A method for manufacturing a Ti foil diamond grinding wheel by vacuum pressure welding

Abstract

The present invention discloses a method for manufacturing a Ti foil diamond grinding wheel by vacuum pressure welding, specifically relating to a method for manufacturing a single-layer diamond grinding wheel by vacuum pressure welding. The materials required for the present invention are a grinding wheel steel matrix, elemental metal powder, and diamond abrasive grains. First, the grinding wheel steel matrix is cleaned, and a CuNi alloy coating is fused in a vacuum furnace. Then, a layer of Ti foil is laid on the CuNi alloy layer. Next, the diamond abrasive grains are pressed into the CuNi alloy coating by rolling, and the pressed diamond abrasive grains are pressed with a ceramic plate. Finally, the diamond is firmly connected through high-temperature heating and diffusion. This technology uses the method of pressing diamonds into the Ti foil at the interface, which can keep the surface of the diamond and the Ti foil clean by friction in real time, and form carbides after subsequent heating, improving the holding strength of the diamond. The manufactured grinding wheel has the advantages of small thermal damage of the abrasive grains and high precision.

Description

Technical Field

[0001] The present invention belongs to the field of superhard material tools, and particularly relates to a manufacturing method of a single-layer diamond grinding wheel. Background Art

[0002] Diamond has extremely high hardness and good wear resistance, and is an ideal material for machining hard and brittle materials such as glass, ceramics, granite, and cemented carbide. However, there is a high interfacial energy between diamond and general metals and their alloys, the wettability with metals and their alloys is very poor, and it is prone to graphitization at high temperatures, resulting in very poor weldability of diamond. The main difficulties in connecting diamond with metal are as follows: First, the welding temperature is limited by the graphitization of diamond, resulting in graphitization at the interface or ineffective welding, so that the joint strength is low; Second, the wettability of the metal material to diamond is poor, and the holding strength of the matrix to diamond after welding is low, causing diamond to fall off during the use of the tool and unable to fully exert the excellent properties of diamond; Third, the linear expansion coefficient of diamond does not match that of most alloys, and cracks are prone to appear during welding.

[0003] To improve the wettability of the alloy to diamond, a diamond surface coating process can also be used, that is, a thin layer of metal coat is wrapped on the diamond surface, but it is not necessarily possible to form a carbide transition layer on the diamond surface. If the surface coating metal is reasonable, it can avoid the direct action of catalyst metals such as Ni and Fe on diamond to a certain extent and effectively avoid diamond graphitization. For example, salt bath infiltration of Ti is used, and then the titanium-coated diamond is placed in a vacuum furnace, heated at 900 °C (1 h) under a vacuum degree of 1.33×10-4 Pa and then cooled with the furnace. Since titanium is a strong carbide-forming element, it combines with the carbon atoms on the diamond surface during heating to form the nuclei of TiC and gradually grow until a thin layer of TiC transition layer is formed on the diamond surface. However, this process has complex processes and certain environmental pollution.

[0004] The manufacturing methods of diamond grinding wheels mainly include processes such as sintering, brazing, electroplating, etc. Among them, due to the low holding force of abrasive grains in sintering and electroplating, they often fail due to the premature shedding of abrasive grains. Brazing can form a chemical metallurgical bond between diamond and filler metal, but it is also restricted by the brazing temperature and the high-vacuum requirements of active elements in the filler metal. The common methods of brazing diamond mainly include vacuum brazing, laser brazing, protective atmosphere brazing, etc. Diamond brazing mainly uses Ag, Cu-based or Ni-based filler metals. Among them, Ag, Cu-based filler metals have poor wettability to diamond, and at the same time, Ag, Cu-based filler metals have low hardness and poor wear resistance, resulting in excessive exposure of abrasive grains due to the wear of the brazed layer and subsequent shedding. Ni-based filler metals have better wettability to diamond than Cu-based filler metals, but Ni-based filler metals have too high melting points and are catalysts. Therefore, Ni elements will cause greater thermal damage to diamond. At the same time, Ni-based sometimes has too high wear resistance, resulting in lower exposure of abrasive grains. It can be seen that Ti, Cr, etc. are mostly used as active elements in diamond brazing, and Cu, Ni-based filler metals are mostly used for brazing. Considering that Cu, Ni alloys can regulate the strength, wear resistance, etc. of the alloy, and the two can be infinitely miscible, CuNi-based alloys are selected. In terms of diamond connection, considering that it is precisely because Ni contacts diamond at too high brazing temperatures that diamond graphitization occurs. If the welding temperature can be effectively reduced and the contact between Ni and diamond can be avoided, the thermal damage to diamond can be reduced. In terms of welding, by directly forming an effective chemical metallurgical bond through high-temperature interdiffusion of active elements, high-strength connection of diamond can be achieved, and thermal damage to diamond can be avoided. Summary of the Invention

