A method for vacuum diffusion welding of cBN abrasive grains with an alloy

Abstract

The present invention discloses a method for vacuum diffusion welding of novel alloy cBN abrasives, belonging to the manufacturing method of single-layer cBN grinding wheels. The materials required for the present invention are a grinding wheel steel matrix, elemental metal powder, and cBN abrasives. First, the steel matrix of the grinding wheel is cleaned, and an AlCoCrFeNiTi alloy layer is fused in a vacuum furnace. Then, a layer of Ti foil is laid on the AlCoCrFeNiTi alloy layer. Next, the cBN abrasives are pressed into the AlCoCrFeNiTi alloy layer by rolling. Finally, high-temperature heating diffusion welding is carried out to achieve firm connection of cBN. Due to the fact that during the pressing process, cBN cleans the surface of the cBN abrasives through friction, subsequent welding can achieve chemical metallurgical bonding of cBN. The annular protrusions formed around the cBN abrasives by the pressing method increase the holding force of the cBN abrasives. The manufactured grinding wheel can be used for high-efficiency grinding of tough metal materials.

Description

Technical Field

[0001] The invention belongs to the field of superhard abrasives, and particularly relates to a grinding wheel for manufacturing single-layer cBN abrasive grains. Background Art

[0002] Cubic boron nitride has excellent properties such as high hardness, thermal stability and chemical inertness. Its hardness is second only to diamond, but its thermal stability is much higher than diamond, so it has good chemical stability to ferrous metals. The grinding performance of cubic boron nitride abrasive tools is very excellent. It is very suitable for efficient grinding of strong and tough metal materials, has high productivity, and can effectively improve the grinding quality of workpieces.

[0003] The manufacturing process of cBN abrasive wheels can be roughly divided into the following five types: electroplating, sintering, resin, ceramic, and brazing. Using electroplating, sintering, resin, and ceramic methods, due to the inherent chemical inertness of cBN, it is difficult to achieve chemical metallurgical bonding of cBN abrasives using general metals or at low temperatures. The reason is that it is difficult for cBN abrasives to have an interface reaction with the bonding agent of the grinding wheel. To achieve high-strength connection of cBN abrasives, it is necessary to contain certain active elements and achieve it through interface reaction at high temperatures, but the active elements are easily oxidized and ineffective, and the adsorbents on the surface of cBN abrasives have a great influence on the interface reaction. Although vacuum brazing containing active elements can remove the adsorbed substances on the surface of cBN abrasives and achieve effective interface reactions, it is usually only possible to use low-melting point brazing materials such as AgCuTi and CuSnTi. Although these brazing materials can achieve interface reactions, they generally have low alloy melting points. During the grinding wheel processing process, their low melting point alloys are limited by the grinding temperature and cannot give full play to the advantages of high temperature stability of cBN abrasives. If high melting point alloys containing active elements are used for brazing, extremely high requirements are placed on the vacuum degree, which makes the production cost extremely high and cannot be industrialized. If metals containing active elements are used for sintering, the diffusion coefficient of the active elements is extremely low when the metal is in a solid state, making it difficult to form effective diffusion and thus impossible to make effective connections. Therefore, how to keep the surface of cBN abrasives clean in real time during manufacturing and ensure full contact with the active elements is the key to achieving high-strength connection of cBN abrasives. Summary of the invention

[0004] Based on the above problems, to ensure that the surface of cBN particles is clean and in full contact with active elements in real time, a Ti foil is placed on top of the binder, and the cBN particles are pressed in. By this pressing method, on the one hand, the surfaces of the cBN particles and the Ti foil are cleaned to expose fresh surfaces and ensure full contact. On the other hand, a ring-shaped bulge can be formed around the cBN, which can wrap the cBN and enhance the holding force of the binder on the cBN particles. After a long-time high temperature treatment, a high-strength connection can be ensured. In addition, by using an AlCoCrFeNiTi high-entropy alloy to replace the low-melting-point filler metal and using the high-entropy alloy with good high-temperature performance and high strength as the binder, the good high-temperature performance of cBN during the grinding process can be fully utilized.

[0005] The manufacturing method adopted in the present invention includes the following technological steps:

[0006] A method for vacuum diffusion welding of a novel alloy cBN abrasive includes the following technological steps:

[0007] Step 1: Select carbon steel as the grinding wheel base body, use a grinding wheel or sandpaper to polish the surface of the carbon steel base body to remove oxides and rust, and at the same time use alcohol or acetone to remove the oil stains on the base body surface.

