JPH05188B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention is applicable to metal plates having a flat surface, for example,
Aluminum alloy disk master (hereinafter abbreviated as aluminum disk), which is the material of the magnetic disk base
This invention relates to a synthetic whetstone used for grinding and polishing the surface of soft metals such as metals. <Conventional technology> Conventionally, surface polishing of relatively soft metal plates with flat surfaces, such as aluminum disks, has been carried out using
Machining using a precision lathe, so-called lapping processing using a slurry of fine powder such as silicon carbide, or processing using a synthetic grindstone such as a resinoid grindstone or a urethane grindstone were common. However, machining using precision lathes, etc. has different finishing accuracy and work efficiency depending on the skill level of the worker, and is generally poor in workability, and when processing a large number of small objects to be polished, The low efficiency was remarkable. In addition, in the case of rapilling processing using a slurry of fine abrasive powder such as silicon carbide, it is economically disadvantageous due to the large amount of slurry lost and used, and it also contaminates the surrounding working environment and workers, and is even more expensive. There was a problem that processing the concentrated waste liquid required a great deal of effort and expense. If existing solid grinding wheels such as resinoid grinding wheels or urethane grinding stones are used instead of the lapping process using a fine abrasive powder slurry, the polishing performance is insufficient and sufficient finishing accuracy cannot be achieved. There have been problems such as insufficient grinding power, insufficient grinding force, or undesirable phenomena such as clogging, making it impossible to obtain a certain level of performance with high efficiency. In other words, when polishing a flat surface, especially when polishing an aluminum disk that requires flatness and surface precision at the same time, the surface of the object to be polished and the surface of the polishing material are brought into contact with each other, and the polishing is carried out at once. For example, if a resinoid-based or urethane-based synthetic whetstone with an independent pore structure is used, polishing debris, fallen abrasive grains, etc. from the abrasive action can enter these pores and cause clogging. The polishing effect is not long-lasting, and frequent dressing (surface renewal) work is required. On the other hand, those using polyvinyl acetal resin with continuous pores as a bonding material are easy to discharge polishing debris, fallen abrasive grains, etc. to the outside of the pores, and are less likely to cause clogging, making them excellent synthetic grindstones. Although it is generally known, it has relatively poor water resistance and is unsuitable for such precision polishing applications. In addition, there are also products containing a cured thermosetting resin for the purpose of imparting water resistance.
It was proposed in Japanese Patent No. 53-6752 and is known as a water-resistant synthetic whetstone. In particular, in the latter invention, by changing the blending ratio of the thermosetting resin, abrasives with properties ranging from elastic to rigid can be obtained. Although it has been generally and qualitatively disclosed that it is useful for polishing difficult-to-cut materials, it is suitable as a precision polishing whetstone suitable for flat polishing of soft metal plates with flat surfaces, especially aluminum disks. Conditions regarding physical properties, such as the coordination and distribution of abrasive grains and the required value of grindstone surface hardness relative to abrasive grain size, have not yet been clarified.
No artificial grinding wheel useful and suitable for such uses has yet appeared. <Problems to be Solved by the Invention> The inventors of the present invention have completed the present invention as a result of intensive research in view of the above-mentioned technical current state and problems. Where to do it is
Efficiently obtain soft metal plates finished to satisfy both excellent flatness and high surface precision, especially aluminum disks, and especially annular disks made of special aluminum alloys that can be used for extremely precise purposes. It is in. Another object of the present invention is to provide an artificial grindstone that is suitable for such precision surface polishing and exhibits excellent performance especially when applied to a double-sided lapping polisher. <Means for solving the problem> The above object is to provide a three-dimensional network structure having continuous fine pores with an average pore diameter of 10 to 100 μm and a porosity of 60 to 85% by volume, The structure is composed of a cured product of a polyvinyl acetal resin, a cured product of a melanin resin, and a cured product of other thermosetting resins, and is the sum of a cured product of a melamine resin and a cured product of other thermosetting resins relative to the polyvinyl acetal resin. The ratio of 40 to 40 in weight ratio
It consists of a mixture of a matrix of 150% by weight and low-grain fine particles that are interconnected and exist in a substantially continuous state in the matrix, and has a surface hardness (H) and abrasive grain count (G). is the formula, -230≦H+G/55≦-80, however, H: Rockwell hardness tester, Super Physical 15
