JP2009154249A - Grinding wheel for grain polishing and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the occurrence rate of crushed grains as much as possible, improve grinding operation, and prolong the life of a grinding wheel even when polishing parboiled rice. <P>SOLUTION: The grinding wheel 1 for grain polishing is formed of composite abrasive grains comprising first abrasive grains 4 and second abrasive grains 5 having a grain size equal to or smaller than those of the first abrasive grains 4 and of a binder 6, and has many micropores 7 therein. The first abrasive grains 4 have weak joining strength between the binder 6 and themselves, and pores 9 for clogging prevention are formed on the surface part 10 of the grinding wheel by releasing the first abrasive grains 4. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a grinding grindstone for cereals that can be used for molting of polished rice, barley, or beans, and a method for producing the same.

Conventional grinding grindstones use silicon carbide (SiC) abrasive grains as abrasive grains having cutting edges, and the number of grain sizes is # 30, # 36, # 46, etc. for general polished rice (rice rice) Use a medium eye, and if it is for sake brewed rice, the grain size number is fine like # 60, # 70, # 80, and if it is parboiled rice, the grain size number is # 16, # 20, # 24 The coarse grain is used. Here, the number of particle sizes is the number of particles arranged between 25.4 mm.

Also known is a porous grinding wheel for milling rice for the purpose of improving grindability of the grinding wheel (see Patent Document 1). This is a method for producing a porous grindstone in which abrasive grains, a binder, a temporary binder and a pore agent are mixed and stirred, then molded into an appropriate shape, dried, and then fired. It is characterized by using rice husk powder arbitrarily selected in size as an agent. As a result, the burning of rice husk powder during firing increases the SiO ₂ concentration at the interface between the pores and the binder, resulting in a porous grindstone with a high bond bridge effect, and the grinding layer is embedded in the pores, resulting in reduced grindability. It is possible to prevent this, and there is an action and effect that the abrasive grains are not easily detached and the surface portion is not roughened by weakening the degree of bonding.

However, when milling parboiled rice, using a grindstone with a grain size number of # 16 will cause problems such as a decrease in yield due to the generation of crushed grains, a decrease in effective grinding action, and a shortened life of the grindstone. On the other hand, when the particle size number # 24 is used, there is a problem that crushing becomes difficult due to clogging. In order to eliminate the clogging, it is conceivable to enlarge the pores in the structure. However, a new problem arises in that the bonding strength between the abrasive grains becomes weak, the strength is inferior, and the wear resistance is also inferior. Moreover, even if it is a porous grindstone which heightened the bond bridge effect of patent document 1, when the perboiled rice is polished, the same clogging problem as described above occurs.
JP-A-2-30470

In view of the above-mentioned problems, the present invention is capable of reducing the rate of generation of crushed grains as much as possible, improving the grinding action, and further extending the service life of the grindstone, even when milling perboiled rice. It is a technical problem to provide a grinding wheel for manufacturing and a manufacturing method thereof.

In order to solve the above-mentioned problem, the invention according to claim 1 is formed from a composite abrasive comprising a first abrasive grain and a second abrasive grain having a particle size equal to or less than that of the first abrasive grain, and a binder. Has a large number of micropores, and the first abrasive grains are formed with low bonding strength with the binder, and the first abrasive grains are separated to form pores for preventing clogging on the surface of the grindstone. Provided is a grinding wheel for polished grains.

Further, in the invention according to claim 2, the composite abrasive grains constituting the grinding grindstone for grain use SiC grains having a grain size of # 24 as the first abrasive grains, and Al ₂ having a grain size of # 24 to # 120. O ₃ abrasive grains are used as the second abrasive grains.

