Micro channel aluminum flat tube is mainly used in air conditioning systems of various refrigerants. As a pipe component carrying new environmental protection refrigerant, the new environmental protection system is the key material of the new generation of parallel flow microchannel air conditioning heat exchanger.
Micro channel aluminum flat tube is a new type of environmentally friendly refrigerant bearing pipe component, which was first used in automobile air conditioning system (EU Regulation 1996, China Regulation 2002). Due to its high technical content and great production difficulty, this product was produced by only a few manufacturers such as Norway's hydro, Japan's Mitsubishi, Guhe and South Korea's Yijin before 2010, and its production technology was basically monopolized by them. Domestic enterprises simply could not produce it. The material required by domestic automobile air-conditioning heat exchanger manufacturers can only be obtained from the wholly-owned subsidiaries of the above-mentioned foreign manufacturers in China or directly imported.
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 and the thickness is only 1mm, but there are 12-16 holes. The difficulties are mainly reflected in the following six aspects:
1. Super large extrusion ratio
Extrusion ratio refers to the ratio between the cross-sectional area of the material before hot extrusion and the cross-sectional area after extrusion. Generally, it is 8-50 times, while the cross-sectional area of the Micro channel aluminum flat tube is only about 4px2. The extrusion ratio should be more than 400 times, which is more than 8 times that of the aluminum extrusion process.
2. Ultra high dimensional accuracy
The dimensional accuracy of Micro channel aluminum flat tube is much higher than the domestic standard of hot extrusion tube for aluminum and aluminum alloy research. According to the domestic standards, the width deviation of typical varieties of 16mm is ± 0.3mm, while the width deviation of Micro channel aluminum flat tube is ± 0.03mm, which needs to be increased to ± 0.01 - ± 0.02mm for high requirements.
3. Air tightness
There are about 50-150 Micro channel aluminum flat tube in a set of microchannel heat exchangers. As long as one of them has air tightness defects (such as pores and inclusions), the whole air conditioner will be scrapped. Therefore, the quality standard is calculated in ppm (1 million pieces), and the measurement standard is below 15ppm.
4. High quality bar
The small wall thickness of the Micro channel aluminum flat 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 pore or inclusion, the thin wall of the Micro channel aluminum flat tube will leak. Therefore, high-purity refining rod must be used, with hydrogen content ≤ 0.09%.
5. Surface zinc spraying technology
Since there is refrigerant medium inside the Micro channel aluminum flat tube and atmospheric corrosion outside, it is easy to leak due to point corrosion. A thin layer of zinc must be sprayed on its outer surface to protect the pipe wall from corrosion. Up to now, there is no manufacturer in China that can provide qualified zinc spraying equipment, and only a few manufacturers in China can provide it.
6. Online flaw detection and inspection technology
As the technology of Micro channel aluminum flat tube is difficult and difficult, how to use scientific and effective on-line flaw detection, surface quality and other inspection methods in the production process to detect (mark) defective products in time is extremely critical to the quality control of Micro channel aluminum flat tube .