[0008] Step 2: Mix Ni-Cr-B-Si, Co-Cr-B-Si, Al, Fe, and Ti into a mixed powder in a certain proportion, and use a ball mill to perform ball milling and mixing. The particle size of the used powder is 30 - 70 μm; the component mass percentages of Ni-Cr-B-Si are Cr: 15 - 18, B: 2.5 - 4.5, Si: 3 - 4.5, C: 0.6 - 1, and the rest is Ni; the component mass percentages of Co-Cr-B-Si are Cr: 15 - 18, B: 2.5 - 4.5, Si: 3 - 4.5, C: 0.6 - 1, and the rest is Co; the purities of Al powder and Fe powder are both higher than 99.5%; the purity of Ti powder is higher than 99%; the mass percentages of the mixed powder Ni-Cr-B-Si, Co-Cr-B-Si, Al, Fe, and Ti are 24 - 30: 24 - 30: 18 - 26: 8 - 16: 8 - 16. Use a steel ball milling tank for ball milling and mixing. The mass ratio of the grinding balls to the mixed powder is 2.5 - 3.2∶1. After sealing, open the vacuum valve to evacuate for 35 - 50 minutes. Put the ball milling tank into a planetary ball mill, with a rotation speed of 260 - 300 r / min and a reverse frequency of 30 - 45 Hz, and perform ball milling and mixing for 20 - 40 minutes.

[0009] Step 3: Mix the mixed powder and the pressure-sensitive adhesive in a weight ratio of 1: 1.3 - 1.4 to make a sintered powder, coat it on the surface of the grinding wheel carbon steel base body, with a coating thickness of 120 - 300 μm, and dry it at 150 - 200 °C for 1 - 2 h to obtain a grinding wheel coating layer.

[0010] Step 4: Heat the grinding wheel coating layer in a vacuum furnace to 1050 - 1080°C under a vacuum degree of 10⁻³ Pa - 10⁻⁴ Pa, and keep it warm for 5 - 8 minutes for vacuum fusion bonding to obtain a fusion-bonded coating.

[0011] Step 5: Cover the fusion-bonded coating with a Ti foil with a thickness of 1 - 3 μm, arrange cBN particles on the Ti foil as required, and use a roller to press cBN particles with a particle size range of 60 - 240 μm into the Ti foil and the AlCoCrFeNiTi coating. The pressing depth is 60 - 100 μm to obtain a grinding wheel blank.

[0012] Step 6: Heat the grinding wheel blank in a vacuum furnace to 1000 - 1030°C under a vacuum degree of 10⁻³ Pa - 10⁻⁴ Pa, keep it warm for 15 - 30 minutes for diffusion welding of cBN, and after cooling, it is a single-layer cBN grinding wheel.

[0013] The beneficial effects of the present invention are as follows:

[0014] (1) The present invention uses the method of pressing cBN particles into the Ti foil with a roller. During pressing, the adsorbents on the surface of cBN and the Ti foil can be cleaned by friction, exposing a certain active surface. During the subsequent heating process, the interfacial reaction is enhanced through diffusion, ultimately improving the holding force of cBN. Secondly, after the cBN particles are pressed in, due to the extrusion, bulges are formed around the cBN particles and wrap the cBN, which further alloy improves the holding force of the cBN particles, ultimately improving the durability of the brazed cBN grinding wheel and reducing the abrasive grain shedding.

[0015] (2) The present invention uses a high-entropy alloy, making full use of the good high-temperature performance and toughness of the high-entropy alloy, being able to give full play to the advantages of cBN with good high-temperature performance and high wear resistance, and avoiding the disadvantages of the high-temperature performance of the binder and the shedding of cBN during the high-speed grinding process of the grinding wheel. Specific embodiments

[0016] Example 1:

[0017] Step 1: Select Q235 steel as the grinding wheel base body, use a grinding wheel or sandpaper to polish the surface of the carbon steel base body to remove oxides and rust, and at the same time use alcohol or acetone to remove the oil stains on the base body surface.

