KR20040009712A - Vitrified diamond stone for grinding tungsten carbide - Google Patents

Abstract

PURPOSE: A vitrified diamond wheel for grinding a cemented tungsten carbide is provided to maintain the sharpness of grains at the time of grinding the cemented tungsten carbide and to extend a lifetime of the wheel. CONSTITUTION: Diamond grains(2) for grinding a cemented tungsten carbide include a non coating diamond and a coating diamond coated with aluminum oxide, copper, and nickel on a diamond surface. The concentration ratio of grains in a wheel(1) is 23 to 50% in volume. The blowhole ratio is in a range of 5 to 30% in volume. The composition of a bonding agent(3) is composed of 47 to 53%(wt) of silicon oxide, 17 to 30%(wt) of aluminum oxide, 9 to 15%(wt) of boron oxide, 6 to 14%(wt) of RO, and 4 to 16%(wt) of R2O. The diamond grains are mixed with metal powders(4) of copper, cobalt, nickel, tungsten, and iron or at least two kinds of alloy powders with the bonding agent to sinter these mixtures.

Description

Vitrified diamond stone for grinding tungsten carbide}

The vitrified binder 3 is a ceramic binder formed mainly of grass. The vitrified binder 3 has a high melting point, and when the diamond particles are mixed and sintered in the air, oxidation of the diamond particles occurs around 700 ° C. and the surface starts to deteriorate. need.

In the related art, such a point has been one of the problems in manufacturing a vitrified diamond grindstone, but recently, as a low melting point glass such as PbO-B ₂ O ₅ -SiO ₂ is produced, the vitrified binder 3 Many diamond sharpeners were made.

In addition, diamond grains have wider application range than other various abrasives in view of the sharpness of particles during grinding, ease of dressing, abrasion resistance, high thermal conductivity during grinding, and high machinability.

Cemented carbide is very hard and hard, so it is widely used in tools such as DRILL and REAMER and wear-resistant materials such as cemented carbide.However, because of this property, it is the hardest diamond grindstone among the materials. It is difficult to obtain surface roughness, and when grinding cemented carbide with other abrasive materials, the grinding properties are very poor, the grinding resistance is very high, and the abrasive grains are easily broken, falling off or macroscopic fractures are likely to occur. Conventionally, cemented cemented carbides are made of resin-bonded diamond grindstones prepared by mixing diamond powders with thermosetting resins of plastics and pressing and heating them at around 160 ° C. These resin diamond grindstones contain diamonds. Grinding ability is better than that of grindstone, but due to the physical properties of the binder, it is a kind of plastics, and due to the limitation of strength and toughness, the diamond particles fall off and break up to about 30% or more when grinding, resulting in poor grindingability and severe shape change. In use, there is an inconvenience in that a molding process (Dressing) that needs to be frequently formed during use.

In addition, the metal bond diamond grindstone is a diamond grindstone that is mixed with metal powder and diamond and sintered in the range of about 600 to 800 ° C. As a result, it is difficult to protrude the diamond by increasing the toughness and hardness of the metal alloy. Unfortunately, this metal diamond grindstone is also a grindstone that often requires dressing. However, these two types of grindstones are used because they have better grinding and cutting properties than ordinary grindstone grindstones. In the past, non-refined diamond grindstones were not used.

In addition, conventionally, the grinding of cemented carbide is not used because the non-refined diamond grindstone is a conventional grinding tool for grinding grinding cemented carbide, but the material and manufacturing cost is higher than that of resin and metal diamond grindstone. It is about 3 times higher, and when used for cemented carbide grinding, the life of the grindstone is considerably shorter than that of the resin diamond grindstone, and due to the binder composition, the bonding force of the diamond particles is reduced, so the shape deformation is severe. This is because it was perceived as not suitable for grinding.

When grinding cemented carbide with conventional diamond grinding wheel, it is easy to cause welding or blindness, diamond holding is low, so excessive crushing or dropping of diamond particles occurs, and the grinding ratio is very low. In dry grinding, in particular, due to the difference in the coefficient of thermal expansion of the binder and the diamond particles, the grinding was not possible to the extent that it was impossible to use, and it was difficult for the diamond particles to stand up to the eyes (protrusion of the particles), and the life of the grindstone Because of the short and frequent damage caused by the dropping of the particles, the grinding wheel was not used for grinding cemented carbides.

