一、 较强的氧化能力
1、 Strong oxidation ability
铝与氧的亲和力强，容易与空气中的氧结合，形成致密、强的AL2O3膜，厚度约为0。1微米，熔点可达2050℃，远远超过铝合金和铝合金板的熔点，且密度很高，约为1。4倍。在焊接过程中，氧化铝薄膜会阻碍金属间良好的结合，容易产生夹渣。氧化膜还吸收水分，导致气孔形成焊接。这些缺陷会降低焊接接头的性能。为了保证焊接的质量,有必要严格清理氧化表面的焊接部分焊接前,焊接过程中,防止再氧化,有效地保护熔融金属和金属在高温下,它是铝和合金铝板焊接的一个重要特性。
Aluminum has a strong affinity for oxygen and is easy to combine with oxygen in the air to form a dense and strong AL2O3 film with a thickness of about 0. 1 micron, with a melting point of up to 2050 ℃, far exceeding the melting point of aluminum alloys and aluminum alloy plates, and a high density of about 1. 4x. During the welding process, the aluminum oxide film can hinder the good bonding between metals and easily generate slag inclusions. The oxide film also absorbs moisture, causing pores to form welds. These defects can reduce the performance of welded joints. In order to ensure the quality of welding, it is necessary to strictly clean the welding portion of the oxidized surface before and during welding to prevent reoxidation and effectively protect the molten metal and metal under high temperatures. It is an important feature of welding aluminum and alloy aluminum plates.
具体保护措施有:
Specific protective measures include:
1. 焊接前用机械或化学方法清除焊缝沟槽及工件周围零件和焊丝表面的氧化物;
Before welding, use mechanical or chemical methods to remove oxides from the weld groove, parts around the workpiece, and the surface of the welding wire;
2. 焊接过程中应采用合格的保护气体;
Qualified shielding gas shall be used during welding;
3、在气焊中，使用焊剂，在焊接过程中不断使用焊丝将熔池表面的氧化膜打破。
3. In gas welding, welding flux is used, and during the welding process, welding wires are continuously used to break the oxide film on the surface of the weld pool.
二、导热系数和比热系数高，导热速度快
2、 High thermal conductivity and specific heat coefficient, fast thermal conductivity
虽然铝及铝合金的熔点远低于钢,但铝及铝合金的导热系数,热容大,比钢的两倍多,大量的热能在焊接的过程中很快传导到贱金属,为了获得高质量的焊接接头,必须使用能量浓度,大功率的热量来源,有时预热过程的措施,如实现熔焊工艺。
Although the melting point of aluminum and aluminum alloys is much lower than that of steel, the thermal conductivity and heat capacity of aluminum and aluminum alloys are greater than twice that of steel. A large amount of heat energy is quickly transferred to base metals during the welding process. In order to obtain high-quality welding joints, it is necessary to use energy concentration, high-power heat sources, and sometimes measures such as preheating the process, such as achieving fusion welding processes.
三、线性膨胀系数大
3、 Large linear expansion coefficient
铝及铝合金的线膨胀系数约为钢的2倍，体积收缩率达到6。5%——6。6%，易发生焊接变形。除了选择合理的工艺参数和焊接顺序外，使用合适的焊接工具来防止变形也是非常重要的，尤其是在焊接薄板时。此外,一些铝和铝合金焊接时,倾向于形成晶体裂纹在焊缝金属和趋势形成液化裂纹的热影响区都大,而且经常出现热裂纹的脆性温度范围由于过度的内部压力。这是铝合金尤其是高强度铝合金常见的严重缺陷之一。防止此类裂纹在实际焊接现场产生的主要措施是改进接头设计，选择合理的焊接工艺参数和焊接顺序，并采用适合基材特点的焊接填料材料。
The linear expansion coefficient of aluminum and aluminum alloys is about twice that of steel, and the volume shrinkage rate reaches 6. 5%——6。 6%, prone to welding deformation. In addition to selecting reasonable process parameters and welding sequences, it is also important to use suitable welding tools to prevent deformation, especially when welding thin plates. In addition, some aluminum and aluminum alloys tend to form crystal cracks during welding, both in the weld metal and in the heat affected zone where liquefaction cracks tend to form, and the brittle temperature range where thermal cracks often occur is due to excessive internal pressure. This is one of the most common serious defects in aluminum alloys, especially high-strength aluminum alloys. The main measures to prevent such cracks from occurring on the actual welding site are to improve the joint design, select reasonable welding process parameters and welding sequence, and use welding filler materials suitable for the characteristics of the base material.