- Values measured on the y scale. G: Abrasive grain count classified according to JIS-R-6001. This is achieved by an alloyed grindstone for soft metals characterized by a relationship that satisfies the following. The first point of the present invention is that a three-dimensional network structure having continuous fine pores is used as a grindstone for polishing relatively soft metal surfaces such as aluminum disks. In other words, the three-dimensional network structure of the present invention has a completely different structure from the closed-cell structure of resinoid-based urethane-based artificial grindstones, and there are no closed cells, and it looks like branches are extending three-dimensionally into the voids. The structure is such that the pores are infinitely connected. Therefore, the abrasive grains and the like that have fallen off are easily discharged from the system through these gaps, and even if they are captured, they are less likely to cause clogging. This effect can be sufficiently obtained within the range of average pore diameter of 10 to 100 μm; below this range, the pores become too dense and phenomena such as clogging tend to occur. Moreover, if it exceeds this, the structure is too rough and there is a problem in terms of uniformity of physical properties. Further, the porosity is preferably in the range of 60 to 85% by volume. If it is less than 60% by volume, independent pores will exist, and if it exceeds 85% by volume, the strength will be insufficient. The second point of the present invention is that a mixture of polyvinyl acetal resin, cured melamine resin, and other thermosetting resins is used as the matrix that binds the abrasive grains. It is in. As mentioned above, polyvinyl acetal resin mixed with a cured thermosetting resin for the purpose of imparting water resistance is known as a water-resistant synthetic whetstone. The object of the present invention is to select a polyvinyl acetal resin and use other thermosetting resins in combination so that the total ratio by weight is within the range of 40 to 150% by weight based on the polyvinyl acetal resin. It has been found that this method is suitable for polishing the surface of relatively soft metals such as aluminum disks. That is, by setting the binder at such a ratio and performing heat treatment in the manner described below, the hardness, sharpness (grinding force), and appropriateness necessary for surface polishing of soft metals, which is the purpose of the present invention, can be obtained. This makes it possible to create a grindstone with excellent elasticity. In particular, in order to meet the objectives of the present invention, it is necessary that the grinding wheel has low toughness (stickiness), and if the toughness is high, the sharpness deteriorates and clogging becomes more likely to occur. Polyvinyl acetal resin has excellent abrasive grain retention, binding strength, and hydrophilicity, but
Since it has a high degree of toughness, by using a cured melamine resin, its toughness is reduced and brittleness is imparted, and the lack of hardness is compensated for by using other thermosetting resins. Other thermosetting resins include phenolic resins, urea resins,
Examples include thermosetting urethane resins, epoxy resins, etc., but phenolic resins are particularly suitable for achieving the purpose of the present invention, and these thermosetting resins are superior to the melamine resins. , it is particularly suitable to use it in a proportion of 20 to 40% by weight. That is, in the present invention, the combined use of a polyvinyl acetal resin, a cured melamine resin, and other cured thermosetting resins as a matrix improves the abrasive retention, hydrophilicity, and elasticity of the polyvinyl acetal resin. Combined with other resin's excellent properties such as hardness, brittleness, and water resistance, it has sharpness and polishing power suitable for polishing soft metal surfaces, and is resistant to clogging, which means that the effect lasts for a long time. It can be used as a whetstone with excellent properties. A characteristic value that symbolizes the above-mentioned features is the surface hardness (H) of the grinding wheel measured using the Rockwell hardness tester Superphysical 15-Y scale.If this value satisfies the inequality shown in the formula below, the grinding wheel is It has physical properties suitable for flat surface polishing of soft metals, which is the object of the present invention. -230≦H+G/55≦-80 (G: Abrasive grain count classified according to JIS-R-6001) If it is below the lower limit of the above formula, it will be too brittle and the cutting quality will be poor, and the whetstone itself will wear out. On the other hand, if it exceeds the upper limit, the hardness and toughness will be too high and clogging will easily occur, making it difficult to exhibit the desired performance as a grindstone, which is the objective of the present invention. As is clear from the above formula, the lower the abrasive grain count, the
That is, it is preferable that the larger the diameter of the abrasive grains, the higher the hardness. The third point of the present invention is related to the coordination and distribution state of abrasive grains having polishing performance. In other words, in this type of synthetic whetstone, abrasive grain particles are distributed in a binder such as a resin matrix, and in the polishing action, the abrasive grains on which the polishing surface is present slide against the object to be polished due to friction. and fell off,
By repeating the phenomenon of being discharged out of the system, the whetstone reduces its own thickness and polishes the surface of the object to be polished. However, if the ratio of abrasive grains is small,
One abrasive grain exists independently, and after that abrasive grain falls off, from a microscopic point of view, only the binder rubs the surface. In other words, since the rubbing is performed in areas where there is no abrasive blade, the sharpness (grinding power) is inferior. Particularly when the purpose is to polish the surface of a soft metal such as an aluminum disk as in the present invention, such a phenomenon is undesirable and tends to lead to problems such as surface unevenness and polishing unevenness. In the present invention, in order to avoid such undesirable phenomena, individual abrasive grains do not exist independently in the matrix, but are interconnected with adjacent abrasive grains and are distributed in a substantially continuous state. are doing. Such a state of the abrasive grains is such that the matrix of the grinding wheel according to the present invention has a high porosity of 60 to 85% by volume, is uniformly connected three-dimensionally, and has an average pore diameter of 10.