The present invention is to solve the above problems, the purpose of the grinding of cemented carbide using a non-refined diamond grinding wheel, the fall of the diamond particles is less, the sharpness of the diamond particles is maintained for a long time, so that the grinding is good, high efficiency Grinding is possible, it is difficult to create a blindness, high grinding ratio, and the use of non-refined diamond grinding wheel, without the need for dressing (Dressing) and diamond grain protruding due to the shape deformation and deterioration of the grinding during use.

BRIEF DESCRIPTION OF THE DRAWINGS The state diagram which shows the structure structure of the non-refined diamond grinding wheel of this invention.

<Explanation of symbols for main parts of drawing>

1: non-refined diamond grinding wheel 2: diamond particles

3: non-lipid binder 4: metal particles

5: impregnation resin 6: pore

The unrefined diamond grindstone of the present invention is composed of diamond particles, binders and pores. In the manufacture of this non-refined grinding wheel, the key is to find a product that can exert superior performance by testing by varying the degree of bonding, concentration, and various types of diamonds that determine the characteristics of the components in addition to the components. Technology. The present invention is a non-refined diamond grindstone that has been modified and changed by various components, and because the binder has a higher rigidity and particle bonding strength than resin bond grindstones, the retention between particles is excellent, and diamond particles fall out. This is difficult, and it is less likely to cause blinding as compared to the metal-bond diamond grinding wheel. Therefore, unlike resin bonds and metal bond diamond grindstones, if the grinding wheel can be manufactured suitable for grinding cemented carbides, it is possible to maintain the minimum porosity appropriate to the grindstone and to easily discharge the grinding chips. Many experimental studies have been conducted in view of the superior performance compared to resin bonds and metal bonds. It has been found that the following conditions for manufacturing non-refined diamond grinding wheels are suitable for grinding cemented carbides.

In the present invention, the grinding wheel is composed of abrasive grains, binders, and pores. The diamond grinding wheel for grinding cemented carbides has a concentration of diamond particles in the constituent elements of the diamond particles. It is made to be% (Vol)-50% (Vol), and the porosity of a bit refined grindstone is made into the range of 5%-30% (Vol), but it is manufactured so that a minimum porosity can be maintained, and the chemistry of the bit binder binder (3) The composition is SiO ₂ 47-53% (wt), Al ₂ O ₃ 17-30% (wt), B ₂ O ₃ 9-15% (wt), RO 6-14% (wt), R ₂ O 4-16 It is in the range of% (wt), and is a single metal particle such as copper (Cu), cobalt (Co) and nickel (Ni), tungsten (W), iron (Fe), and two or more kinds of metal compounds (CuSn, CuZn, etc.). The powder particles are mixed with a vitrified diamond whetstone binder and shaped to sinter. Subsequently, the impregnated resin 5 is cured by heating after impregnating a liquid solution made by dissolving at least one kind or one or more kinds of a phenol resin and an epoxy resin in a liquid or solid phase by adding a sintered bituminous grindstone. To make it.

Since the non-refined diamond grinding wheel of the present invention has a greater stiffness and particle binding strength of the binder than the resin bond grinding wheel, it has excellent holding force between particles, difficult to drop diamond particles, and eye filling is generated as compared to metal bonded diamond grinding wheels. It is difficult and, unlike resin bond and metal bond diamond grindstone, maintains the minimum porosity appropriate to the grindstone, so that the grinding chips can be easily discharged. The diamond bituminous grinding wheel plays an important role in the abrasives that drive the grinding, the pores that bring about the discharge and cooling effect of the chips during grinding, and the binder that binds the abrasives. The effective combination of these properties allows for better grinding, longer service life and lower COST. The concentration of diamond particles, which lead the grinding of cemented carbide grinding wheels for cemented carbides, is good at 25% to 50% (Vol), and the low concentrations of less than 24% are good for grinding of cemented carbides, but have good shape deformation. When the service life is low and the concentration is over 51%, grinding is hardly performed and heat is generated, resulting in thermal deformation of the base metal (carbide alloy). Since there is little shape deformation and relatively long service life occurs. The concentration is optimal between 25% and 50% (Vol).

