Due to the high technical content of the Microchannel aluminum flat tube, it is extremely difficult to produce. The minimum width of the aluminum tube is 12mm and the thickness is only 1mm, but 12-16 holes are required.Its difficulties are mainly reflected in the following six aspects:
1. Super large extrusion ratio
The extrusion ratio refers to the ratio between the material's broken area before hot extrusion and the broken area after extrusion, which is generally 8 ~ 50 times, while the micro-channel aluminum tube's broken area is only about 4px2. The extrusion ratio is more than 400 times, which is more than 8 times of the aluminum extrusion limit process.
2. Ultra-high dimensional accuracy
The dimension precision of micro-channel aluminum tube is much higher than the national standard of Hot Extrusion Tube for Research on Aluminum and Aluminum alloy.According to the national standard, the size deviation of 16mm width of typical varieties is ±0.3mm, while the width deviation of micro channel aluminum tube is ±0.03mm. The high requirement even needs to be increased to ±0.01 ~ ±0.02mm.
3. The air tightness
A set of microchannel heat exchanger has about 50 ~ 150 microchannel aluminum tubes. As long as one of them has air tightness defect (such as air hole, inclusion, etc.), the whole air conditioner will be scrapped. Therefore, the quality standard is calculated as PPM (1 million pieces) and the measurement standard is below 15PPM.
4. High quality bar
The minimum limit wall thickness of the micro channel aluminum tube is only 0.13mm. If the casting rod material purity and hydrogen content do not meet the requirements, as long as there is a very small pores or inclusions, the thin wall of the micro-channel aluminum tube will leak. Therefore, the high-purity refining rod must be used, with hydrogen content ≤0.09%.
5. Surface spraying zinc technology
Because there is refrigerant medium inside the Microchannel aluminum flat tube and atmospheric corrosion outside, it is easy to leak due to point corrosion effect, so a thin layer of zinc must be sprayed on the outside surface to protect the tube wall from corrosion.Domestic has not been able to provide qualified zinc spraying equipment manufacturers, international only a few manufacturers can provide.
6. Online flaw detection and detection technology
Due to the great technical difficulties and difficulties of Microchannel aluminum flat tube, how to use scientific and effective on-line inspection and surface quality inspection means to timely detect (mark) defective products in the production process is very critical to the quality control of microchannel aluminum tube.
