【摘要】：鋁及鋁合金激光焊接存在著焊接過程不穩(wěn)定性、焊縫成形差、焊接氣孔多(小孔型氣孔傾向嚴重)等問題。雙光束、焦點旋轉(zhuǎn)和擺動的方法能夠穩(wěn)定焊接過程,改善小孔行為,減少焊接氣孔,但都會導(dǎo)致焊縫熔深的減小,降低焊接制造效率。本文提出了一種焦點旋轉(zhuǎn)和垂直振動的焊接方法,設(shè)計了焦點運動參數(shù)可控的焊接裝置。使用該裝置進行焊接試驗,研究了焦點運動參數(shù)對焊縫表面成形、焊縫宏觀形貌及氣孔的影響規(guī)律,并通過高速攝像拍攝并分析焊接熔池和深熔小孔的動態(tài)行為,闡述了焦點運動參數(shù)改善焊縫成形、減少氣孔的機理。試驗結(jié)果表明,采用焦點旋轉(zhuǎn)和垂直振動的方法可有效改善焊縫表面成形,提高焊縫質(zhì)量。通過對焦點運動控制,可調(diào)控熔池的流動和凝固行為,熔池規(guī)律而穩(wěn)定的流動使焊接過程穩(wěn)定性得到改善,焊縫成形良好,焊縫表面魚鱗紋由角狀變?yōu)閳A弧狀。焦點旋轉(zhuǎn)對小孔型氣孔的抑制作用明顯,優(yōu)化的參數(shù)下,氣孔的尺寸顯著減小、數(shù)量顯著減少。焦點的旋轉(zhuǎn)使深熔小孔擴大,不易坍塌和閉合,進而提高小孔穩(wěn)定性,實現(xiàn)抑制小孔型氣孔的目的。在優(yōu)化的參數(shù)下,焦點的垂直振動可增加焊縫熔深,提高焊接效率。垂直振動對焊縫熔深的影響與小孔行為有關(guān)。焦點的垂直振動使小孔深度周期性增加,由于焦點振動頻率較高,較深的小孔形成的熔池搭接在一起,使焊縫的熔深增大。本論文的研究內(nèi)容表明:針對鋁及鋁合金激光焊接,焦點旋轉(zhuǎn)和振動方法可顯著降低小孔型氣孔,提高焊縫成形質(zhì)量,同時有益于提高焊接效率。該方法對于一些不允許焊透的結(jié)構(gòu),如鎖底接頭,具有明顯的技術(shù)優(yōu)勢和廣闊的應(yīng)用前景。
[Abstract]:Laser welding of aluminum and aluminum alloy has some problems, such as instability of welding process, poor weld formation, and many holes in welding (the porosity tendency of small hole type is serious). The method of double beam, focus rotation and swing can stabilize the welding process, improve the behavior of the small hole and reduce the weld porosity, but it will lead to the reduction of weld penetration and the reduction of welding manufacturing efficiency. In this paper, a welding method of focus rotation and vertical vibration is proposed, and a welding device with controllable focus motion parameters is designed. The influence of focus motion parameters on weld surface forming, weld macroscopic appearance and porosity was studied by using this device. The dynamic behavior of weld pool and deep melting hole was analyzed by high speed video camera. The mechanism of focus motion parameters to improve weld formation and reduce porosity is described. The experimental results show that the method of focus rotation and vertical vibration can effectively improve the weld surface forming and the weld quality. The flow and solidification behavior of the weld pool can be controlled by controlling the focus motion. The stability of the welding process can be improved by the regular and stable flow of the molten pool. The weld is well formed and the surface scale of the weld is changed from angle to arc. The focus rotation obviously inhibited the pore size and the number of pores decreased significantly under the optimized parameters. The rotation of the focus makes the deep melting pores expand, and are not easy to collapse and close, thus improving the stability of the pores and achieving the purpose of suppressing the pore type. Under the optimized parameters, the vertical vibration of focus can increase weld penetration and improve welding efficiency. The effect of vertical vibration on weld penetration is related to the behavior of small holes. The vertical vibration of the focus increases the depth of the hole periodically. Because of the higher frequency of the focus vibration, the weld pool formed by the deeper hole is joined together, which makes the weld penetration increase. The research contents of this paper show that the focus rotation and vibration method can significantly reduce the pore shape of small hole and improve the quality of weld forming, and it is beneficial to improve the welding efficiency for laser welding of aluminum and aluminum alloy. This method has obvious technical advantages and broad application prospects for some structures which are not allowed to be welded through, such as locking bottom joint.
【學位授予單位】：北京工業(yè)大學
【學位級別】：碩士
【學位授予年份】：2016
【分類號】：TG456.7

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