In addition, among the components of the diamond abrasive grinding stone for cemented carbide grinding, the change of the pores 6 is a very important factor. The abrasive grains are changed as described above depending on the content thereof, but the pores 6 are the diamond bits for grinding cemented carbide. The porosity of the fed grindstone should be maintained at 5% to 30% (Vol). If the porosity is 4% or less, the grinding property is poor, the shape deformation is small, and the life is long. On the contrary, the porosity is 31% or more. In this case, the grinding property is good, but the shape deformation is severe and the life is shortened, so the porosity is appropriate within 5% to 30% (Vol).

The cemented carbide bituminous carbide binder (3) is a diamond whose oxidation proceeds at about 700 ° C. Therefore, a binder having a composition that is susceptible to being changed to glassy at a low temperature should be selected. ₂ 47-53% (wt), Al ₂ O ₃ 17-30% (wt), B ₂ O ₃ 9-15% (wt), RO 6-14% (wt), R ₂ O 4-16% ( A binder, wt), has been shown to be an optimal composition according to application tests. In the above chemical composition, RO is an alkaline earth metal oxide, at least one oxide selected from ZnO, PbO, CaO, MgO, BaO, FeO, and R ₂ O is an alkali metal oxide, which is Li ₂ O, Na ₂ O, K. _At least one oxide selected from ₂ O is represented.

The content of B ₂ O ₃ is set to 9 to 15% because if the content of B ₂ O ₃ is too low, a high sintering temperature is required for sufficient sintering and it is difficult to achieve the object of the present invention. If the content of B ₂ O ₃ is too high, the melt viscosity is low and the fluidity is increased is because the bonding strength is lowered.

The content of SiO _{2 in} the bitifier binder (3) of the present invention is 47 to 53%. If the content of SiO ₂ is too low, the bond strength is lowered. If the content of SiO ₂ is too high, a high sintering temperature is required for sufficient sintering, and it becomes difficult to achieve the object of the present invention.

The content of Al ₂ O ₃ according to the present invention is 17-30%. If the content of Al ₂ O ₃ is too low, the stability of the binder after sintering is lowered. If the content of Al ₂ O ₃ is too high, the melt viscosity is increased and the wettability with the particles is lowered.

If the content of CaO and MgO is too low, a high sintering temperature is necessary for sufficient sintering. If the content of CaO and MgO is too high, the melt viscosity is low, the fluidity is increased, the particle retention force is low, and the brittleness is high, and the impact resistance is low. . CaO and MgO are preferably in the range of 2.2 to 2.4% and the content of MgO to be 3.9 to 4.1% from the viewpoint of the stability of the binder after sintering.

In the present invention, an appropriate amount of MgO and ZnO should be added as an oxide that prevents oxidation of the mixed particles, decreases the coefficient of thermal expansion, lowers the surface tension of the binder in the molten state, and increases wettability to the particles, thereby obtaining strong particle support. MgO and ZnO lower the coefficient of thermal expansion of the binder when both components coexist, reduce shrinkage due to sintering, and form a uniform and strong bonding structure. A proper amount of ZnO is added to the binder to lower the viscosity of the melted binder to lower the coefficient of thermal expansion and to increase the bearing capacity of the particles when cooling is completed after sintering. In the case of a large amount, the amorphous viscosity at the time of melting is so low that the particle holding power is weak, and in the case of a small amount of ZnO less than 3%, the effect of having a stable and dense grindstone structure with a binder layer is small with the decrease of the coefficient of thermal expansion. On the contrary, in a large amount exceeding 9%, the fire resistance becomes remarkable and the fusion to the particle surface is hindered, which is not preferable. In addition, the solubility, workability, and uniformity of the glass can be improved by containing 3% or less of PbO. However, if the content exceeds 3%, the amount of matrix glass after crystallization is increased to increase the dielectric loss, which is not preferable.

If the content of K ₂ O, Na ₂ O, Li ₂ O is too low, a high sintering temperature is necessary for sufficient sintering. If the content is too high, the coefficient of thermal expansion is high, causing stress concentration at the boundary with the particles and dropping. In addition, the difference in the coefficient of thermal expansion with the particles increases, and the bonding force is lowered. Thus, _{K 2 O 3.1~3.3%, Na 2} O 7.8~8.0%, it is preferable that the content of Li ₂ O 2.0~2.2%.

