JP5963586B2 - Vitrified bond whetstone - Google Patents

Description

  The present invention relates to a vitrified bond grindstone that can reduce grinding resistance by mixing an aggregate having lower strength than abrasive grains into the grindstone.

  In a grinding wheel, in order to reduce the grinding resistance during grinding, the abrasive grain spacing was increased by mixing an aggregate having lower strength than the abrasive grains in the binder (the concentration of abrasive grains was reduced). ) Things are known. As the aggregate, for example, as described in Patent Document 1, a porous ceramic that is easily crushed and does not rub against the material to be ground is used.

JP 2009-83036 A

  However, in the thing of patent document 1, depending on the kind of binder which couple | bonds an abrasive grain and an aggregate, the melt | dissolved binder may infiltrate in a porous ceramic hole at the time of baking of a binder. . In this case, since the binder that has entered the porous ceramic holes is cured by cooling, the porous ceramics are difficult to crush during grinding, causing friction with the material to be ground, resulting in grinding burns or grinding. There is a problem that hinders the reduction of resistance.

  The present invention has been made to solve the above-mentioned conventional problems. Porous ceramic pores are blocked by a material that is more brittle than porous ceramics and does not disappear even with the firing temperature of vitrified bonds. An object of the present invention is to provide a vitrified bond grindstone that suppresses the intrusion of vitrified bonds into the porous ceramic pores and can promote the crushing of the porous ceramics during grinding.

  In order to solve the above problems, the invention according to claim 1 is characterized in that in the vitrified bond grindstone in which superabrasive grains and aggregates composed of cubic boron nitride grains or diamond grains are contained in a vitrified bond, The aggregate is composed of a porous ceramic and a substance that closes the pores of the porous ceramic, and the substance is more brittle than the porous ceramic and has physical properties that do not disappear due to the firing temperature of the vitrified bond.

  A feature of the invention according to claim 2 is that, in claim 1, the pores of the porous ceramics are closed by filling the pores of the porous ceramics with the substance.

  According to the first aspect of the present invention, since the aggregate is mixed in the vitrified bond grindstone, the interval between the superabrasive grains is increased, the grinding resistance can be reduced, and the grindstone life can be increased. . In addition, the aggregate is composed of porous ceramics that are easily crushed by contact with the material to be ground, and a material that is more brittle than the porous ceramics that close the pores of the porous ceramics. Heat generation can be suppressed, grinding burn can be prevented, and even if the vitrified bond is melted at the time of grinding wheel manufacture, the vitrified bond does not penetrate into the pores of the porous ceramics. The bond does not hinder the friability of the porous ceramics.

  According to the second aspect of the present invention, the pores of the porous ceramics are closed by filling the material into the pores of the porous ceramics. Therefore, it is easy for the vitrified bond to enter the pores of the porous ceramics. Can be prevented.

1 is an overall view of a vitrified bond grindstone showing an embodiment of the present invention. It is an enlarged view of the grindstone layer of a vitrified bond grindstone. It is an enlarged view of a grindstone layer at the time of grinding.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an overall view of a vitrified bond grindstone, and FIG. 2 is an enlarged view showing a structure near a grinding surface of the vitrified bond grindstone.

  As shown in FIG. 1, the vitrified bond grindstone 10 includes a disk-shaped core 21 and a ring-shaped grindstone layer 22 fixed to the outer periphery of the core 21 by an adhesive or sintering. The core 21 is formed of a metal material such as steel, aluminum, or titanium, an FRP (fiber reinforced plastic) material, or a ceramic (ordinary grindstone). The grindstone layer 22 is formed by fixing the grindstone layer 22 fired in a ring shape to the outer periphery of the core 21. Alternatively, a plurality of grindstone segments may be bonded to the outer periphery of the core 21 to form a ring shape.

  In the center of the core 21, a center hole 23 that fits into a centering boss that protrudes from the shaft end of the grinding wheel shaft of a grinding wheel base (not shown) is provided, and around the center hole 23 is opened at the shaft end of the grinding wheel shaft. A plurality of bolt holes 24 through which bolts to be screwed into the screw holes to be inserted are formed. By inserting bolts into the bolt holes 24 and screwing the bolts into the screw holes, the vitrified bond grindstone 10 is fixed to the grindstone shaft.

