphology and evolution of transverse weld in hollow profile were studied. The microstructure, texture composition, content and tensile fracture morphology of transverse weld were observed and analyzed by SEM and EBSD. The results show that the grain size of the new and old billets in the transverse weld zone, The mechanical properties and thermophysical properties of 7N01 aluminum alloy ingot were tested by experiments. Different strain rates and different deformation temperatures were obtained by thermal compression test. Stress-strain data of 7N01 aluminum alloy under degree, Based on the modified data, the strain compensated Arrhenius constitutive model and hot working diagram of 7N01 aluminum alloy are established. A simulation model of transverse weld evolution of 7N01 hollow aluminum profile was established by using HyperXtrude software. The results were compared with the results obtained from extrusion experiments, such as head shape, extrusion pressure curve, transverse weld appearance and transverse weld extension length, etc. The accuracy of the mechanical and thermal physical parameters, constitutive model and numerical model of transverse weld are verified by using the established transverse weld simulation model. The influence of extrusion process parameters and die structure parameters on the extension length of transverse weld is studied. It is found that, besides extrusion temperature, extrusion speed, extrusion ratio and block height should be adjusted properly. The angle radius of welding chamber and the sinking depth of shunt bridge can effectively reduce the extension length of transverse weld.
【學(xué)位授予單位】：山東大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TG379

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