四、易形成气孔
4、 Easy to form pores
焊接接头气孔是铝及铝合金焊接中容易产生的缺陷，尤其是纯铝和防锈铝的焊接。实践证明，氢是铝及铝合金焊接中产生气孔的主要原因。氢的来源主要是电弧柱气氛中的水，焊接材料和基体材料吸附的水，其中吸附在焊丝和基体材料表面的水，以及焊缝气孔的形成，往往占据着突出的位置。
Weld joint porosity is a defect that easily occurs in the welding of aluminum and aluminum alloys, especially in the welding of pure aluminum and rustproof aluminum. Practice has proven that hydrogen is the main reason for the formation of pores in aluminum and aluminum alloy welding. The main source of hydrogen is water in the arc column atmosphere, water adsorbed by welding materials and base materials, and water adsorbed on the surface of welding wires and base materials, as well as the formation of weld pores, often occupy prominent positions.

铝和铝合金液体池是容易吸收气体,溶解在大量的气体在高温下,液体凝固,溶解度急剧下降,焊接冷却和凝固过程中来不及沉淀,并聚集在焊缝形成气孔。为了防止气孔的形成，为了获得良好的焊接接头，应严格控制氢的来源，焊接前必须严格限制焊接材料(包括焊丝、焊条、焊剂、保护气体)的含水量，使用前要进行干燥处理。清洗后的基材和焊丝应在2-3小时内焊接，多不超过24小时。TIG焊接时，焊接电流大，焊接速度快。在MIG焊接中，采用大焊接电流和慢焊接速度来提高焊接熔池的存在时间。铝锂合金焊接时应加强前后保护，刮槽可去除氧化膜，有效防止气孔。
Aluminum and aluminum alloy liquid pools are easy to absorb gases, which dissolve in a large amount of gas. At high temperatures, the liquid solidifies, and the solubility drops sharply. During welding cooling and solidification, there is no time to precipitate, and they accumulate in the weld to form pores. In order to prevent the formation of air holes and obtain good welding joints, the source of hydrogen should be strictly controlled. Before welding, the water content of welding materials (including welding wires, electrodes, fluxes, and shielding gas) must be strictly limited, and drying treatment should be carried out before use. The cleaned substrate and welding wire should be welded within 2-3 hours, with a maximum of 24 hours. During TIG welding, the welding current is high and the welding speed is fast. In MIG welding, large welding current and slow welding speed are used to improve the lifetime of the weld pool. During welding of aluminum lithium alloy, front and rear protection should be strengthened, and groove scraping can remove the oxide film and effectively prevent air holes.
五、焊接接头易软化
5、 Welded joints tend to soften
铝和铝合金液体池是容易吸收气体,溶解在大量的气体在高温下,液体凝固,溶解度急剧下降,焊接冷却和凝固过程中来不及沉淀,并聚集在焊缝形成气孔。为了防止气孔的形成，为了获得良好的焊接接头，应严格控制氢的来源，焊接前必须严格限制焊接材料(包括焊丝、焊条、焊剂、保护气体)的含水量，使用前要进行干燥处理。清洗后的基材和焊丝应在2-3小时内焊接，多不超过24小时。TIG焊接时，焊接电流大，焊接速度快。在MIG焊接中，采用大焊接电流和慢焊接速度来提高焊接熔池的存在时间。铝锂合金焊接时应加强前后保护，刮槽可去除氧化膜，有效防止气孔。
Aluminum and aluminum alloy liquid pools are easy to absorb gases, which dissolve in a large amount of gas. At high temperatures, the liquid solidifies, and the solubility drops sharply. During welding cooling and solidification, there is no time to precipitate, and they accumulate in the weld to form pores. In order to prevent the formation of air holes and obtain good welding joints, the source of hydrogen should be strictly controlled. Before welding, the water content of welding materials (including welding wires, electrodes, fluxes, and shielding gas) must be strictly limited, and drying treatment should be carried out before use. The cleaned substrate and welding wire should be welded within 2-3 hours, with a maximum of 24 hours. During TIG welding, the welding current is high and the welding speed is fast. In MIG welding, large welding current and slow welding speed are used to improve the lifetime of the weld pool. During welding of aluminum lithium alloy, front and rear protection should be strengthened, and groove scraping can remove the oxide film and effectively prevent air holes.