Furthermore, the invention according to claim 3 according to the method for producing a grinding wheel for fine grains is a composite abrasive in which second abrasive grains equal to or smaller than the first abrasive grains are mixed with the first abrasive grains at a predetermined ratio. The composite abrasive grain preparation step, the composite abrasive grain, the binder, and the temporary binder are put into a predetermined mixing container and stirred and mixed by a mixer, and obtained by the stirring and mixing step. A forming step of forming the fluid raw material in a predetermined mold, a semi-processing step of drying the finished product in the forming step to finish it in a semi-processed state, and a molded product in a semi-processed state. A blasting process equipped with a firing process for firing for a predetermined time in a firing furnace and a shot blasting process in which a projection material is blown against the surface of the grindstone after firing with high-pressure air to collide to form pores for preventing clogging. A method for producing a grinding wheel, wherein the stirring and mixing step The composite abrasive grains, the binder, and the temporary binder are stirred and mixed without using an agent, and the firing step maintains the oxygen concentration in the firing furnace at 5 to 10%, and at the time of firing. Baking is performed while maintaining the maximum temperature at 1200 ° C to 1350 ° C.

According to the invention of claim 1, it is composed of composite abrasive grains composed of first abrasive grains and second abrasive grains that are equal to or smaller than the grain size of the first abrasive grains, and is bonded to each other by a binder melted during firing, The binder is configured with relatively small pores. The first abrasive grains and the binder are formed with low bonding strength, while the second abrasive grains and the binder are formed with high bonding strength, and surface treatment such as shot blasting is performed on the surface of the grindstone. As a result, the first abrasive grains are preferentially detached, and the removal results in the formation of pores for preventing clogging of the grindstone surface in a depressed state. And the 2nd abrasive grain which has many cutting edges precipitates in this pore, The aggregate abrasive grain group by this 2nd abrasive grain will be reproduced | regenerated. The second abrasive grains slightly protrude from the binder and have a smaller particle diameter than the first abrasive grains. The second abrasive grains are bonded with a strong holding force, and chipping (chips) from the surface of the grindstone is less likely to occur. There are advantages. In addition, when parboiling rice is ground, the second abrasive grain cuts the chips short to prevent friction, even when large chips such as rice husks appear, compared to one type of conventional abrasive grains, Generation of broken rice can be reduced. Furthermore, pores for preventing clogging are formed on the surface of the grindstone so as to prevent clogging due to chips. Further, the pores in the binder are relatively small, and it is possible to prevent weakening in the tissue.

Further, according to the invention of claim 2, SiC abrasive grains having a particle size of # 24 are used as the first abrasive grains as composite abrasive grains constituting the grinding wheel for fine grains, and particles having a grain size of # 24 to # 120 are used. Al ₂ O ₃ abrasive grains are used as the second abrasive grains. As a result, when milling parboiled rice, it is possible to prevent a decrease in yield due to the occurrence of crushed grains, a reduction in effective grinding action, and a shortening of the life of the grindstone.

Furthermore, according to the invention described in claim 3, the first abrasive grains and the binder are formed to have a weak joint strength by the firing step, and the pores in the binder are formed to be relatively small so that the structure is weakened. Can be prevented. Also, when the grinding wheel surface treatment is performed by the shot blasting process, the first abrasive grains are preferentially detached, and the grinding wheel surface for grinding is formed by forming the pores for preventing clogging of the grinding stone surface due to the separation. can do.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an exemplary embodiment for carrying out the invention will be described with reference to the drawings. FIG. 1 is a process diagram illustrating a process for producing a grinding wheel for milling rice according to the present invention, FIG. 2 is a relationship diagram between a firing temperature during firing and an oxygen concentration in a firing furnace, and FIG. 3 is a polished rice according to the present invention. FIG. 4 is an enlarged view showing the configuration of the grinding wheel for milling rice in FIG. 3.

As shown in FIG. 1, as the abrasive grains, mixed abrasive grains obtained by mixing # 24 silicon carbide (SiC) abrasive grains and # 24 alumina oxide (Al ₂ O ₃ ) abrasive grains in a weight ratio of 45 to 55, # 24 abrasive grains mixed with # 70 Al ₂ O ₃ abrasive grains in a weight ratio of 30 to 70, or # 24 SiC abrasive grains and # 80 Al ₂ O ₃ abrasive grains in a weight ratio of 30 pairs Composite abrasives mixed at 70 can be used.

