For the repair of machine tools and other wear parts, metal plates and polymer materials are often used for affixing or replacing, which requires not only a large number of precise machining operations, but also often requires manual scraping of the machined surfaces. long. In recent years, in the repair of the guide rails of the milling machine, Luo Copper has explored and tested the wear-resistant coatings and achieved success.
First, the concept of wear-resistant coatings
The role of the wear-resistant coating in the friction pair is to effectively protect the other side from wear or to reduce wear.
The machine tool guide wear-resisting coating is a solid coating with good lubrication conditions and corresponding resistance to mechanical force. It can not only compensate for the wear defects caused by friction between the two contact surfaces, but also make the two relative motion surfaces have good Lubrication anti-friction effect. At the same time, the wear-resistant coating should also have a certain degree of burying of metal impurities that enter between the two contact surfaces of the friction pair.
Second, the composition of wear-resistant coatings
1. The adhesive binder is an important component of the wear-resistant coating. Its role is to firmly bond the other components of the coating together and produce a good bond with the substrate to form a strong bond on the surface of the substrate. The coating. For ease of construction, the binder should have good fluidity and room temperature cure properties. The adhesive used for wear-resistant coatings generally uses typical structural adhesives such as epoxy resins, phenolic resins, polyester resins, and the like.
2. Lubricant Lubricant is the main component to improve the wear-reducing performance of wear-resistant coatings, so that the coating has a small friction coefficient and self-lubricating properties. Solid lubricants used for wear-resistant coatings include colloidal molybdenum disulfide, colloidal graphite powder, and some powdered high-molecular polymers.
3, enhancer enhancer generally use reduced iron powder, copper oxide powder, quartz powder and some other metal powder, can improve the mechanical strength and surface hardness of the coating to a certain extent, improve the anti-wear properties of the coating.
Third, the reaction mechanism of wear-resistant coating
1, the binder reaction mechanism In the composition of all the components of the coating, the most important active ingredient material is a binder, other materials are non-active filler material, so the wear resistance of the coating curing reaction mechanism lies mainly in the binder. In practice, our choice of binder is bisphenol A low molecular weight epoxy resin.
The technical performance of the epoxy resin after curing is related to the type of curing agent used and the amount of curing. The reaction mechanism of different curing agents and epoxy resin is different. The most commonly used curing agent is a polyamine curing agent. When the epoxy resin reacts with the aliphatic polyamine curing agent, the reaction type is as follows.
When the primary amine reacts with the epoxy resin, the epoxy group of the resin breaks to form a secondary amine; the secondary amine continues to react with the epoxy group to form a tertiary amine; and the hydroxyl and epoxy groups in the secondary and tertiary amine molecules are etherified Finally, a huge mesh structure is formed so that the epoxy resin does not melt and has excellent performance of epoxy plastic.
2. Lubrication principle Solid lubricants in wear-resistant coatings are usually selected from molybdenum disulfide and graphite. Molybdenum disulfide is a kind of metal sulfide. The molybdenum disulfide particles that are generally used as the lubricating material are very fine. The diameter of the molybdenum disulfide particles is about 10 μm or less and belongs to the colloidal substance in the dispersion system. It is also called colloidal molybdenum disulfide. Molybdenum disulfide has excellent lubricating properties and is hexagonal crystal layered structure. Its molecular arrangement is that the outer layer is a sulfur atom and the middle is a molybdenum atom. When the colloidal molybdenum disulfide molecules are distributed on the contact surfaces of a pair of friction pairs, a molecular layer is formed on the surface.
Because the MoS2 particles are very fine and have good adsorption ability with the matrix, the combination of Mo atoms and S atoms is chemically bonded and therefore very strong. However, the binding ability between the S atoms in the molecular layer itself is extremely weak, which results in a good lubrication condition for the interface molecules to move easily. In fact, the surface of the substrate between the two interfaces adsorbs one layer of molecular layer. From a microscopic point of view, although it is only a very thin layer, it also forms a very easy to slide interface. In practical applications, the MoS2 layer is much thicker and there are n molecular layers. Thus, there are (n-1) extremely slidable interfaces, so that the two friction surfaces have very good lubrication conditions.