In addition, B ₂ O ₃ , Li ₂ O, F ₂ , P ₂ O ₅ , Na ₂ O, K ₂ O are various solvents that melt at a relatively low temperature of 700 ° C. so as to facilitate the amorphousization of SiO _{2 in} the binder component. In order to prevent oxidation of diamond and TiC, which are fine particles, it is recommended to contain a large amount of strong melts in the binder, B ₂ O ₃ , Li ₂ O, F ₂ , P ₂ O ₅ , Na ₂ O, and K ₂ O. not.

In addition, at least one or at least one metal powder or alloy powder is dispersed in a vitrified binder phase. This metal powder 4 has a standard production free energy ΔG of oxide at 700 ° C. of 1600 kJ / mol / O. _{2 or} more, the average particle diameter depends on the diamond MESH, and it is preferable to use a metal powder (4) smaller than the diamond particle size, and the thermal expansion coefficient of all is in the range of 0 to 100 ° C to 10 to 20 × 10 ^-6 / ° C. The conditions must be satisfied, and sintering is carried out under the condition that the metal particles are not oxidized in the pressure sintering process, and the metal particles satisfying these conditions should be selected and added according to their use characteristics, for example, when grinding cemented carbide. In the case of dry working condition, Cu powder with good thermal conductivity is added as a binder, and W, Co powder, etc. are used to minimize wear resistance and deformation. In case of toughness, Ni powder is used, and if brittleness is required, Fe powder should be used to select binder according to the characteristics of cemented carbide grinding wheel for cemented carbide grinding. Single metal powder particles such as W, Fe, and alloy powder particles (CuSn, CuZn) are used. Such a metal powder has good affinity with the bit binder agent 3, and exists in a fused state between the bit binder particles 3. Metal powder suppresses the occurrence of problems such as cracking due to the difference in thermal expansion coefficient between the bitifier binder (3) and diamond during sintering, prevents premature dropping of diamond particles during grinding, and improves the grinding resistance according to the characteristics thereof. It has a lowering effect.

In addition, alcohol or other volatile substances (benzene, thinner, etc.) are added to the liquid resin or the solid resin in a weight ratio of about 2 to 5 times, stirred until completely dissolved, and then sintered grinding grinding stone in this solution. After shaking for more than 1 hour, the resin dissolved with alcohol, etc., will penetrate between the pores of the vitrified whetstone. When the impregnated diamond whetstone is taken out and dried, the volatiles are removed, and when the whetstone impregnated with the resin is sintered at about 150 to 400 ° C., the temperature at which the impregnated resin 5 is sintered, the impregnated resin 5 is cured. Since the pores are appropriately filled by the resin 5, it is difficult for the grinding chip to fill the chip pocket, and the occurrence of welding and glazing is suppressed. In addition, since the impregnated resin 5 filling the pores is softer than the diamond particles, the abrasive chips wear and become concave when grinding the cemented carbide, which is the workpiece, and the diamond particles are not excessively destroyed or dropped. Properly done, grinding and burning are prevented, and bite-filled diamond grindstones are kept from filling up, and the elasticity of the solidified resin prevents damage or damage to diamond particles even by excessive grinding. . In addition, since the diamond particles bonded by the inorganic binder are held together more strongly by the resin, the holding force of the diamond particles is increased, so that the premature dropout of the diamond particles is suppressed, and thus a high grinding ratio is obtained.

<Example>

As shown in Examples (1) to (4) shown in Table 1 below, the chemical constituents of all the binder binders (3) of the Examples were SiO ₂ 50% (wt), Al ₂ O ₃ 20% ( wt), B ₂ O ₃ 11% (wt), RO 9% (wt), R ₂ O 10% (wt) was constant, Comparative Examples (1) to Comparative Example (3) of Table 1 is conventional Resin bond diamond grindstone was used, and Comparative Example (4) and Comparative Example (5) used a normal metal bond diamond grindstone, and Comparative Examples (6) to (8) were compared with the non-refined grinding wheel of the present invention. Used another conventional bitifier diamond grindstone. In addition, as shown in Table 2, Examples (1) to (4) show the volume fraction of diamond particles after sintering, the volume of the non-lipid binder (3), the volume ratio of Cu, the volume ratio of the impregnated resin (5), and the pore size. The volume ratio was changed in various ways, and Comparative Examples (1), (2) and (4) in Table 2 set the volume fraction of diamond particles after sintering to 25%, and Comparative Examples (3) and (5) The volume fraction of the diamond grains was 35%, and Comparative Examples (6) to (8) in Table 2 changed the volume fraction of the diamond grains after sintering, the volume fraction of the bitifier binder (3), and the volume fraction of the pores.