[0018] Step 2: Mix Ni-Cr-B-Si, Co-Cr-B-Si, Al, Fe, and Ti in a certain proportion to form a mixed powder, and use a ball mill to mill and mix them. The particle size of the powder used is 30 - 70 μm. The mass percentage of components in Ni-Cr-B-Si is Cr: 15 - 18, B: 2.5 - 4.5, Si: 3 - 4.5, C: 0.6 - 1, and the rest is Ni; the mass percentage of components in Co-Cr-B-Si is Cr: 15 - 18, B: 2.5 - 4.5, Si: 3 - 4.5, C: 0.6 - 1, and the rest is Co; the purity of Al powder and Fe powder is higher than 99.5%; the purity of Ti powder is higher than 99%. The mass percentage of the mixed powder Ni-Cr-B-Si, Co-Cr-B-Si, Al, Fe, and Ti is 30:30:18:12:10. Use a steel ball mill tank for ball milling and mixing. The mass ratio of the grinding balls to the mixed powder is 2.5∶1. After sealing, open the vacuum valve to evacuate for 35 minutes. Place the ball mill tank in a planetary ball mill with a rotation speed of 260 r / min and a reverse frequency of 30 Hz, and carry out ball milling and mixing for 20 minutes.

[0019] Step 3: Mix the mixed powder and the pressure-sensitive adhesive in a weight ratio of 1:1.3 to form a sintered powder, coat it on the surface of the grinding wheel carbon steel substrate, with a coating thickness of 120 μm, and dry it at 150°C for 1 h to obtain a grinding wheel coating layer.

[0020] Step 4: Heat the grinding wheel coating layer in a vacuum furnace to 1050°C under a vacuum of 10-3Pa - 10-4Pa and hold for 5 minutes for vacuum sintering to obtain a sintered coating.

[0021] Step 5: Cover the sintered coating with a 1-μm-thick Ti foil, arrange cBN particles on the Ti foil as needed, and use a roller to press cBN particles with a particle size range of 60 - 120 μm into the Ti foil and the AlCoCrFeNiTi coating. The pressing depth is 60 μm to obtain a grinding wheel blank.

[0022] Step 6: Heat the grinding wheel blank in a vacuum furnace to 1000°C under a vacuum of 10-3Pa - 10-4Pa and hold for 15 minutes for diffusion welding of cBN. After cooling, a single-layer cBN grinding wheel is obtained.

[0023] The results show that by using the method of pressing cBN, not only can cBN be fully contacted with the Ti foil, but also the friction surface is relatively clean. During the subsequent heating and diffusion welding process, Ti can react with cBN at the interface, and there can be a certain diffusion with AlCoCrFeNiTi, ensuring a high-strength connection of cBN.

[0024] Example 2:

[0025] Step 1: Select 35 steel as the grinding wheel base body. Use a grinding wheel or sandpaper to polish the surface of the carbon steel base body to remove oxides and rust. At the same time, use alcohol or acetone to remove the oil stains on the base body surface.

[0026] Step 2: Combine Ni-Cr-B-Si, Co-Cr-B-Si, Al, Fe, and Ti into a mixed powder in a certain proportion, and use a ball mill to ball-mill and mix them. The particle size of the used powder is 30 - 70 μm; among them, the mass percentage of the components of Ni-Cr-B-Si is Cr: 15 - 18, B: 2.5 - 4.5, Si: 3 - 4.5, C: 0.6 - 1, and the rest is Ni; the mass percentage of the components of Co-Cr-B-Si is Cr: 15 - 18, B: 2.5 - 4.5, Si: 3 - 4.5, C: 0.6 - 1, and the rest is Co; the purity of Al powder and Fe powder is higher than 99.5%; the purity of Ti powder is higher than 99%; the mass percentage of the mixed powder Ni-Cr-B-Si, Co-Cr-B-Si, Al, Fe, and Ti is 24:24:20:16:16. Use a steel ball mill tank for ball-milling and mixing. The mass ratio of the grinding balls to the mixed powder is 3.2∶1. After sealing, open the vacuum valve to evacuate for 50 minutes. Put the ball mill tank into a planetary ball mill, with a rotation speed of 300 r / min and a reverse frequency of 45 Hz, and carry out ball-milling and mixing for 40 minutes.

