Metal bond grinding wheel and preparation method thereof

Abstract

The present application provides a metal bond grinding wheel and a preparation method thereof. The metal bond grinding wheel comprises a grinding wheel base and an abrasive layer, wherein the abrasive layer is made of raw materials according to the following mass ratio: 45%-50% diamond abrasive grains, 20%-25% tungsten carbide powder, 15%-20% copper powder, 3%-5% tin powder, 3%-5% zinc powder, 3%-5% nickel powder, and 2% cobalt powder; wherein the surface of the diamond abrasive grains is coated with a tungsten carbide powder coating by plasma spraying, which significantly increases the wear resistance and service life of the diamond abrasive grains; and the tungsten carbide powder, as the most important component of the metal binder, can be bonded to the tungsten carbide powder coating on the surface of the diamond abrasive grains under the bonding action of cobalt powder and nickel powder, so that the diamond abrasive grains and the metal binder form a strong bond, further improving the wear resistance and service life of the grinding wheel.

Description

Technical Field

[0001] The present application belongs to the technical field of grinding tools, and more specifically, to a metal bond grinding wheel and a preparation method thereof. Background Art

[0002] Grinding wheels, also known as bonded abrasives, are usually abrasives bonded into a certain shape and have a certain strength. According to the type of bond, the common types are metal bond grinding wheels, vitrified bond grinding wheels, resin bond grinding wheels, and rubber bond grinding wheels. Grinding wheels are the most widely used type of abrasives, and can be used for rough grinding, semi-finishing grinding, and fine grinding of the outer circle, inner circle, plane, and various profiles of metal or non-metal workpieces, as well as grooving and cutting.

[0003] With the development of new material technology and advanced manufacturing industry, various new hard-to-grind materials with high strength, high hardness and high toughness continue to emerge, which puts higher requirements on the wear resistance of grinding wheels, and wear resistance is also a key factor affecting the service life of grinding wheels. Diamond grinding wheels use hard diamond as abrasives. The abrasives themselves have high wear resistance, but the holding force of the binder on the diamond abrasives is also an important factor restricting the wear resistance and service life of the grinding wheels. For grinding wheels made with conventional binder components and processes, the binder usually only physically coats the abrasives, and it is difficult to achieve a stronger bond between the binder and the abrasive. As a result, when grinding harder and hard-to-grind materials, the diamond abrasives are prone to fall off prematurely, and the wear rate of the grinding wheel is relatively high, which reduces the service life of the grinding wheel. Summary of the invention

[0004] The purpose of the embodiments of the present application is to provide a metal bond grinding wheel and a preparation method thereof, so as to improve the wear resistance of the grinding wheel in the prior art and enhance the bonding strength between the binder and the abrasive.

[0005] To achieve the above-mentioned purpose, the technical solution adopted in the present application is: to provide a metal bond grinding wheel, comprising a grinding wheel base and an abrasive layer, wherein the abrasive layer is bonded to the outer periphery of the grinding wheel base, and the abrasive layer is made of raw materials according to the following mass ratio:

[0006] Diamond abrasive 45%-50%

[0007] Tungsten carbide powder 20%-25%

[0008] Copper powder 15%-20%

[0009] Tin powder 3%-5%

[0010] Zinc powder 3%-5%

[0011] Nickel powder 3%-5%

[0012] Cobalt powder 2%;

[0013] The surface of the diamond abrasive is coated with a tungsten carbide powder coating by plasma spraying.

[0014] In one embodiment, the abrasive layer includes two diamond abrasive grains of different sizes, and the two diamond abrasive grains of different sizes are evenly dispersed in the abrasive layer.

[0015] In one embodiment, the particle size of a portion of the diamond abrasive grains is 300-400 mesh and the thickness of the tungsten carbide powder coating on the surface of the diamond abrasive grains is 250 μm;

[0016] The particle size of another part of diamond abrasive grains is 500-600 mesh and the thickness of the tungsten carbide powder coating on the surface of the diamond abrasive grains is 150 μm.

[0017] In one embodiment, a surface of the abrasive layer facing the grinding wheel base is fixedly bonded to the grinding wheel base via a nickel bonding layer.

