JP7716734B2 - Porous metal bond grinding wheel and its manufacturing method - Google Patents

Description

Article 30, paragraph 2 of the Patent Act applies 1. Publication name Proceedings of the Japan Society for Precision Engineering Spring Meeting Academic Lecture Series Publication date March 1, 2020 Publisher Japan Society for Precision Engineering Relevant pages Pages 490-491 Disclosed by Takayuki Sakurai, Junichi Muraoka, Takayoshi Izumi, Hitoshi Goto Title of publication "Development of a grinding wheel with an air release mechanism for CFRP machining" 2. Publication name Proceedings of the Japan Society for Abrasive Technology Academic Lecture Series 2020 Publication date August 21, 2020 Publisher Japan Society for Abrasive Technology Relevant pages Pages 95-96 Disclosed by Takayuki Sakurai, Junichi Muraoka Title of publication "Evaluation of the machining performance of an air release type grinding wheel for CFRP machining"

The present invention relates to a porous metal bonded grinding wheel and its manufacturing method. The bond material that bonds the abrasive grains together is a porous metal body with continuous, interconnected pores and a high porosity, and the method for manufacturing the same.

Carbon fiber reinforced plastic (CFRP), characterized by its light weight and high rigidity, is widely used as a material in the automotive, medical, aerospace, etc. Products made from CFRP require the removal of excess material (trimming) after laminating and molding CFRP plates.
CFRP is known to be a material that causes rapid wear on the cutting edge because it requires processing of hard carbon fibers.
Known grinding wheels that have high resistance to wear of the cutting edges include diamond grinding wheels that have many diamond cutting edges and are resistant to wear of the cutting edges.

However, when diamond grinding wheels are used to process CFRP, CFRP chips tend to accumulate between the numerous cutting edges, and it is known that CFRP processing, which requires dry processing, can easily clog. In other words, with CFRP, the resin layer that connects the carbon fibers melts due to the heat generated during processing, causing the diamond grinding wheel to clog.

As a method for solving such clogging, a method has been proposed in which pores are formed in the grinding wheel to promote the self-sharpening action of the grinding wheel and suppress clogging.
For example, Patent Document 1 discloses a method in which a substance (spacer) that is soluble in a solvent and has a melting point of 500°C or higher and superabrasive grains are mixed into a metal bond powder, the mixture is sintered by hot pressing, and the sintered body is then immersed in a solvent to remove the substance (spacer) and form pores in the sintered body.

In addition, as a porous metal material, although not a grinding wheel, Patent Document 2 discloses a method for forming porous metal with pores in a three-dimensional network structure, in which an inorganic compound such as sodium nitrite is formed into a predetermined shape and sintered, and then molten metal is injected into the voids of the sintered body, solidified, and then treated with a solvent to elute the inorganic compound.

Japanese Unexamined Patent Publication No. 118469/1983 Japanese Unexamined Patent Publication No. 59-038343

In the metal bonded grinding wheel disclosed in Patent Document 1, although pores are formed in the sintered body, the pores are not connected but are dispersed as independent pores, so air or cutting oil does not flow inside the metal bonded grinding wheel, which means that chips cannot be discharged well and clogging cannot be suppressed.
Furthermore, since the pores formed in the sintered body are closed pores, if NaCl is used as a spacer, there is a risk that NaCl will remain in the sintered body, causing the grinding wheel to oxidize significantly, making it difficult to store.

The present inventors have conducted extensive research into a grinding wheel that can suppress clogging and perform suitable grinding even on materials such as CFRP, which are subject to rapid wear of the cutting edge.
In this study, the method disclosed in Patent Document 2 was also considered, but there were problems with the method, such as the large number of steps and the time required for each step, resulting in high manufacturing costs, and there was also the problem of a large environmental load, since the spacer-forming materials, such as sodium nitrite, are hazardous substances.
To solve this problem, we discovered that clogging can be suppressed by using a metal bonded grinding wheel with excellent thermal conductivity, making the metal bond porous (formed with interconnected pores), and supplying a fluid such as air to the surface of the grinding wheel from inside, which led to the completion of this invention.

The present invention was made in light of the above-mentioned circumstances, and aims to provide a porous metal-bonded grinding wheel that has interconnected pores formed inside, has a high porosity, and is able to suppress clogging, as well as a method for manufacturing the same.

