KR20020075541A - High strength abrasive wheel - Google Patents

Abstract

PURPOSE: A high strength polishing wheel is provided to manufacture the high strength polishing wheel having a durability and an abrasion resistance by mixing and sintering a binder alloy having a sintering temperature lower than 1400°C and a hard particle. CONSTITUTION: A high strength polishing wheel is obtained by mixing and sintering a sintering binder alloy powder and a hard particle. The sintering binder alloy powder includes a transition metal having an atomic rate of 65-97%, one or two of a precipitation strengthening element and a precipitate stabilizing element having an atomic rate of 2-25%, and impurities. The transition metal includes an early transition metal of 6-35% and a late transition metal of 45-90%. The precipitation strengthening element and the precipitate stabilizing element are selected from elements which belongs to IB, IIB, IIIA, and IVA groups.

Description

High Strength Polishing Wheels {HIGH STRENGTH ABRASIVE WHEEL}

The present invention relates to a high-strength abrasive wheel, and more particularly, to a high-strength alloy powder in sintering various types of carbides, such as tungsten carbide, titanium carbide and boron nitride, sintered hard ceramic particles such as nitride, boride, oxide and diamond. The present invention relates to improving wear resistance and durability.

An object of the present invention is to provide an alloy having improved strength and corrosion resistance, which are problems which are not solved in a conventional abrasive wheel using cobalt and nickel as a binder alloy.

Conventionally, the hard particle powder and the cobalt powder are mixed together and sintered by liquid sintering, which is performed by heating at a high temperature of about 1400 to 1550 ° C. for 1 to 2 hours depending on the particle size and composition of the powder. This is effective in reducing the porosity and improving the density by the reaction of the liquid binder metal and the hard particles, there is a problem that the diamond particles are graphitized due to heating at a high temperature for a long time.

Cobalt is widely used due to its excellent wettability with hard particles such as carbides and nitrides while having a wider strength than other metals because of the tensile strength of about 250 to 700 MPa depending on the alloy. The content of cobalt varies depending on the required hardness and toughness. The range of HRA 90 ~ 92 is sintered by adding 6 ~ 12wt%. In this case, however, the hardness was high, but there was a weak point of impact. Therefore, when toughness is required, cobalt is added up to 18 to 27% to secure toughness.

However, at this time, a problem of deterioration of wear resistance occurred while the hardness was lowered to HRA 84 to 87. Moreover, cobalt has a low corrosion resistance, which is a serious problem due to the fact that it is easily oxidized by frictional heat generated during grinding or cutting and oxygen effects in the atmosphere.

In order to improve this, US Pat. No. 6,056,795 discloses a technique for adding a strengthening element such as molybdenum, tungsten, or rhenium to a nickel-tin alloy. However, the alloy had a hardness of only HRC 29.

This fundamental solution to wettability, sintering strength, corrosion resistance, and heat resistance must be sintered using alloys of high corrosion resistance and high strength, but wetting and coercivity are rarer than those of cobalt. In most cases wetting is inferior For example, pressure sintering does not deteriorate the diamond particles during sintering, and increases the pressure to about 5 atmospheres among the factors that affect the energy of the pores and the grain boundary system to maintain the spherical shape. Suppressed. However, this technique also requires expensive pressurization devices or pressure vessels, and there are many limitations in practical applications due to various restrictions in the manufacturing process. In addition, there is a method of forming and sintering at a low temperature and sintering using a high energy source such as plasma, laser, or microwave, but it is not preferable because it requires a double heating process, expensive equipment cost, and production cost.

Accordingly, in order to solve the above problems, the present invention provides a high-strength abrasive wheel having a durability and abrasion resistance and a manufacturing method by mixing and sintering a binder alloy having a sintering temperature of less than 1400 ° C. and hard particles using an existing facility. The purpose of the invention is to.

In order to achieve the above object, the present invention is characterized by producing a binder alloy powder for sintering having excellent wettability, high strength and low cost by using a matrix material of LTM element to which cobalt belongs and an alloy thereof.

In the present invention, the binder alloy contains 65 to 97% of the transition metal of the periodic table in an atomic ratio, among which ETM (Early Transition Metal) is 6 to 35% of the total alloy, LTM (Late Transition Metal) is 45 to 90%, In addition, as an precipitate strengthening element and a precipitate stabilizing element, an element belonging to groups IB, IIB, IIIA and IVA, alone or in combination, is an alloy composed of 2 to 25% of other unavoidable impurities. Preferably, diamond or hard precipitate is added in a volume ratio of about 15 to 35% to secure an appropriate fraction of hard precipitate.