[0018] According to another aspect of the present application, the present application further provides a method for preparing a metal bond grinding wheel, comprising the following steps:

[0019] Plasma spraying step: spraying tungsten carbide powder onto the surface of diamond abrasive grains by plasma spraying;

[0020] Mixing step: uniformly mix the raw material components in the following mass ratios to obtain a mixture: 45%-50% diamond abrasive grains, 20%-25% tungsten carbide powder, 15%-20% copper powder, 3%-5% tin powder, 3%-5% zinc powder, 3%-5% nickel powder, and 2% cobalt powder;

[0021] Pre-pressing step: adding the mixed material into the cavity of the cold pressing mold and pre-pressing it into an abrasive layer embryo;

[0022] Induction heating step: placing the grinding wheel base and the prepared abrasive layer embryo body into the cavity of a refractory mold so that the abrasive layer embryo body is located at the periphery of the grinding wheel base body, and a nickel bonding layer is set between the abrasive layer embryo body and the grinding wheel base body; then placing the refractory mold into a medium frequency or high frequency induction heating furnace for heating to sinter the abrasive layer embryo body, and at the same time melt the nickel bonding layer to combine the abrasive layer embryo body and the grinding wheel base into one.

[0023] In one embodiment, during the induction heating step, the nickel bonding layer is a nickel sheet placed between the abrasive layer blank and the grinding wheel substrate.

[0024] In one embodiment, in the induction heating step, the nickel bonding layer is nickel powder brushed onto the surface of the abrasive layer blank and / or the grinding wheel substrate.

[0025] In one embodiment, in the plasma spraying step, tungsten carbide powder coating is sprayed on the surfaces of two diamond abrasive grains of different particle sizes;

[0026] In the mixing step, two diamond abrasive grains of different particle sizes and sprayed with tungsten carbide powder coating are uniformly mixed with other raw material components.

[0027] In one embodiment, a portion of the diamond abrasive grains has a particle size of 300-400 mesh, and in the plasma spraying step, the thickness of the tungsten carbide powder coating sprayed on the surface of the diamond abrasive grains is 250 μm; another portion of the diamond abrasive grains has a particle size of 500-600 mesh, and in the plasma spraying step, the thickness of the tungsten carbide powder coating sprayed on the surface of the diamond abrasive grains is 150 μm.

[0028] In one embodiment, in the induction heating step, the heating temperature is 900° C. and the heating time is 2 hours.

[0029] The beneficial effects of the metal bond grinding wheel and the preparation method thereof provided by the present application are as follows: compared with the prior art, the metal bond grinding wheel provided by the present application, on the one hand, significantly increases the wear resistance and service life of the diamond abrasive grains by coating the tungsten carbide powder coating on the surface of the diamond abrasive grains by plasma spraying; on the other hand, in addition to the diamond abrasive grains in the abrasive layer of the grinding wheel, the tungsten carbide powder as the main component of the binder can be bonded to the tungsten carbide powder coating on the surface of the diamond abrasive grains under the bonding action of cobalt powder and nickel powder, so that the diamond abrasive grains and the metal binder form a strong bond, thereby further improving the wear resistance and service life of the grinding wheel. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0031] Figure 1 A flow chart of a method for preparing a metal bond grinding wheel is provided for an embodiment of the present application. DETAILED DESCRIPTION

[0032] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0033] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0034] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0035] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0036] The metal bond grinding wheel provided in the embodiment of the present application is now described. The metal bond grinding wheel comprises a grinding wheel base and an abrasive layer, wherein the abrasive layer is bonded to the outer periphery of the grinding wheel base, and the abrasive layer is made of raw materials according to the following mass ratio:

[0037] Diamond abrasive 45%-50%

[0038] Tungsten carbide powder 20%-25%

[0039] Copper powder 15%-20%

[0040] Tin powder 3%-5%

[0041] Zinc powder 3%-5%

[0042] Nickel powder 3%-5%

[0043] Cobalt powder 2%;

[0044] The surface of the diamond abrasive is coated with a tungsten carbide powder coating by plasma spraying.

[0045] Specifically, the grinding wheel base can be made of steel or aluminum, which mainly supports and fixes the abrasive layer and transmits power. It has good mechanical properties and heat resistance, and can ensure that the grinding wheel maintains stability and safety during high-speed rotation and grinding. The abrasive layer is combined with the outer periphery of the grinding wheel base, and the abrasive layer is the part of the grinding wheel used to contact and grind the workpiece. According to the different structural designs of the grinding wheel, the grinding wheel base and the abrasive layer can be designed into different shapes. For example, the grinding wheel base is a circle with a through hole in the middle, and the abrasive layer is a ring surrounding the outer periphery of the grinding wheel base; for another example, the abrasive layer is composed of a plurality of arc-shaped flakes matching the outer periphery of the grinding wheel base, and the number of the arc-shaped flakes is multiple and fixed to the outer periphery of the grinding wheel base at intervals, so that the gap formed between two adjacent arc-shaped flakes can facilitate chip removal during grinding.