3. Filler Function Add appropriate amount of reinforcing agent (mainly iron powder and quartz powder) and thinner to the wear-resistant coating, which can enhance the mechanical strength and wear resistance of the coating, as well as improve the impact toughness and uneven peeling performance of the coating. In construction, if the amount of filler is not used properly, it will cause the coating's bonding ability and mechanical strength to decrease.
Fourth, the application of wear-resistant coatings in the repair of rail guide milling machine
The Luoyang copper gantry milling machine was manufactured by the former Soviet Union during the "1st Five-Year Plan" period. The total guide rail length is 8.5m. The transmission principle is shown in Figure 1.
1. Determination of the thickness of the wear-resistant coating The thickness of the wear is measured to determine the amount of repaired work and the thickness of the wear-resistant coating required. The cross-section of the rail is shown in Figure 2.
Wear-resistant coating layer thickness: H = H1-H2 (mm)
Through careful mapping, consider the normal meshing conditions of the worm and worm gear, and determine the thickness of the wear-resistant coating layer to be (9.9±0.1) mm. During construction, in order to accurately control the thickness of the wear-resistant coating layer, a layer having a thickness of (9.7±0.05) mm was prepared and stuck on the bed in advance.
The bead is first attached to the bed surface of the bed, and the well-distributed and uniformly-mixed wear-resistant coating is evenly coated on the surface of the rail, the pressure plate is pressed, and the hand hammer continuously strikes the pressure plate along the arrow to make the excess coating. Overflow from the outside.
2, bed (substrate) surface degreasing cleaning degreasing cleaning is to ensure that the wear-resistant coating layer and the substrate is an important link. In the construction of old equipment, it is common to first perform rough washing with gasoline, perform general cleaning on the slick dirt on the surface of the substrate, and then use NaOH, Na3PO4, Na2CO3, and water as the cleaning liquid (heated to 60°C to 80°C. ) Perform alkaline elution of the oil until all oil has been removed. Rinse with hot water and dry twice. Finally, wipe with carbon tetrachloride and acetone for 1 or 2 times.
3. After the coating of the coating agent is cured, in order to facilitate die-cutting, a separating agent shall be applied on the working surface of the pressing plate before the construction. The release agent is typically formulated from organic glass frits and chloroform or vinyl chloride resins and acetone.
4. Preparation, coating and wear-resisting coating According to the proportion, the various components are mixed and stirred evenly, coated on the repair surface, compacted with a pressure plate, and cured after being cured (generally 24h-36h).
5. After the mold is repaired, the existing defects are repaired to ensure that the surface of the coating is smooth, smooth, uniform in color, uniform in quality, and free of defects such as large pores.
In order to improve the lubrication conditions of the wear-resistant coating, according to the lubrication principle of the original equipment, a once-formed lubricant groove is designed on the surface of the coating to reduce the machining procedure.
Lubrication principle: When the bed reciprocates on the guide rail, the wear-resistant paint layer presses down the sprayed steel ball, the lubricant oil is sprayed, and the fuel injection groove is filled. With the sliding of the bed, the lubricant oil fills the lubrication groove 1, and the lubrication The entire friction surface. At the time of construction, an oil tank model was made and stuck to the working surface of the pressure plate and molded directly. In order to easily remove the oil tank model after the mold is drawn, the oil tank model is made into a trapezoid (oil tank cross section), and a spacer agent is rubbed around the model.
In 1993 and 2004, Luo Copper used the method of repairing wear-resistant coatings to repair the guide surface of the gantry milling machine. After the first repair, it was used for 10 years. In addition, the track surfaces of the C630 lathe, G607 saw, and C616 lathe were also repaired. The service life is generally 5 to 6 years. Practice has proved that the use of wear-resistant paint repair method, not only simple process, easy maintenance, save time, and the construction is not subject to temperature, humidity and other external environmental conditions. And it has reached the processing precision of the equipment and can be used to quickly repair the wearing parts in use, which has promotion value.