The porous metal bonded grinding wheel according to the present invention, which has been made to solve the above-mentioned problems, comprises a porous metal body as a bond material for abrasive grains, in which a plurality of spherical metal particles are connected by sintering and have through holes through which a fluid flows, formed by melting a plurality of spacers made of water-soluble inorganic salts or organic salts, and a plurality of abrasive grains arranged in the porous metal body. In the porous metal body, the spherical metal particles are made of Cu or a metal element having a melting point higher than Cu, or a metal of an alloy element based on Cu, and the porous metal body In the porous metal body, a plurality of the spherical metal particles are connected to each other at their contact points by sintering, and gaps exist as pores between adjacent spherical metal particles. Furthermore, the porous metal body does not have any independent pores through which fluid does not flow, and a plurality of the pores are continuously connected to connect the inner and outer surfaces of the porous metal body, forming a plurality of long communicating pores with a width of at most 1 mm. The porous metal body has a porosity of 40% to 60%, and the communicating pores function as passages for fluids such as gases such as oxygen and nitrogen, or liquids such as cutting oil.

With this configuration, the porous metal body has interconnected pores, and the porosity is 40% to 60%, so that grinding can be performed while air or the like is flowing through the grinding wheel to prevent clogging of the material to be ground. Furthermore, because the interconnected pores are formed by connecting multiple pores in the porous metal body, no spacers (such as NaCl) remain inside the grinding wheel, preventing oxidation of the grinding wheel.
In addition, the metal porous body, which is the bond material for the abrasive grains, can be formed by sintering multiple spherical metal particles made of Cu, or a metal element with a higher melting point than Cu, or an alloy element based on Cu, thereby achieving high thermal conductivity and high strength.
Furthermore, since the porous body is a metal body with high thermal conductivity, it is very effective for processing plastics and heat-resistant metals, which are highly susceptible to heat damage.

Further, the manufacturing method of the porous metal bonded grinding wheel according to the present invention, which has been made to solve the above-mentioned problems, comprises a porous metal body as a bond material for abrasive grains, in which a plurality of spherical metal particles are connected by sintering and have communicating holes through which a fluid flows, formed by melting a plurality of spacers made of a water-soluble inorganic salt or organic salt, and a plurality of abrasive grains arranged in the porous metal body,
The method comprises the steps of mixing a plurality of abrasive grains, spacers made of a water-soluble inorganic or organic salt and having a particle size in the range of 75 μm to 300 μm, and a plurality of spherical metal particles made of Cu or a metal element having a melting point higher than Cu, or a Cu-based alloy element, and having a particle size in the range of 75 μm to 300 μm, and molding the mixture; sintering the mixture to form a first sintered body; and removing the spacers from the first sintered body by melting them, wherein the amount of the spacers added in the molding step of the mixture is 40 to 60 vol.%.

It is preferable that the spherical metal particles are formed to have the same particle size as the spacers. Also, it is preferable that the method further comprises a step of heat-treating the first sintered body again after the step of removing the spacers from the first sintered body to form a second sintered body having improved strength than the first sintered body .

This method makes it possible to obtain the porous metal bonded grinding wheel. Furthermore, by manufacturing it by, for example, discharge sintering, the manufacturing process can be simplified, speeded up, and manufacturing costs reduced.

The present invention provides a porous metal bonded grinding wheel with interconnected pores formed inside, a high porosity, and reduced clogging, as well as a method for manufacturing the same.

FIG. 1 is an enlarged cross-sectional view schematically showing a part of a porous metal bonded grinding wheel according to the present invention. FIG. 2 is a cross-sectional view showing an example of a grinding device using the porous metal bonded grinding wheel of FIG. FIG. 3 is an enlarged cross-sectional view schematically showing a part of the mixture before sintering that forms the porous metal bonded grinding wheel of FIG. FIG. 4 is a cross-sectional view schematically showing the state in which the mixture of FIG. 3 has been sintered and the spacer has been removed. FIG. 5 is a graph showing the results of the example. 6(a) and (b) are micrographs of the example.

The porous metal bonded grinding wheel according to the present invention and the method for manufacturing the same will be described below.
The porous metal bonded grinding wheel of the present invention is a grinding wheel into which a gas such as oxygen or nitrogen, or a liquid such as cutting oil, is continuously supplied to cool the abrasive grains and the bond material surface (grinding wheel surface) and to perform grinding while discharging chips.

