JP2007136559A - Vitrified grinding stone, and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a vitrified grinding stone by a pouring operation without using an inorganic adhesive, which may cause a problem of discoloration. <P>SOLUTION: The method for manufacturing the vitrified grinding stone having pores therein formed by fixing abrasive grains with an inorganic bonding material, comprises a step of uniformly mixing the abrasive grains, the inorganic bonding material, water, and starch powder, a step of pouring the fluid mixture obtained by the mixing process into a specified mould, a step of primarily curing the fluid mixture at a temperature of 50 to 100°C, and a step of baking the primarily cured substance, which has been obtained by the primary curing process, at a temperature of 700 to 900°C. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a vitrified grindstone. More particularly, the present invention relates to a method for producing a multi-porous vitrified grinding stone by pouring without using an inorganic adhesive with the problem of discoloration.

When the main types of grinding and polishing wheels are distinguished by the binder used, vitrified wheels, resinoid wheels, metal wheels, and electrodeposition wheels can be mentioned.
Among these, vitrified grindstones are mainly used because of their good sharpness, high durability, and good dressability.

  This vitrified grinding stone is made by mixing abrasive grains and an inorganic binder together with a primary binder, filling the resulting mixture into a mold, press-molding, passing through a drying step, and firing at a high temperature of 600 to 1300 ° C. Generally, it is manufactured by.

  On the other hand, a method for producing a vitrified grindstone by casting instead of press molding has been developed (see Patent Document 1). In this method, an inorganic adhesive is added to abrasive grains, an inorganic binder, and a foaming agent, mixed with water to form a fluid mixture, poured into a predetermined mold, and heated at room temperature to 300 ° C. In this method, the pores are formed in the dried cured body by the action of the foaming agent, and then are firstly cured by the action of the inorganic adhesive, and then fired at 600 to 1000 ° C.

However, according to the above method, when CBN or silicon carbide is used as the abrasive grains, the grindstone discolors black in the grindstone after firing, and in particular, the inside of the grindstone discolors. This is because, in the case of CBN, a decomposition reaction occurs due to the reaction with the inorganic adhesive. In the case of silicon carbide, the silicon carbide and the inorganic adhesive cause a chemical reaction during firing, so that the silicon carbide (SiC) decomposes and the carbon element is decomposed. This is thought to be due to precipitation. A grindstone in which such an action has occurred cannot be used because its mechanical strength decreases and there is a possibility of cracking or breaking during use.
Japanese Patent Application No. 2004-112028

  Therefore, this invention makes it a subject to provide the method which can manufacture a vitrified grindstone by pouring, without using the inorganic adhesive accompanying the problem of discoloration.

  The method for producing a vitrified grindstone of the present invention is a method for producing a vitrified grindstone in which abrasive grains are fixed by an inorganic binder and have pores in the structure thereof, comprising abrasive grains, an inorganic binder, water, and starch powder. Obtained by the step of uniformly mixing, the step of pouring the fluid mixture obtained in the step into a predetermined mold, the step of primary curing the fluid mixture at a temperature of 50 to 100 ° C., and the curing step. And a step of firing the cured body at a temperature of 700 to 900 ° C.

  In the manufacturing method of the vitrified grindstone of the present invention, an inorganic filler, a pore forming agent of an inorganic hollow body or an organic powder, and a liquid or powder foaming agent can be further added in the mixing step.

In one aspect of the method for producing a vitrified grindstone of the present invention, it is preferable that the abrasive grains contain at least CBN.
Moreover, in another aspect of the manufacturing method of the vitrified grindstone of this invention, it is preferable that an abrasive grain contains a silicon carbide type abrasive grain at least.

  According to the present invention, there is provided a method capable of producing a vitrified grindstone by pouring without using an inorganic adhesive with a problem of discoloration. According to the present invention, it is possible to stably manufacture a multi-porous vitrified grinding stone using CBN or silicon carbide as abrasive grains by pouring.

