一、 較強(qiáng)的氧化能力
1、 Strong oxidation ability
鋁與氧的親和力強(qiáng)，容易與空氣中的氧結(jié)合，形成致密、強(qiáng)的AL2O3膜，厚度約為0。1微米，熔點(diǎn)可達(dá)2050℃，遠(yuǎn)遠(yuǎn)超過鋁合金和鋁合金板的熔點(diǎn)，且密度很高，約為1。4倍。在焊接過程中，氧化鋁薄膜會(huì)阻礙金屬間良好的結(jié)合，容易產(chǎn)生夾渣。氧化膜還吸收水分，導(dǎo)致氣孔形成焊接。這些缺陷會(huì)降低焊接接頭的性能。為了保證焊接的質(zhì)量,有必要嚴(yán)格清理氧化表面的焊接部分焊接前,焊接過程中,防止再氧化,有效地保護(hù)熔融金屬和金屬在高溫下,它是鋁和合金鋁板焊接的一個(gè)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.
具體保護(hù)措施有:
Specific protective measures include:
1. 焊接前用機(jī)械或化學(xué)方法清除焊縫溝槽及工件周圍零件和焊絲表面的氧化物;
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. 焊接過程中應(yīng)采用合格的保護(hù)氣體;
Qualified shielding gas shall be used during welding;
3、在氣焊中，使用焊劑，在焊接過程中不斷使用焊絲將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、導(dǎo)熱系數(shù)和比熱系數(shù)高，導(dǎo)熱速度快
2、 High thermal conductivity and specific heat coefficient, fast thermal conductivity
雖然鋁及鋁合金的熔點(diǎn)遠(yuǎn)低于鋼,但鋁及鋁合金的導(dǎo)熱系數(shù),熱容大,比鋼的兩倍多,大量的熱能在焊接的過程中很快傳導(dǎo)到賤金屬,為了獲得高質(zhì)量的焊接接頭,必須使用能量濃度,大功率的熱量來源,有時(shí)預(yù)熱過程的措施,如實(shí)現(xiàn)熔焊工藝。
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、線性膨脹系數(shù)大
3、 Large linear expansion coefficient
鋁及鋁合金的線膨脹系數(shù)約為鋼的2倍，體積收縮率達(dá)到6。5%——6。6%，易發(fā)生焊接變形。除了選擇合理的工藝參數(shù)和焊接順序外，使用合適的焊接工具來防止變形也是非常重要的，尤其是在焊接薄板時(shí)。此外,一些鋁和鋁合金焊接時(shí),傾向于形成晶體裂紋在焊縫金屬和趨勢(shì)形成液化裂紋的熱影響區(qū)都大,而且經(jīng)常出現(xiàn)熱裂紋的脆性溫度范圍由于過度的內(nèi)部壓力。這是鋁合金尤其是高強(qiáng)度鋁合金常見的嚴(yán)重缺陷之一。防止此類裂紋在實(shí)際焊接現(xiàn)場(chǎng)產(chǎn)生的主要措施是改進(jìn)接頭設(shè)計(jì)，選擇合理的焊接工藝參數(shù)和焊接順序，并采用適合基材特點(diǎn)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、易形成氣孔
4、 Easy to form pores
焊接接頭氣孔是鋁及鋁合金焊接中容易產(chǎn)生的缺陷，尤其是純鋁和防銹鋁的焊接。實(shí)踐證明，氫是鋁及鋁合金焊接中產(chǎn)生氣孔的主要原因。氫的來源主要是電弧柱氣氛中的水，焊接材料和基體材料吸附的水，其中吸附在焊絲和基體材料表面的水，以及焊縫氣孔的形成，往往占據(jù)著突出的位置。
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.

