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Plasma surfacing technology is one of the effective technical methods to improve the wear resistance, corrosion resistance and impact resistance of metal surfaces. Plasma surfacing technology is a surface metallurgical method that uses the nozzle of the water cooling system to constrain the arc, uses the transferred arc as the heat source to obtain a high energy density plasma arc, and cooperates with alloy powder materials. The two parts of the plasma torch, the cathode electrode and the nozzle (anode), are connected to the negative and positive electrodes respectively. The working gas passes through the plasma torch and is ignited using high-frequency sparks. The gas is heated to a very high temperature (approximately) to produce a compression effect. Under the combined action of magnetic compression, thermal compression and mechanical compression, a plasma jet with extremely high temperature and extremely high speed is ejected from the nozzle. After the alloy powder enters the plasma beam, it is instantly heated and accelerated to form particle rays. The particles are in a molten or semi-molten state and are sprayed onto the surface of the workpiece to be processed. Physical and chemical changes such as melting, mixing, and solidification occur on the surface of the part. Finally, they are mixed with the surface of the part. Metallurgical bonding.
Characteristics of plasma surfacing due to the combined influence of thermal compression effect, magnetic compression effect and mechanical compression effect, the formation of non-transfer plasma arc can obtain or higher temperature, heat concentration, it can melt high melting point, high Hardness of powder material. Therefore, a coating with dense structure, low porosity, high bonding strength to the substrate and easy control of the coating thickness can be obtained. During the plasma surfacing process, the heat-affected zone is relatively small, and the deformation of the parts is small. During the surfacing process, the microstructure and properties are not changed, and the properties are not changed. Especially suitable for high-strength steel, thin-walled parts, and slender parts.
Plasma surfacing has the following advantages?
The heat affected zone is small and the structure does not change. The temperature of the workpiece can be controlled to less than ℃.
The coating contains less oxides and impurities, and is thicker, harder, and more anti-corrosive than electroplating, carburizing, and nitriding coatings.
The surfacing layer is metallurgically bonded to the workpiece, resistant to impact and will not fall off.
The coating is smooth and flat, and the thickness can be precisely controlled.
The cladding speed is fast and the dilution rate of plasma arc cladding can be controlled at one or lower.
The cladding layer has a dense structure and beautiful shape. The cladding process can be easily mechanized and automated.
Good controllability. The arc parameters such as the atmosphere temperature of the plasma arc can be adjusted by changing the power, changing the gas type, flow rate and the structural size of the nozzle, thereby achieving efficient automated production and improving labor productivity.
Wide range of materials used. As a deposited material, cladding alloy powder is not restricted by casting, rolling, wire drawing and other processing techniques. Alloy powders of different compositions can be configured according to different performance requirements. It is especially suitable for hard wear-resistant alloys that are difficult to wire but easy to powder. , to obtain the surfacing layer with the required performance.
Application of Plasma Surfacing Technology in Coal Mines
Due to the very complex underground production environment of coal mines, underground equipment is required to be both sturdy and durable and have high explosion-proof performance. The scraper conveyor, loader, shearer and other equipment used in the coal mine underground working face are responsible for the mining and transportation tasks of the entire working face. The scraper conveyor also serves as the walking track of the scraper conveyor, and the wear is very serious. At the same time, the value of these equipment is relatively high. The scraper conveyor in a modern mine generally costs more than five to six million yuan. The main wear parts of a coal shearer are the drum and pick. The value of each drum is hundreds of thousands to several hundred thousand yuan. The annual consumption of millions of picks is more than hundreds of thousands of yuan. Coal mining enterprises lose nearly 10 million yuan every year due to wear and tear problems, which greatly affects the improvement of coal mine economic benefits. Especially as the coal mining industry has entered a cold winter period in recent years, it is imperative to do everything possible to reduce production costs.
Application of a scraper conveyor wear-resistant treatment
The main wear parts of the scraper conveyor in the coal mine are?
The middle plate bottom plate and channel steel of the head frame and tail frame.
The middle plate, bottom plate groove and sliding shoe track of the middle groove.
The middle plate, bottom plate and trough side of the cable duct transition trough.
The chain nest of the sprocket.
The treatment plan uses special plasma surfacing equipment to weld a wear-resistant layer of a certain shape on the wear-prone parts of the scraper conveyor (such as the middle plate, bottom plate, groove, shoe track, etc.). When the scraper conveyor is running, The scraper and chain no longer directly wear the equipment body, but only wear the surfacing wear-resistant layer. After one or two working surfaces are harvested, the base of the scraper conveyor is basically not worn, which can greatly extend the service life of the scraper conveyor. Losses caused to coal mining enterprises due to wear and tear.
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