[0046] The abrasive layer is formed by mixing, pressing and sintering diamond abrasive grains, tungsten carbide powder, copper powder, tin powder, zinc powder, nickel powder and cobalt powder. Among them, diamond abrasive grains are the main grinding component in the abrasive layer. Diamond is hard and very suitable for grinding high-strength, high-hardness and difficult-to-grind materials.

[0047] In particular, the surface of the diamond abrasive is coated with a tungsten carbide powder coating by plasma spraying. The plasma spraying process is a material protection technology that uses a plasma arc as a heat source to heat the metal or non-metallic material of the powder or wire to a molten or semi-molten state, and then sprays it onto the surface of the substrate to form a coating. Specifically, the process first generates a high-temperature and high-energy-density heat source through a plasma arc driven by direct current, which can heat the spraying material, i.e., tungsten carbide powder, to a molten or semi-molten state; then, using a protective gas as a carrier, the molten or semi-molten material is sprayed at high speed onto the surface of the pretreated diamond abrasive; the molten or semi-molten tungsten carbide powder material is deposited on the surface of the diamond abrasive and rapidly cooled and solidified to form a tungsten carbide coating with high wear resistance. ‌‌ Before the abrasive layer is pressed and sintered, the tungsten carbide powder needs to be evenly sprayed and coated on the surface of the diamond abrasive by plasma spraying, thereby effectively improving the wear resistance and corrosion resistance of the diamond abrasive. In order to better combine the diamond abrasive grains and the tungsten carbide powder coating, the diamond abrasive grains can be cleaned, degreased and nickel-plated before the plasma spraying process, and the diamond abrasive grains can be protected by the nickel layer plated on the surface of the diamond abrasive grains. In addition, in order to obtain a tungsten carbide powder coating with uniform thickness on the surface of the diamond abrasive grains, a specific mechanical device can be designed to turn over or roll the diamond grains during the plasma spraying process; multiple spraying and cross-spraying methods can also be used to ensure that the tungsten carbide coating is evenly covered in all directions on the surface of the diamond abrasive grains, thereby obtaining a tungsten carbide powder coating with a predetermined thickness and uniform distribution.

[0048] Tungsten carbide powder, copper powder, tin powder, zinc powder, nickel powder, cobalt powder and other powders are used as metal binders. After the metal binder is mixed with diamond abrasive grains, it is pressed and sintered to form an abrasive layer of a predetermined shape. Among them, tungsten carbide powder, as the main component of the metal binder, can be consolidated with the tungsten carbide powder coating on the surface of the diamond abrasive grains under the bonding action of cobalt powder and nickel powder, so that a strong bond is formed between the diamond abrasive grains and the metal binder, which greatly improves the holding force of the binder on the diamond abrasive grains, thereby improving the wear resistance and service life of the abrasive layer of the grinding wheel. Copper powder has good compatibility with both diamond and tungsten carbide, and copper powder has good thermal conductivity and wear resistance, which can improve the heat dissipation, shock resistance and wear resistance of the grinding wheel. In addition, the addition of copper powder can also make the abrasive layer of the grinding wheel have a lower sintering forming temperature. Tin powder and zinc powder both have good compatibility with copper powder and form alloys, which can also significantly improve the heat dissipation, shock resistance, compactness and wear resistance of the grinding wheel. In addition, the addition of zinc powder can also help improve the self-sharpening of the abrasive layer of the grinding wheel, and can adjust the hardness and toughness of the metal binder, thereby improving the grinding performance of the grinding wheel; nickel is also known for its high wear resistance and corrosion resistance, so the addition of nickel powder can also significantly improve the wear resistance of the abrasive layer of the grinding wheel. In summary, the abrasive layer with the above components and proportions has good compatibility and strong bonding between the components, which can significantly improve the wear resistance and service life of the abrasive layer of the grinding wheel. ‌

[0049] Compared with the prior art, the metal bond grinding wheel provided by the present application, on the one hand, significantly increases the wear resistance and service life of the diamond abrasive grains by coating the surface of the diamond abrasive grains with a tungsten carbide powder coating by plasma spraying; on the other hand, in addition to the diamond abrasive grains, the tungsten carbide powder as the main component of the binder in the abrasive layer of the grinding wheel can be bonded with the tungsten carbide powder coating on the surface of the diamond abrasive grains under the bonding action of cobalt powder and nickel powder, so that the diamond abrasive grains and the metal binder form a strong bond, thereby further improving the wear resistance and service life of the grinding wheel.

