氩弧焊在铝合金气缸盖腐蚀修复工艺中的应用研究

发布时间：2019-01-04 08:35

【摘要】：近年来氩弧焊方法在合金材料的焊接修复中应用越来越广泛,但在铝合金气缸盖修复方面较少。本文针对铝合金气缸盖腐蚀问题,对氩弧焊修复技术进行了研究,其目的是将腐蚀损坏的铝合金气缸盖修复后继续使用,提高发动机工作性能与使用寿命。研究内容对减少车主支出,提高铝合金的利用率,减轻铝合金在汽车工业的压力具有重要意义。焊接工艺参数的选择以及气缸盖表面处理质量等对氩弧焊焊接过程焊缝的成型都会带来不同程度影响,本文主要分析了焊接电流和保护气体流量不同时对焊接质量、焊缝成型、力学性能的影响;利用金相显微镜、万能拉伸试验机观察与测试了铝合金缸盖焊缝的形貌与力学特性;分析了焊接过程中产生裂纹和气孔的原因,提出了避免产生气孔和裂纹的防范措施。试验结果显示,当铝合金气缸盖表面存在氧化膜时,焊缝的深宽比小,焊接质量差;焊接过程中,随着焊接电流的不断增大,焊缝的熔深熔宽逐渐增大;保护气体流量不断增大,焊缝的熔深先增大,后减小。铝合金气缸盖的焊缝和热影响区分界较为明显,通过显微镜观察,焊缝的晶粒为细小的等轴晶粒,热影响区的晶粒较为粗大。通过拉伸试验表明,断裂一般都发生在热影响区,焊接接头断裂的情况多为脆性断裂。焊接电流是影响焊接质量的重要因素,焊接电流过大或者过小都会影响焊接接头的力学性能。试验中控制保护气体流量为15L/min,使用不同的焊接电流对铝制汽缸盖进行焊接,结果表明,当电流为45A时,焊接接头的力学性能可以达到最高,为母材的80%左右。添加焊丝和焊后的热处理,都可以进一步的增强焊接接头的组织性能。铝合金气缸盖焊缝中存在气孔的主要原因为焊接的冷却过程中,氩气溶解度下降速率较快,形成的氩气孔,以及母材中存在的气孔,在焊接过程中小气孔聚集形成大气孔,因此,消除焊缝中气孔可以通过表面处理以及选择合理的焊接工艺。裂纹主要形成的原因是铝制汽缸盖中存在其他的低熔点的金属,焊接过程中易蒸发所致,因此,选择合理的焊接工艺、焊前的预热与焊后的热处理、减少焊接的热输出、填充焊丝等可以有效的防止焊接结晶裂纹。
[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.
【学位授予单位】：吉林农业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG444

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