What is the key technology to realize the industrialization of the vacuum coating of steel belt?

With vacuum technology and materials technology development and the iron and steel industry on the development of new steel urgent requirements, vacuum strip coating is becoming strip surface treatment of an important technology, has good prospects for development. At present, it has become more mature and can quickly realize the industrialized vacuum coating technology. Practice has proved that the electron beam vacuum coating has many advantages: (1) the choice of coating material is not limited by the melting point of the material. High energy density of the electron beam can make the coating material in a very short period of time to reach 3000 ~6000. Therefore, in addition to the common in hot dip galvanizing zinc, aluminum, tin, almost all of the metal material can evaporation, but also many kinds of metal nitride film plating, metal oxide film and the metal carbide and composite membrane. This provides a great degree of freedom for the development of new steel strip material. (2) the coating material utilization rate is high, the environmental pollution is small. Vacuum coating is a dry coating, there is no harmful liquid, gas generation. (3) strip coating quality is good, can get uniform, smooth, and very thin coating, high purity of the coating, corrosion resistance and adhesion good. Strip coating can be by electron beam heating surface activation, coating with high purity, no intermediate rigid alloy layer, can be formed by a stamping forming, even can be rolled into a straight through a small tube without falling off the coating. (4) the technology is flexible and convenient to change, it can be based on the requirements of the products and flexible to realize the steel strip plating on one side, two sides, one layer, multilayer, two kinds of materials can be plated at the same time. Coating thickness is easy to control, and can be coated with ultra thin film.

However, vacuum strip coating in general is still in its initial stage, in the strip surface treatment for share is far not with hot dipping and electroplating. The main reason that hinders the development of strip vacuum coating is that the productivity is low and the cost is high. The most effective solution is to develop a high speed, stable, high power evaporation source.

Development and use of high power electron gun is the key technology in vacuum coating of strip. The general vacuum evaporation coating can be heated by resistance and induction heating. Its equipment is relatively simple, but the heating temperature and evaporation rate is low. To meet the needs of continuous industrial production of steel strip vacuum coating, it is necessary to use the heat source with high heating speed and high melting temperature. The practice at home and abroad proves that the high power electron gun is the ideal heat source for the continuous vacuum coating process of the steel strip. This is because the electron beam emitted by (1) electron gun can reach a very high energy density after focusing, and the coating material of the crucible can cause the temperature to reach more than 3000 degrees Celsius, and the temperature is higher than that of the arc. (2) the electron beam energy conversion rate is as high as 80%-90%, which can be easily carried out by the magnetic deflection system, which can be easily carried out by the electron beam focusing and scanning. (3) the surface of the coating material is only bombarded by the electron beam, and the inclusion problem can not be caused by the incorporation of other materials. (4) the beam spot diameter, electric power, beam voltage, scanning track, frequency and other parameters of the electron gun evaporation coating machine are easy to be adjusted. (5) using the electron gun can also be used in the production process of steel strip to be plated steel strip for vacuum preheating, is to use the electron gun to clean the steel strip, the impact of the surface to activate. By scanning electron beam, the surface temperature of the steel strip is controlled at 200~550 degrees C, which is necessary for the steel strip coating and the adhesion of the coating.