[0050] In another embodiment of the present application, the abrasive layer includes two diamond abrasive grains of different particle sizes, and the two diamond abrasive grains of different particle sizes are evenly dispersed in the abrasive layer. For example, diamond abrasive grains of 550 mesh and 300 mesh can be used, so that the two diamond abrasive grains of different particle sizes are mixed and evenly dispersed in the abrasive layer, so that the finer diamond abrasive grains can be filled in the gaps between the coarser diamond abrasive grains, so that the diamond abrasive grains can be more evenly and densely distributed in various areas of the abrasive layer as a whole, thereby improving the wear resistance of the grinding wheel.

[0051] In another embodiment of the present application, the particle size of one part of the diamond abrasive grains is 300-400 mesh and the thickness of the tungsten carbide powder coating on the surface of the diamond abrasive grains is 250 μm; the particle size of another part of the diamond abrasive grains is 500-600 mesh and the thickness of the tungsten carbide powder coating on the surface of the diamond abrasive grains is 150 μm.

[0052] It is understandable that, relatively speaking, diamond grains with larger grain sizes have a larger contact surface with the workpiece to a certain extent during the grinding process, and play a greater grinding role. Therefore, the thickness of the tungsten carbide powder coating on the surface of diamond grains with larger grain sizes can be designed to be thicker, which is beneficial to protect the diamond grains with larger grain sizes and improve the wear resistance of the diamond grains. The thickness of the tungsten carbide powder coating on the surface of diamond grains with smaller grain sizes should not be designed to be too thick, but should be correspondingly thinner, otherwise the small-grained diamond grains will be more rounded after being wrapped by the thick tungsten carbide powder coating, reducing the sharpness of the small-grained diamond grains, thereby weakening the grinding effect of the small-grained diamond grains. Based on this, the particle size of some diamond abrasive grains is 300-400 mesh, such as 300 mesh, 350 mesh, 380 mesh or 400 mesh, and the thickness of the tungsten carbide powder coating on the surface of the diamond abrasive grains is 250 μm; while the particle size of another part of the diamond abrasive grains is 500-600 mesh, such as 500 mesh, 550 mesh or 600 mesh, and the thickness of the tungsten carbide powder coating on the surface of the diamond abrasive grains is 150 μm. Such a mixture of two different sizes of diamond abrasive grains with different coating thicknesses can significantly improve the wear resistance of the diamond abrasive grains. In addition, spraying tungsten carbide powder coatings of different thicknesses on two different sizes of diamond abrasive grains respectively and accurately controlling the coating thickness is also conducive to saving tungsten carbide powder raw materials and improving the utilization rate of tungsten carbide powder.

[0053] In another embodiment of the present application, a surface of the abrasive layer facing the grinding wheel base is fixedly bonded to the grinding wheel base via a nickel bonding layer.

[0054] The grinding wheel base is generally made of steel or aluminum. If the grinding wheel base and the abrasive layer are fixedly bonded by bonding, the bonding strength is usually weak. During the grinding process of high-hardness, high-strength wear-resistant materials, the abrasive layer is easy to fall off during the grinding process. Therefore, the abrasive layer and the grinding wheel base are fixedly bonded by a nickel bonding layer. Under high temperature conditions, the nickel bonding layer, as an intermediate layer, has good compatibility with the grinding wheel base and the abrasive layer, and can achieve metallurgical bonding between the grinding wheel base and the abrasive layer, greatly improving the firmness of the bonding between the grinding wheel base and the abrasive layer and increasing the service life of the grinding wheel. For example, a layer of nickel material can be brazed between the grinding wheel base and the abrasive layer; or a nickel sheet can be placed between the grinding wheel base and the pre-pressed abrasive layer for high-temperature sintering, so that the grinding wheel base and the abrasive layer can be well fixed together after the nickel sheet melts; or a layer of nickel powder can be brushed on the surface of the grinding wheel base and the pre-pressed abrasive layer, and then the grinding wheel base and the abrasive layer can be fixed together as one after the nickel powder melts during the high-temperature sintering process.

[0055] According to another aspect of the present application, the present application also provides a method for preparing a metal bond grinding wheel, the method for preparing a metal bond grinding wheel comprising the following steps:

[0056] Plasma spraying step: spraying tungsten carbide powder onto the surface of diamond abrasive grains by plasma spraying;

[0057] Mixing step: uniformly mix the raw material components in the following mass ratio to obtain a mixture: 45%-50% diamond abrasive, 20%-25% tungsten carbide powder, 15%-20% copper powder, 3%-5% tin powder, 3%-5% zinc powder, 3-5% nickel powder, and 2% cobalt powder;

[0058] Pre-pressing step: adding the mixed material into the cavity of the cold pressing mold and pre-pressing it into an abrasive layer embryo;

[0059] Induction heating step: placing the grinding wheel base and the prepared abrasive layer embryo body into the cavity of a refractory mold so that the abrasive layer embryo body is located at the periphery of the grinding wheel base body, and a nickel bonding layer is set between the abrasive layer embryo body and the grinding wheel base body; then placing the refractory mold into a medium frequency or high frequency induction heating furnace for heating to sinter the abrasive layer embryo body, and at the same time melt the nickel bonding layer to combine the abrasive layer embryo body and the grinding wheel base into one.

