1 Development of surface treatment technology for automotive aluminum wheels
In order to improve the appearance of automotive aluminum wheels, chrome plating, polishing, painting and other surface treatments on automotive wheels can play a significant role in improving the corrosion resistance and stone-strike resistance of the wheels. At the same time, the appearance of automobile wheels and tire patterns are the first visual impression provided to people in addition to the body. Therefore, doing a good job in the appearance of automobile wheels can not only attract the attention of potential customers and stimulate their desire to buy, but also to others. Show the taste of the owner.
Compared with traditional steel wheels, aluminum wheels have lighter weight and stronger heat dissipation capacity, and are easy to be chrome-plated, polished, painted, etc., after the above treatments, the appearance of aluminum wheels is more beautiful, and at the same time it is corrosion-resistant Sex has also been greatly improved. In addition, with the increasing maturity of the electrolytic production technology of aluminum metal, the production cost of aluminum is getting lower and lower, and more and more automobile manufacturers have begun to choose aluminum as the raw material for the production of automobile wheels.
2 The impact of the concept of green environmental protection on the surface treatment technology of automotive aluminum wheels
As mentioned above, compared with steel wheels, aluminum wheels have the advantages of good balance, strong rigidity, light weight, and high appearance precision. Electroplating of aluminum wheels can make the appearance of aluminum wheels more eye-catching and improve the overall appearance of the car. degree. However, the treatment of electroplated aluminum wheels will cause great production pollution, which will seriously pollute the natural ecological environment, which is contrary to the global consensus on the concept of green environmental protection. At this stage, in order to implement the concept of green environmental protection and sustainable development, automobile manufacturers not only pay more attention to the application of new energy power and other technologies when manufacturing complete vehicles, but also pay more attention to the energy saving and reduction of auto parts such as wheels and interiors. Schedule production. Traditional electroplated wheels mainly include electroplated silver, water electroplating and pure electroplating. Compared with purely electroplated wheels, the appearance of electroplated silver and water electroplated wheels is smoother and more beautiful, but their stone-strike resistance and corrosion resistance are poor, so their retention time is shorter. The general audience pursues the ultimate beauty and freshness. Sensual young man. However, pure electroplated wheels have higher production costs and stronger stability, and their color retention time is long, and their audiences are mainly middle-aged people. At the same time, in the production of automobile wheels, the appropriate wheel processing technology is often selected according to the appearance of the automobile itself and the application requirements. At this stage, the commonly used wheel surface treatment processes mainly include paint baking and electroplating. The paint baking process is a common surface treatment process for automobile wheels. Its production cost is lower and the appearance of the wheels lasts longer. Statistics show that the wheels with baking paint treatment have not faded even if the vehicle has been scrapped.
The use of electroplating treatment makes the wheels of automobiles more beautiful, but the pollution is more serious than that of paint treatment. Specifically, it mainly includes the following two aspects: First, when electroplating, nickel and chromium are used. , Copper and other heavy metals. After the electroplating treatment of automobile aluminum wheels is completed, these heavy metals will be discharged along with electroplating wastewater, causing serious environmental pollution. Second, a certain amount of cyanide will be generated when the electroplating process is used to treat automobile wheels. These cyanide will also be discharged into the natural water system along with the electroplating wastewater, causing environmental pollution.
With the reduction of aluminum alloy production costs, aluminum alloy wheels have become the first choice for automobile manufacturers to manufacture auto parts. In the production of aluminum alloy wheels, forging and assembly processes are usually selected, which can effectively reduce the weight of the wheel. According to the data, the use of assembly technology and forging technology for the production of wheels can reduce the weight of the wheels by more than 20%. In the surface treatment of aluminum alloy wheels, the application of vacuum electroplating technology can effectively reduce the energy consumption, noise pollution and the discharge of heavy metals and cyanide electroplating wastewater during wheel treatment.
3 Surface treatment methods of automotive aluminum wheels at this stage
At this stage, automobile companies mainly use spraying technology and decorative electroplating technology when performing surface treatment of aluminum wheels. The two processes are now introduced as follows:
3.1 Spraying technology
Spraying technology is a technology for coloring and polishing the surface of the wheel to enhance the aesthetics of the wheel. Before the spraying technology was produced, the surface treatment of aluminum wheels was mainly through heat treatment machine heating and coating drying. The surface of aluminum wheels treated by this process was unevenly sprayed and the aesthetics was not enough; at the same time, the corrosion resistance and resistance of aluminum wheels The stone-strike ability is not strong, and the quality is not well guaranteed. The use of spraying technology can achieve uniform spraying of the surface of the wheel, which greatly improves the appearance of the aluminum wheel. At the same time, the bright surface, polishing and powder spraying technology of the wheel can improve the metallic light color of the aluminum wheel surface, thereby achieving replacement The purpose of electroplating treatment is to minimize the pollutants produced by electroplating technology. In addition, in order to further respond to the concept of sustainable development and green environmental protection, the use of electroplating technology and paint spraying technology will be less and less, replaced by powder spraying technology and water-based spraying technology.