First, the concept of wear-resistant coatings
The role of the wear-resistant coating in the friction pair is to effectively protect the other side from wear or to reduce wear.
The machine tool guide wear-resisting coating is a solid coating with good lubrication conditions and corresponding resistance to mechanical force. It can not only compensate for the wear defects caused by friction between the two contact surfaces, but also make the two relative motion surfaces have good Lubrication anti-friction effect. At the same time, the wear-resistant coating should also have a certain degree of burying of metal impurities that enter between the two contact surfaces of the friction pair.
Second, the composition of wear-resistant coatings
1. The adhesive binder is an important component of the wear-resistant coating. Its role is to firmly bond the other components of the coating together and produce a good bond with the substrate to form a strong bond on the surface of the substrate. The coating. For ease of construction, the binder should have good fluidity and room temperature cure properties. The adhesive used for wear-resistant coatings generally uses typical structural adhesives such as epoxy resins, phenolic resins, polyester resins, and the like.
2. Lubricant Lubricant is the main component to improve the wear-reducing performance of wear-resistant coatings, so that the coating has a small friction coefficient and self-lubricating properties. Solid lubricants used for wear-resistant coatings include colloidal molybdenum disulfide, colloidal graphite powder, and some powdered high-molecular polymers.
3, enhancer enhancer generally use reduced iron powder, copper oxide powder, quartz powder and some other metal powder, can improve the mechanical strength and surface hardness of the coating to a certain extent, improve the anti-wear properties of the coating.
Third, the reaction mechanism of wear-resistant coating
1, the binder reaction mechanism In the composition of all the components of the coating, the most important active ingredient material is a binder, other materials are non-active filler material, so the wear resistance of the coating curing reaction mechanism lies mainly in the binder. In practice, our choice of binder is bisphenol A low molecular weight epoxy resin.
The technical performance of the epoxy resin after curing is related to the type of curing agent used and the amount of curing. The reaction mechanism of different curing agents and epoxy resin is different. The most commonly used curing agent is a polyamine curing agent. When the epoxy resin reacts with the aliphatic polyamine curing agent, the reaction type is as follows.
When the primary amine reacts with the epoxy resin, the epoxy group of the resin breaks to form a secondary amine; the secondary amine continues to react with the epoxy group to form a tertiary amine; and the hydroxyl and epoxy groups in the secondary and tertiary amine molecules are etherified Finally, a huge mesh structure is formed so that the epoxy resin does not melt and has excellent performance of epoxy plastic.
2. Lubrication principle Solid lubricants in wear-resistant coatings are usually selected from molybdenum disulfide and graphite. Molybdenum disulfide is a kind of metal sulfide. The molybdenum disulfide particles that are generally used as the lubricating material are very fine. The diameter of the molybdenum disulfide particles is about 10 μm or less and belongs to the colloidal substance in the dispersion system. It is also called colloidal molybdenum disulfide. Molybdenum disulfide has excellent lubricating properties and is hexagonal crystal layered structure. Its molecular arrangement is that the outer layer is a sulfur atom and the middle is a molybdenum atom. When the colloidal molybdenum disulfide molecules are distributed on the contact surfaces of a pair of friction pairs, a molecular layer is formed on the surface.
Because the MoS2 particles are very fine and have good adsorption ability with the matrix, the combination of Mo atoms and S atoms is chemically bonded and therefore very strong. However, the binding ability between the S atoms in the molecular layer itself is extremely weak, which results in a good lubrication condition for the interface molecules to move easily. In fact, the surface of the substrate between the two interfaces adsorbs one layer of molecular layer. From a microscopic point of view, although it is only a very thin layer, it also forms a very easy to slide interface. In practical applications, the MoS2 layer is much thicker and there are n molecular layers. Thus, there are (n-1) extremely slidable interfaces, so that the two friction surfaces have very good lubrication conditions.
