1、极易氧化。在空气中，铝容易同氧化合，生成致密的三氧化二铝薄膜（厚度约0．1－0．2μm），熔点高（约2050℃），远远超过铝及 肯德基门型材的熔点（约600℃左右）。氧化铝的密度3．95－4．10g/cm3，约为铝的1．4倍，氧化铝薄膜的表面易吸附水分，焊接时，它阻碍基本金属的熔合，极易形成气孔、夹渣、未熔合等缺陷，引起焊缝性能下降。
1, easy oxidation. In the air, aluminum easily with oxygen, the oxidation of three compact two aluminum thin film (thickness of about 0.1 - 0.2 m), high melting point (2050 C), far more than the melting point of aluminum and Kentucky door profiles (about 600 degrees Celsius). Alumina density 3.95 4.10g/cm3, about 1.4 times of aluminum, alumina film surface adsorbed water, fusion welding, it hinders the basic metal, very easy to form pores, slag inclusion, incomplete fusion defects caused by weld performancedegradation.
2、易产生气孔。铝和 肯德基门型材焊接时产生气孔的主要原因是氢，由于液态铝可溶解大量的氢，而固态铝几乎不溶解氢，因此当熔池温度快速冷却与凝固时，氢来不及逸出，容易在焊缝中聚集形成气孔。氢气孔目前难于完全避免，氢的来源很多，有电弧焊气氛中的氢，铝板、焊丝表面氧化膜吸附空气中的水分等。实践证明，即使氩气按GB/T4842标准要求，纯度达到99．99% 以上，但当水分含量达到20ppm时，也会出现大量的致密气孔，当空气相对湿度超过80%时，如果不采取加热等措施，焊缝就会明显出现气孔。同时，采用小电流慢速焊，加大焊缝冷却时间，并利用焊丝电弧进行熔池搅动，可以较好的帮助气体排出熔池。
2, easy to produce pores. Aluminum and Kentucky door profiles generated during welding porosity is the main reason of hydrogen, because a lot of liquidaluminum can be dissolved hydrogen, and solid aluminum hardly dissolved hydrogen, so when the rapid cooling and solidification of molten pool temperature, hydrogen can escape easily in the weld together to form pores. Hydrogen pores are difficult to avoid completely at present, the source of hydrogen is many, there are hydrogen in the arc welding atmosphere, aluminum plate, the surface of the oxide film adsorption of water in the air, etc.. Practice has proved that even if the argon gas according to GB/T4842 standard requirements, the purity reached more than 99.99%, but when the water content reaches 20ppm, there will be a large number of stomata density, when the relative humidity of the air is more than 80%, if not to take measures such as heating, weld porosity will be significantly. At the same time, the use of small current slow welding, increase the cooling time of the weld, and the use of welding wire arc molten pool agitation, can better help the gas out of the molten pool.
3、焊缝变形和形成裂纹倾向大。铝的线膨胀系数和结晶收缩率约比钢大两倍，易产生较大的焊接变形的内应力，对刚性较大的结构将促使热裂纹的产生。
3, weld deformation and crack tendency. The coefficient of shrinkage and crystallization is two times bigger than steel aluminum expansion line, easy to produce welding deformation of large internal stress, will lead to hot cracks on the structure more rigid.
4、铝的导热系数大（纯铝0．538卡/Cm．s．℃）。约为钢的4倍，因此，焊接铝和 肯德基门型材时，比焊钢要消耗多的热量。
4, the coefficient of thermal conductivity of aluminum (pure aluminum 0.538 card /Cm.s. C). About 4 times of steel, therefore, when welding aluminum and KFC door profiles, more heat than welding steel.
5、合金元素的蒸发的烧损。 肯德基门型材中含有低沸点的元素（如镁、锌、锰等），在高温电弧作用下，极易蒸发烧损，从而改变焊缝金属的化学成分，使焊缝性能下降。
5, the evaporation loss of alloy elements. KFC door profiles contain low boiling point elements (such as magnesium, zinc, manganese, etc.), under the action of high temperature electric arc, it is easy to evaporation loss, thus changing the chemical composition of weld metal, so that the performance of the weld.
6、高温强度和塑性低。高温时铝的强度和塑性很低，破坏了焊缝金属的成形，有时还容易造成焊缝金属塌落和焊穿现象。
6, high temperature strength and low plasticity. When the high temperature strength of aluminum and plastic is very low, destruction of the forming of weld metal, sometimes easy to cause the weld metal Caveand welding wear phenomenon.
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