3.2 Decorative plating
Decorative electroplating, that is, casting heat treatment machine and polishing electroplating treatment on the surface of automobile aluminum wheel hub. Through the drying treatment of the casting heat treatment machine and the polishing and electroplating, the surface of the aluminum wheel can be made to show a brighter metallic luster than the spraying technology, and the corrosion resistance of the automotive aluminum wheel after this treatment is better, and its production cost Higher, so it is often used in high-end car brands. Decorative electroplating is similar to ordinary electroplating and requires pre-nickel plating. At the same time, due to the complex shape of automobile wheels, the time for pre-nickel plating is longer than that of ordinary nickel plating. Generally, it takes about 30-40 minutes. The purpose of this pre-nickel plating is different from traditional electroplating. The pre-nickel plating is only for the surface treatment of acid copper electroplating. Therefore, when performing decorative electroplating treatment, the electroplating plant needs to invest a lot of capital cost. In recent years, the purchase cost price of metallic nickel has risen sharply, making electroplating companies encounter the cold winter of wheel electroplating. How to reduce the cost of decorative electroplating has become an issue of great concern for wheel electroplating companies. At this stage, advanced Western wheel processing companies have developed the "cyanide-free high-density copper plating" wheel processing technology, using this technology to replace the pre-nickel process and reduce the cost of electroplating.
In western developed countries, the application of casting heat treatment machine plus polishing electroplating is extremely wide, because the wheel hub after this process has high value preservation, and its added value is higher than that of spraying technology. In order to effectively reduce the emission of pollutants caused by decorative electroplating treatment, at this stage, Western automobile wheel processing enterprises have begun to gradually use vibrating light decoration technology. After the automotive aluminum alloy wheels are polished, there is basically no difference in appearance, stone-strike resistance, and corrosion resistance from the casting heat treatment machine plus polishing electroplating technology.
4 Spraying method and process flow for surface treatment of automobile aluminum wheel hub
4.1 Spraying method for surface treatment of automobile aluminum wheel hub
In the surface treatment of automobile aluminum wheels, the spraying methods mainly include manual spraying and automatic spraying. Manual spraying, as the name suggests, is that the staff of the automobile wheel processing enterprise spray manually. This spraying method is prone to problems such as inconsistent coating thickness and poor spraying quality, which leads to problems such as insufficient appearance of the wheel and difficult to attract customers to buy. The emergence of automatic spraying technology perfectly solves the problems of manual spraying. It can keep the spraying thickness within 10mm, and at the same time, it can evenly spray the coating on the car wheel, and the spraying thickness can be carried out according to the actual requirements of customers. Change. When spraying the surface of the wheel hub, electrostatic spray guns and air spray guns are usually used. Air spray guns have a smaller scope of application and cannot spray powder and other new spray materials. Spraying is the final process in the production of automotive aluminum wheels. The sprayed automotive aluminum wheels can effectively improve their aesthetics and corrosion resistance.
4.2 Process flow of surface spraying of automobile aluminum wheel hub
At this stage, with the rapid development of science and technology and the continuous research and development of advanced spraying equipment, automobile wheel spraying companies have basically realized automatic spraying production lines. The automatic production line of general automobile spraying consists of surface pretreatment, drying, electrostatic powder spraying, painting and curing. The entire production line is also connected with handling robots, spraying material recycling system, spraying material replacement system and spraying waste treatment equipment, so as to increase the spraying rate of the production line while realizing the timely treatment of waste generated by the spraying process. In the automatic spraying assembly line, the spraying technology used is generally a high-speed electrostatic spinning cup spray gun technology to ensure that the surface of the processed aluminum wheel hub is evenly sprayed.
5 The development trend of surface treatment of automotive aluminum wheels
5.1 The application of nanotechnology in automotive aluminum wheels
Nano-mirror spraying technology can realize the technology of spraying specific spraying materials directly on the aluminum wheel through chemical reaction to make it show heavy metal luster. In addition, through the research of nanotechnology, the hydrophobicity and oleophobicity of the sprayed material have been realized, so that the sprayed material is not easy to be contaminated with water, oil and dust, and it is convenient for car owners to clean the car wheel.
5.2 Vacuum plating processing technology
Vacuum electroplating treatment technology can realize the concept of green and environmentally friendly production, and achieve the metallic luster that is difficult to obtain by ordinary electroplating. Specifically, vacuum electroplating refers to the high-temperature spraying of two layers of primer on the aluminum wheels of automobiles, and then placing these wheels with sprayed materials in a vacuum metal spraying room with rare gas, and achieving high-temperature steam. For spraying of heavy metals such as nickel and chromium, on this basis, an acrylic protective layer is sprayed. This spraying technology not only greatly reduces the amount of heavy metals such as nickel and chromium required for wheel plating, but also reduces the quality of the wheel. In addition, this spraying method does not produce hexavalent chromium, trivalent chromium, etc. Heavy metal wastewater has achieved the goal of green and environmental protection.
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