表１は砥粒の硬度を示す表である。表１中、ヌープ硬度は単結晶の結晶面での値であって、低純度又は焼成後の研削砥粒の硬度はこの値より低いと思料されるが、Ａｌ_２Ｏ_３砥粒よりもＳｉＣ砥粒のほうが硬度の大きいことが分かる。本実施形態で使用した複合砥粒は、第１砥粒として使用するＳｉＣ砥粒がヌープ硬度２５００であり、第２砥粒として使用するＡｌ_２Ｏ_３砥粒がヌープ硬度２０００であった。

Table 1 is a table showing the hardness of the abrasive grains. In Table 1, Knoop hardness is a value on the crystal plane of a single crystal, and it is thought that the hardness of the abrasive grains after low purity or after firing is lower than this value, but SiC than the Al ₂ O ₃ abrasive grains. It can be seen that the abrasive grains have a higher hardness. In the composite abrasive used in the present embodiment, the SiC abrasive used as the first abrasive has a Knoop hardness of 2500, and the Al ₂ O ₃ abrasive used as the second abrasive has a Knoop hardness of 2000.

The composite abrasive prepared as described above is put into a predetermined mixing container together with a binder (powder of feldspar, porcelain stone, clay, etc.) and a temporary binder, and stirred and mixed by a mixer (process P1). . At this time, pores such as styrene spheres, wrapping agents, and wood chips that disappear during firing in the subsequent step are connected to each other, forming large pores in the entire grindstone, which makes the grindstone structure fragile. Do not mix. The mixing ratio of each substance is a binder 50 and a temporary binder 0.8 with respect to the composite abrasive grain 100 by weight ratio, and a mixture of about 12 water and hot water is mixed therewith.

The obtained fluid grindstone raw material is pulverized and hardened while gradually pouring into a predetermined mold placed in a molder (step P2). The finished molded body is dried for about 2 days with hot air at 80 to 90 ° C. in a drying furnace (process P3), and finished into a raw product (process P4). The green processed product is continuously fired in a firing furnace for about 70 hours (step P5). In the firing furnace, it is preferable that firing is performed according to a predetermined temperature pattern, and the atmosphere in the firing furnace is made oxidizing. FIG. 2 shows the relationship between the firing temperature during firing and the oxygen concentration in the firing furnace. According to this, the oxygen concentration in the firing furnace is maintained at 3% or more, preferably the oxygen concentration is maintained at 5-10%. In addition, by carrying out firing while maintaining the maximum temperature at 1200 ° C. to 1350 ° C., the SiC abrasive grains are altered and weakened to improve the detachability of the SiC abrasive grains. there are actions and effects to strengthen the bonding of holding the concentration at a high concentration and Al ₂ O ₃ abrasive grains and a binder.

The grindstone baked by firing is naturally dried for about one week, and the outer periphery and necessary portions are cut and polished to finish a grinding grindstone for polished rice (process P6). Further, as a final surface finish, shot blasting is performed in which the projection material is blown against the grindstone surface with high-pressure air to collide (step 7). In this shot blasting, SiC abrasive grains having improved detachability in the firing step are preferentially separated, and pores for preventing clogging are formed by the separation. Then, Al ₂ O ₃ abrasive grains having many cutting edges are formed on the grindstone surface as aggregated abrasive grain groups. As a substitute for shot blasting, a dressing tool for eliminating clogging on the grindstone surface and sharpening may be used.

FIG. 3 is a perspective view showing an embodiment of the grinding wheel for polishing rice according to the present invention, and FIG. 4 is an enlarged view showing the configuration of the grinding wheel for polishing rice of FIG. 3 and 4, a grinding grindstone 1 for rice milling includes a SiC grain 4 having a large particle size and an Al having a small particle size on the circumference of a boss 3 provided with a hole 2 for attaching to a rotating shaft of a rice milling machine. _A grinding grindstone for polished rice made of ₂ O ₃ abrasive grains 5 is formed. The SiC grain 4 having a large particle size and the Al ₂ O ₃ abrasive particle 5 having a small particle size are bonded to each other by a binder 6 melted at the time of firing. It is configured to have relatively small pores 7 formed without using the. The SiC abrasive grains 4 and the Al ₂ O ₃ abrasive grains 5 may be bonded to each other by the binder 6 with the same particle diameter.

