JP2958349B2 - Porous grinding wheel and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The porous grinding wheel according to the present invention is used for stone, concrete,
It is used for cutting and grinding in civil engineering construction related fields such as asphalt, electronic related fields such as silicon and ferrite, or machines and metal materials related fields.

[Related Art] In recent years, super-abrasive grinding wheels have been used for processing the above-described various materials, but in many cases, non-porous grinding wheels are used for both metal bonds and resin bonds.

[Problems to be Solved by the Invention] Metal bond or resin bond superabrasive grinding wheels are manufactured by pressing and firing a powder material, so that it is generally difficult to form pores which are one of the components of the grinding wheel. Many of the superabrasive grinding wheels widely used in the market are non-porous grinding wheels.

The problems of this non-porous grinding wheel are that it is difficult to remove chips due to the absence of pores, that the coolant does not easily penetrate into the processed part, and that the processed material and the binder are easily rubbed. As a result, grinding efficiency due to temperature rise at the processing point, grinding resistance increase due to grinding wheel clogging, decrease in sharpness and life, generation of scratches and cracks, etc., make it impossible to increase processing efficiency, and That led to a problem. In addition, there were many cases where clogging occurred during processing and the work had to be interrupted and dressed.

[Means for Solving the Problems] As a method for solving the above-mentioned problems, there has been proposed a method of implanting pore-forming projections in a molding die and forming pores with the projections. (Publication No. 60-53467, PR No. 62-92158) However, in these methods, a large number of fine projections must be planted in the mold, and pressurization due to the fine projections is required. Easy to break during firing. Further, in order to change the porosity, it is necessary to prepare various molds having different sizes and quantities of protrusions, and there is a problem in manufacturing technology and manufacturing cost. The proposal also states that "wood chips in the binder,
It may be possible to disperse and mix fine coals and the like, and to burn out at the time of firing to form desired pores. "However, in the manufacturing method of firing under pressure, the cavities formed by firing almost disappear due to the molding pressure. In many cases, they do not serve as pores.

The present invention provides a novel measure that eliminates the above-mentioned disadvantages. That is, heat-resistant fine powder is converted into granules and added to a kind of the grindstone composition. Pores are not formed in the grinding wheel manufacturing process of pressurization and firing, but in the truing and dressing of the grinding wheel finishing process, the granules consisting of heat-resistant fine particles are removed from the surface of the grinding wheel components sequentially from the surface when using, and the pores are removed. The object of the present invention is to provide a porous grinding wheel having a desired size of pores or porosity by selecting the size and amount of granules.

[Operation] When a metal bond or resin bond grinding wheel is manufactured by pressurizing and firing, it is difficult to manufacture a porous grinding wheel by generating or burning gas. This is because even if pores are created temporarily by gas or combustion, the pores disappear due to the pressure during pressurization and firing. In this proposal, a heat-resistant granule was used, and a non-porous grinding wheel was used in the pressurization and firing process. However, pores were naturally formed during use, and as a result, a manufacturing means that effectively worked as a porous grinding wheel was adopted. The manufacturing process and a manufacturing example will be described.

a) Production of granules that play the role of pores As granule raw materials, Al ₂ O ₃ , MgO,
Fine powders such as ZrO ₂ , SeO ₂ , SiC, and Si ₃ N ₄ are used. An example in which SeO ₂ fine powder is used will be described. The SeO ₂ fine powder was mixed with liquid paraffin to obtain granules having a particle size of 0.3 mm to 0.5 mm using a commercially available granulation apparatus by a known granulation method. The particle size of the granules varies depending on the size of the superabrasives used, but it is preferably approximately the same as that of the superabrasives to about 1/2.

