Method for eliminating water stain defects of micro-channel aluminum flat tube

Abstract

The application discloses a method for eliminating water stain defects of micro-channel aluminum flat tubes, and the continuously extruded micro-channel aluminum flat tube is cooled through a liquid nitrogen cooling box after being treated by zinc spraying, and then is wound on a winding drum. The method adopts the liquid nitrogen cooling mode to replace the traditional water cooling, so that the water stain defects caused by water cooling can be completely avoided, and the product yield and the product qualification rate are improved.

Description

Technical Field

[0001] This invention relates to the field of microchannel aluminum flat tube manufacturing technology, and specifically to a method for eliminating water stain defects in microchannel aluminum flat tubes. Background Technology

[0002] Microchannel aluminum flat tubes have been available in China for fifteen years. However, the yield and quality of these tubes have been plagued by a defect called "water stains." This defect is caused by the cooling method.

[0003] During the manufacturing of microchannel aluminum flat tubes, to prevent surface oxidation and increase their potential difference, a very thin layer of zinc must be sprayed onto the surface within the shortest possible time after extrusion. Since the freshly sprayed zinc cannot be touched before it has fully solidified with the aluminum, the microchannel aluminum flat tubes are often immersed directly in a cold water tank after zinc spraying. (See [reference needed]). Figure 1 In this way, the microchannel aluminum flat tube coming out of the cold water tank solidifies with the zinc layer. Then, the moisture adhering to the aluminum flat tube is dried through the drying tunnel to obtain a qualified product.

[0004] Existing water cooling methods can achieve a strong bond between the zinc layer and the aluminum flat tube, but they have the following problems:

[0005] Because the extrusion speed of microchannel aluminum flat tubes is so high, the extruded tubes often carry a large amount of water from the tank forward at high speed. Despite various methods, such as using air knives to try to stop the water before the tubes enter the drying oven, it is impossible to completely dry them. Even if only a small layer of water remains, it is impossible to completely dry them within the limited length of the drying tunnel. Those microchannel aluminum flat tubes that have not been completely dried are then wound onto the top of the roll, and these tubes become water-stained. Microchannel aluminum flat tubes with water stains can only be picked out by quality inspectors after cutting, resulting in a low yield. However, if they are not picked out, the product qualification rate will be low. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a method for eliminating water stain defects in microchannel aluminum flat tubes.

[0007] The technical solution adopted in this invention is:

[0008] A method for eliminating water stain defects in microchannel aluminum flat tubes involves spraying zinc onto continuously extruded microchannel aluminum flat tubes, cooling them in a liquid nitrogen cooling box, and then winding them onto a roll.

[0009] Furthermore, the extrusion speed of the microchannel aluminum flat tube is 100–130 m / min.

[0010] Furthermore, the zinc spraying thickness is controlled at (6~12)±2g / m. 2 .

[0011] Furthermore, it is cooled to below 60°C using a liquid nitrogen cooling tank.

[0012] Furthermore, the liquid nitrogen cooling box includes a box body, with an aluminum flat tube inlet and an aluminum flat tube outlet on the front and rear sides of the box body, respectively. Liquid nitrogen inlet A and liquid nitrogen inlet B are located at the top and bottom of the box body, respectively. Liquid nitrogen inlet A is connected to a first liquid nitrogen pipe via a cryogenic electronic control valve A, and liquid nitrogen inlet B is connected to a second liquid nitrogen pipe via a cryogenic electronic control valve B. Both the first and second liquid nitrogen pipes are connected to a liquid nitrogen tank. When the extruder starts extruding, cryogenic electronic control valves A and B open simultaneously. Liquid nitrogen from the liquid nitrogen tank enters the box body via the first and second liquid nitrogen pipes. The microchannel aluminum flat tube, after being treated with zinc spraying, enters the box body through the aluminum flat tube inlet and exits through the aluminum flat tube outlet. At the instant cryogenic electronic control valves A and B open, the liquid nitrogen vaporizes and absorbs heat, instantly cooling the microchannel aluminum flat tube.

[0013] Furthermore, cryogenic electronic control valve A and cryogenic electronic control valve B are interlocked with the extruder for control.

[0014] Furthermore, a ring of felt is provided inside the outlet of the aluminum flat tube, and the felt is in frictional contact with the surface of the aluminum flat tube.

[0015] Furthermore, the volume of the enclosure is 0.3–0.5 m³. 3 The time it takes for the microchannel aluminum flat tube to pass through the chamber is 0.23 to 0.8 seconds.

[0016] The beneficial effects of this invention are: by using liquid nitrogen cooling instead of traditional water cooling, the defects caused by water stains due to water cooling can be completely avoided, thereby improving the yield and qualification rate of the products. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the existing microchannel aluminum flat tube cooling method.

[0018] Figure 2 This is a schematic diagram of the microchannel aluminum flat tube cooling method of the present invention. Detailed Implementation

[0019] The present invention will be further illustrated below with specific examples to facilitate understanding of the invention, but this does not limit the invention.

[0020] See Figure 1 ,from Figure 1As can be seen, the existing cooling water tank 10 has an aluminum flat tube inlet 12 on the front side, an aluminum flat tube outlet 13 on the rear side, a water inlet 13 at the bottom, and an open top. A ring of felt 131 is provided inside the aluminum flat tube outlet 13. The continuously extruded microchannel aluminum flat tube 1, after being treated with zinc spraying, enters the cooling water tank 10 from the aluminum flat tube inlet 12 and exits from the felt ring 131 at the aluminum flat tube outlet 13. Cooling water enters the cooling water tank 10 from the bottom water inlet 13 and sprays upward to cool the microchannel aluminum flat tube 1. The microchannel aluminum flat tube 1 exiting from the aluminum flat tube outlet 13 still carries water.