It has a continuous pore structure of ~100μm, and in the microskeleton of such a matrix, a sufficient amount of abrasive particles of appropriate size are arranged and uniformly distributed. It comes from this. In order to ensure such coordination and distribution, the preferred abrasive grain count is at least 800, and the content is at least 25% by weight, more preferably at least 40% by weight of the weight of the mixture. The grindstone according to the present invention is manufactured by the following method. That is, polyvinyl alcohol or a derivative thereof having an average degree of polymerization of 300 to 2000 and a degree of saponification of 80 mol% or more,
One or more modified products are mixed to form an aqueous solution, and an aqueous solution, non-aqueous solvent solution, emulsion, etc. of a precursor made of monomers, oligomers, or polymers of melamine resin and other thermoplastic resins is added to the mixture to form a homogeneous solution. Then, abrasive grains, aldehydes as a crosslinking agent, acids as a catalyst,
and starch as a pore-forming agent to prepare a uniformly viscous slurry, which is poured into a predetermined mold. After that, uniform day and night at a temperature of 40 to 100℃.
After reaction solidification in a hot water bath or other bath, take out and wash with water to remove excess aldehydes, acids,
Remove pore formers. Although the thus obtained intermediate has the shape of a grindstone, the resin has not undergone a curing reaction and its performance is insufficient. Therefore, by heating this intermediate at a temperature of about 100℃,
After removing moisture by evaporation and drying, heat treatment (curing) must be performed to cure the resin, but the temperature and time required for curing are as follows:
It differs slightly depending on the type and amount of resin used. Generally 20 to 250℃ at 100 to 250℃
After curing for 100 hours, the curing reaction is almost completed. If the curing is insufficient, the toughness will be high, and if the curing conditions are harsh and the curing progresses too much, thermal decomposition will occur at the same time, which is likely to cause undesirable phenomena, so the conditions must be carefully specified. In order to avoid rapid temperature rise in the secure ring, it is also effective to raise the temperature in stages or to perform it in an inert gas atmosphere. As mentioned above, resins other than polyvinyl alcohol may be mixed (premixed) at the stage of the reaction stock solution, but they may also be cured after impregnating the intermediate with the liquid precursor after the completion of the reaction. A method of premixing a resin and post-treating another resin may be used, and the method is not particularly limited. Furthermore, it is also effective to use a catalyst to promote thermal curing. The liquid resin can be an aqueous solution, a solution dissolved in an organic solvent, an emulsion, or a resin stock solution, but in terms of workability and ease of controlling the mixing ratio, it is most preferable to use an aqueous solution. It is. In addition, the abrasive fine particles referred to in the present invention are made by grinding either a compound or a single abrasive material having grinding power such as diamond, boron nitride, silicon carbide, fused alumina, garnet, emery, cerium oxide, chromium oxide, etc. , JIS standard by appropriate method
This refers to those classified to the particle size specified in R6001, but in order to achieve the purpose of the present invention, at least one of the cemented carbide ceramic abrasive grains consisting of carbon silicon, fused alumina, chromium oxide, and cerium oxide must be used. It is preferable to select one type. <Function> After the grindstone obtained as described above is molded into a desired shape, it is used for surface polishing of soft metals, especially for surface polishing of annular disks made of special aluminum alloys such as aluminum disks. When used for extremely precise applications, the thickness before and after polishing, that is, the amount of cutting, is determined with high precision, and variations in flatness and thickness are extremely suppressed, making it difficult to use general polishing equipment. Therefore, it is preferable to use it by attaching it to extremely precise equipment, such as a double-sided wrapping type polishing machine. The double-sided wrapping type polishing machine referred to here is equipped with circular or ring-shaped metal surface plates on the upper and lower surfaces, and one or more objects to be polished are sandwiched and crimped between them, and the upper and lower surface plates are rotated in opposite directions. Alternatively, in the case of the same direction, it refers to a device that performs polishing by rotating at different speeds and sliding and rubbing the surface of the object to be polished.When applying the grindstone of the present invention, the grindstone forms a uniform plane. This is used by attaching it to both surface plates so that it can be used. During operation, polishing is performed by pouring an appropriate amount of a polishing aid liquid to wet the polishing surface. Solvents, etc. Thus, when the grinding wheel of the present invention is installed in a double-sided lapping type grinding machine to polish, for example, an aluminum disk, the grinding wheel is uniformly and densely filled into the matrix resin, which has excellent water resistance and abrasive grain retention.