b) Manufacture of a grinding wheel A metal bond grinding wheel will be described as an example. Cobalt powder was used as the binder, 40/50 mesh synthetic diamond was used as the superabrasive, and 800 mesh alumina powder was used as the filler. The above granules were added and mixed. The volume mixing ratio in this example is 65% for binder, 2.5% for superabrasives, 2.5% for filler,
And 30% granules. These materials were sufficiently stirred and mixed using an ordinary mixer, filled in a mold, and formed into a grindstone chip by a heat molding press. The mixing ratio varies depending on the purpose of use or the type of workpiece, but when sharpness is emphasized, the ratio of granules is increased, and when the grinding ratio (life) is increased, the ratio of granules is decreased. The molding conditions were a temperature of about 900 ° C., a pressure of about 300 kgf / cm ² , and a time of about 40 minutes in an inert gas atmosphere. After the molding, the chip was gradually cooled, and the chip was taken out from the mold and brazed to a base metal to form a grindstone. The chip may be formed by cold molding or sintering in a furnace instead of the hot molding method, but the chip strength is slightly reduced. FIG. 1 shows an example of a schematic view of the manufactured whetstone, and FIG. 2 shows an example of a cross-sectional view of the chip. Bonding material in the chip,
The abrasive grains, fillers, and granules are uniformly dispersed, and no pores have been formed yet. The void space is still dispersed in the form of granules, and there is no true space in the chip. Therefore, the compressive strength is higher than that of the chip having space, and the elastic deformation and plastic deformation due to the pressure during processing are small.

FIG. 3 shows pores formed on the tip surface when the tip is dressed or used. In the granules dispersed in the chips, liquid paraffin, which holds the fine powder in a granular state, is decomposed and disappeared in the heating step, and is simply an aggregate of fine powder. Therefore, it is easily broken during dressing or use, and easily falls off. Further, the dropped holes become complete pores due to the cleaning action by the grinding fluid.

When a fine powder having a lubricating property such as SeO _{2 is} used as the fine powder for the granules as in the present example, the fine particles for the granules are selected depending on the processed product and the purpose because the dropped fine particles also act as a lubricant.

The formed pores can prevent clogging of chips and friction between the workpiece and the binder. Furthermore, since there is a pore space as shown in the figure, the coolant (grinding fluid) easily penetrates into the contact surface between the grindstone and the workpiece (grinding action surface), the temperature rise of the grinding point can be prevented, and the temperature rise of the machined parts is small. High quality parts without grinding burns and cracks can be obtained. In addition, clogging is difficult and grinding resistance is small, so that the removal efficiency can be increased.

[Example] A surface grinding test of granite was performed on a porous grinding wheel manufactured by the method described in the previous section and a non-porous grinding wheel manufactured by a conventional method, and the removal efficiency was compared.

a) Grinding test conditions Workpiece: Granite whetstone: 8-inch segmented porous and non-porous Segment dimensions: 45 mm x 20 mm Number of segments: 12 Wheel rotation speed: 450 rpm Wheel feed speed: 3.5 m / min Grinding stone pressing force: 60 kgf and 120 kgf Grinding time: 5 minutes Grinding fluid supply: 12 L / min b) Test result (removal amount) The grinding sound during the test of the porous stone was low and showed good sharpness, and the removal amount was about 1.3 times that of the conventional non-porous stone.

[Effects of the Invention] As described above, the advantages of the open-hole grindstone are as follows: a) Since dressing during use is unnecessary, the grindstone is not consumed by the dressing, and waste time due to the dressing can be saved.

b) The removal efficiency is high because the sharpness is good and it is hard to be clogged.

c) The coolant easily penetrates into the machined part, the grinding temperature is low, and the quality of the machined part is improved.

As described above, the present invention provides a manufacturing method capable of accurately controlling the size and distribution of pores that bring about this effect,
It is possible to combine the effects of lubricant.

[Brief description of the drawings]

Fig. 1 Side sectional view of a grinding wheel according to one embodiment 1 ... Base metal, 2 ... Grindstone tip Fig. 2 Cross section of pressed and fired chip 3 ... Abrasive grains (diamond), 4 ... Filler Fig. 3 Cross-sectional view of chip showing pores formed during use 6 ... Pores formed by falling off granules

Continuation of the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) B24D 3/02 310 B24D 3/00 300 B24D 3/10 B24D 3/32

Claims (3)

(57) [Claims] 1. A grinding wheel obtained by mixing, pressing, and firing superabrasive grains, a binder, and a filler, and adding a binder such as liquid paraffin to a heat-resistant fine powder to form a granule. , Pressurized and fired porous grinding wheel. 2. A method for producing a grinding wheel by mixing, pressing, and firing a superabrasive, a binder, and a filler, wherein the binder is formed by adding a binder such as liquid paraffin to heat-resistant fine powder. Is further added, mixed, pressurized and fired to produce a porous grinding wheel. 3. The method for producing a porous grinding wheel according to claim 2, wherein a lubricating powder is used as the heat-resistant fine powder.