Hereinafter, a suitable embodiment of a manufacturing method of a vitrified whetstone of the present invention is described.
The method for producing a vitrified grindstone of the present invention is a method for producing a vitrified grindstone in which abrasive grains are fixed by an inorganic binder and have pores in the structure thereof, comprising abrasive grains, an inorganic binder, water, and starch powder. A step of uniformly mixing, a step of pouring the fluid mixture obtained in the step into a predetermined mold, a step of curing the fluid mixture at a temperature of 50 to 100 ° C., and a curing obtained by the curing step And a step of firing the body at a temperature of 700 to 900 ° C.

In the present invention, first, abrasive grains, an inorganic binder, water, and starch powder are uniformly mixed.
The present invention is characterized in that starch powder is used as a primary curing agent for the material constituting the grindstone. Starch is a high-molecular substance connected in the form of chains or tufts of hundreds to thousands or tens of thousands of glucose as a unit, and is composed of two kinds of components, amylose and amylopectin. Starch extracted from seeds and rhizomes is a fine white powder, but depending on the type, the size and shape of the particles are different, and the composition ratios of amylose and amylopectin are also different. Starch does not dissolve even when water is added, but only precipitates, but when heated, the particles swell several tens of times including water and become sticky and paste-like. If this paste solution is left as it is, it gradually becomes cloudy and gels. The manufacturing method of the vitrified grindstone of the present invention utilizes such a gelling action of starch, and primary hardening of the material constituting the grindstone by such action. In the conventional method for producing a vitrified grindstone, primary curing is performed with an inorganic adhesive, but the present invention enables primary curing without using an inorganic adhesive.

  Examples of starch powder that can be used in the present invention include potato starch, corn starch, and tapioca starch. Various other starches can also be used as long as they do not depart from the spirit of the present invention in which the material constituting the grindstone is primarily hardened by the gelling action.

The usage-amount of starch powder shall be 0.1-1.0 weight% with respect to the fluid mixture whole quantity.
As abrasive grains that can be used in the present invention, fused alumina abrasive grains, sol-gel alumina abrasive grains, silicon carbide abrasive grains, alumina-zirconia abrasive grains, cerium oxide abrasive grains, silica abrasive grains, and And superabrasive grains such as CBN or diamond. One or more kinds of abrasive grains can be selected and used from those listed above according to grinding conditions and the like. The abrasive preferably contains at least CBN or silicon carbide-based abrasive.

The grain size of the abrasive grains can be widely used from 1 mm to submicron.
Examples of the inorganic binder that can be used in the present invention include inorganic powders such as glass frit, clay, and feldspar. One or more of these inorganic binders can be appropriately selected and used according to grinding conditions and the like.

In this invention, the usage-amount of water shall be 30 to 45 weight% with respect to the fluid mixture whole quantity.
Moreover, in this invention, you may add an inorganic filler as needed. The inorganic filler can also act as a viscosity adjusting agent in a fluid mixture in which materials constituting the grindstone are mixed in water. Examples of the inorganic filler that can be used in the present invention include silica fine powder, cryolite, mullite fine powder, and the like. The inorganic filler is preferably silica fine powder. The inorganic filler can be appropriately selected according to grinding conditions and the like. Also, other materials can be used without departing from the spirit of the invention.

  A predetermined amount of the material constituting the grindstone as described above is weighed, put into a mixer, and uniformly mixed by the mixer. About mixing time etc., it can determine suitably considering conditions, such as a mixer to be used, mixing capacity, and a mixed material.

In the present invention, the fluid mixture obtained by the above process is then poured into a predetermined mold.
In the present invention, the fluid mixture is then cured at a temperature of 50 to 100 ° C. By maintaining the temperature at 50 to 100 ° C., the fluid mixture can be primarily cured and moisture can be dried by the curing action of starch. The curing temperature is preferably 60 to 80 ° C. Primary curing and drying may be performed for 36 to 60 hours. The time may be further extended depending on the size and volume of the grindstone to be manufactured.

