【摘要】：隨著人們對環(huán)境保護、資源節(jié)約意識的不斷深入與提高,結(jié)構(gòu)輕量化已成為現(xiàn)代工業(yè)發(fā)展的必然趨勢。鎂及鎂合金是目前可應(yīng)用的最輕的結(jié)構(gòu)材料,鋼鐵材料則依然是未來汽車材料的中堅力量,為了減輕汽車自重并保證其安全性能,多元材料結(jié)構(gòu)型車體設(shè)計越來越受到汽車行業(yè)的青睞,而鎂和鋼的連接件既能減輕整體結(jié)構(gòu)的重量,又能保證結(jié)構(gòu)的強度,因而有著良好的應(yīng)用前景。但鎂合金與鋼之間的物理性質(zhì)差異巨大,使得兩者很難實現(xiàn)有效的連接,這已成為國內(nèi)外共同關(guān)注并且急需解決的問題。攪拌摩擦點焊因其接頭質(zhì)量高、經(jīng)濟、高效、清潔節(jié)能等優(yōu)點而具有很高的應(yīng)用價值與市場潛力,故各個國家的焊接界都對攪拌摩擦點焊技術(shù)與新型攪拌摩擦點焊設(shè)備進行了大量研究。本文通過對實驗室原有無匙孔攪拌摩擦點焊設(shè)備及其運行原理的分析,設(shè)計制造了“偏心”無匙孔攪拌摩擦點焊設(shè)備,與原有設(shè)備相比,新設(shè)備主要在機身結(jié)構(gòu)、傳動方案、焊接方法及控制方式等方面做了改進設(shè)計,提高了機身穩(wěn)定性,減少了噪音和震動,實現(xiàn)了主軸電機和攪拌頭之間的“零傳動”。通過設(shè)計可旋轉(zhuǎn)的工作臺,改變了原有的焊接方法,增大了焊點面積,得到了成型美觀的圓形焊點;在控制系統(tǒng)方面,采用以PLC與矢量控制變頻器為核心的硬件與軟件系統(tǒng)設(shè)計,使用手動與自動兩種控制方式,操作簡單,使用方便,提高了焊接效率。使用新設(shè)備對3mm厚的AZ31B鎂合金和1mm厚DP600鍍鋅鋼進行搭接點焊試驗,通過正交試驗分析點焊接接頭的力學(xué)性能,并對接頭宏觀、微觀組織形貌及斷口進行分析,研究在新設(shè)備與不同的焊接方法下接頭的連接機理與斷裂方式,結(jié)果表明:(1)鎂鋼無匙孔攪拌摩擦點焊接頭質(zhì)量的影響因素從大到小依次為:軸肩下壓量、攪拌頭旋轉(zhuǎn)速度、攪拌針伸出量,綜合考慮接頭力學(xué)性能和表面成形效果,得出最優(yōu)工藝參數(shù)為攪拌頭轉(zhuǎn)速1200r/min、軸肩下壓量0.2mm、攪拌針伸出量1.7mm;(2)與實驗室原有設(shè)備相比,新設(shè)備在相應(yīng)的參數(shù)范圍內(nèi)得到的點焊接頭整體力學(xué)性能更好,接頭最大抗剪切載荷達到10.1KN;(3)接頭軸肩作用區(qū)結(jié)合界面平整,結(jié)合界面處生成了寬度為6~9μm不等的“竹節(jié)狀”中間層,竹節(jié)狀之間存在裂紋且竹節(jié)狀的長度各不相同,在一定范圍內(nèi),隨著攪拌頭轉(zhuǎn)速與軸肩下壓量的增加,中間層的厚度增加;(4)鎂鋼無匙孔攪拌摩擦點焊接頭存在兩種斷裂方式,軸肩作用區(qū)為解理斷裂,即脆性斷裂;攪拌區(qū)為韌脆混合斷裂;在原位拉伸過程中發(fā)現(xiàn)應(yīng)力集中最大的部位在點焊接頭鎂鋼兩板之間的焊點邊緣處;另外,斷裂發(fā)生在鎂與中間層的結(jié)合面,即鎂鋼的拉伸斷裂面靠近鎂側(cè),脆性中間層基本上留在了鋼側(cè)。
文內(nèi)圖片：
圖片說明：Fe-Mg二元相圖
[Abstract]:With the development and improvement of environmental protection and resource saving awareness, the light of structure has become an inevitable trend of the development of modern industry. The magnesium and magnesium alloy are the lightest structural materials that can be applied at present, and the steel material is still the medium and strong force of the future automobile materials. In order to reduce the self-weight of the automobile and ensure the safety performance of the automobile, the multi-component material structure type vehicle body design is more and more popular with the automobile industry, The connecting piece of the magnesium and the steel can not only reduce the weight of the whole structure but also ensure the strength of the structure, and therefore has good application prospect. However, the physical property difference between the magnesium alloy and the steel is great, making it difficult to realize the effective connection, which has become a common concern at home and abroad and needs to be solved urgently. The friction spot welding of friction stir welding has high application value and market potential because of its high joint quality, economy, high efficiency, clean energy and so on. In this paper, through the analysis of the original non-key-hole friction spot-welding equipment and its running principle in the laboratory, the "off-center"-free hole-free stirring friction spot-welding equipment is designed and manufactured, and compared with the original equipment, the new equipment is mainly in the body structure and the transmission