[0060] ‌ Before the plasma spraying step, the diamond abrasive grains are pre-laid flat at the predetermined position. The diamond abrasive grains are spread as evenly as possible and the thickness is thinner, which is conducive to the surface of the diamond abrasive grains being evenly sprayed with tungsten carbide powder coating. In addition, the diamond abrasive grains can be pre-treated before the plasma spraying step, that is, the diamond abrasive grains are cleaned, degreased and nickel-plated, and the diamond abrasive grains are protected by the nickel layer plated on the surface of the diamond abrasive grains.

[0061] Then the plasma spraying process begins. The plasma spraying process is a material protection technology that uses a plasma arc as a heat source to heat the metal or non-metallic material of powder or wire to a molten or semi-molten state, and then sprays it onto the surface of the substrate to form a coating. Specifically, a plasma arc driven by direct current generates a high-temperature and high-energy-density heat source, which can heat the spraying material, i.e., tungsten carbide powder, to a molten or semi-molten state; then, using a protective gas as a carrier, the molten or semi-molten material is sprayed at high speed onto the surface of the pretreated diamond abrasive; the molten or semi-molten tungsten carbide powder material is deposited on the surface of the diamond abrasive and rapidly cooled and solidified to form a tungsten carbide coating with high wear resistance, thereby effectively improving the wear resistance and corrosion resistance of the diamond abrasive.

[0062] In the mixing step, the raw materials of the diamond abrasive and the metal binder are mixed uniformly according to a predetermined ratio. All the raw materials can be added to a three-dimensional mixer and mixed for a predetermined time, such as 2 hours, to obtain a mixture.

[0063] In the pre-pressing step, the mixture is added to the cavity of the cold pressing mold, and the shape and size of the mold match the shape and size of the abrasive layer. A press is used to apply sufficient pressure to the powder in the mold to create close contact and bonding between the powder particles, thereby forming an abrasive layer embryo of a predetermined shape. For example, the grinding wheel base is a circle with a through hole in the middle, and the abrasive layer embryo after pre-pressing is a ring surrounding the outer periphery of the grinding wheel base; for another example, the abrasive layer is composed of a plurality of arc-shaped flakes that match the outer periphery of the grinding wheel base, and the number of the arc-shaped flakes is multiple and fixed to the outer periphery of the grinding wheel base at intervals, so that the gap formed between two adjacent arc-shaped flakes can be used for chip removal during grinding.

[0064] In the induction heating step, a refractory mold matching the shape of the grinding wheel is prepared in advance, and the grinding wheel base and the abrasive layer embryo are first placed in the cavity of the refractory mold, with the grinding wheel base located at the center of the cavity and the abrasive layer embryo located at the periphery of the grinding wheel base. A nickel bonding layer is provided between the abrasive layer embryo and the grinding wheel base, for example, a nickel sheet can be placed between the grinding wheel base and the abrasive layer embryo, or a layer of nickel powder can be brushed on the respective opposite surfaces of the grinding wheel base and the abrasive layer embryo. The refractory mold is placed in an induction heating furnace for heating, and according to the requirements of the sintering temperature, a medium frequency or high frequency induction heating furnace can be used to heat and sinter the abrasive layer embryo, and at the same time, the nickel bonding layer melts under high temperature conditions, thereby fixing the abrasive layer embryo and the grinding wheel base together to obtain the metal bond grinding wheel.

[0065] In one embodiment of the present application, in the induction heating step, the nickel bonding layer is a nickel sheet placed between the abrasive layer blank and the grinding wheel base. For example, the grinding wheel base is a circle with a through hole in the middle, and the abrasive layer is a ring surrounding the outer periphery of the grinding wheel base. A ring-shaped nickel sheet is embedded between the grinding wheel base and the abrasive layer, so that when the nickel sheet is heated to a molten state in an induction heating furnace, the nickel sheet can serve as an intermediate bonding layer to fix the grinding wheel base and the abrasive layer together. For another example, the grinding wheel base is a circle with a through hole in the middle, and the abrasive layer is composed of a plurality of arc-shaped lamellar bodies matching the outer peripheral contour of the grinding wheel base. The number of arc-shaped lamellar bodies and nickel sheets is multiple, and a nickel sheet is embedded between each arc-shaped lamellar body and the grinding wheel base. So that when the nickel sheet is heated to a molten state in an induction heating furnace, each arc-shaped lamellar body can be fixed to the outer periphery of the grinding wheel base through the corresponding nickel sheet, and all the arc-shaped lamellar bodies are distributed at intervals around the outer periphery of the grinding wheel base. ‌