[0005] A new method is proposed. In the present invention, diamond particles are pressed into an alloy of Ti foil and binder. Not only are the diamond particles separated from the alloy by the Ti foil, but during the pressing process of the diamond particles, the diamond and Ti foil are cleaned and brought into full contact through friction, preparing for subsequent welding. Secondly, a bulge is formed around the diamond to wrap the diamond particles, which is beneficial to improving the holding force of the matrix on the diamond particles. After pressing in the diamond particles, high-temperature pressure diffusion welding is carried out in a vacuum furnace while pressing on the diamond abrasive grains. Since this temperature is lower than the original brazing temperature, it will not cause thermal damage to the diamond. Due to the full contact between Ti and diamond, subsequent high temperature can promote full contact between diamond and Ti foil and form an interfacial bond. At the same time, diffusion will also occur between Ti foil and CuNi alloy, ensuring high connection strength between diamond and CuNi alloy, and the CuNi alloy can also be appropriately adjusted as needed.

[0006] The method for manufacturing a grinding wheel by vacuum pressure welding Ti foil diamond of the present invention includes the following process steps:

[0007] Step 1: Pretreat the surface of the carbon steel matrix of the grinding wheel. Use a grinding wheel or sandpaper to polish the surface of the carbon steel matrix to remove oxides and rust, and use alcohol or acetone to remove the oil stains on the surface.

[0008] Step 2: Combine elemental metal Cu and Ni powders in a certain proportion to form a mixed powder, and use a ball mill to mix them by ball milling. Among the Cu and Ni mixed powders, the mass fraction of Cu metal powder is 30 - 70%, and the rest is Ni metal powder. The particle sizes of Cu and Ni metal powders are 30 - 50 μm. The ball milling and mixing are carried out in a steel ball milling tank. 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 20 - 30 minutes. Then put the ball milling tank into a planetary ball mill, with a rotation speed of 260 - 300 r / min, a reverse frequency of 30 - 45 Hz, and the ball milling and mixing time is 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 carbon steel matrix, with a coating thickness of 300 - 450 μm, and then dry it at 150 - 200 °C for 1 - 2 h.

[0010] Step 4: Use a vacuum furnace to heat the coated sintered powder for sintering and then cool it with the furnace. The heating temperature for sintering is 980 - 1030 °C, heat the powder until it melts and keep it warm for 5 - 8 minutes, and then cool it with the furnace to obtain a CuNi sintered coating.

[0011] Step 5: Cover the coating with a Ti foil with a thickness of 1 - 3 μm, and arrange diamond particles with a particle size of 120 - 450 μm as required on the Ti foil. Use a roller to press the diamond particles into the Ti foil and the CuNi coating, and use a ceramic plate to press - fix the pressed - in diamond abrasive grains. The pressed - in depth is controlled at 80 - 100 μm to obtain a diamond grinding wheel blank.

[0012] Step 6: Use a vacuum furnace to heat - weld the diamond grinding wheel blank. Specifically, evacuate the vacuum furnace to 10⁻³ - 10⁻⁴ Pa, then heat the diamond grinding wheel blank to 850 - 900 °C, keep it warm for 20 - 30 minutes, and then cool it with the furnace to obtain a single - layer diamond grinding wheel.

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

[0014] (1) The present invention uses Ti foil as an active material, and adopts a pressing - in method to make Ti and diamond rub against each other to achieve full contact. Then, through the action of high temperature, a carbide layer is formed at their interface, enhancing the holding force of the metal for the diamond abrasive grains. Moreover, the diamond no longer undergoes thermal damage during the connection process, effectively improving the holding force and reducing the thermal damage of the diamond.

[0015] (2) The present invention uses a rolling mill to press diamond particles into a Ti foil and a CuNi coating, which can form a bulge around the diamond particles, effectively wrap the diamond, further enhance the holding force of the solder on the diamond particles, improve the durability of the single-layer diamond grinding wheel, and reduce the abrasive grain shedding. Detailed implementation mode

[0016] Example 1:

[0017] Step 1: Select 45 steel as the substrate of the grinding wheel, use a grinding wheel to polish the surface of the grinding wheel substrate to remove oxides and rust, and use alcohol to remove the oil stains on the surface;

[0018] Step 2: Mix elemental metals Cu and Ni powders in a certain proportion to form a mixed powder, and use a ball mill to perform ball milling and mixing; among them, the mass fraction of Cu metal powder in the Cu and Ni mixed powder is 30%, and the rest is Ni metal powder. The particle sizes of the Cu and Ni metal powders are 30 - 50 μm. The ball milling and mixing is carried out in a steel ball milling tank. The mass ratio of the grinding balls to the mixed powder is 2.5:1. After sealing, open the vacuum valve to evacuate for 20 minutes. Then put the ball milling tank into a planetary ball mill, with a rotation speed of 260 r / min, a reverse frequency of 30 Hz, and the ball milling and mixing time is 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 carbon steel substrate, with a coating thickness of 300 μm, and then dry it at 150°C for 1 h.