[0021] See Figure 2 This invention provides a method for eliminating water stain defects in microchannel aluminum flat tubes, comprising:

[0022] Step one: First, construct a liquid nitrogen cooling tank. For example... Figure 2 As shown, the liquid nitrogen cooling tank includes a tank body 20, which can be made of steel plate of a certain thickness. The middle section is rectangular, while the top and bottom are conical. The conical top and bottom design facilitates the uniform spraying of liquid nitrogen from the control valve onto the aluminum flat tube. Preferably, the volume of the tank body is 0.3–0.5 m³. 3 The microchannel aluminum flat tube passes through the chamber in 0.23–0.8 seconds, allowing for instantaneous cooling and saving liquid nitrogen usage, thus reducing operating costs. The chamber 20 has an aluminum flat tube inlet 21 and an outlet 22 on its front and rear sides, respectively, and a liquid nitrogen inlet A23 and an outlet B24 on its top and bottom, respectively. The dimensions of both the aluminum flat tube inlet 21 and outlet 22 are larger than the cross-sectional dimensions of the aluminum flat tube, ensuring that the passing aluminum flat tube does not contact the inlet 21 or outlet 22, and that the vaporized nitrogen can be discharged from the inlet 21. To ensure product quality, a felt ring 221 can be installed inside the outlet 22 to remove stains from the surface of the aluminum flat tube after nitrogen cooling.

[0023] Step two: Connect liquid nitrogen inlet A23 to the first liquid nitrogen pipe 27 via cryogenic electronic control valve A25, and connect liquid nitrogen inlet B24 to the second liquid nitrogen pipe 28 via cryogenic electronic control valve B26. The other ends of both the first liquid nitrogen pipe 27 and the second liquid nitrogen pipe 28 are connected to a liquid nitrogen tank (not shown in the diagram). Both the first liquid nitrogen pipe 27 and the second liquid nitrogen pipe 28 are made of double-layered copper tubing with a vacuum jacket, which reduces the loss of cold liquid nitrogen during transport, thus ensuring that the liquid nitrogen inside the pipes remains in a liquid state. Both cryogenic electronic control valves A25 and B26 can withstand temperatures as low as -200℃.

[0024] Step 3: Connect cryogenic electronic control valves A25 and B26 to the extruder via wires and set them to interlock control, so that the two cryogenic electronic control valves are linked to the extrusion action of the extruder.

[0025] Step four involves introducing the zinc-sprayed microchannel aluminum flat tube 1 into the housing 20 at a speed of 100-130 m / min through the aluminum flat tube inlet 21 and out through the aluminum flat tube outlet 22. As the extruder begins extrusion, the microchannel aluminum flat tube 1 moves rapidly forward. Simultaneously, the cryogenic electronic control valves A25 and B26 are opened. The liquid nitrogen in the liquid nitrogen delivery pipe, still in a liquid state at -200℃, instantly vaporizes upon exiting the cryogenic control valve. The -200℃ liquid nitrogen absorbs a massive amount of heat during vaporization, thus instantly cooling the zinc-sprayed microchannel aluminum flat tube, which still has a temperature of over 500℃. The cooled microchannel aluminum flat tube 1 is then wound onto a roll, permanently eliminating the water stain defect.

[0026] The zinc spraying thickness of the preferred microchannel aluminum flat tube 1 is controlled at (6~12)±2g / m. 2 This not only meets the usage requirements but also ensures high efficiency in liquid nitrogen cooling.

[0027] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications are also within the protection scope of the present invention.

Claims

1. A method for eliminating water stain defects in microchannel aluminum flat tubes, characterized in that, The continuously extruded microchannel aluminum flat tubes are treated with zinc spraying, cooled in a liquid nitrogen cooling box, and then wound onto a roll. The extrusion speed of the microchannel aluminum flat tube is 100-130 m / min; the zinc spraying thickness is controlled at (6-12) ±2 g / m2; The liquid nitrogen cooling chamber includes a chamber body. The front and rear sides of the chamber body are respectively equipped with aluminum flat tube inlets and aluminum flat tube outlets. The top and bottom of the chamber body are respectively equipped with liquid nitrogen inlet A and liquid nitrogen inlet B. Liquid nitrogen inlet A is connected to a first liquid nitrogen pipe via cryogenic electronic control valve A, and liquid nitrogen inlet B is connected to a second liquid nitrogen pipe via cryogenic electronic control valve B. Both the first and second liquid nitrogen pipes are connected to a liquid nitrogen tank. When the extruder starts extrusion, cryogenic electronic control valves A and B open simultaneously. Liquid nitrogen in the liquid nitrogen tank enters the chamber body through the first and second liquid nitrogen pipes. The microchannel aluminum flat tube, after being treated with zinc spraying, enters the chamber body from the aluminum flat tube inlet and exits from the aluminum flat tube outlet. The moment cryogenic electronic control valves A and B open, the liquid nitrogen vaporizes and absorbs heat, instantly cooling the microchannel aluminum flat tube to below 60°C. The volume of the enclosure is 0.3–0.5 m³. 3 The time for the microchannel aluminum flat tube to pass through the chamber is 0.23 to 0.8 seconds.

2. The method for eliminating water stain defects in microchannel aluminum flat tubes according to claim 1, characterized in that, The cryogenic electronic control valves A and B are interlocked with the extruder for control.

3. The method for eliminating water stain defects in microchannel aluminum flat tubes according to claim 1, characterized in that, A ring of felt is installed inside the outlet of the aluminum flat tube, and the felt is in frictional contact with the surface of the aluminum flat tube.

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