The interconnected fine abrasive particles, combined with the appropriate hardness, elasticity, and brittleness of the matrix, exhibit sharp cutting power, or grinding power, and even if the abrasive particles fall off one after another due to the abrasive abrasive action, there is no backing. New abrasive grains connected to the abrasive grains appear on the surface and the abrasive surface is immediately renewed and regenerated. Grinding debris and fallen abrasive grains are easily discharged from the continuous fine pores, which prevents clogging and maintains high polishing power for a long time. maintained throughout. Also,
The above-mentioned special coordination and
Due to the distribution state, during polishing work, the abrasive particles come in contact with and rub over the entire surface of the flat object, without causing any rubbing phenomenon caused only by the matrix resin.
Uniform polishing action is always performed. Therefore, the grindstone of the present invention efficiently provides a soft metal plate having a flat surface with high smoothness and excellent finished surface accuracy without polishing unevenness. <Examples> Embodiments of the present invention will be described below with reference to Examples. The devices and instruments used in this example are as follows. ●Polishing equipment...Double-sided polishing machine manufactured by Speedhuam Co., Ltd. (Model: SFDL 9B-5SSG) ●Surface roughness meter...Surface roughness meter made by Tokyo Seimitsu Co., Ltd. (Model: Surfcom 553A) ●Degree of bonding...Okoshi type grindstone bonding Hardness tester (manufactured by Tokyo Koki Co., Ltd.) ●Hardness tester: Matsuzawa Seiki Rotsuwell hardness meter (model SF-15Y) ●Material to be polished: An annular plate made of aluminum alloy.
A JIS standard AA5086 alloy was used. Further, the polishing conditions and the measurement conditions for surface accuracy, hardness, and degree of bonding are as follows. ●Polishing conditions (SFDL-9B-5SSG) ●Pressure 100gr/cm ² ●Polishing time...3 minutes/1 batch ●Upper surface plate rotation speed...20R/M (counterclockwise) ●Lower surface plate rotation speed...60R /M (clockwise) ●Carrier surface plate rotation speed...20R/M (clockwise) ●Water supply rate...5/min ●Surface accuracy measurement conditions ( ^Ra _Rnax ) (Surfcom 553A) ●Surface accuracy measurement conditions (W) _CM ) ●Cut-off value...0.8mm or more ●Measurement length...2.5mm ●Cut-off value...0.8mm or less ●Measurement length...80mm Regarding Ra, Rmax, W _CM mentioned here,
Ra is a parameter expressed by the following formula...Center line average roughness Ra=1/L∫ ^L _O |f(x)|dx Rmax...Maximum height Rmax=Pmax−Vmin W _CM ...Maximum undulation of 3 waves W _CM = Pmax - Vmin Ra Calculated from roughness curve Rmax Calculated from cross-sectional curve W _CM Calculated from 3-wave waviness curve ◎Surface hardness measurement conditions Rotsuwell Super Financial 15-Y scale working load 15Kg Gauge head 1/2 inch steel ball ◎Degree of bond Measurement example using a method compliant with JIS R-6240 method using a load of 10 kg 1 The abrasive grains were No. 2000 C abrasive grains (silicon carbide, average particle size)
7.1-8.9 micron meter) was used. Completely saponified polyvinyl alcohol with a degree of polymerization of 1700 was used to make an aqueous solution, and to this was added PR-96IA manufactured by Sumitomo Durez Co., Ltd. as a water-soluble phenol resin and SM- manufactured by Showa Kobunshi Co., Ltd. as a water-soluble melami resin.
700 in predetermined amounts, and further added sulfuric acid as a catalyst, formaldehyde as a crosslinking agent, and corn starch as a pore-forming agent.
A uniform slurry liquid was prepared by mixing with the abrasive grains described above. This slurry liquid was poured into a specified mold and heated to 60°C.
An intermediate was obtained by solidifying the reaction for one day in a water bath, and then washed with water to remove excess acid, formaldehyde,
After removing corn starch etc. and drying,
The desired grindstone was obtained by heat treatment at a temperature of 130°C for about 50 hours. The composition of the grindstone used in this example is shown in Table 1.