[0020] Step 4: Use a vacuum furnace to heat the coated sintered powder for sintering and cool it with the furnace. The heating temperature for sintering is to heat the powder to melt at 980°C and keep it warm for 5 minutes, and then cool it with the furnace to obtain a CuNi sintered coating.

[0021] Step 5: Cover the coating with a 1-μm-thick Ti foil, arrange diamond particles with a particle size of 120 - 180 μm on the Ti foil as needed, use a rolling mill to press the diamond particles into the Ti foil and the CuNi coating, and use a ceramic plate to press and fix the pressed diamond abrasive grains. The pressing depth is controlled at 80 μm to obtain a diamond grinding wheel blank;

[0022] Step 6: Use a vacuum furnace to heat and pressure-weld the diamond grinding wheel blank. Specifically, evacuate the vacuum furnace to 10-3 - 10-4 Pa, then heat the diamond grinding wheel blank to 850°C, keep it warm for 20 minutes, and then cool it with the furnace to obtain a single-layer diamond grinding wheel.

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

[0024] Example 2:

[0025] Step 1: Use 35 steel as the grinding wheel base body, polish the surface of the carbon steel base body with sandpaper to remove oxides and rust, and clean the oil stain on the surface with alcohol.

[0026] Step 2: Mix the elemental metals Cu and Ni powders in a certain proportion to form a mixed powder, and use a ball mill to ball-mill and mix them. Among the Cu and Ni mixed powders, the mass fraction of Cu metal powder is 70%, and the rest is Ni metal powder. The particle sizes of the Cu and Ni metal powders are in the range of 30 - 50 μm. The ball-milling and mixing are carried out in a steel ball-milling tank. The mass ratio of the grinding balls to the mixed powder is 3.2:1. After sealing, open the vacuum valve to evacuate for 30 minutes, put the ball-milling tank into a planetary ball mill, with a rotation speed of 300 r / min, a reverse frequency of 45 Hz, and the ball-milling and mixing time is 40 minutes.

[0027] Step 3: Mix the mixed powder and the pressure-sensitive adhesive in a weight ratio of 1:1.4 to form a sintered powder, coat it on the surface of the carbon steel base body, with a coating thickness of 450 μm, and then dry it at 200 °C for 2 h.

[0028] Step 4: Use a vacuum furnace to heat the coated sintered powder for sintering and cool it with the furnace. The heating temperature for sintering is to heat the powder to melt at 1030 °C and hold for 8 minutes, and then cool it with the furnace to obtain a CuNi sintered coating.

[0029] Step 5: Cover the coating with a Ti foil with a thickness of 3 μm, arrange the diamond particles with a particle size of 300 - 450 μm on the Ti foil as needed, press the diamond particles into the Ti foil and the CuNi coating with a roller, and use a ceramic plate to press and fix the pressed diamond abrasive grains. The pressing depth is controlled at 100 μm to obtain a diamond grinding wheel blank.

[0030] Step 6: Use a vacuum furnace to heat and pressure-weld the diamond grinding wheel blank. Specifically, evacuate the vacuum furnace to 10-3 - 10-4 Pa, then heat the diamond grinding wheel blank to 900 °C, hold for 30 minutes, and then cool it with the furnace to obtain a single-layer diamond grinding wheel.

[0031] The results show that by pressing in the diamond, not only can the diamond be fully contacted with the Ti foil, but also the friction surface is relatively clean. During the subsequent heating and welding process, Ti can react with the diamond at the interface, and there can be a certain diffusion with the CuNi alloy, ensuring a high-strength connection of the diamond. The grinding wheel manufactured by this method can be used for efficient grinding of hard and brittle materials.

[0032] Example 3:

[0033] Step 1: Use Q235 steel as the grinding wheel base body, grind the surface of the carbon steel base body with a grinding wheel to remove oxides and rust, and use acetone to remove the oil stains on the surface.

[0034] Step 2: Mix elemental metals Cu and Ni powders in a certain proportion to form a mixed powder, and use a ball mill to perform ball milling and mixing; among the Cu and Ni mixed powders, the mass fraction of Cu metal powder is 50%, and the rest is Ni metal powder. The particle sizes of Cu and Ni metal powders are 40 μm. The ball milling and mixing is carried out in a steel ball milling tank. The mass ratio of the grinding balls to the mixed powder is 2.7:1. After sealing, open the vacuum valve to evacuate for 25 minutes. Then put the ball milling tank into a planetary ball mill, with a rotation speed of 280 r / min, a reverse frequency of 40 Hz, and a ball milling and mixing time of 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, coat it on the surface of the carbon steel base body, with a coating thickness of 350 μm, and then dry it at 180 °C for 1.5 h.