焊接可热处理铝合金时，由于焊接热的影响，焊接接头的热影响区会软化，即强度降低，这将使焊缝附近的基体金属的一些力学性能变差。冷硬合金也是如此，它削弱了接头的性能，焊缝能量越大，性能降低的过程越严重。针对这些问题，采取的措施主要是开发符合具体材料的焊接工艺，如限制焊接条件，采用合适的焊接顺序，控制预热温度和层间温度，焊后热处理等。对于焊接后不能恢复的铝合金，好采用固溶态退火或焊接，焊接后再进行热处理。焊接后不允许进行热处理的，应采用能量集中的焊接方法和小线能量焊接，以降低接头强度的降低。
When welding heat treatable aluminum alloys, due to the influence of welding heat, the heat affected zone of the welded joint will soften, i.e., its strength will decrease, which will worsen some mechanical properties of the base metal near the weld. The same is true for cold hard alloys, which weaken the performance of joints. The greater the weld energy, the more severe the process of performance degradation. To address these issues, the main measures taken are to develop welding processes that meet specific materials, such as limiting welding conditions, adopting appropriate welding sequences, controlling preheat and interpass temperatures, and post weld heat treatment. For aluminum alloys that cannot be restored after welding, it is best to use solution annealing or welding, followed by heat treatment after welding. If heat treatment is not allowed after welding, energy concentrated welding methods and low wire energy welding should be used to reduce the reduction in joint strength.
六、合金元素的蒸发和燃烧
6、 Evaporation and combustion of alloy elements
有些合金铝板含有低沸点的合金元素，在高温下容易蒸发和燃烧，从而改变了焊缝金属的化学成分，降低了焊接接头的性能。为了弥补这些损失，在调整过程中，往往使用这些沸点元素含量比母材金属丝或其他焊接材料高。
Some aluminum alloy plates contain alloy elements with low boiling points, which are prone to evaporation and combustion at high temperatures, thereby changing the chemical composition of the weld metal and reducing the performance of the welded joint. In order to compensate for these losses, during the adjustment process, it is often used to have a higher boiling point element content than the base metal wire or other welding materials.
七、铝在高温下的强度和塑性较低
7、 Aluminum has low strength and plasticity at high temperatures
当铝在370℃的强度仅为10Mpa时，焊接将无法支撑液态金属焊缝成形不良，甚至形成塌陷或烧穿，为了解决这一问题，焊接铝和铝合金时经常使用垫板。
When the strength of aluminum at 370 ℃ is only 10Mpa, welding will not be able to support poor weld formation of liquid metal, even leading to collapse or burn through. To solve this problem, backing plates are often used when welding aluminum and aluminum alloys.
八、 焊接接头的耐腐蚀性能低于基材
8、 The corrosion resistance of welded joints is lower than that of the base material
热处理强化的铝合金(如硬铝)接头的耐蚀性明显降低。焊缝金属的纯度或致密性也会影响接头的耐腐蚀性。杂质较多，粗晶和脆性相析出，耐蚀性会明显下降，不仅产生局部表面腐蚀，而且常常出现晶间腐蚀，此外，对于铝合金来说，焊接应力的存在也是影响耐蚀性的重要因素。
The corrosion resistance of aluminum alloy (such as duralumin) joints strengthened by heat treatment significantly decreases. The purity or compactness of the weld metal can also affect the corrosion resistance of the joint. With more impurities, coarse grains and brittle phases precipitate, the corrosion resistance will significantly decrease, resulting in not only local surface corrosion, but also frequent intergranular corrosion. In addition, for aluminum alloys, the presence of welding stress is also an important factor affecting the corrosion resistance.
九、为了提高焊接接头的耐腐蚀性，主要采取以下措施:
9、 In order to improve the corrosion resistance of welded joints, the following measures are mainly taken:
1. 改善关节组织结构的不均匀性。主要方法是通过焊接材料对焊缝进行合金化，细化晶粒，防止缺陷。同时，调整焊接工艺，减少受热面积，防止过热，焊后热处理。
1. Improve the nonuniformity of joint tissue structure. The main method is to alloy the weld through welding materials, refine the grain size, and prevent defects. At the same time, adjust the welding process, reduce the heating area, prevent overheating, and conduct post weld heat treatment.
2.消除焊接应力，如局部表面拉应力可采用局部锤击法消除。
2. Eliminate welding stress, such as local surface tensile stress, which can be eliminated by local hammering.
3.采取保护措施，如阳极氧化或涂层。
3. Take protective measures such as anodizing or coating.
4.无变色，给焊接操作带来困难
4. No discoloration, making welding operation difficult
5.铝与合金铝板的焊接从固态到液态，没有明显的颜色变化，所以在焊接过程中给操作者带来了很多困难。因此，要求焊工掌握良好的焊接加热温度，尽量采用平焊，在引(灭)弧板上引(灭)弧。
5. The welding of aluminum and alloy aluminum plates has no significant color change from solid to liquid, which brings many difficulties to the operator during the welding process. Therefore, welders are required to master a good welding heating temperature, try to use flat welding, and start (extinguish) the arc on the arc striking (extinguishing) plate.
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