JPH02194152A - Manufacture of aluminum alloy stock for laser mirror - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method of manufacturing an aluminum alloy material for a laser reflecting mirror.

[Prior art] Laser reflectors are important functional parts for computer data output devices (laser printer optical disk devices, etc.), automatic price reading devices (POS), digital audio disks (DAD), surface inspection devices, etc. The materials used are aluminum alloy, steel, brass, glass, etc., but after processing the surface of the material to make it smooth, it is treated with a surface treatment that has a high reflectance to the laser. used.

In order to be used as a laser mirror, the final reflectance of the laser beam must be 90% or more, and for this reason, the material is required to have as good flatness as possible and a low surface roughness value.
Furthermore, a rotating polygon mirror that uses laser light as a scanning means is required to have mechanical strength that can withstand high-speed rotation.

When using aluminum alloy as a material for laser mirrors, conventionally the material is first processed into a flat surface using a precision grinder or precision cutting lathe, then electroless nickel plating is applied to the surface of the material, and finally lapping is performed. It was. However, this method requires a complicated process to form a bright nickel plating layer on the surface of the material and requires a very long time for the lapping process, resulting in high costs.Also, since the process involves multiple steps, the surface may be scratched. The number of occurrences has increased, and this has been a cause of lower product yield.

As a method to avoid these problems, a method has recently been developed in which an aluminum alloy material is subjected to ultra-precision cutting using a diamond cutting tool, followed by surface protection treatment. When this method is used, the process of mirror finishing is relatively simple, so processing costs can be significantly reduced, but since the surface of the machined aluminum alloy material is used as it is as a mirror for the laser beam, the material As a result, the aluminum alloy material used in the conventional method, which combines plating and lapping, is unable to satisfy these required characteristics for the side sole. It's becoming difficult.

[Problems to be Solved by the Invention] That is, the following characteristics are required of the aluminum alloy material used in the method of manufacturing a laser mirror by combining ultra-precision cutting with a diamond bite and surface protection treatment.

+1) The diamond cutting tool has excellent cutting performance, that is, the amount of elastic deformation against compressive stress at the cutting edge is small, and it is difficult to form a damaged layer. Also, there should be no traces of the cutting edge left on the machined surface.

(2) The surface roughness of the first surface is small, and R11 is 0.02
Must be less than μm. Therefore, steps at grain boundaries and inclusions must not remain on the machined surface, or recesses formed by cutting by the cutting edge must not remain.

(3) The flatness of the machined surface is good. Especially for rotating polygon mirrors that use flat side surfaces as reflecting mirrors, it is desirable that the parallelism of the upper and lower surfaces is 1 μm or less, so that processing distortion is difficult to remain. It is necessary that the material is the same.

(4) It is desirable that the reflectance to laser light be as high as possible, and that the processed surface of the material should have a reflectance of at least 87% or more, preferably 90% or more.

(5) The material for the rotating polygon mirror is intended to undergo surface vibration and elastic deformation during high-speed rotation of 20,000 to 80,000 revolutions per minute.

[Means for Solving the Problems] In order to achieve the above object, the present inventors have conducted intensive experimental research on a method for manufacturing an aluminum alloy for laser mirrors, focusing on the combination of the alloy composition used and the alloy processing technology. As a result of repeating this process, the present invention was completed.

That is, the present invention uses Mg2.0 to 6.0% by weight as an essential element.
0%, Be0.001-0. Contains 1% O and further contains Cub
, 0.02 to 0.25%, and Zn of 0.02 to 0.5%, or both, with the balance consisting of aluminum and unavoidable impurities, and Mn and Cr as impurities are each 0.03% or less. , Fe and St are each 0.05% or less, T
i is 0.02% or less, and + of impurities other than the above
It is necessary to have strength.

The present invention provides a method for manufacturing an aluminum alloy material for laser mirrors that can simultaneously satisfy the various required properties as described above, and then casts the ingot into a predetermined ingot. 2 to 550℃ temperature range
After performing heat treatment for 24 hours, hot working is performed so that the temperature at the end of hot working is 400 ° C. or less, and cold working is performed so that the degree of working is 30% or more in the first stage,
This is a method for producing an aluminum alloy material for a laser mirror, characterized in that the material is then annealed to obtain a material having an average grain size of 100 μm or less.

When the manufacturing method of the present invention is used, the obtained aluminum alloy material has excellent machinability with a diamond cutting tool, and has excellent smoothness by controlling inclusions and crystallized substances to a minimum and adjusting the crystal grain size. In addition, since a reflectance of 90% or more can be obtained, it is suitable for use as a material for a laser reflecting mirror.

[Operation] Next, details and operation of the method for manufacturing an aluminum alloy material for a laser mirror according to the present invention will be described in detail.

In order to obtain good surface properties as shown in the above-mentioned required property (2), coarse intermetallic compound particles and nonmetallic inclusion particles should be prevented from being present in the material as much as possible.

If these particles are present, they will remain as protrusions on the surface after cutting, or traces of them falling off due to cutting will remain on the surface in the form of hole-like depressions, which will generate [L] of the laser beam.