In the present invention, the ETM elements are elements belonging to groups IIIB, IVB, VB, and VIB in the long period table. In particular, the chromium of the VIB group is used in the present invention due to the high solubility and low price for iron groups such as iron, cobalt, and nickel among the LTM elements belonging to Group V and Group VIII. This solid solution forms fine borides and carbides together with boron and carbon, which is advantageous in terms of processability and strength. Except for chromium, ETM elements are mainly used to aid chromium. However, unlike chromium, they have low solubility at room temperature for LTM and usually add up to 15% or less in atomic ratio. Of these, molybdenum is formed in the present invention to form a tremor solid solution and strengthen the matrix structure, it is characterized by stabilizing borides, carbides. In addition, other ETM elements such as titanium, vanadium, zirconium, niobium, hafnium, tantalum, tungsten, lanthanide, and actinides also have the effect of strengthening the matrix and forming stable borides and carbides, resulting in spalling and fitting. Resistance to fatigue wear such as chipping, heat checking and heat checking. In addition, during the sintering process, the oxidation of LTM, IB, IIB, IIIA and IVA is inhibited to reduce impurities and contribute to lower porosity. However, if the total amount of ETM elements is less than 6% in atomic ratio, it does not have sufficient strength and toughness, and it is limited because it is difficult to obtain an alloy of wettability or low melting point. In addition, if the amount exceeds 35%, the IIIA and IVA groups and precipitates are excessively made, so that the wheel is weak to impact and is limited.

In the present invention, the LTM element serves as a matrix of the binder alloy and is an element belonging to Group B and Group V in the long period table. In the present invention, inexpensive and abundant iron is mainly used, and other LTM elements such as nickel, cobalt, etc. may be added to improve corrosion resistance or heat resistance. Nickel is cheaper than cobalt, which is mainly used as a binder, and has an effect of promoting sintering by activating high melting point metals such as tungsten and molybdenum. Cobalt has excellent wettability against steel and ceramics and has an effect of improving heat resistance. Other LTM elements can also be added as matrix elements. However, most of these elements are low in use due to their high price or low chromium solubility. In the present invention, when the LTM elements are less than 45% by an atomic ratio, the toughness required as the polishing wheel is lowered. In addition, if it exceeds 90%, the matrix strength is insufficient and wear resistance is lowered.

In the present invention, groups IB and IIB strengthen the matrix of the binder alloy, and groups IIIA and IVA form and strengthen hard precipitates. Boron and carbon are mainly used in IIIA and IVA groups, and silicon and aluminum play a role in stabilizing these compounds. If the sum of these elements is less than 2% by the atomic ratio, the matrix strengthening effect is small. If the sum of these elements exceeds 25%, brittleness is increased.

The mixing ratio is determined according to the hardness required for the above binder alloy. In the engine valve train system, in order to improve the internal pressure resistance of the hard layer, the hard particles are mixed in consideration of specific gravity so as to occupy 15 to 35% by area ratio.

Since the binder alloy of the present invention has a large surface energy and excellent wettability with metals or ceramics, it is suitable as a binder of hard ceramic particles. By using this property, it is possible to replace cobalt widely used as a binder alloy. Therefore, the sintered product using the binder alloy proposed in the present invention is excellent in surface pressure resistance, heat resistance and corrosion resistance, so that various fields such as sintered binder materials for engine wear parts, die punches, drawing dies, guides, bearings, processing tools and cutters Available for

The present invention will be described in detail through the following examples. However, the following examples do not limit the scope of the present invention.

In the embodiment of the present invention, the binder alloy is used in the form of a powder. Particle size, particle size distribution, shape, purity, and surface state affect the quality of the product. After the binder alloy powder having the above composition ratio is manufactured by the gas atomization method, the powder for sintering is classified into particles having a size of 45 μm or less in consideration of filling with hard particles. Rather than having a narrow particle size distribution of the binder alloy powder, the use of a rather wide distribution of powders of adequately mixed sizes of particles increases the density, strength and elastic limit of the molded article. However, if the size of the particles is too large, there is a problem that the density of the sintered product is lowered, so the maximum size is limited to the fine particles having a size of 45㎛ or less.

On the other hand, the binder alloy powder of the present invention includes a method of separately preparing pre-alloy powders and mixing them, or mixing a single metal powder with these pre-alloy powders in composition ratio to obtain a desired alloy composition in the final composition.

This is because when the particles having an average size of hard particles exceeding about 25.0 μm are mixed, the (001) plane becomes a cleaved surface with a Miller index, and cracks parallel to the crystal plane are likely to occur.