Table 3 shows the grinding conditions at the time of experiment, and the workpiece was cemented carbide P ₂ O grade. In this experiment, the grinding ratio, surface roughness and surface current consumption of the machine tool spindle motor were measured.

Grinding ratio means the reduction in the amount of workpiece divided by the amount of abrasive wear.

Table 4 shows the grinding ratio, surface roughness of the machined surface and current consumption of the spindle motor when the grinding is performed under the grinding conditions shown in Table 3. As shown in Table 4, the grinding ratios and current consumption of the spindle motor of the embodiments (1) to (4) of the present invention are significantly higher than those of the resin bond diamond grindstone, the metal bond diamond grindstone, and the conventional non-refined diamond grindstone. The grinding ratios of Examples (1) to (4) of the present invention are significantly higher than those of resin bond diamond grindstones, metal bond diamond grindstones and ordinary bituminous diamond grindstones, and according to Examples (1) to (4) of the present invention The value of the machined surface roughness (R _max ) was lower than that of resinbonded diamond grindstones, metalbonded diamond grindstones and ordinary bituminous diamond grindstones.

As described above, the cemented carbide grinding wheel for grinding cemented carbide of the present invention always maintains the sharpness of the particles during grinding of the cemented carbide, the grinding ratio is large, and the grindstone life is long. In the grinding of the non-refined diamond grindstone of the present invention, welding or glazing is less likely to occur during grinding of the cemented carbide, the retaining force of the diamond particles is high, so that the grinding ratio of the diamond particles is small, so that the grinding ratio is very low, and the grinding burn is difficult to occur. .

Claims (6)

The concentration of the diamond particles is 25% to 50% (Vol), the porosity is 5% to 30% (Vol) in the components of the bitless binder (3), and the chemistry of the bitifier binder (3) The composition is SiO ₂ 47-53% (wt), Al ₂ O ₃ 17-23% (wt), B ₂ O ₃ 9-15% (wt), RO 6-14% (wt), R ₂ O 4-16 Bitifier diamond grindstone prepared by sintering at% (wt). The metal powder (4) single particles such as copper (Cu), Co (cobalt), nickel (Ni), tungsten (W), iron (Fe), or two or more kinds of alloy powders (CuSn, CuZn, etc.). ) Is mixed with a binder and sintered, and the volume fraction after sintering the metal powder particles is 3% to 15%, wherein the diamond grinding wheel. 2. The method according to claim 1, wherein the metal particles are dispersed in the phase of the vitrified binder 3 at the time of sintering by mixing at least one or more kinds of metallic particles and alloy powder particles with the vitrified binder 3, A cemented carbide grindstone for grinding cemented carbide, in which the impregnated resin 5 is cured by heating after impregnating the resin in the pores 6 of the grinding wheel. The metal powder (4) has a standard production free energy ΔG of oxide at 700 ° C. of 160 kJ / mol / O _{2 or} more, and the average particle diameter of the metal powder (4) depends on the size of the diamond particles. A non-refined diamond grindstone characterized by using a metal powder (4) smaller than the diamond particle size and satisfying all conditions in which the coefficient of thermal expansion is in the range of 0 to 100 ° C to 10 to 20 × ^-6 / ° C. The bituminous grinding wheel according to claim 3, wherein at least one or more first-class thermosetting resins selected from phenol resins and epoxy resins are used for impregnation of the resin. The impregnation of the liquid and solid resin according to claim 3, wherein the solution of alcohol, banzen, thinner or the like is added to the resin in a weight ratio of 2 to 5 times, and then stirred until it is dissolved, and the resin is sintered in the melted solution. A vitrified diamond whetstone in which a whetstone is slowly dried after putting a vitrified diamond whetstone for 1 to 2 hours, and then heated to 150 to 400 ° C. to cure the impregnating resin 5.