Aluminum alloy cables have natural defects in fire protection and corrosion protection

Update:20-04-2018
Summary:

From the perspective of the characteristics of aluminum […]

From the perspective of the characteristics of aluminum alloy cables, aluminum alloy cables have natural defects in fire protection and corrosion protection.

Performance in the following areas:

1, corrosion resistance, 8000 series aluminum alloy is not as good as aluminum

GB/T19292.2-2003 Standard Table 1 Note 4: Aluminum alloy corrosion resistance worse than ordinary aluminum worse than copper, this is because aluminum alloy cable added magnesium, copper, zinc, iron elements, it is prone to localized corrosion Such as stress corrosion cracking, layer erosion, intergranular corrosion, and 8000 series aluminum alloy is an easily corrosive formula, aluminum alloy cable increases the heat treatment process, easy to cause uneven physical conditions, more easily than aluminum cable corrosion. The aluminum alloys currently used in our country are basically 8000 aluminum alloy series.

2, the temperature performance, aluminum alloy difference from copper

The melting point of copper is 1080 °C and the melting point of aluminum and aluminum alloy is 660 °C, so copper conductors are a better choice for fire-resistant cables. Some aluminum alloy cable manufacturers now claim to be able to produce fire-resistant aluminum alloy cables and have passed relevant national standards tests. However, aluminum alloy cables and aluminum cables have no difference in this respect. If they are in the center of fire (above), the temperature is higher than the melting point of aluminum alloy and aluminum cables. At that time, no matter what kind of insulation measures the cable takes, the cable would melt in a very short time and lose its conductive function. Therefore, aluminum and aluminum alloys should not be used as fire-resistant cable conductors, nor should they be used in densely populated urban distribution networks and buildings. Used in factories and mines.

3, aluminum alloy does not solve the problem of aluminum oxidation

Aluminum or aluminum exposed to the atmosphere quickly forms a hard, strong but brittle, about 10 nm thick film with a high resistivity. Its hardness and cohesive force make it difficult to form conductive contacts. This is the reason why the surface oxide layer must be removed before aluminum and aluminum alloys are installed. The surface of copper is also oxidized, but the oxide layer is soft and easily breaks down into a semiconductor when it withstands the force, forming a metal-metal contact.

4, aluminum alloy cable has improved in stress relaxation and creep resistance but far less than copper

The addition of specific elements to Pu aluminum can improve the creep performance of Pu aluminum, but its degree of improvement is also very limited compared to Pu aluminum, and there is still a huge gap compared to copper. And whether the aluminum alloy cable can really improve the creep resistance is closely related to the level of process, technology, and quality control of each company. This kind of uncertainty is a risk factor in itself. If there is no strict control of the mature process, the aluminum alloy cable will improve creep. Variable performance is also not guaranteed.

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