In the grinding grindstone 1 for rice milling configured as described above, the SiC abrasive grains 4 are preferentially separated by the projection material 8 in the shot blasting process ((b) in FIG. 4). The pores 9 for preventing clogging are formed ((c) in FIG. 4). The depression-like pores 9 have a diameter of about 500 μm, and even when large chips such as rice husks are produced, clogging by the chips is prevented. Then, Al ₂ O ₃ abrasive grains having many cutting edges are deposited on the grindstone surface 10, and the aggregated abrasive grains group of the Al ₂ O ₃ abrasive grains is regenerated.

In addition, the Al ₂ O ₃ abrasive grains slightly protrude from the binder ((c) in FIG. 4), but the abrasive grains are smaller in size than the SiC abrasive grains. So that chipping (chips) from the surface of the grindstone is less likely to occur. When parboiled rice is ground, compared to conventional single abrasive grains, even when large chips such as rice husks appear, the second abrasive grains cut the chips short to prevent the friction of the binder, Generation can be reduced.

In the above embodiment shows a combination of SiC abrasive grains and Al ₂ O ₃ abrasive grains as abrasive grains is not limited thereto, CBN abrasive grains, the same even if you appropriately selected such diamond abrasive grains Such an effect is obtained. Moreover, the grindstone for cereals of this embodiment can also be used for molting of barley or beans.

It is process drawing explaining the manufacturing process of the grinding wheel for polished rice of this invention. It is a related figure of the calcination temperature at the time of baking, and the oxygen concentration in a calcination furnace. It is a perspective view which shows one Example of the grinding wheel for polished rice of this invention. It is a figure which expands and shows the structure of the grinding wheel for polished rice of FIG.

Explanation of symbols

1 rice for grinding wheel 2 holes 3 boss portion 4 SiC abrasive grains 5 _Al 2 _{O 3} abrasive grains 6 binder 7 pores 8 shot material 9 clogging preventive pores 10 grindstone surface portion

Claims (3)

The first abrasive grain is composed of a composite abrasive grain composed of a first abrasive grain and a second abrasive grain equal to or smaller than the grain size of the first abrasive grain, and a binder, and has a large number of micropores inside. Is formed with weak bonding strength with the binder, and the first abrasive grains are detached to form clogging prevention pores on the surface of the grindstone. The composite abrasive grains using SiC abrasive grain # 24 as a first abrasive, grain size # 24 to # using _Al 2 _{O 3} abrasive grains of 120 claim 1 grain milling according as the second abrasive grains For grinding wheels. A composite abrasive grain preparation step of preparing a composite abrasive grain prepared by mixing a first abrasive grain with a second abrasive grain equal to or less than the first abrasive grain in a predetermined ratio;
Stirring and mixing step of charging the composite abrasive grains, the binder and the temporary binder into a predetermined mixing container and stirring and mixing with a mixer;
A molding step of molding the fluid raw material obtained by the stirring and mixing step in a predetermined molding die;
A semi-processing step of drying the finished product in the forming step to finish it in a semi-processed state;
A firing step of firing the molded body in a semi-processed state for a predetermined time in a firing furnace;
A shot blasting process in which a blasting material is blown and collided with a high-pressure air on the surface of the grindstone after firing, and a method for producing a grinding grindstone for a cereal with a shot blasting process for forming pores for preventing clogging,
In the stirring and mixing step, the composite abrasive grains, the binder and the temporary binder are stirred and mixed without using a pore agent, and the baking step maintains the oxygen concentration in the baking furnace at 5 to 10%. And a method for producing a grinding grindstone for cereals, wherein the firing is carried out while maintaining the maximum temperature during firing at 1200 ° C to 1350 ° C.

Images