JPH087864B2 - Aluminum alloy substrate grinding fluid for magnetic disks - Google Patents

Description

TECHNICAL FIELD The present invention relates to a grinding liquid used for grinding an aluminum alloy substrate for a magnetic disk.

[Conventional technology]

A magnetic disk has a structure in which a magnetic layer, a protective layer, and the like are laminated on a nonmagnetic substrate. When manufacturing a magnetic disk, it is important to finish the surface of this non-magnetic substrate to the required surface roughness and flatness. Aluminum alloy substrates are mainly used as non-magnetic substrates, but in order to keep the surface roughness and flatness within the required range, generally the substrate surface is roughly cut by a lathe, or a grindstone of about # 800. After being processed by rough grinding with a double-sided grinder, it is subjected to finish grinding with a double-sided grinder using a # 3000 grindstone. In these grinding processes, a water-soluble grinding fluid is used to reduce frictional resistance and prevent heat generation due to friction.

[Problems to be Solved by the Invention]

Conventionally commercially available water-soluble grinding fluids contain fats and oils and fatty acids in order to secure an appropriate grinding speed and to achieve a desired surface roughness. However,
Since these oils and fats and fatty acids are contained, grinding dust generated during grinding (aluminum powder, abrasive particles scraps separated from the grindstone, etc.) adheres to the grindstone and causes clogging, or adheres to the aluminum alloy substrate surface. Then, there is a problem that surface defects such as scratches occur. Conventionally, in order to solve this problem, a work called dressing was carried out to remove the clogging by grinding the clogged stone surface with diamond pellets,
There is a drawback that the dressing work requires a long time, the grindstone is consumed much, the productivity is bad, and the cost is increased.

The present invention has been made in view of these points, and significantly reduces the occurrence of clogging of a grindstone and surface defects of an aluminum alloy substrate, and an aluminum alloy substrate having a required surface roughness can be manufactured with low productivity. It is an object of the present invention to provide an aluminum alloy substrate grinding fluid for a magnetic disk, which can be supplied at a cost.

[Means for solving the problem]

According to the present invention, the above object is achieved by an aluminum alloy grinding fluid for a magnetic disk in which a linear alkylbenzene sulfonate is added to a water-soluble grinding fluid containing fats and oils and fatty acids.

[Action]

When a grinding fluid containing straight chain alkylbenzene sulfonate is used, the cleaning action, that is, the dispersing action of this salt,
Prevents grinding dust generated during grinding from adhering to the surface of the grindstone or aluminum alloy substrate, and prevents clogging of the grindstone.
The occurrence of surface defects on the aluminum alloy substrate can be significantly reduced. Therefore, it is possible to significantly increase the number of machining operations in which grinding can be continuously performed after dressing the grindstone until the next dressing is required.

〔Example〕

After roughly cutting the surface of a disc-shaped aluminum alloy substrate with a lathe, a commercially available water-soluble grinding fluid (20% by weight of fatty acids and oils, 25% by weight of alkanolamines, 30% by weight of nonionic surfactant, residual water) (Palace Chemical PS-3105 manufactured by Co., Ltd.)
Using a grinding fluid prepared by diluting 1% by volume of water with 25% by volume of a 30% by weight aqueous solution of linear alkylbenzene sulfonate, diluted with a double-sided grinding machine, manufactured by Kanebo Co., Ltd.
Using 3000 PVA whetstones, finish grinding was performed with a surface pressure of 20 gf / cm ² , a rotation speed of 60 rpm, and a grinding time of 60 seconds. Further, as a comparative example, finish grinding was performed in the same manner as in the example except that a grinding liquid to which linear magnesium alkylbenzenesulfonate was not added was used.

FIG. 1 is a diagram showing the relationship between the number of times of grinding and the amount of grinding (both sides of the substrate) when grinding is continuously performed without dressing a grindstone in the example.
Even after the 20th continuous machining, the amount of grinding was hardly reduced. On the other hand, in the comparative example, as shown in the diagram of FIG. 2, the grinding amount decreases with the number of continuous grinding processes, and in the 15th time, the grinding amount decreases by about 30%. This is a phenomenon caused by the clogging of the grindstone, and it can be seen that the clogging in the example is significantly reduced as compared with the comparative example.

Table 1 shows the substrates of Examples and Comparative Examples.
The results of examining the surface shape for each number of continuous grinding processes are shown.

In Table 1, for the examples, both the surface roughness (centerline average roughness Ra, maximum height Rmax) and flatness showed good values with no tendency to increase even after 20 continuous machining steps and no large fluctuations. Shows. For the comparative example, the flatness is the same as that of the example, but it is considered to be particularly related to clogging.
Rmax has rapidly increased since the 15th continuous machining, and Ra has increased accordingly. Practically, the flatness is required to be 10 μm or less, Rmax is 0.4 μm or less, and Ra is 0.03 μm or less. The flatness is sufficient in both Examples and Comparative Examples. Rmax, R
a approaches the limit. Incidentally, the reason why the Rmax and Ra at the fourth and seventh machining times of the comparative example are remarkably larger than those at the machining times before and after that are considered to be due to temporary large clogging.

From the results of Table 1 and FIG. 2, it is considered that dressing of the grindstone is required after 15 to 20 times of continuous grinding in the comparative example. On the other hand, according to the results of Table 1 and FIG. 1, in the example, it is considered that the continuous grinding can be performed 20 times without any trouble, and at least 30 times or more and up to about 50 times. The dressing frequency of the grindstone can be significantly reduced compared to. Furthermore, there is no need to worry about temporary clogging.

〔The invention's effect〕

According to the present invention, a solution obtained by adding a linear alkylbenzene sulfonate to a water-soluble grinding fluid containing fats and oils and fatty acids is used as a grinding fluid for an aluminum alloy substrate for magnetic disks. By performing grinding with such a grinding liquid,
It is possible to significantly reduce the clogging of the grindstone and the surface defects of the aluminum alloy substrate, the number of dressing operations to remove the clogging of the grindstone is reduced, and the aluminum alloy substrate for magnetic disk with the required surface roughness is produced. It can be supplied with good performance and at low cost.

[Brief description of drawings]

1 and 2 are diagrams showing the relationship between the number of times of grinding and the amount of grinding when grinding is continuously performed without dressing a grindstone, and FIG. 1 is an embodiment of the present invention. FIG. 2 is a diagram for the case of using the example grinding liquid, and FIG. 2 is a diagram for the case of using the conventional grinding liquid.

Claims (1)

[Claims] 1. An aluminum alloy substrate grinding fluid for a magnetic disk, characterized in that a linear alkylbenzene sulfonate is added to a water-soluble grinding fluid containing fats and oils and fatty acids.