Important uses of electroplating equipment and electroplating technology in the automotive parts industry
As an important means to extend the service life of the car, improve its power performance, and improve the appearance of the decorative performance, the electroplating process has put forward more stringent quality requirements with the rapid development of the automobile industry. The application of electroplating in the automotive industry is also becoming more and more extensive.
①Shock absorber connecting rod
In the past, the shock absorber connecting rod used the electroplating of the Chiefton hard chrome process, and the corrosion resistance could not meet the requirements. Recently, the HEEF25 micro-crack chrome plating process is used, and the coating thickness is 20±5μ; and the specification is 10l±3μ. Generally, the number of cracks is required to be 400-600/cm, which has a positive effect on ensuring the corrosion resistance and lubricity of the shock absorber connecting rod. In this process, the current density has a significant relationship with the number of micro-cracks, crack morphology and permeation of the chrome plating layer. It is generally controlled at 58A/dm2. The design of the cylindrical anode and the polishing after plating have an impact on the quality.
② Bearings
In order to prevent the Sn in the coating from thermally diffusing to the body to form a brittle phase, a nickel grid needs to be plated on the bearings of high-power engines, and the Pb-Sn-Cu alloy is electroplated instead of the Pb-Sn binary alloy coating.
③ Piston, piston ring, connecting rod
The piston, piston ring, and connecting rod are the three moving parts of the automobile engine, and their friction loss accounts for about 40-50% of the total engine loss. Reducing the weight of the piston, piston ring, and connecting rod and improving their friction environment are of great significance to reducing engine vibration, noise, and fuel consumption.
In the past, pistons did not undergo any surface treatment or only chemically dipped tin (forming an initial running-in layer): the piston ring was chrome-plated and phosphated: the connecting rod only had an oxidation treatment on the connecting rod; the bearings on the connecting rod were electroplated with Pb-Sn binary alloy and electroplated with Sn. These electroplating layers can no longer meet the needs of modern engines for high speed, high power, compactness, and the development of ECR technology.
④ Inlet and exhaust valves
The friction loss of the inlet and exhaust valves is about 2% of the engine energy loss. Measures to reduce losses: reduce the structural dimensions of the inlet and exhaust valves, and use lightweight materials, such as titanium alloy instead of ordinary heat-resistant steel. Working at a high temperature of 750℃, there is friction from the scales in the engine exhaust gas, and the titanium exhaust valve will undergo intense oxidation, so it must be treated on the surface, usually by molybdenum spraying and salt bath furnace nitriding.
The treatment method that has attracted attention recently is plasma carburizing treatment, which has little impact on the environment. The TiC hardened layer formed on the surface is 50μm deeper than the rutting layer treated by the heat-resistant steel salt bath furnace, and the hardness reaches HV700. The oxidation resistance and wear resistance are the same as those of the heat-resistant steel valves, and the treatment cost is more expensive than that of the salt bath furnace treatment.
⑤ Exhaust pipe, muffler
The exhaust system installed in the chassis of the car is not only subject to environmental corrosion such as the impact of road mud and gravel, but also to the scouring and oxidation corrosion of high-temperature exhaust gas above 400℃, and the working environment is very harsh. Exhaust system materials are mostly stainless steel and hot-dip aluminum plates. During use, aluminum plates often experience black coating and rust. In the 40 cycles of the vehicle corrosion test, 5 levels of corrosion occurred, and the corrosion resistance is not as good as stainless steel. Adding silicon to hot-dip aluminum can inhibit the growth of the iron-aluminum alloy layer and improve the processing performance. The service life of hot-dip aluminum plates is related to the thickness of the coating, the molding process, and the working temperature.
⑥Automobile decorative parts
Modern automobile decorative parts are mostly plastic parts. High-end automobile plastic decorative electroplating parts require extremely high corrosion resistance, thermal vibration resistance, and decorativeness.