3. Filler Function Add appropriate amount of reinforcing agent (mainly iron powder and quartz powder) and thinner to the wear-resistant coating, which can enhance the mechanical strength and wear resistance of the coating, as well as improve the impact toughness and uneven peeling performance of the coating. In construction, if the amount of filler is not used properly, it will cause the coating's bonding ability and mechanical strength to decrease.
Fourth, the application of wear-resistant coatings in the repair of rail guide milling machine
The Luoyang copper gantry milling machine was manufactured by the former Soviet Union during the "1st Five-Year Plan" period. The total guide rail length is 8.5m. The transmission principle is shown in Figure 1.
1. Determination of the thickness of the wear-resistant coating The thickness of the wear is measured to determine the amount of repaired work and the thickness of the wear-resistant coating required. The cross-section of the rail is shown in Figure 2.
Wear-resistant coating layer thickness: H = H1-H2 (mm)
Through careful mapping, consider the normal meshing conditions of the worm and worm gear, and determine the thickness of the wear-resistant coating layer to be (9.9±0.1) mm. During construction, in order to accurately control the thickness of the wear-resistant coating layer, a layer having a thickness of (9.7±0.05) mm was prepared and stuck on the bed in advance.
The bead is first attached to the bed surface of the bed, and the well-distributed and uniformly-mixed wear-resistant coating is evenly coated on the surface of the rail, the pressure plate is pressed, and the hand hammer continuously strikes the pressure plate along the arrow to make the excess coating. Overflow from the outside.
2, bed (substrate) surface degreasing cleaning degreasing cleaning is to ensure that the wear-resistant coating layer and the substrate is an important link. In the construction of old equipment, it is common to first perform rough washing with gasoline, perform general cleaning on the slick dirt on the surface of the substrate, and then use NaOH, Na3PO4, Na2CO3, and water as the cleaning liquid (heated to 60°C to 80°C. ) Perform alkaline elution of the oil until all oil has been removed. Rinse with hot water and dry twice. Finally, wipe with carbon tetrachloride and acetone for 1 or 2 times.
3. After the coating of the coating agent is cured, in order to facilitate die-cutting, a separating agent shall be applied on the working surface of the pressing plate before the construction. The release agent is typically formulated from organic glass frits and chloroform or vinyl chloride resins and acetone.
4. Preparation, coating and wear-resisting coating According to the proportion, the various components are mixed and stirred evenly, coated on the repair surface, compacted with a pressure plate, and cured after being cured (generally 24h-36h).
5. After the mold is repaired, the existing defects are repaired to ensure that the surface of the coating is smooth, smooth, uniform in color, uniform in quality, and free of defects such as large pores.
In order to improve the lubrication conditions of the wear-resistant coating, according to the lubrication principle of the original equipment, a once-formed lubricant groove is designed on the surface of the coating to reduce the machining procedure.
Lubrication principle: When the bed reciprocates on the guide rail, the wear-resistant paint layer presses down the sprayed steel ball, the lubricant oil is sprayed, and the fuel injection groove is filled. With the sliding of the bed, the lubricant oil fills the lubrication groove 1, and the lubrication The entire friction surface. At the time of construction, an oil tank model was made and stuck to the working surface of the pressure plate and molded directly. In order to easily remove the oil tank model after the mold is drawn, the oil tank model is made into a trapezoid (oil tank cross section), and a spacer agent is rubbed around the model.
In 1993 and 2004, Luo Copper used the method of repairing wear-resistant coatings to repair the guide surface of the gantry milling machine. After the first repair, it was used for 10 years. In addition, the track surfaces of the C630 lathe, G607 saw, and C616 lathe were also repaired. The service life is generally 5 to 6 years. Practice has proved that the use of wear-resistant paint repair method, not only simple process, easy maintenance, save time, and the construction is not subject to temperature, humidity and other external environmental conditions. And it has reached the processing precision of the equipment and can be used to quickly repair the wearing parts in use, which has promotion value.
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