Fig. 1 is an enlarged cross-sectional view of a portion of a porous metal bonded grinding wheel according to the present invention. As shown in Fig. 1, the porous metal bonded grinding wheel 1 is composed of a porous metal body 2 in which a plurality of spherical metal particles are connected by sintering, a plurality of abrasive grains 3 (e.g., diamond abrasive grains) disposed in the porous metal body 2, and long communicating holes 4 formed in the porous metal body 2.
In the porous metal body 2, the communicating holes 4 are formed by a plurality of pores continuously connected together, and the porosity of the porous metal bond grinding wheel 1 is 40% to 60%.
The communication hole 4 functions as a passage for gases such as oxygen and nitrogen, or liquids such as cutting oil.

The metal porous body 2 is made of Cu, a metal having a melting point higher than that of Cu, or an alloy formed from Cu or a metal having a melting point higher than that of Cu.
Specifically, examples of metals having a melting point higher than that of Cu include W, Fe, Ni, Co, and Mo. Also, an alloy of Cu and any of the above metals having a melting point higher than that of Cu may be used.
By using these metals, it is possible to obtain a grinding wheel 1 having excellent thermal conductivity.

The metal porous body 2 is made up of multiple spherical metal particles connected to each other at their contact points by sintering, and so is evenly arranged except for the locations where the long communicating holes 4 are located, and gaps (not shown) exist uniformly between adjacent spherical metal particles as pores smaller than the communicating holes 4.
The communication holes 4 are formed to connect the inner and outer peripheral surfaces of the metal porous body 2 and have a width of several tens of μm to 1 mm, thereby significantly improving the fluidity of gases such as air or liquids such as cutting oil within the grinding wheel 1.

When the porous metal bonded grinding wheel 1 is used to grind a CFRP material, it is used in an apparatus configuration such as that shown in FIG.
In FIG. 2, the porous metal bond grinding wheel 1 is formed in an annular shape, and a rotating shaft 10 extending in the vertical direction, for example, is inserted into the center of the grinding wheel 1 and fixed around the rotating shaft 10 .
The rotating shaft 10 is formed in a tubular shape, and high-pressure air is allowed to flow through the tube.
In addition, multiple communication holes 10a are formed on the side of the tube, and air flows through these communication holes 10a, allowing air to flow through the grinding wheel 1 from the center side of the porous metal bond grinding wheel 1 toward the radially outward direction.

The rotating shaft 10 is rotated at a predetermined speed (for example, 188 m/min), and the CFRP material 20 to be ground is brought into contact with the rotating porous metal bond grinding wheel 1, and grinding is performed.
At this time, high-pressure air (air with an input pressure of 0.5 MPa) is sprayed out mainly through the communicating holes 4 of the porous metal bond grinding wheel 1 (air flows from the inner surface to the outer surface of the grinding wheel 1 and is sprayed out from the outer surface), so grinding can be performed without clogging with chips of the CFRP material 20.
In addition, the abrasive grains 3 and the porous metal body 2 are cooled by the air passing through the communication holes 4, and the adverse effects of the heat of the grinding wheel on the CFRP material 20 are suppressed.
Depending on the object to be ground, a cutting oil other than air may be used.

Next, a method for manufacturing the porous metal bonded grinding wheel 1 will be described.
First, as shown in FIG. 3, spherical metal particles 11 made of Cu, a metal element with a melting point higher than Cu, or an alloy element of Cu and any of these metal elements, inorganic salt spacers 12, and abrasive grains 3 made of, for example, Cu-Ni coated diamond are mixed and molded (forming a mixture).
Examples of inorganic salts that can be used include NaCl, KCl, etc. In particular, it is preferable to use NaCl as the spacer 12 because it is easily dissolved in water at room temperature.
Although NaCl and KCl have a lower melting point than the spherical metal particles 11 made of Cu or the like, by using an electric current sintering method in the sintering step described below, sintering can be performed at a temperature lower than the sintering temperature in a normal hot press method, etc. Therefore, the spacers 12 are less likely to be adversely affected by their low melting point.

Here, the present invention is characterized in that the particles of the spacer 12 are easily arranged continuously in the mixture, and the communicating holes 4 are formed.
In order to arrange the spacers 12 continuously, the spacers 12 having a particle size in the range of 75 μm or more and 300 μm or less are mixed in an amount of 40 vol% or more and 60 vol% or less, which makes it easier to arrange the spacers 12 continuously as shown in Figure 3.