On the other hand, in order to increase the formability and increase the density, the particles formed by mixing the above hard particles and binder alloy particles to 15wt% or less in advance may be used. In this case, the mixed particles are made into a size of 45 ~ 125㎛ Also used. Hard particles include diamond particles, tungsten carbide, titanium carbide, zirconium carbide, tantalum carbide, silicon carbide, chromium carbide, boron nitride, zirconium nitride, titanium nitride, silicon nitride and hafnium boride, titanium boride and zirconium boride. Carbohydrates, chromium borides, aluminum borides, cobalt borides, iron borides, aluminum oxides, zirconium oxides and complex compounds thereof or other hard ceramics may be used.

When explaining the embodiment of the present invention configured as described above in detail. However, the following examples do not limit the scope of the present invention.

Examples 1 to 10

The binder alloy fraction (the remaining fraction is a hard particle) and the chemical composition ratio of the binder alloy are prepared as shown in Table 1, and then the binder alloy powder is prepared by gas atomization method, and the powder for sintering is considered to be filled with hard particles. Powders of 45 μm or less were used, and the composition and average particle size of the hard particles were as shown in Table 1, and the above materials and the organic binder were uniformly mixed with a kneader. As an organic binder, a polymer component such as paraffin, polyethylene wax or EBS wax and a liquid binder such as stearic acid, glycol or polyvinyl alcohol are mixed according to the size and shape of the product. In the present invention, 0.5 wt% of paraffin was added to the organic binder. . In some cases, graphite, resin, soap, etc. are added to the organic binder to improve the compression ratio of the powder and to reduce the friction with the mold to help the particles flow. .

In some cases, it is necessary to have a high density of the abrasive wheel, but on the contrary, it may be desirable to have pores in order to help the abrasive particles fall out. In this case, as in Examples 6 to 10 of Table 1, pores are deliberately formed by sintering using only large particles at a low temperature of 1350 ° C. or less. These pores will seep into the coolant and lubricant. They prevent the wheel from sintering with the cutting material due to the frictional heat of the abrasive wheel. In addition, during friction, hard particles that have been used to some extent are dropped, and new hard particles are exposed to maintain the machinability. The abrasive wheel of the present invention can satisfy all of these needs.

At this time, it was difficult to atomize the alloy powder to obtain a size of about 15 μm or less, and as a result of using only large particles, fine segregation and formability were reduced. Accordingly, in the present invention, a method of satisfying the binder material chemical composition may be used by mixing iron powder of 10 μm or less with the alloy powder.

As a result, it was found that the sintering temperature was relatively low compared with the conventional one, but the hardness of the binder and the whole was improved.

Comparative Examples 1 to 5

Of the comparative examples illustrated in Table 1, Comparative Example 1 is a conventional technique to manufacture by plating. Comparative Examples 2 to 5 were mixed with the hard particles using a conventional binder alloy powder and sintered. As the binder alloy powder for sintering, particles having an average size of 4 to 45 μm were used, and the hard particles of Table 1 and 0.5 wt% of paraffin were uniformly mixed with a kneader.

As a result, it was found that the binder and the hardness were low while the sintering temperature was relatively high.

Table 1

division Metal binder fraction (Vol%) Binder Material Chemical Composition (at-%) Hard particle type and average size (㎛) Sintering Temperature (℃) Hardness (HV) bookbinder all Example 1 85 Ni 15, Co 10, Cr 25, Mo 3, W 2, B 10, Fe bal. Diamond, 4 1370 703 1280 Example 2 80 Ni 34, Co 10, Cr 18, Mo 5, W 5, B 6, Fe bal. Diamond, 2 1370 623 1254 Example 3 70 Ni 40, Co 10, Cr 25, Mo 5, B 10, Fe bal. Diamond, 4 CBN, 45 1370 644 1153 Example 4 70 Ni 45, Co 20, Mo 12, B 8, Fe bal. Diamond, 2 1380 685 1231 Example 5 70 Cr 18, Mo 2, B 9, Si 1, Fe bal. Diamond, 4 CBN, 45 1380 558 1137 Example 6 * 70 Ni 15, Co 10, Mo 12, B 6, Fe bal. Diamond, 2 1350 529 964 Example 7 * 65 Ni 15, Co 10, Cr 25, Mo 3, W 2, B 6, Fe bal. Diamond, 4 1350 568 937 Example 8 * 70 Ni 0.66, Cr 15.8, Mn 0.4, Mo 1.8, Si 0.39, B 2.0, C 1.3, Fe bal. Diamond, 2 1350 376 953 Example 9 * 70 Ni 5.7, Cr 21.5, Mn 1.7, Mo 0.5, Si 3.3, B 17.25, Fe bal. Diamond, 4 1330 608 975 Example 10 * 70 Ni 16.0, Co 7.8, Cr 27.5, Mo 3, W 2, Cu 1.6, Si 2.6, B 17.7, Fe bal. Diamond, 2 1330 789 1012 Comparative Example 1 65 Ni plating Diamond, 4 - 320 785 Comparative Example 2 65 Ni 97.8, Al 2.2 Diamond, 2 1400 380 864 Comparative Example 3 70 Ni 64.9, Co 35.1 Diamond, 2 1450 260 519 Comparative Example 4 70 Ni 80, Co 20 Diamond, 4 1400 320 906 Comparative Example 5 70 Ni 95.1, Co 1.1, Al 1.4, Si 2.4 Diamond, 4 1380 395 831