[0066] In one embodiment of the present application, in the induction heating step, the nickel bonding layer is nickel powder brushed on the surface of the abrasive layer embryo and / or the grinding wheel base. Specifically, a layer of nickel powder is brushed on the surface of the grinding wheel base or the surface of the abrasive layer embryo. Under the heating and temperature rising effect of the induction heating furnace, the nickel powder melts and can serve as an intermediate bonding layer to fix the grinding wheel base and the abrasive layer into one. In addition, in order to ensure the strength of the bonding between the grinding wheel base and the abrasive layer, a layer of nickel powder can be brushed on the surfaces of the grinding wheel base and the abrasive layer embryo that face each other, thereby increasing the thickness of the nickel bonding layer.

[0067] In one embodiment of the present application, two diamond abrasive grains of different particle sizes are prepared in advance, for example, diamond abrasive grains of 550 mesh and 300 mesh can be selected. In the plasma spraying step, the surfaces of the two diamond abrasive grains of different particle sizes are sprayed with tungsten carbide powder coatings respectively. In the mixing step, the two diamond abrasive grains of different particle sizes and sprayed with tungsten carbide powder coatings are uniformly mixed with other components such as tungsten carbide powder, copper powder, tin powder, zinc powder, nickel powder, cobalt powder and wetting agent to obtain a mixture. After cold pressing and high-temperature sintering of such a mixture, the two diamond abrasive grains of different particle sizes are uniformly dispersed in the abrasive layer, and the finer diamond abrasive grains of 550 mesh can be filled in the gaps between the coarser diamond abrasive grains of 300 mesh, so that the diamond abrasive grains can be more evenly and densely distributed in various areas of the abrasive layer as a whole, thereby improving the wear resistance of the grinding wheel.

[0068] In one embodiment of the present application, a portion of the diamond abrasive grains has a particle size of 300-400 mesh, and in the plasma spraying step, the thickness of the tungsten carbide powder coating sprayed on the surface of the diamond abrasive grains is 250 μm; another portion of the diamond abrasive grains has a particle size of 500-600 mesh, and in the plasma spraying step, the thickness of the tungsten carbide powder coating sprayed on the surface of the diamond abrasive grains is 150 μm.

[0069] In the plasma spraying step, two diamond abrasive grains of different particle sizes are subjected to the plasma spraying process separately, so as to facilitate spraying tungsten carbide powder coatings of different thicknesses on the surfaces of the two diamond abrasive grains of different particle sizes. Specifically, for diamond abrasive grains with a particle size of 300-400 mesh, the thickness of the tungsten carbide powder coating sprayed on the surface of the diamond abrasive grains is 250μm; and for diamond abrasive grains with a particle size of 500-600 mesh, the thickness of the tungsten carbide powder coating sprayed on the surface of the diamond abrasive grains is 150μm. In this way, the tungsten carbide powder coating on the surface of the diamond abrasive grains with larger particle sizes is thicker, which is beneficial to protect the diamond abrasive grains with larger particle sizes and improve the wear resistance of the diamond abrasive grains; while the diamond abrasive grains with smaller particle sizes will not be weakened by the overly thick tungsten carbide powder coating. Mixing and matching two diamond abrasive grains with different particle sizes and coatings of different thicknesses can significantly improve the wear resistance of the diamond abrasive grains. In addition, spraying tungsten carbide powder coatings of different thicknesses on two diamond abrasives of different particle sizes and accurately controlling the coating thickness are also beneficial to saving tungsten carbide powder raw materials and improving the utilization rate of tungsten carbide powder.

[0070] In one embodiment of the present application, in the induction heating step, the heating temperature is 900°C and the temperature is kept for 2 hours. According to the abrasive layer components and ratios of the above-mentioned metal bond grinding wheel, the sintering temperature of the induction heating furnace is set at 900°C and kept at this temperature for 2 hours. The obtained abrasive layer has a relatively dense structure, and the strength, hardness and wear resistance of the abrasive layer are relatively excellent. Example

[0071] A preparation method of a metal bond grinding wheel is as follows:

[0072] Plasma spraying step: spraying tungsten carbide powder onto the surface of diamond abrasive grains by plasma spraying; wherein the particle size of the diamond abrasive grains is 450 mesh, and the thickness of the sprayed tungsten carbide powder coating is 200 μm.

