【摘要】：近年來(lái)氬弧焊方法在合金材料的焊接修復(fù)中應(yīng)用越來(lái)越廣泛,但在鋁合金氣缸蓋修復(fù)方面較少。本文針對(duì)鋁合金氣缸蓋腐蝕問(wèn)題,對(duì)氬弧焊修復(fù)技術(shù)進(jìn)行了研究,其目的是將腐蝕損壞的鋁合金氣缸蓋修復(fù)后繼續(xù)使用,提高發(fā)動(dòng)機(jī)工作性能與使用壽命。研究?jī)?nèi)容對(duì)減少車主支出,提高鋁合金的利用率,減輕鋁合金在汽車工業(yè)的壓力具有重要意義。焊接工藝參數(shù)的選擇以及氣缸蓋表面處理質(zhì)量等對(duì)氬弧焊焊接過(guò)程焊縫的成型都會(huì)帶來(lái)不同程度影響,本文主要分析了焊接電流和保護(hù)氣體流量不同時(shí)對(duì)焊接質(zhì)量、焊縫成型、力學(xué)性能的影響;利用金相顯微鏡、萬(wàn)能拉伸試驗(yàn)機(jī)觀察與測(cè)試了鋁合金缸蓋焊縫的形貌與力學(xué)特性;分析了焊接過(guò)程中產(chǎn)生裂紋和氣孔的原因,提出了避免產(chǎn)生氣孔和裂紋的防范措施。試驗(yàn)結(jié)果顯示,當(dāng)鋁合金氣缸蓋表面存在氧化膜時(shí),焊縫的深寬比小,焊接質(zhì)量差;焊接過(guò)程中,隨著焊接電流的不斷增大,焊縫的熔深熔寬逐漸增大;保護(hù)氣體流量不斷增大,焊縫的熔深先增大,后減小。鋁合金氣缸蓋的焊縫和熱影響區(qū)分界較為明顯,通過(guò)顯微鏡觀察,焊縫的晶粒為細(xì)小的等軸晶粒,熱影響區(qū)的晶粒較為粗大。通過(guò)拉伸試驗(yàn)表明,斷裂一般都發(fā)生在熱影響區(qū),焊接接頭斷裂的情況多為脆性斷裂。焊接電流是影響焊接質(zhì)量的重要因素,焊接電流過(guò)大或者過(guò)小都會(huì)影響焊接接頭的力學(xué)性能。試驗(yàn)中控制保護(hù)氣體流量為15L/min,使用不同的焊接電流對(duì)鋁制汽缸蓋進(jìn)行焊接,結(jié)果表明,當(dāng)電流為45A時(shí),焊接接頭的力學(xué)性能可以達(dá)到最高,為母材的80%左右。添加焊絲和焊后的熱處理,都可以進(jìn)一步的增強(qiáng)焊接接頭的組織性能。鋁合金氣缸蓋焊縫中存在氣孔的主要原因?yàn)楹附拥睦鋮s過(guò)程中,氬氣溶解度下降速率較快,形成的氬氣孔,以及母材中存在的氣孔,在焊接過(guò)程中小氣孔聚集形成大氣孔,因此,消除焊縫中氣孔可以通過(guò)表面處理以及選擇合理的焊接工藝。裂紋主要形成的原因是鋁制汽缸蓋中存在其他的低熔點(diǎn)的金屬,焊接過(guò)程中易蒸發(fā)所致,因此,選擇合理的焊接工藝、焊前的預(yù)熱與焊后的熱處理、減少焊接的熱輸出、填充焊絲等可以有效的防止焊接結(jié)晶裂紋。
[Abstract]:In recent years, argon arc welding is more and more widely used in the welding repair of alloy materials, but it is less in the repair of aluminum alloy cylinder head. Aiming at the corrosion problem of aluminum alloy cylinder head, argon arc welding repair technology is studied in this paper. The purpose of this paper is to continue to use the corroded aluminum alloy cylinder head after repairing, and to improve the engine performance and service life. The research content is of great significance to reduce car owner's expense, improve the utilization ratio of aluminum alloy and reduce the pressure of aluminum alloy in automobile industry. The selection of welding process parameters and the surface treatment quality of cylinder head have different effects on the weld formation during argon arc welding. This paper mainly analyzes that the welding current and gas flux are not the same as the welding quality and the weld formation. The influence of mechanical properties; The morphology and mechanical properties of aluminum alloy cylinder head welds were observed and tested by metallographic microscope and universal tensile testing machine, the causes of cracks and pores in the welding process were analyzed, and the preventive measures to avoid them were put forward. The test results show that the weld depth to width ratio is small and the welding quality is poor when there is oxide film on the surface of the aluminum alloy cylinder head, and the weld penetration width increases gradually with the increasing of welding current during the welding process. The penetration of weld increases first and then decreases as the flux of shielded gas increases. The weld seam and thermal effect of aluminum alloy cylinder head are more obvious. The grain of weld is fine equiaxed grain by microscope, and the grain of heat affected zone is coarse. The tensile test shows that the fracture usually occurs in the heat affected zone, and the fracture of welded joint is brittle fracture. Welding current is an important factor that affects welding quality, too large or too small welding current will affect the mechanical properties of welded joints. The aluminum cylinder head is welded with different welding current by controlling the gas flux of 15L / min. The results show that the mechanical properties of the welded joint can reach the highest when the current is 45A, which is about 80% of the base metal. The microstructure and properties of welded joints can be further enhanced by adding welding wire and heat treatment after welding. The main reason for the existence of porosity in the welding seam of aluminum alloy cylinder head is that during the cooling process of welding, the dissolution rate of argon gas decreases faster, the argon gas hole is formed, and the pore exists in the base metal, and during the welding process, the small porosity accumulates to form the large porosity. Therefore, the elimination of porosity in the weld can be through surface treatment and selection of a reasonable welding process. The main reason for the crack is that there are other low melting point metals in the aluminum cylinder head, which is easy to evaporate during welding. Therefore, choosing reasonable welding technology, preheating before welding and heat treatment after welding can reduce the heat output of welding. Filling welding wire and so on can effectively prevent welding crystal crack.
【學(xué)位授予單位】：吉林農(nóng)業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TG444

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