  A grindstone table (not shown) and a table are slidably guided in a direction orthogonal to each other on the grinder on which the vitrified bond grindstone 10 is mounted. A grinding wheel shaft is rotatably supported by the grinding wheel table about an axis parallel to the longitudinal direction of the workpiece (workpiece) W to be ground by the vitrified bond grinding wheel 10, and is rotated by a motor installed on the grinding wheel table. It is like that. An unillustrated headstock and tailstock are placed on the table, and the workpiece W is supported between the spindle stock and the tailstock so as to be rotatable about an axis parallel to the moving direction of the table. Yes.

  As shown in FIG. 2, the grindstone layer 22 includes superabrasive grains 12 made of, for example, CBN (cubic boron nitride) abrasive grains, aggregates 14 having weaker strength than the superabrasive grains 12, and the superabrasive grains 12. A vitrified bond 16 that joins the aggregate 14 is formed. The aggregate 14 includes a porous ceramic 14a as a base material, and is composed of a substance 14b that blocks pores of the porous ceramic 14a and prevents the intrusion of the vitrified bond 16. As the substance 14b for closing the pores of the porous ceramic 14a, a substance (for example, glassy carbon) that is more brittle than the porous ceramic 14a as a framework and does not disappear even by the firing temperature of the vitrified bond 16 is used.

Such aggregate 14 is, for example, during manufacture of the aggregate 14, a mix of a porous ceramic 14a and the substance 14b, depending on a method of firing a porous ceramic 14a, blocking the pores of the porous ceramics 14a be able to.

  The vitrified bond 16 bridges and bonds between the adjacent superabrasive grains 12, between the adjacent aggregates 14, and between the adjacent superabrasive grains 12 and the aggregates 14, and forms pores 18 between the bridging portions 20. Yes. The porosity of the porous ceramic 14a is, for example, 10% to 80%. Preferably, by setting it to 30% to 60%, it is possible to effectively generate crushing at the time of grinding and to maintain the strength for maintaining the configuration of the grindstone. The average particle diameter of the super abrasive grains 12 of CBN is, for example, 115 μm (# 170), and the average particle diameter of the porous ceramic 14a is, for example, 100 μm (# 200). In this case, the average particle diameter of the porous ceramics 14a is about 87% of the average particle diameter of the superabrasive grains 12. Thus, the intensity | strength which comprises a grindstone as an aggregate is maintained by making the particle size of the porous ceramics 14a as an aggregate into the range of 70%-150% with respect to the particle size of the superabrasive grain 12. It is considered from experience that the strength can be maintained because the porous ceramic 14 a does not weaken the bridging portion (bridge) 20 formed by the vitrified bond 16. In addition, a diamond abrasive grain can also be used instead of a CBN abrasive grain.

  Next, the manufacturing method of the vitrified bond grindstone 10 concerning embodiment is demonstrated. First, the grindstone layer 22 made of CBN abrasive grains is manufactured. In this case, the porous ceramics filled with CBN superabrasive grains 12 and a material such as glassy carbon (a material that is more brittle than the porous ceramic 14a and does not disappear even by the firing temperature of the vitrified bond 16) 14b. 14a and vitrified bond 16 are kneaded at a preset mixing ratio.

  For example, the amount of the porous ceramic 14a used is 50% by volume or less of the entire grindstone layer. In addition, when mixing, if the volume% of vitrified bond 16 with respect to CBN superabrasive grains 12 and porous ceramics 14a is too large, between adjacent porous ceramics 14a, between porous ceramics 14a and adjacent superabrasive grains 12 Thus, it is difficult to form a bridge (crosslinking portion 20) of the binder, and when the volume percentage of the porous ceramic 14a is too small with respect to the superabrasive grains 12 of CBN, the concentration of the superabrasive grains 12 increases. Therefore, the mixing ratio is determined in consideration of these factors. This mixture is filled in a not-illustrated form forming a space corresponding to the ring-shaped grindstone layer 22 and pressure-molded.

  Next, the pressure-molded ring-shaped grindstone layer 22 is extracted from the mold and baked at an appropriate firing temperature (for example, around 1,000 ° C.) of the vitrified bond 16 to form the ring-shaped grindstone layer 22. Manufactured. At this time, the vitrified bond 16 forms bridging portions (bridges) 20 and pores 18 between adjacent superabrasive grains or the like by melting at the time of heating and firing, but the vitrified bond 16 has no pores in the porous ceramic 14a. Since the substance 14b such as glassy carbon that does not disappear at the firing temperature is filled, the vitrified bond 16 does not enter the pores of the porous ceramic 14a even when the vitrified bond 16 is melted. Thereafter, the fired grindstone layer 22 is fixed to the outer periphery of the core 21 using an adhesive, and the vitrified bond grindstone 10 is completed.