The spherical metal particles 11 serving as the bonding material are formed to have the same particle size as the spacers 12 (it is desirable that the particle size is uniform).
This is because if the particle size of the spacers 12 is larger than the diameter of the spherical metal particles 11, the spacers 12 will become large pores in the sintered body after sintering, making it difficult to obtain uniform flow paths. Conversely, if the particle size of the spacers 12 is smaller than the diameter of the spherical metal particles 11, the spacers 12 will surround the spherical metal particles 11, which may hinder sintering.
The amount of diamond added as the abrasive grains 3 is, for example, 12.5 vol. %, and the amount of spacer 12 added is preferably 40 vol. % or more and 60 vol. % or less.

Next, the mixture is molded into a predetermined shape.
Then, this compact is pre-sintered using a plasma discharge sintering apparatus under a vacuum condition with an internal furnace pressure of 10.2 MPa at 650° C. for 15 minutes, thereby forming a pre-sintered compact (first sintered compact).
The pre-sintered body is immersed in distilled water to remove (desalt) the spacers 12 (NaCl), and the through holes 4 are formed as shown in FIG.
Finally, the porous metal bonded grinding wheel 1 (second sintered body) is obtained by sintering the grinding wheel 1 at 750°C or 820°C for 2 hours in a vacuum without pressure. This additional heat treatment improves the strength.

Although the strength of the grinding wheel is increased by this sintering, it is also possible to adjust the strength of the grinding wheel (bond material strength) depending on the object to be ground.
That is, in grinding, it may be necessary to reduce the strength of the bond material and encourage the cutting edge to grow naturally, thereby improving sharpness and minimizing damage to the material being ground.
Therefore, the strength of the porous metal bonded grinding wheel 1 (second sintered body) may be intentionally reduced by adjusting the sintering time and heating temperature in the above manufacturing process.

As described above, according to this embodiment, the porous metal body 2 has long communicating holes 4 formed therein and a porosity of 40% to 60%, so that grinding can be performed while flowing air or the like inside the grinding wheel to prevent clogging of the material to be ground. Furthermore, since the porous metal body 2 has a plurality of pores connected to form the communicating holes 4, no spacer 12 (such as NaCl) remains inside the grinding wheel, preventing oxidation of the grinding wheel.
Furthermore, the metal porous body 2, which is the bond material for the abrasive grains 3, is made by sintering multiple spherical metal particles made of Cu, or a metal element with a higher melting point than Cu, or an alloy element based on Cu, and therefore can achieve high thermal conductivity and high strength.
Furthermore, since the porous body 2 is a metal body with high thermal conductivity, it is very effective in processing plastics and heat-resistant metals, which are highly susceptible to heat damage.
Furthermore, by manufacturing the element by discharge sintering, the manufacturing process can be simplified, the manufacturing speed can be increased, and the manufacturing cost can be reduced.

In the above embodiment, the spherical metal particles 11 are made of Cu, a metal element with a melting point higher than that of Cu, or an alloy element based on Cu, but the present invention is not limited to this. For example, the spherical metal particles 11 may be made of Fe, Ni, Mo, W, Sn, or alloys thereof.
In the above embodiment, NaCl and the like are used as spacers, but the present invention is not limited to this, and water-soluble crystalline materials such as KCl may also be used. Furthermore, as long as the salt is water-soluble, it is not limited to inorganic salts and organic salts may also be used. Furthermore, salts having elongated crystal shapes, such as needle-like crystals, may also be used as spacers.

The porous metal bond grinding wheel and its manufacturing method according to the present invention will be further explained based on examples.

(Experiment 1)
In Experiment 1, a porous metal bonded grinding wheel was manufactured according to the present embodiment. Specifically, a porous metal bonded grinding wheel was manufactured using bronze (Cu-10Sn: a base metal Cu mixed with 10 wt% Sn) as spherical metal particles, NaCl as a spacer, and diamond abrasive grains, and its performance was evaluated.

Example 1
In Example 1, a compact was formed by mixing 25.2 vol% bronze (Cu-10Sn), 40 vol% NaCl as a spacer, and 34.8 vol% diamond abrasive grains. The metal particle diameter of the bronze was in the range of 75 μm to 125 μm, and the particle diameter of the spacer was the same as the metal particle diameter.
Thereafter, the compact was subjected to a preliminary sintering temperature of 650°C and a main sintering temperature of 750°C to produce a porous metal bond grinding wheel having a porosity of 40% and an abrasive grain concentration of 100. The porosity of the produced grinding wheel was measured in accordance with "JIS R1634 (1998) Method for measuring sintered density and open porosity of fine ceramics."
The porous metal bonded grinding wheel was formed into a circular ring shape, and in the apparatus shown schematically in Figure 2, a CFRP material was ground while air was flowing at an input pressure of 0.5 MPa, and the normal grinding resistance (N) relative to the grinding distance (mm) was measured.
The results are shown in Figure 5.