[0027] Step 3: Mix the mixed powder and the pressure-sensitive adhesive in a weight ratio of 1:1.3 - 1.4 to make a fused powder, coat it on the surface of the grinding wheel carbon steel base body, with a coating thickness of 300 μm, and dry it at 200°C for 2 h to obtain a grinding wheel coating layer.

[0028] Step 4: Heat the grinding wheel coating layer in a vacuum furnace to 1080°C under the condition of a vacuum degree of 10-3Pa - 10-4Pa, and keep it warm for 8 minutes for vacuum fusion bonding to obtain a fused coating.

[0029] Step 5: Cover the fused coating with a Ti foil with a thickness of 3 μm, and arrange cBN particles on the Ti foil as needed. Use a rolling mill to press cBN particles with a particle size range of 180 - 240 μm into the Ti foil and the AlCoCrFeNiTi coating, and the pressing depth is 100 μm to obtain a grinding wheel blank.

[0030] Step 6: Heat the grinding wheel blank in a vacuum furnace to 1030°C under the condition of a vacuum degree of 10-3Pa - 10-4Pa, keep it warm for 30 minutes for diffusion welding of cBN, and after cooling, it is a single-layer cBN grinding wheel.

[0031] The results show that by using this high-entropy alloy as the binder and combining the method of pressing cBN into the Ti foil, the holding force of cBN can be significantly improved. The manufactured grinding wheel can withstand higher grinding forces and grinding temperatures, so it is suitable for high-efficiency machining of strong and tough ferrous metal materials.

[0032] Example 3:

[0033] Step 1: Select 45 steel as the grinding wheel base body, and use a grinding wheel or sandpaper to polish the surface of the carbon steel base body to remove oxides and rust. At the same time, use alcohol or acetone to remove the oil stains on the base body surface.

[0034] Step 2: Mix Ni-Cr-B-Si, Co-Cr-B-Si, Al, Fe, and Ti in a certain proportion to form a mixed powder, and use a ball mill to perform ball milling. The particle size of the used powder is 30 - 70 μm; among them, the component mass percentage of Ni-Cr-B-Si is Cr: 15 - 18, B: 2.5 - 4.5, Si: 3 - 4.5, C: 0.6 - 1, and the rest is Ni; the component mass percentage of Co-Cr-B-Si is Cr: 15 - 18, B: 2.5 - 4.5, Si: 3 - 4.5, C: 0.6 - 1, and the rest is Co; the purity of Al powder and Fe powder is higher than 99.5%; the purity of Ti powder is higher than 99%; the mass percentage of the mixed powder Ni-Cr-B-Si, Co-Cr-B-Si, Al, Fe, and Ti is 26:26:26:11:11. Use a steel ball milling tank for ball milling. The mass ratio of the grinding balls to the mixed powder is 2.7∶1. After sealing, open the vacuum valve to evacuate for 45 minutes. Put the ball milling tank into a planetary ball mill, with a rotation speed of 280 r / min and a reverse frequency of 35 Hz, and perform ball milling for 30 minutes.

[0035] Step 3: Mix the mixed powder and the pressure-sensitive adhesive in a weight ratio of 1:1.35 to make a sintered powder, and coat it on the surface of the grinding wheel carbon steel base body. The coating thickness is 180 μm, and dry it at 180℃ for 1.5 h to obtain a grinding wheel coating layer.

[0036] Step 4: Heat the grinding wheel coating layer in a vacuum furnace to 1060℃ under the condition of a vacuum degree of 10-3Pa~10-4Pa, and keep it warm for 6 minutes for vacuum sintering to obtain a sintered coating.

[0037] Step 5: Cover the sintered coating with a Ti foil with a thickness of 2 μm, and arrange cBN particles on the Ti foil as required. Use a roller to press cBN particles with a particle size range of 100 - 150 μm into the Ti foil and the AlCoCrFeNiTi coating. The pressing depth is 80 μm to obtain a grinding wheel blank.

[0038] Step 6: Heat the grinding wheel blank in a vacuum furnace to 1020℃ under the condition of a vacuum degree of 10-3Pa~10-4Pa and keep it warm for 20 minutes for diffusion welding of cBN. After cooling, it is a single-layer cBN grinding wheel.

