本文選題：激光深熔焊接 + 底部駝峰缺陷��； 參考：《湖南大學(xué)》2015年碩士論文

【摘要】：近年來,隨著高功率、高光束質(zhì)量光纖激光器的出現(xiàn)和發(fā)展,使激光深熔焊接技術(shù)在中厚板焊接制造領(lǐng)域中得到更進(jìn)一步的研究。高功率光纖激光焊接中厚板過程中,激光功率密度可達(dá)106~108 W/cm2,導(dǎo)致其熔池在其動態(tài)過程中受力不平衡而極不穩(wěn)定,容易形成飛濺、表面塌陷及底部駝峰等各種焊接缺陷,從而影響焊縫的各項性能�；谝陨锨闆r,為了能夠?qū)崿F(xiàn)高質(zhì)高效的激光焊接中厚板,本文針對高功率光纖激光焊接厚度為5 mm的SUS 304不銹鋼鋼板的過程中出現(xiàn)底部駝峰的問題,研究小孔及熔池的動態(tài)變化過程,分析孔外金屬蒸汽/等離子體的變化與底部駝峰的關(guān)系,對底部駝峰產(chǎn)生的機(jī)理進(jìn)行試驗研究。(1)闡述高功率激光焊接以及底部駝峰的研究現(xiàn)狀,搭建基于高速相機(jī)拍攝的高功率光纖激光焊接實驗平臺。(2)基于改進(jìn)的“三明治”新方法,采用高速相機(jī)從側(cè)面直接觀測到底部駝峰形成時整個焊接熔池下掉導(dǎo)致焊縫上表面塌陷,結(jié)果表明孔內(nèi)金屬蒸汽壓力以及前沿孔壁液體凸起的向下動量克服小孔底部熔池表面張力的作用,導(dǎo)致熔融金屬被推出內(nèi)部熔池,繼而向后流入駝峰。(3)使用高速相機(jī)從不同角度直接拍攝小孔開口、熔池及孔外金屬蒸汽/等離子體動態(tài)流動過程,研究結(jié)果表明:表面張力作用是導(dǎo)致第一個底部駝峰產(chǎn)生及長大的重要原因;孔內(nèi)熔融金屬流動不連續(xù),前沿孔壁凸起向下移動以及金屬蒸發(fā)反沖壓力,導(dǎo)致小孔底部熔池形成多個具有輪廓的熔滴,熔滴在表面張力以及熔池內(nèi)部流動特征的作用下不斷向后流動匯聚凝固形成底部駝峰。(4)在上下表面保護(hù)氣體為Ar,維持流量及其吹氣角度不變的情況下,采用改變單一變量的試驗方法研究了激光功率,焊接速度,離焦量,下表面保護(hù)氣體流量和焊接方位的變化對底部駝峰傾向的影響。結(jié)果表明合理的工藝措施,可有效地抑制底部駝峰的產(chǎn)生,改善焊縫質(zhì)量。
[Abstract]:In recent years, with the emergence and development of high power and high beam quality fiber lasers, laser deep penetration welding technology has been further studied in the field of plate welding. In the process of high power fiber laser welding of medium and thick plate, the laser power density can reach 106108W / cm ~ 2, which results in unbalanced force and extremely unstable weld pool during its dynamic process, which is easy to form various welding defects such as spatter, surface collapse and bottom hump, etc. Thus, the properties of the weld are affected. Based on the above situation, in order to realize high quality and high efficiency laser welding plate, this paper aims at the problem of bottom hump in the process of high power fiber laser welding SUS 304 stainless steel plate with thickness of 5 mm. The dynamic process of the pore and molten pool is studied, and the relationship between the metal vapor / plasma outside the hole and the bottom hump is analyzed. The mechanism of bottom hump is studied experimentally. 1) the research status of high power laser welding and bottom hump is described, and the experimental platform of high power fiber laser welding based on high speed camera is built. A high-speed camera is used to observe directly from the side to the bottom of the hump, the whole weld pool falls down and the upper surface of the weld collapses. The results show that the pressure of metal vapor in the hole and the downward momentum of liquid protruding in the front hole wall overcomes the surface tension of the molten pool at the bottom of the hole, which results in the molten metal being pushed out into the inner molten pool. Then it flows backward into the hump. 3) using a high speed camera to directly photograph the orifice, the molten pool and the metal vapor / plasma flow outside the hole from different angles. The results show that the surface tension is the important cause of the first bottom hump, the flow of molten metal in the hole is discontinuous, the protruding and downward moving of the front hole wall and the recoil pressure of metal evaporation. Resulting in the formation of a plurality of profiled droplets in the molten pool at the bottom of the orifice, Under the action of surface tension and internal flow characteristics of the molten pool, the droplets continuously flow backward and solidify to form the bottom hump. 4) under the condition that the upper and lower surface protective gas is Arand the flow rate and the blowing angle are not changed, The effects of laser power, welding speed, defocusing amount, flow rate of lower surface shielding gas and welding azimuth on the bottom hump tendency were studied by changing a single variable. The results show that reasonable technological measures can effectively restrain the production of bottom hump and improve weld quality.
【學(xué)位授予單位】：湖南大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TG456.7

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1 夏海龍;光纖激光焊接中厚板的底部駝峰形成機(jī)理的研究[D];湖南大學(xué);2015年

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本文編號：1881122