The grindstone thus obtained was cut and formed into a substantially fan-shaped shape 1 as shown in FIG. 1, bonded to a metal mounting plate 2, and mounted with bolts to the upper and lower lapping machines 3 of a polishing device SFDL-9B5SSG. The material to be polished was fixed using a carrier and polished under predetermined conditions of the polishing device. Water was used as the polishing liquid (coolant), and after polishing for a predetermined period of time, the surface shape of the polished material was inspected. In addition, in order to confirm the clogging condition of the grinding wheel surface, 15 batches of continuous polishing were performed without dressing the grinding wheel, and the condition of the grinding surface and the polishing condition were inspected. The results are shown in Table 1.

【table】

[Table] As is clear from Table 1, those with hardness within the specified range have good surface finish accuracy and 15
The deterioration in polishing performance after batching is not so significant. Those in which the ratio of the sum of melamine resin and phenol resin to polyvinyl acetal resin exceeds 150% (Test No. 1) have high hardness and poor surface finish accuracy. When a continuous test is performed, the value of Rmax increases, indicating that the occurrence of striations increases. Also, the ratio is less than 40% (Test No. 5)
The grinding force is low and clogging occurs easily, and the value of W _CM is especially high, and the flatness tends to be poor. The one with a low abrasive grain content and no continuous abrasive grains (Test No. 6) has no grinding power at all and is unsuitable. Furthermore, the one in which the thermosetting resin is composed only of melamine resin (Test No. 7) is also unsuitable because it is too brittle and the grinding wheel is subject to severe abrasion, especially local abrasion. Example 2 Grindstones with various grain sizes were prepared in the same manner as described in Example 1, and the same polishing operations were carried out and the results of inspection are shown in Table 2.

【table】

[Table] As is clear from Table 2, the lower the grit, that is, the coarser the abrasive grains, the greater the grinding power, and the greater the wear of the grindstone, but this is natural due to the nature of polishing, and there are no particular problems. do not have. From a comprehensive perspective, the grindstone of the present invention is
It is fully applicable to polishing soft metals such as aluminum disks, and if you perform dressing (surface renewal) work approximately once every 10 to 12 batches during operation, there will be little change in polishing power, and it will be sufficient. It can be used for many years. <Effects of the Invention> According to the present invention, it is possible to efficiently obtain a soft metal plate, for example, an aluminum disk, which simultaneously has excellent flatness and high surface precision, which could never be achieved with existing grindstones. As a result, it is possible to fully meet the rapid increase in demand for high-precision finished aluminum disks as information storage media due to the development of the electronics industry, office equipment industry, etc., and the increase in polishing work efficiency is due to production processing. The contribution to industry is significant, such as by making it possible to reduce costs.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a lapping machine of a lapping type polishing machine for explaining how the grindstone of the present invention is used. 1... Grinding wheel, 2... Mounting plate, 3... Wrapping board.

Claims (1)

[Claims] 1. Average pore diameter is 10-100 μm and porosity is 60-100 μm.
A structure having a three-dimensional network structure with continuous fine pores of 85% by volume, the structure consisting of a cured product of a polyvinyl acetal resin, a cured product of a melanin resin, and a cured product of other thermosetting resins, A matrix in which the ratio of the sum of the cured product of melamine resin and the cured product of other thermosetting resin to polyvinyl acetal resin is 40 to 150% by weight; It is composed of a mixture of low grain and fine particles that exist in a continuous state, and the surface hardness (H) and abrasive grain count (G) are expressed by the formula: −230≦H+G/55≦−80, where H: Rockwell hardness tester , super ficial
Values measured on a 15-y scale. G: Abrasive grain count classified according to JIS-R-6001. A synthetic whetstone for soft metals characterized by a relationship that satisfies the following. 2 Other thermosetting resins include phenolic resins,
or a derivative thereof, which is used in an amount of 20 to 40% by weight based on the melamine resin. 3 The abrasive fine particles are made of silicon carbide, fused alumina,
The polishing wheel for soft metals according to claim 1, which is made of at least one cemented carbide ceramic selected from the group consisting of cerium oxide and chromium oxide. 4. The polishing wheel for soft metals according to claim 1, wherein the abrasive grain count (G) is at least No. 800. 5. A polishing wheel for soft metals as claimed in claim 1, wherein the abrasive fine particles are contained in an amount of at least 25% by weight based on the weight of the mixture. 6 The content of abrasive fine particles is at least 40% by weight
A polishing wheel for soft metals according to claim 1.