In the present invention, the cured body obtained by the curing step is then fired at a temperature of 700 to 900 ° C.
Vitrified wheels produce pores after firing, but if a more multi-porous stone is desired, pores can be formed in the binder structure of the stone by using a pore former. What is necessary is just to add a pore formation agent in a mixing process.

  As the pore forming agent, an organic or inorganic pore forming agent can be used. The organic pore-forming agent is, for example, an organic powder, which decomposes and disappears upon firing, and the occupied portion becomes a cavity to form pores. The inorganic pore forming agent is, for example, an inorganic hollow body that remains in the grindstone even after firing, but the hollow portion forms pores.

  A foaming agent may be used to form pores. What is necessary is just to add a foaming agent in a mixing process. The foaming agent exhibits a foaming action by heating in the primary curing step, and the foaming action is completed before the fluid mixture is completely cured. As the foaming agent, a liquid or powder foaming agent can be used.

  Examples of the liquid blowing agent include dialkylazodi represented by the general formula ROOC-N = N-COOR (wherein each R represents 1 to 4 lower alkyl groups which may be linear or branched). Carboxylates are mentioned. A preferred dialkyl azodicarboxylate is diisopropyl azodicarboxylate. Other dialkyl azodicarboxylates that can be used in the present invention include dimethyl azodicarboxylate, diethyl azodicarboxylate, dipropyl azodicarboxylate, ditert-butyl azodicarboxylate, and those Of the mixture.

  Examples of the powder blowing agent include azo compounds such as azodicarbonamide and azobisisobutyronitrile, p, p′-oxybisbenzenesulfonyl hydrazide, 4,4′-oxybisbenzenesulfonyl hydrazide, dinitrosopentanemethylenetetramine. And hydrazide compounds such as benzenesulfonyl hydrazide and p-toluenesulfonyl hydrazide.

  Substances other than those exemplified above can be used as the liquid and powder foams without departing from the spirit of the present invention. A foaming agent can use 1 type, or 2 or more types of mixtures, and may use it together with a pore formation agent.

  The composition of the vitrified grindstone manufactured according to the manufacturing method of the present invention described above is in the following range. That is, the abrasive volume ratio is 5 to 55 volume%, the pore volume ratio is 5 to 85 volume%, and the binder ratio is [100− (abrasive volume%) − (pores]. Volume%)] (%). The specific gravity of the vitrified grinding wheel manufactured according to the manufacturing method of the present invention is 0.7 to 2.0.

  Hereinafter, examples of the present invention will be described, but these illustrate the feasibility and usefulness of the present invention, and do not limit the configuration of the present invention.