scheme, The welding method and the control method have the advantages of improving design, improving the stability of the body, reducing noise and vibration, and realizing the "zero drive" between the spindle motor and the stirring head. by designing the rotatable work table, the original welding method is changed, the area of the welding spot is increased, and the round welding point with attractive appearance is obtained; in the aspect of the control system, the hardware and the software system design with the core of the PLC and the vector control frequency converter are adopted, The manual and automatic two control modes are used, the operation is simple, the use is convenient, and the welding efficiency is improved. A new equipment was used to weld the 3mm thick AZ31B magnesium alloy and the 1 mm thick DP600 galvanized steel, and the mechanical properties of the joint were analyzed by the orthogonal test, and the macroscopic and microscopic structure of the joint and the fracture were analyzed. The connection mechanism and fracture mode of the joint between the new equipment and the different welding methods are studied. The results show that: (1) The influence factors of the quality of the welding head of the non-key hole of the magnesium steel are as follows: the pressing amount of the shoulder, the rotating speed of the stirring head, the extension of the stirring needle, the mechanical property and the surface forming effect of the joint are comprehensively considered, the optimal process parameters are obtained, the rotating speed of the stirring head is 1200r/ min, the pressing amount of the shaft shoulder is 0.2 mm, the extension amount of the stirring needle is 1.7 mm, and (2) compared with the original equipment of the laboratory, the whole mechanical property of the spot welding head obtained by the new equipment in the corresponding parameter range is better, the maximum shear load of the joint reaches 10.1 KN; (3) the joint shaft shoulder action area is smooth in combination with the interface, and a "bamboo-section" intermediate layer with the width of 6 to 9 & mu; m is generated at the bonding interface; and the thickness of the middle layer is increased with the increase of the rotating speed of the stirring head and the pressing amount of the shoulder and the shoulder, the thickness of the intermediate layer is increased in a certain range, that is, the brittle fracture is broken; the stirring region is a phloem-brittle mixed fracture; the point where the maximum stress concentration is found in the in-situ stretching process is at the edge of the welding spot between the point welding head magnesium steel and the magnesium steel plate; in addition, the fracture occurs between the bonding surface of the magnesium and the middle layer, that is, the tensile fracture surface of the magnesium steel is close to the magnesium side, The brittle intermediate layer is substantially left on the steel side.
【學(xué)位授予單位】：蘭州理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TG453.9

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