Due to the high technical content of the micro-channel aluminum flat tube, the production is extremely difficult. The width of the small variety is 12mm, the thickness is only 1mm, but there are 12-16 holes. The difficulties are mainly reflected in the following six aspects:
- Large extrusion ratio
The extrusion ratio refers to the ratio between the cross-sectional area of the material before hot extrusion and the cross-sectional area after extrusion, which is generally 8 to 50 times, while the cross-sectional area of the micro-channel aluminum tube is only about 4px2, and the extrusion ratio is It is more than 400 times, which is more than 8 times that of the aluminum extrusion process.
- Ultra-high dimensional accuracy
The dimensional accuracy of micro-channel aluminum tubes is much higher than the domestic standard of "Hot Extrusion Tubes for Research on Aluminum and Aluminum Alloys". According to domestic standards, the dimensional deviation of typical varieties with a width of 16mm is ±0.3mm, while the dimensional deviation of the microchannel aluminum tube width is ±0.03mm, and those with high requirements need to be increased to ±0.01~±0.02mm.
- Air tightness
A set of micro-channel heat exchangers has about 50 to 150 micro-channel aluminum tubes. As long as one has air tightness defects (such as pores, inclusions, etc.), the entire air conditioner will be scrapped, so the quality standard is PPM (1 million Pieces), the measurement standard is below 15PPM.
- High quality bar
The small wall thickness of the micro-channel aluminum tube is only 0.13mm. If the purity and hydrogen content of the cast rod material cannot meet the requirements, as long as there is a very fine air hole or inclusion, the thin wall of the micro-channel aluminum tube will be produced. Therefore, high-purity refining rods must be used, and the hydrogen content should be less than or equal to 0.09%.
- Surface spray zinc technology
Because there is a refrigerant medium in the micro-channel aluminum tube, and there is atmospheric corrosion outside, it is easy to cause leakage due to pitting corrosion. A thin layer of zinc must be sprayed on the outer surface to protect the tube wall from corrosion.