  Since the vitrified bond grindstone 10 manufactured in this way has a particle size of the porous ceramic 14a as an aggregate that is close to the particle size of the superabrasive particles 12, the vitrified bond 16 has the vitrified bond 16 in the porous ceramic 14a. It becomes the core of the network to be formed, and the bridging portion 20 is effectively formed between the adjacent porous ceramics 14a or between the adjacent superabrasive grains 12 and the porous ceramics 14a. As a result, the structural strengthening of the vitrified bond grindstone 10 can be enhanced, and the abrasive wear of the superabrasive grains 12 can be prevented, thereby extending the life of the vitrified bond grindstone 10.

  Next, the operation | movement in the grinding process using the vitrified bond grindstone 10 in this Embodiment is demonstrated below. First, the vitrified bond grindstone 10 manufactured as described above is fixed to the grindstone shaft of the grindstone table, and the vitrified bond grindstone 10 is rotated by driving the grindstone shaft with a motor. Further, the work W supported between the unillustrated spindle stock and the tailstock is rotated around the axis line by rotating the spindle of the spindle stock. Then, the grindstone is advanced from a direction perpendicular to the axial direction of the workpiece W to perform grinding.

  As shown in FIG. 2, the grindstone layer 22 of the vitrified bond grindstone 10 has the aggregate 14 and the grindstone outer peripheral surface (the protruding position of the superabrasive grains 12) at substantially the same position. Is made of porous ceramics 14a that are highly brittle and brittle, so that they are crushed by contact with the surface of the workpiece W during grinding and become a cutting edge facing the workpiece W as shown in FIG. It retracts from the front end position of the superabrasive grains 12. The pores of the porous ceramic 14a are filled with a substance 14b such as glassy carbon. However, since the substance is more brittle than the ceramic 14a, the crushability of the porous ceramic 14a during grinding may be deteriorated. Absent.

  As described above, according to the present embodiment, since the aggregate 14 is mixed in the grindstone layer 22 of the vitrified bond grindstone 10, the abrasive grain spacing of the superabrasive grains can be increased, and the grinding resistance can be reduced. it can. Moreover, since the aggregate 14 is composed of the porous ceramics 14a that are easily crushed by contact with the workpiece W, the porous ceramics 14a are crushed and broken when the porous ceramics 14a touch the workpiece W during grinding. Since it retreats from the position of the abrasive grains serving as the blade, heat generation due to rubbing between the aggregate 14 and the material to be ground W can be suppressed, and grinding burn can be prevented. In addition, the crushed porous portion forms a chip pocket for holding and discarding chips, and promotes the circulation of the cooling liquid, so that the grinding efficiency can be improved.

  Moreover, since the pores of the porous ceramic 14a as the aggregate 14 are filled with a substance 14b that is more brittle than the ceramic 14a, the vitrified bond 16 melted during the production of the grindstone penetrates into the pores of the porous ceramic 14a. Therefore, the vitrified bond 16 that penetrates into the pores of the porous ceramic 14a and hardens after firing does not hinder the crushability of the porous ceramic 14a.

  In the above-described embodiment, glassy carbon has been described as an example of the material to be filled in the pores of the porous ceramic 14a. However, the material is not limited to this, and is brittle than the ceramic 14a as a framework and is vitrified. Any substance having physical properties that do not disappear depending on the firing temperature of the bond 16 can be appropriately selected and used.

  Although the present invention has been described with reference to the embodiments, the present invention is not limited to the configurations described in the above embodiments, and departs from the gist of the present invention described in the claims. Various modifications are possible without departing from the scope.

DESCRIPTION OF SYMBOLS 10 ... Vitrified bond grindstone, 12 ... Super abrasive grain, 14 ... Aggregate, 14a ... Porous ceramic, 14b ... Substance, 16 ... Vitrified bond, W ... Material to be ground.

Claims (2)

In a vitrified bond grindstone in which superabrasive grains and aggregates composed of cubic boron nitride grains or diamond grains are contained in a vitrified bond,
The aggregate consists of porous ceramics and a substance that closes the pores of the porous ceramics,
The vitrified bond grindstone is characterized in that the substance is more brittle than the porous ceramic and has a physical property that does not disappear depending on the firing temperature of the vitrified bond. 2. The vitrified bond grindstone according to claim 1, wherein the pores of the porous ceramics are filled by filling the substance into the pores of the porous ceramics. 3.

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