In Example 2, a compact was formed by mixing bronze (Cu-10Sn), NaCl, and diamond abrasive grains in the same compounding ratio as in Example 1. The metal particle diameter of the bronze was in the range of 75 μm to 125 μm, and the particle diameter of the spacer was the same as the metal particle diameter.
Thereafter, the molded body was subjected to a preliminary sintering temperature of 650°C and a main sintering temperature of 750°C to produce a porous metal bond grinding wheel with a porosity of 40% and an abrasive grain concentration of 100. In the apparatus shown schematically in Figure 2, without air flowing inside, a CFRP material was ground and the normal grinding resistance (N) versus grinding distance (mm) was measured.
The results are shown in Figure 5.

In Example 3, a compact was formed by mixing 42.6 vol% bronze (Cu-10Sn), 40 vol% NaCl as a spacer, and 17.4 vol% diamond abrasive grains. The metal particle diameter of the bronze was in the range of 75 μm to 125 μm, and the particle diameter of the spacer was the same as the metal particle diameter.
Thereafter, the molded body was subjected to a preliminary sintering temperature of 650°C and a main sintering temperature of 750°C to produce a porous metal bond grinding wheel with a porosity of 40% and an abrasive grain concentration of 50. In the apparatus shown schematically in Figure 2, a CFRP material was ground while air was flowing at an input pressure of 0.5 MPa, and the normal grinding resistance (N) versus grinding distance (mm) was measured.
The results are shown in Figure 5.

In Example 4, a compact was formed by mixing 22.6 vol% bronze (Cu-10Sn), 60 vol% NaCl as a spacer, and 17.4 vol% diamond abrasive grains. The metal particle diameter of the bronze was in the range of 125 μm to 250 μm, and the particle diameter of the spacer was the same as the metal particle diameter.
Thereafter, the molded body was subjected to a preliminary sintering temperature of 650°C and a main sintering temperature of 750°C to produce a porous metal bond grinding wheel with a porosity of 60% and an abrasive grain concentration of 50. In the apparatus shown schematically in Figure 2, a CFRP material was ground while air was flowing at an input pressure of 0.5 MPa, and the normal grinding resistance (N) versus grinding distance (mm) was measured.
The results are shown in Figure 5.

In Example 5, a compact was formed by mixing bronze (Cu-10Sn), NaCl, and diamond abrasive grains in the same compounding ratio as in Example 4. The metal particle diameter of the bronze was in the range of 125 μm to 250 μm, and the particle diameter of the spacer was the same as the metal particle diameter.
Thereafter, the molded body was subjected to a preliminary sintering temperature of 650°C and a main sintering temperature of 820°C to produce a porous metal bond grinding wheel with a porosity of 60% and an abrasive grain concentration of 50. In the apparatus shown schematically in Figure 2, a CFRP material was ground while air was flowing at an input pressure of 0.5 MPa, and the normal grinding resistance (N) versus grinding distance (mm) was measured.
The results are shown in Figure 5.

The horizontal axis of the graph in FIG. 5 represents the grinding distance (mm), and the vertical axis represents the normal grinding force (N).
As shown in Figure 5, in Example 1, the normal grinding resistance was kept low up to a grinding distance of 400 mm, demonstrating the effect of air supply. However, in Example 2, because air was not supplied, clogging occurred from the beginning of processing, and the normal grinding resistance increased.

In addition, in Example 3, the abrasive grain concentration was 50, so the vertical grinding resistance was kept low regardless of the grinding distance.
Furthermore, in Examples 4 and 5, the porosity was as large as 60%, so that the vertical grinding resistance was kept lower regardless of the grinding distance, and clogging could also be suppressed.
From the above, it can be seen that the grinding wheel using the present invention has a lifespan several times longer than that of a conventional grinding wheel without pores.