According to the production method of the present invention, a vitrified grindstone was produced using abrasive grains having different particle sizes, and a grinding test was performed using the obtained grindstone.
(Raw material mixture ratio)
Example 1
Abrasive grain: GC # 1000 1500g
Binder: Glass frit 240g
Filler: Silica fine powder (Aerosil) 10g
Foaming agent: Liquid foaming agent (diisopropyl azodicarboxylate) 7g
Starch flour: Tapioca starch 9g
700g of water
Example 2
Abrasive: GC # 3000 1400g
Binder: Glass frit 240g
Filler: Silica fine powder (Aerosil) 13g
Foaming agent: Liquid foaming agent (diisopropyl azodicarboxylate) 7g
Starch flour: Tapioca starch 9g
750g of water
Example 3
Abrasive grain: GC # 6000 1400g
Binder: Glass frit 240g
Filler: Silica fine powder (Aerosil) 3g
Foaming agent: Liquid foaming agent (diisopropyl azodicarboxylate) 7g
Starch flour: Tapioca starch 9g
750g of water
(Whetstone manufacturing procedure)
A predetermined amount of abrasive grains, binder, filler, starch powder, foaming agent, and water were weighed, put into a mixer, and mixed until uniform to obtain a fluid mixture. The fluid mixture was poured into a mold having an outer diameter of 210 mm and a shaft hole of 50 mm until the thickness became 18 mm, and heated at 60 ° C. for 48 hours. The obtained cured product was taken out of the mold and fired at a maximum holding temperature of 900 ° C. for 4 hours. After firing, finishing was performed to obtain a 1A grindstone having an outer circumference of 205 mm, a thickness of 15 mm, and a shaft hole diameter of 50.8 mm.
(Whetstone composition)
The grindstone composition after firing in each example is shown below.
Example 1
Abrasive volume fraction = 26.6, binder volume fraction = 11.0, pore volume fraction = 62.4
Example 2
Abrasive volume fraction = 25.6, binder volume fraction = 10.6, pore volume fraction = 63.8
Example 3
Abrasive grain volume ratio = 25.1, binder volume ratio = 10.4, pore volume ratio = 64.5
(Grinding test conditions)
1. Material: Copper (Vickers hardness Hv = 101.2)
Acrylic (Vickers hardness Hv = 22.9)
Dimensions: 50x30mm
2. Grinding machine Type: Okamoto machine tool horizontal axis surface grinding machine
Model: CNC-52B (7.5kw)
3. Grinding fluid Name: Crecut NS201 (Soluble type)
Dilution ratio: 50-fold dilution 4. Dress condition Dresser: Single stone diamond dresser
Wheel peripheral speed: 33.3 m / s
Dress cutting: 0.001mm / pass x 4pass
Dress lead: 0.01mm / rev
5. Grinding conditions Grinding method: Wet traverse grinding
Wheel peripheral speed: 33.3 m / s
Cross feed: 2mm / pass (one reciprocation)
Spark out: 1mm / pass (1 round trip)
Stock removal: Copper; 0.003mm
Acrylic; 0.010mm
6). Evaluation item Finished surface roughness Rmax μm
7). Surface roughness (Rmax μm) of the ground surface of the work material before grinding test
The surface roughness (Rmax μm) of the ground surface of the work material before the grinding test was adjusted as shown in Table 1.

(Grinding test result)
Table 2 shows the surface roughness (Rmax μm) of the work material after the grinding test performed according to the above conditions.

  For copper, the surface roughness after grinding was smaller than that before grinding, and the smallest value in Example 3 was obtained depending on the grain size of the abrasive grains used. It was shown that grinding was successful.

  As for acrylic, the surface roughness after grinding was larger than that before grinding. Although the processed surface of the work material became rough by grinding, the smallest value was obtained in Example 3 depending on the grain size of the abrasive grains used. It was shown that grinding was successful.

  The grindstone manufactured according to the present invention can be used for rough grinding and finish polishing, and can be applied not only to cylindrical grinding and surface grinding, but also to final finishing such as lapping and honing, and applied to ferrous materials as work materials. It can also be applied to non-ferrous metals such as copper. Grinding and polishing of non-ferrous materials such as carbide, silicon, alumina, carbide, nitride, sapphire, quartz, various glasses, and other hard and brittle materials such as ceramic materials. Is preferably used.

Claims (6)

  A method for producing a vitrified grindstone in which abrasive grains are fixed by an inorganic binder and have pores in the structure thereof, wherein the abrasive grains, the inorganic binder, water, and starch powder are uniformly mixed, The step of pouring the obtained fluid mixture into a predetermined mold, the step of primary curing the fluid mixture at a temperature of 50 to 100 ° C., and the cured product obtained by the curing step at a temperature of 700 to 900 ° C. And the step of firing.   The method for producing a vitrified grindstone according to claim 1, wherein an inorganic filler is further added in the mixing step.   The method for producing a vitrified grindstone according to claim 1 or 2, wherein a pore forming agent of an inorganic hollow body or an organic powder is further added in the mixing step.   The method for producing a vitrified grindstone according to any one of claims 1 to 3, wherein a powder or liquid foaming agent is further added in the mixing step.   The method for producing a vitrified grindstone according to any one of claims 1 to 4, wherein the abrasive grains contain at least CBN.   The method for producing a vitrified grindstone according to any one of claims 1 to 4, wherein the abrasive grains include at least silicon carbide-based abrasive grains.