1. Overextrusion ratio
The extrusion ratio refers to the ratio of the cross-sectional area of the material before hot extrusion to the cross-sectional area after extrusion, which is generally 8 ~ 50 times, while the cross-sectional area of the microchannel aluminum tube is only about 4px2, and the extrusion ratio should reach more than 400 times, which is more than 8 times that of the aluminum extrusion limit process.
2. Ultra-high dimensional accuracy
The dimensional accuracy of microchannel aluminum tube is much higher than the national standard "Hot Extruded Tube for Aluminum and Aluminum Alloy Research". According to the national standard, the dimensional deviation of typical variety width 16mm is 0.3mm, while the dimensional deviation of microchannel aluminum tube is 0.03mm, which needs to be improved to 0.0 1 ~ 0.02 mm even if the requirements are high. ..
3. Air tightness
There are about 50 ~ 150 microchannel aluminum tubes in a microchannel heat exchanger. As long as one of them has air tightness defects (such as air holes and inclusions), the whole air conditioner will be scrapped. So the quality standard is calculated as ppm (1 10,000 tablets), and the measurement standard is below 15PPM.
4. Quality bar
The minimum limit wall thickness of microchannel aluminum tube is only 0.13 mm. If the purity and hydrogen content of the cast rod material can't meet the requirements, the thin wall of microchannel aluminum tube will leak as long as there are tiny pores or inclusions, so high-purity refining rod must be used, and the hydrogen content is ≤0.09%.
5. Surface zinc spraying technology
Because there is refrigerant medium in the microchannel aluminum tube and atmospheric corrosion on the outside, it is easy to leak due to pitting corrosion, so a thin layer of zinc must be sprayed on the external surface to protect the tube wall from corrosion. So far, no domestic manufacturer can provide qualified zinc spraying equipment, and only a few international manufacturers can provide it.
6. On-line flaw detection and detection technology
Due to the technical difficulties and difficulties of microchannel aluminum tubes, it is very important for the quality control of microchannel aluminum tubes to use scientific and effective online flaw detection and surface quality detection methods to find (mark) defective products in time.