(Experiment 2)
In Experiment 2, a porous metal bond grinding wheel with a porosity of 60% was produced, and after CFRP grinding was carried out using the configuration shown in Figure 2, the surface condition was observed using an electron microscope.
Specifically, the porous metal bonded grinding wheel shown in Figure 6(a) was made by mixing 22.6 vol% bronze (Cu-10Sn), 60 vol% NaCl as a spacer, and 17.4 vol% diamond abrasive grains to form a compact. The compact was then pre-sintered at a temperature of 650°C, but no main sintering was performed. A porous metal bonded grinding wheel with a porosity of 60% and a concentration of abrasive grains of 50 was produced.
On the other hand, the porous metal bonded grinding wheel shown in Figure 6(b) was made by mixing 22.6 vol% bronze (Cu-10Sn), 60 vol% NaCl as a spacer, and 17.4 vol% diamond abrasive grains to form a compact. The compact was then pre-sintered at 650°C and then sintered at 750°C to produce a porous metal bonded grinding wheel with a porosity of 60% and a grain concentration of 50.

Then, CFRP grinding was performed using each grinding wheel. The grinding conditions for processing were as follows: a CFRP laminated plate measuring 50 mm in length and width and 5 mm in thickness was used as the workpiece; the grinding wheel peripheral speed was 188 m/min, the feed rate was 200 mm/min, and the cutting depth was 0.5 mm. The number of processing passes was 20.
The results are shown in Figure 6. Figure 6(a) shows a micrograph of the case where the re-sintering treatment after desalination was not performed, and Figure 6(b) shows a micrograph of the case where the re-sintering treatment after desalination was performed.

As shown in the photographs in Figure 6, none of the grinding wheels were found to be clogged. Also, in Figure 6(a), the abrasive grains and bond material were found to have fallen off, as shown in the area surrounded by the dotted line. On the other hand, in Figure 6(b), no falling off was observed, confirming the improvement in strength.
In grinding, it may be necessary to lower the strength of the bond material to encourage the cutting edge to grow naturally, thereby improving sharpness and minimizing damage to the workpiece.The method for manufacturing a grinding wheel according to the present invention makes it possible to adjust the strength of the bond material, making it possible to manufacture grinding wheels for a variety of uses.

1 Porous metal bond grinding wheel 2 Porous body 3 Abrasive grains 4 Through holes

Claims (4)

A porous metal bonded grinding wheel is provided, which comprises a porous metal body serving as a bond material for abrasive grains, the porous metal body being formed by sintering a plurality of spherical metal particles together and having through holes through which a fluid flows, the through holes being formed by melting a plurality of spacers made of a water-soluble inorganic salt or organic salt, and a plurality of abrasive grains disposed in the porous metal body,
The metal porous body is made of spherical metal particles of Cu, a metal element having a melting point higher than that of Cu, or a metal of an alloy element based on Cu,
In the metal porous body, the spherical metal particles are connected to each other at their contact points by sintering, and gaps exist as pores between adjacent spherical metal particles,
Furthermore, the metal porous body does not have any independent pores through which a fluid does not flow, and the pores are continuously connected to connect the inner and outer peripheral surfaces of the metal porous body, forming a plurality of long communicating pores each having a width of at most 1 mm;
The porosity of the metal porous body is 40% to 60%;
A porous metal bonded grinding wheel, wherein the communicating holes function as passages for a gas such as oxygen or nitrogen, or a liquid such as cutting oil. A method for manufacturing the porous metal bond grinding wheel according to claim 1, comprising : a porous metal body as a bond material for abrasive grains, the porous metal body being formed by sintering a plurality of spherical metal particles together and having through holes through which a fluid flows , the through holes being formed by melting a plurality of spacers made of a water-soluble inorganic salt or organic salt; and a plurality of abrasive grains disposed in the porous metal body,
a step of mixing a plurality of abrasive grains, spacers made of a water-soluble inorganic salt or organic salt and having a particle size in the range of 75 μm to 300 μm, and a plurality of spherical metal particles made of Cu or a metal element having a melting point higher than Cu, or a metal of an alloy element based on Cu, and having a particle size in the range of 75 μm to 300 μm, and molding the mixture;
sintering the mixture to form a first sintered body;
removing the spacer from the first sintered body by melting it;
Equipped with
In the step of molding the mixture,
A method for manufacturing a porous metal bonded grinding wheel, characterized in that the amount of spacer added is 40 to 60 vol. %. A method for manufacturing a porous metal bonded grinding wheel as described in claim 2, wherein the spherical metal particles are formed to the same particle size as the spacers. After the step of removing the spacer from the first sintered body,
The method for manufacturing a porous metal bonded grinding wheel according to claim 2, further comprising a step of heat-treating the first sintered body again to form a second sintered body having improved strength than the first sintered body.