鋁和鋁合金液體池是容易吸收氣體,溶解在大量的氣體在高溫下,液體凝固,溶解度急劇下降,焊接冷卻和凝固過程中來不及沉淀,并聚集在焊縫形成氣孔。為了防止氣孔的形成，為了獲得良好的焊接接頭，應(yīng)嚴(yán)格控制氫的來源，焊接前必須嚴(yán)格限制焊接材料(包括焊絲、焊條、焊劑、保護(hù)氣體)的含水量，使用前要進(jìn)行干燥處理。清洗后的基材和焊絲應(yīng)在2-3小時(shí)內(nèi)焊接，多不超過24小時(shí)。TIG焊接時(shí)，焊接電流大，焊接速度快。在MIG焊接中，采用大焊接電流和慢焊接速度來提高焊接熔池的存在時(shí)間。鋁鋰合金焊接時(shí)應(yīng)加強(qiáng)前后保護(hù)，刮槽可去除氧化膜，有效防止氣孔。
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、焊接接頭易軟化
5、 Welded joints tend to soften
鋁和鋁合金液體池是容易吸收氣體,溶解在大量的氣體在高溫下,液體凝固,溶解度急劇下降,焊接冷卻和凝固過程中來不及沉淀,并聚集在焊縫形成氣孔。為了防止氣孔的形成，為了獲得良好的焊接接頭，應(yīng)嚴(yán)格控制氫的來源，焊接前必須嚴(yán)格限制焊接材料(包括焊絲、焊條、焊劑、保護(hù)氣體)的含水量，使用前要進(jìn)行干燥處理。清洗后的基材和焊絲應(yīng)在2-3小時(shí)內(nèi)焊接，多不超過24小時(shí)。TIG焊接時(shí)，焊接電流大，焊接速度快。在MIG焊接中，采用大焊接電流和慢焊接速度來提高焊接熔池的存在時(shí)間。鋁鋰合金焊接時(shí)應(yīng)加強(qiáng)前后保護(hù)，刮槽可去除氧化膜，有效防止氣孔。
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.
焊接可熱處理鋁合金時(shí)，由于焊接熱的影響，焊接接頭的熱影響區(qū)會(huì)軟化，即強(qiáng)度降低，這將使焊縫附近的基體金屬的一些力學(xué)性能變差。冷硬合金也是如此，它削弱了接頭的性能，焊縫能量越大，性能降低的過程越嚴(yán)重。針對(duì)這些問題，采取的措施主要是開發(fā)符合具體材料的焊接工藝，如限制焊接條件，采用合適的焊接順序，控制預(yù)熱溫度和層間溫度，焊后熱處理等。對(duì)于焊接后不能恢復(fù)的鋁合金，好采用固溶態(tài)退火或焊接，焊接后再進(jìn)行熱處理。焊接后不允許進(jìn)行熱處理的，應(yīng)采用能量集中的焊接方法和小線能量焊接，以降低接頭強(qiáng)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、合金元素的蒸發(fā)和燃燒
6、 Evaporation and combustion of alloy elements
有些合金鋁板含有低沸點(diǎn)的合金元素，在高溫下容易蒸發(fā)和燃燒，從而改變了焊縫金屬的化學(xué)成分，降低了焊接接頭的性能。為了彌補(bǔ)這些損失，在調(diào)整過程中，往往使用這些沸點(diǎn)元素含量比母材金屬絲或其他焊接材料高。
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、鋁在高溫下的強(qiáng)度和塑性較低
7、 Aluminum has low strength and plasticity at high temperatures
當(dāng)鋁在370℃的強(qiáng)度僅為10Mpa時(shí)，焊接將無法支撐液態(tài)金屬焊縫成形不良，甚至形成塌陷或燒穿，為了解決這一問題，焊接鋁和鋁合金時(shí)經(jīng)常使用墊板。
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、 焊接接頭的耐腐蝕性能低于基材
8、 The corrosion resistance of welded joints is lower than that of the base material
熱處理強(qiáng)化的鋁合金(如硬鋁)接頭的耐蝕性明顯降低。焊縫金屬的純度或致密性也會(huì)影響接頭的耐腐蝕性。雜質(zhì)較多，粗晶和脆性相析出，耐蝕性會(huì)明顯下降，不僅產(chǎn)生局部表面腐蝕，而且常常出現(xiàn)晶間腐蝕，此外，對(duì)于鋁合金來說，焊接應(yīng)力的存在也是影響耐蝕性的重要因素。
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、為了提高焊接接頭的耐腐蝕性，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. 改善關(guān)節(jié)組織結(jié)構(gòu)的不均勻性。主要方法是通過焊接材料對(duì)焊縫進(jìn)行合金化，細(xì)化晶粒，防止缺陷。同時(shí)，調(diào)整焊接工藝，減少受熱面積，防止過熱，焊后熱處理。
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.消除焊接應(yīng)力，如局部表面拉應(yīng)力可采用局部錘擊法消除。
2. Eliminate welding stress, such as local surface tensile stress, which can be eliminated by local hammering.
3.采取保護(hù)措施，如陽極氧化或涂層。
3. Take protective measures such as anodizing or coating.
4.無變色，給焊接操作帶來困難
4. No discoloration, making welding operation difficult
5.鋁與合金鋁板的焊接從固態(tài)到液態(tài)，沒有明顯的顏色變化，所以在焊接過程中給操作者帶來了很多困難。因此，要求焊工掌握良好的焊接加熱溫度，盡量采用平焊，在引(滅)弧板上引(滅)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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