[0039] The results show that by using the method of pressing cBN, not only can cBN be fully contacted with the Ti foil, but also the friction surface is relatively clean. During the subsequent hot diffusion welding process, Ti can react with cBN at the interface. At the same time, there will be a certain interdiffusion between the Ti foil and the high-entropy alloy to form a firm connection, ensuring a high-strength connection of cBN. The grinding wheel manufactured by this method can be used for efficient grinding of strong and tough metal materials.

Claims

1. A method for alloy vacuum diffusion welding of cBN abrasive grains, characterized in that, the method comprises the following technological steps: Step 1: Select carbon steel as the grinding wheel base body, polish the surface of the carbon steel base body with a grinding wheel or sandpaper to remove oxides, and at the same time remove the oil stains on the base body surface with alcohol or acetone; Step 2: Compose a mixed powder from Ni-Cr-B-Si, Co-Cr-B-Si, Al, Fe, and Ti in a certain proportion, and perform ball milling and mixing with a ball mill. The particle size of the used powder is 30 - 70 μm; Step 3: Mix the mixed powder and pressure-sensitive adhesive in a weight ratio of 1:1.3 - 1.4 to make a sintered powder, coat it on the surface of the carbon steel base body of the grinding wheel, with a coating thickness of 120 - 300 μm, and dry it to obtain a coated layer of the grinding wheel; Step 4: Heat the coated layer of the grinding wheel to a certain temperature in a vacuum furnace for vacuum sintering to obtain a sintered coating; Step 5: Cover the sintered coating with a Ti foil with a thickness of 1 - 3 μm, arrange the cBN particles as required on the Ti foil, and press the cBN particles into the Ti foil and the AlCoCrFeNiTi coating with a roller to obtain a grinding wheel blank; Step 6: Heat the grinding wheel blank in a vacuum furnace for diffusion welding of cBN, and after cooling, a single-layer cBN grinding wheel is obtained.

2. A method for alloy vacuum diffusion welding of cBN abrasive grains according to claim 1, characterized in that: the mass percentage of components of the Ni-Cr-B-Si is Cr: 15 - 18, B: 2.5 - 4.5, Si: 3 - 4.5, C: 0.6 - 1, and the rest is Ni; the mass percentage of components of the Co-Cr-B-Si is Cr: 15 - 18, B: 2.5 - 4.5, Si: 3 - 4.5, C: 0.6 - 1, and the rest is Co; the purity of both the Al powder and the Fe powder is higher than 99.5%; the purity of the Ti powder is higher than 99%; the mass percentage of the mixed powder of Ni-Cr-B-Si, Co-Cr-B-Si, Al, Fe, and Ti is 24 - 30: 24 - 30: 18 - 26: 8 - 16: 8 - 16.

3. A method for alloy vacuum diffusion welding of cBN abrasive grains according to claim 1, characterized in that: the ball milling and mixing is carried out using a steel ball milling tank, wherein the mass ratio of the grinding balls to the mixed powder is 2.5 - 3.2∶1. After sealing, open the vacuum valve to evacuate for 35 - 50 minutes, put the ball milling tank into a planetary ball mill, with a rotation speed of 260 - 300 r / min and a reverse frequency of 30 - 45 Hz, and the ball milling and mixing time is 20 - 40 minutes.

4. A method for alloy vacuum diffusion welding of cBN abrasive grains according to claim 1, characterized in that: the drying process is drying at 150 - 200 °C for 1 - 2 h.

5. A method for alloy vacuum diffusion welding of cBN abrasive grains according to claim 1, characterized in that: the cBN particle size is 60 - 240 μm.

6. A method for alloy vacuum diffusion welding of cBN abrasive grains according to claim 1, characterized in that: For the vacuum fusion bonding described above, the process parameters are a vacuum degree of 10 -3 Pa to 10 -4 Pa, a heating temperature of 1050 to 1080 °C, and an insulation time of 5 to 8 minutes.

7. A method for alloy vacuum diffusion welding of cBN abrasive grains according to claim 1, It is characterized in that: The cBN particles are pressed into the Ti foil and the AlCoCrFeNiTi coating by a rolling mill, and the pressing depth is 60-100 μm.

8. A method for alloy vacuum diffusion bonding of cBN abrasive grains according to claim 1, It is characterized in that: For the diffusion welding described above, the process is carried out under a vacuum degree of 10 -3 Pa to 10 -4 Pa, heated to 1000 - 1030 °C and held for 15 - 30 minutes, and finally cooled in the furnace.