[0036] Step 4: Use a vacuum furnace to heat the coated sintered powder for sintering and cool it with the furnace. The heating temperature for sintering is 1000 °C to melt the powder and keep it warm for 6 minutes, and then cool it with the furnace to obtain a CuNi sintered coating.

[0037] Step 5: Cover the coating with a Ti foil with a thickness of 2 μm, arrange diamond particles with a particle size of 180 - 250 μm on the Ti foil as needed, press the diamond particles into the Ti foil and the CuNi coating with a roller, and use a ceramic plate to press and fix the pressed diamond grains. The pressing depth is controlled at 90 μm to obtain a diamond grinding wheel blank.

[0038] Step 6: Use a vacuum furnace to heat and pressure-weld the diamond grinding wheel blank. Specifically, evacuate the vacuum furnace to 10-3 - 10-4 Pa, then heat the diamond grinding wheel blank to 870 °C, keep it warm for 25 minutes, and then cool it with the furnace to obtain a single-layer diamond grinding wheel.

[0039] The results show that by using the method of pressing in diamond, not only can diamond be fully contacted with the Ti foil, but also the surface after friction is relatively clean. During the subsequent heating and welding process, Ti can react with diamond at the interface to form carbides. Moreover, a ring-shaped protrusion is formed after pressing, which can further improve the holding force of diamond. In addition, there is a certain diffusion with the CuNi alloy, ensuring a high-strength connection of diamond.

Claims

1. A method for manufacturing a Ti foil diamond grinding wheel by vacuum pressure welding, characterized in that, the method comprises the following technological steps: Step 1: Pretreat the surface of the carbon steel matrix of the grinding wheel. Use a grinding wheel or sandpaper to polish the surface of the carbon steel matrix to remove oxides, and use alcohol or acetone to remove oil stains on the surface; Step 2: Compose a mixed powder from elemental metals Cu and Ni powders in a certain proportion, and use a ball mill to perform ball milling and mixing; Step 3: Mix the mixed powder and a 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 matrix, with a coating thickness of 300 - 450 μm, and dry it; Step 4: Use a vacuum furnace to heat the coated sintered powder for sintering and cool it with the furnace to obtain a CuNi coating; Step 5: Cover the coating with a Ti foil with a thickness of 1 - 3 μm, arrange diamond particles on the Ti foil as required, use a rolling mill to press the diamond particles into the Ti foil and the CuNi coating, and use a ceramic plate to press and fix the pressed diamond abrasive grains to form a diamond grinding wheel blank; Step 6: Heat and perform pressure welding on the diamond grinding wheel blank using a vacuum furnace, and after cooling, it is a single-layer diamond grinding wheel.

2. A method for manufacturing a Ti foil diamond grinding wheel by vacuum pressure welding according to claim 1, characterized in that: in the elemental metals Cu and Ni powders, the mass fraction of Cu metal powder is 30 - 70%, and the rest is Ni metal powder, and the particle size of the Cu and Ni metal powders is 30 - 50 μm.

3. A method for manufacturing a Ti foil diamond grinding wheel by vacuum pressure welding according to claim 1, characterized in that: the ball milling and mixing is performed using a steel ball milling tank, where 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 20 - 30 minutes, place the ball milling tank in 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 manufacturing a Ti foil diamond grinding wheel by vacuum pressure welding according to claim 1, characterized in that: for the drying, the technological parameters are drying at 150 - 200°C for 1 - 2 h.

5. A method for manufacturing a Ti foil diamond grinding wheel by vacuum pressure welding according to claim 1, characterized in that: for the sintering, the heating temperature is at 980 - 1030°C to melt the powder and keep it warm for 5 - 8 minutes, and then cool it with the furnace to obtain a CuNi sintered coating.

6. A method for manufacturing a Ti foil diamond grinding wheel by vacuum pressure welding according to claim 1, characterized in that: the diamond particle size is 120 - 450 μm.

7. A method for manufacturing a Ti foil diamond grinding wheel by vacuum pressure welding according to claim 1, characterized in that: the diamond particles are arranged according to the required rules and order. The rolling mill needs to press the diamonds into the Ti foil and the CuNi coating, and the pressing depth is 80 - 100 μm.

8. A method for manufacturing a Ti foil diamond grinding wheel by vacuum pressure welding according to claim 1, characterized in that Heating pressure welding, the process is: vacuum furnace to 10 -3 -10 -4 Pa, then heat the diamond grinding wheel blank to 850~900℃, keep it at this temperature for 20~30 minutes, and then cool it with the furnace to obtain a single-layer diamond grinding wheel.