(Remarks * * Porosity 10 ~ 15%)

As described above, the sintered product using the binder material of the present invention has a low melting point to suppress the graphitization of diamond, and has excellent wettability and exhibits high strength, so that the conventional cobalt can be used. In addition, when cutting the lead frame, such as a low hardness with the abrasive wheel made of the alloy of the present invention, since the blinding phenomenon easily occurs, the pores are formed by 10 to 15% by area ratio to facilitate particle dropout.

As a result, the present invention can be applied to various fields such as a wafer dicing wheel, a wafer polishing wheel and a stone cutting blade.

Claims (12)

Among the transition metals of the periodic table, ETM is 6 to 35% in atomic ratio, LTM is 45 to 90%, and elements belonging to Groups IB, IIB, IIIA and IVA as precipitate strengthening elements and precipitate stabilizing elements, alone or in combination, 2 to 25 %, And other sintered binder alloy powder and hard particles made of unavoidable impurities and sintered by sintering. The method of claim 1, wherein the ETM is sintered by mixing a hard particle and a sintered binder alloy powder containing one or two or more of chromium, molybdenum, titanium, vanadium, zirconium, niobium, hafnium, tantalum, tungsten, lanthanide, actinide High strength abrasive wheel, characterized in that. The high-strength abrasive wheel according to claim 2, wherein the sintered binder alloy powder and hard particles containing 15% or less of the sum of the elements other than chromium in the ETM are mixed and sintered. The method of claim 1, wherein the LTM is a high-strength abrasive, characterized in that the sintered binder alloy powder and hard particles containing one or two of manganese, iron, cobalt, and nickel as the elements belonging to the Group VIIB, Group VIII Dragon wheel. The method of claim 1, wherein the sintered binder alloy powder and the hard particles are added to the group IB, IIB alone or in a combination of silver, silver, or group IIIA and IVA alone or in combination in boron, carbon, silicon and aluminum. A high strength polishing wheel, characterized by sintering. The high-strength abrasive wheel according to claim 5, wherein the sintered binder alloy powder and hard particles in which the carbon and boron are added alone or in combination in an atomic ratio of 2 to 25% in the IIIA and IVA groups are sintered. The high-strength polishing wheel according to claim 1, wherein the binder alloy powder is sintered by mixing the sintered binder alloy powder and hard particles to form a hard structure using a particle size of 45 µm or less. The method of claim 1, wherein the material of the hard particles mixed with the binder alloy powder is tungsten carbide, titanium carbide, zirconium carbide, tantalum carbide, silicon carbide, chromium carbide and boron nitride, zirconium nitride, titanium nitride, silicon nitride, hafnium boron Hard tissues added alone or in combination among cargoes, titanium borides, zirconium borides, chromium borides, aluminum borides, cobalt borides, iron borides, aluminum oxides, zirconium oxides and complexes thereof or other hard ceramics or diamond particles. A high-strength abrasive wheel, characterized in that the sintered binder alloy powder and hard particles to form a sintering mixture. The high-strength abrasive wheel according to claim 1, wherein the sintered binder alloy powder and hard particles are sintered by sintering the hard particles using a size of 25 μm or less to improve the fatigue resistance of the hard tissue. The high-strength abrasive wheel according to claim 9, wherein the fatigue resistance of the hard tissue is improved by using carbides having a size of the hard particles of 7.5 µm or less. The high strength abrasive wheel according to claim 1, wherein the hard particles to be mixed with the binder alloy powder are formed to have an area ratio of 15 to 35% to improve hardness. The high-strength polishing wheel according to claim 1, wherein the sintered pores are formed in an area ratio of 10 to 15% to facilitate particle dropping and to improve lubricity.