[0073] Mixing step: uniformly mix the raw material components in the following mass ratio to obtain a mixture: 47% diamond abrasive, 23% tungsten carbide powder, 17% copper powder, 3% tin powder, 4% zinc powder, 4% nickel powder, and 2% cobalt powder.

[0074] Pre-pressing step: adding the mixed material into the cavity of the cold pressing mold and pre-pressing it into an abrasive layer embryo;

[0075] Induction heating step: place the grinding wheel base and the prepared abrasive layer embryo body into the cavity of the refractory mold, so that the abrasive layer embryo body is located at the periphery of the grinding wheel base body, and a nickel sheet is arranged between the abrasive layer embryo body and the grinding wheel base body; then place the refractory mold into a medium frequency or high frequency induction heating furnace and heat it to 900°C and keep it warm for 2 hours to sinter the abrasive layer embryo body, and at the same time melt the nickel sheet to combine the abrasive layer embryo body and the grinding wheel base body into one. Example

[0076] A preparation method of a metal bond grinding wheel is as follows:

[0077] Plasma spraying step: spraying tungsten carbide powder on the surface of diamond abrasive grains by plasma spraying; wherein, the particle size of a part of diamond abrasive grains is 350 mesh, and the thickness of the sprayed tungsten carbide powder coating is 250 μm; the particle size of another part of diamond abrasive grains is 550 mesh, and the thickness of the sprayed tungsten carbide powder coating is 150 μm.

[0078] Mixing step: uniformly mix the raw material components in the following mass ratio to obtain a mixture: 50% diamond abrasive, 20% tungsten carbide powder, 15% copper powder, 5% tin powder, 4% zinc powder, 4% nickel powder, and 2% cobalt powder.

[0079] Pre-pressing step: adding the mixed material into the cavity of the cold pressing mold and pre-pressing it into an abrasive layer embryo;

[0080] Induction heating step: place the grinding wheel base and the prepared abrasive layer embryo body into the cavity of the refractory mold, so that the abrasive layer embryo body is located at the periphery of the grinding wheel base body, and a nickel sheet is arranged between the abrasive layer embryo body and the grinding wheel base body; then place the refractory mold into a medium frequency or high frequency induction heating furnace and heat it to 900°C and keep it warm for 2.5 hours to sinter the abrasive layer embryo body, and at the same time melt the nickel sheet to combine the abrasive layer embryo body and the grinding wheel base body into one. Example

[0081] A preparation method of a metal bond grinding wheel is as follows:

[0082] Plasma spraying step: spraying tungsten carbide powder on the surface of diamond abrasive grains by plasma spraying; wherein, the particle size of a part of diamond abrasive grains is 300 mesh, and the thickness of the sprayed tungsten carbide powder coating is 280 μm; the particle size of another part of diamond abrasive grains is 600 mesh, and the thickness of the sprayed tungsten carbide powder coating is 100 μm.

[0083] Mixing step: uniformly mix the raw material components in the following mass ratio to obtain a mixture: 45% diamond abrasive, 24% tungsten carbide powder, 20% copper powder, 3% tin powder, 3% zinc powder, 3% nickel powder, and 2% cobalt powder.

[0084] Pre-pressing step: adding the mixed material into the cavity of the cold pressing mold and pre-pressing it into an abrasive layer embryo;

[0085] Induction heating step: place the grinding wheel base and the prepared abrasive layer embryo body into the cavity of the refractory mold, so that the abrasive layer embryo body is located at the periphery of the grinding wheel base body, and a nickel sheet is set between the abrasive layer embryo body and the grinding wheel base body; then place the refractory mold into a medium frequency or high frequency induction heating furnace and heat it to 950°C and keep it warm for 1.5 hours to sinter the abrasive layer embryo body, and at the same time melt the nickel sheet to combine the abrasive layer embryo body and the grinding wheel base body into one.

