Anodized Thread Aluminum Adjustable Extension Tube

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The Chemical and Chemical Properties and Welding Characteristics of Aluminum and Aluminum Alloys

1. Easy to oxidize

Aluminum and oxygen have a strong affinity. At room temperature, the aluminum surface can be oxidized into a dense AL2O3 film with a thickness of about 0.1 to 0.2 m. Although this layer of alumina film is denser, can prevent the metal from continuing to oxidize, which is beneficial to natural corrosion protection, but it brings difficulties to welding, because the melting point of alumina (2050 degrees C) far exceeds the melting point of aluminum (about 600 degrees C), the proportion is about 1.4 times that of aluminum. In the welding process, will hinder the fusion between the metal, easy to form slag, and alumina film also adsorption of more water, welding will cause the weld to create pores.

2. Larger thermal conductivity and thermal capacity

The thermal conductivity of aluminum is about four times that of steel, so when welding aluminum tubes, it consumes more heat than steel pipe welding, and in order to obtain high-quality welding joints, it is necessary to use a heat source with concentrated energy and high power.

3. Easy to form hydrogen holes

Welding pores for aluminum and aluminum alloys are the main hydrogen holes. Aluminum can absorb and dissolve hydrogen in large quantities in liquid state, the solubility in the melting state is 0.0069 ml/g, and in the high temperature solidification state is 0.00036 ml/g, the difference between the front and back is nearly 20 times. The thermal conductivity of aluminum is very large, under the same welding process conditions, its cooling speed is 4 to 7 times that of steel, so that metal crystallization accelerates, welding melting pool in the rapid cooling process, the solubility of hydrogen dropped sharply, at this time, a large number of oversaturated gas, hydrogen can not be exhumed in the weld metal to form pores. Therefore, when welding aluminum, the weld has a great tendency to produce pores.

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