[0086] In summary, the metal bond grinding wheel provided in the present application has a tungsten carbide powder coating with high wear resistance sprayed on the surface of the diamond abrasive grains, and the metal bond also correspondingly uses tungsten carbide powder as the main component, and adds cobalt powder and nickel powder as adhesives. Both cobalt powder and nickel powder have good compatibility with tungsten carbide, and can form a strong metallurgical bond between the tungsten carbide powder in the metal bond and the tungsten carbide coating on the surface of the diamond abrasive grains; in addition, the copper powder, tin powder, zinc powder, etc. in the metal bond help to improve the heat dissipation performance on the one hand, and help to improve the wear resistance on the other hand, so that the metal bond grinding wheel provided in the present application has super wear resistance and a long service life. In the preparation process of the metal bond grinding wheel, plasma spraying is used to spray tungsten carbide powder with a high melting point. During the spraying process, the coating thickness on the surface of the diamond abrasive can be accurately controlled, and the coating is uniform; during the sintering process, an induction heating furnace is used to heat the abrasive layer embryo to a high temperature of more than 800°C, and a nickel bonding layer is set between the abrasive layer embryo and the grinding wheel substrate. The nickel bonding layer can also be synchronously melted during the sintering process to achieve metallurgical bonding between the abrasive layer and the grinding wheel substrate, so that there is no need for additional processes to bond or weld the abrasive layer and the grinding wheel substrate, simplifying the process flow. The metal bond grinding wheel has significantly improved wear resistance and service life, and is suitable for processing floor tiles, concrete, stone, etc.

[0087] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A metal bond grinding wheel, characterized in that: It comprises a grinding wheel base and an abrasive layer, wherein the abrasive layer is combined with the outer periphery of the grinding wheel base, and the abrasive layer is made of raw materials according to the following mass ratio: Diamond abrasive 45%-50% Tungsten carbide powder 20%-25% Copper powder 15%-20% Tin powder 3%-5% Zinc powder 3%-5% Nickel powder 3%-5% Cobalt powder 2%; Wherein, the surface of the diamond abrasive grains is coated with a tungsten carbide powder coating by plasma spraying; The abrasive layer comprises two kinds of diamond abrasive grains of different particle sizes, and the two kinds of diamond abrasive grains of different particle sizes are evenly dispersed in the abrasive layer; The particle size of a portion of the diamond abrasive grains is 300-400 mesh and the thickness of the tungsten carbide powder coating on the surface of the diamond abrasive grains is 250 μm; The particle size of another part of the diamond abrasive grains is 500-600 mesh and the thickness of the tungsten carbide powder coating on the surface of the diamond abrasive grains is 150 μm.

2. The metal bond grinding wheel according to claim 1, characterized in that: A surface of the abrasive layer facing the grinding wheel base is fixedly bonded to the grinding wheel base via a nickel bonding layer.

3. A method for preparing a metal bond grinding wheel, characterized in that: The following steps are involved: Plasma spraying step: spraying tungsten carbide powder on the surface of diamond abrasive grains by plasma spraying; spraying tungsten carbide powder coating on the surface of diamond abrasive grains of two different particle sizes, wherein the particle size of one part of the diamond abrasive grains is 300-400 mesh and the thickness of the tungsten carbide powder coating sprayed on the surface of the diamond abrasive grains is 250 μm; the particle size of another part of the diamond abrasive grains is 500-600 mesh and the thickness of the tungsten carbide powder coating sprayed on the surface of the diamond abrasive grains is 150 μm; Mixing step: mix two diamond abrasive grains with different particle sizes and sprayed with tungsten carbide powder coating with other raw material components in the following mass ratio to obtain a mixture: 45%-50% diamond abrasive grains, 20%-25% tungsten carbide powder, 15%-20% copper powder, 3%-5% tin powder, 3%-5% zinc powder, 3-5% nickel powder, and 2% cobalt powder; Pre-pressing step: adding the mixed material into the cavity of the cold pressing mold and pre-pressing it into an abrasive layer embryo; Induction heating step: placing the grinding wheel base and the prepared abrasive layer embryo body into the cavity of a refractory mold so that the abrasive layer embryo body is located at the periphery of the grinding wheel base body, and a nickel bonding layer is set between the abrasive layer embryo body and the grinding wheel base body; then placing the refractory mold into a medium frequency or high frequency induction heating furnace for heating to sinter the abrasive layer embryo body, and at the same time melt the nickel bonding layer to combine the abrasive layer embryo body and the grinding wheel base into one.

4. The method for preparing a metal bonded grinding wheel as claimed in claim 3, wherein: In the induction heating step, the nickel bonding layer is a nickel sheet placed between the abrasive layer embryo and the grinding wheel substrate.

5. The method for preparing a metal bonded grinding wheel as claimed in claim 3, characterized in that: In the induction heating step, the nickel bonding layer is nickel powder brushed on the surface of the abrasive layer embryo and / or the grinding wheel substrate.

6. The method for preparing a metal bonded grinding wheel according to any one of claims 3 to 5, characterized in that: In the induction heating step, the heating temperature was 900°C and kept for 2 hours.

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