To deal with such problems, (a) molten aluminum alloy is filtered using a filter medium with a pore size of 10 μm or less before casting. By doing so, most of the nonmetallic inclusions that would impede the above-mentioned required characteristics are removed. In addition, (0) Regarding insoluble intermetallic compound particles, it is necessary to limit the presence of elements that generate them in the aluminum alloy used as a raw material as much as possible.0 In the present invention, unavoidable impurities in the alloy Among the elements present in the human body, the elements with a large influence, namely iron and silicon, are each reduced to 0.05% or less, and manganese and chromium are reduced to 0.0% or less.
The content of titanium was limited to 3% or less, and titanium was limited to 0.02% or less.

In addition, in order to obtain a reflectance of 90% or more as described in required characteristic (4), it is necessary to suppress the formation of nonmetallic inclusions and intermetallic compounds as described above, and also to suppress the formation of nonmetallic inclusions and intermetallic compounds. - The effect is further ensured by ensuring that the mirror-like state of the new surface created by cutting with a cutting tool does not deteriorate due to chemical changes. In other words, preservation of the mirror-like state is ultimately achieved by forming a surface protective film, but in general, chemical changes due to oxidation of the surface begin immediately after the new surface comes into contact with air during cutting. A slight decrease in reflectance is unavoidable.1 The inventors have conducted various studies on ways to suppress such changes, and found that adding a small amount of beryllium to the alloy further improves the specular reflectance. % or more can be sufficiently ensured. In this case, if the amount of beryllium added is less than 0.01001%, the effect will be small, and if it is added more than 0.01%, no increase in the effect can be expected, therefore, from 0.001% to 0.01%.
A range of is appropriate.

In order to obtain the required properties (+1. Mechanical strength properties such as machining performance for diamond bits, residual stress properties, and rigidity against high-speed rotation as described in (2) and (5)), aluminum alloys are generally used. Instead of using the age hardening method used for strengthening, we adopted a solid solution hardening method.

This is because while the age hardening method can easily obtain high strength and rigidity, the intermetallic compounds precipitated by aging may significantly impede the reflective performance of the material, so it is not an appropriate strengthening method for the purpose of the present invention. This is because it is difficult.

That is, in the present invention, 20-6.0% magnesium is added to aluminum as a final element for solid solution strengthening, and further 0.02-0.25% copper and 0.02-0.02% magnesium are added.
It has been found that the necessary mechanical properties such as machining performance and rigidity can be sufficiently satisfied by adding 5% of zinc or both at the same time. In this case, if the magnesium added is less than 2.0%, it is difficult to obtain sufficient strength, and if it exceeds 6.0%, A 1 z M g s
This results in disadvantages such as easy generation of particles and marked reduction in thermal nfI processability. On the other hand, with regard to copper and zinc, a sufficient strengthening effect cannot be obtained with less than the lower limit of 0.02%, and 0.25% of copper and 0.5% of zinc
Magnesium, copper, and zinc, which are added as six reinforcing elements, must be uniformly distributed in solid solution. It is effective to carry out the heat treatment at a temperature in the range of 550°C for 2 to 24 hours. Heating temperature is 40
If the heating temperature is less than 0°C, or if the treatment time is less than 2 hours even if the heating temperature exceeds 400°C, a uniform solid solution dispersion state of the elements cannot be obtained; If the treatment time exceeds 550°C or exceeds 24 hours, the oxidation of magnesium will become significant, resulting in a decrease in the reflectance of the cut surface, which is inappropriate. In addition, in the present invention, the heat-treated alloy ingot is stretched in the order of hot working and cold working, but during these processing processes, the temperature at the end of hot working is set to 400°C or less. The working temperature is adjusted so that the working temperature is 30% or more.

It is possible to limit each processing condition as described above. The reason why the grain size of the material is kept below 100 μm is that if the grain size exceeds 100 μm, grain boundary steps will appear on the surface after cutting when ultra-precision cutting is performed with a diamond cutting tool. This is because the surface precision is difficult to scratch.

Such grain boundary steps are deeply related to the grain size, and at the same time are also strongly influenced by the elastic deformation of the material in response to the same compressive stress, residual stress, and the formation of a deformed layer M. The composition of the aluminum alloy and its heat treatment and processing conditions in the present invention are effective in solving these problems comprehensively and have a remarkable effect.

Next, the effects of the present invention will be illustrated by examples.

[Example 1] Example 1 was conducted to examine the influence of alloy composition in the production of an aluminum alloy material for a laser mirror. The compositions used were those corresponding to the alloy composition of the present invention and those having other compositions. Table 1 shows the alloy composition used.

Alloys 1 to 14 (alloy number 1 to alloy number 5: the invention alloy, alloy number 6 to alloy number 14. comparative alloy) having the compositions shown in Table 1 were each melted, and the pore size was 10μ.
After passing through a filter with a diameter of 273 mm or less, the ingot was directly cast into a cylindrical ingot with a cross section of 273 mm in diameter using a water-cooled semi-continuous casting device.

Each of these ingots was heat treated at 480°C for 12 hours, then hot extruded at 380°C into a round bar with a diameter of 120mm, and then cold drawn with a cross-sectional reduction rate of 43% to reduce the diameter. A 90 mm round bar was obtained.

Regarding the alloy material obtained in this way, first, the hardness,
Measuring mechanical properties such as tensile strength 5 proof stress and elongation,
Next, the grain size (maximum value) of the crystals was measured. In addition, the surface roughness, the amount of inclusions or crystallization, the presence of marks such as cutting edge marks and scratches, and the presence or absence of streaks such as scratches and parallel incident visible light on the surface that has been precision-cut by cutting with a diamond cutting tool. The 60° reflectance was measured and the suitability as a laser reflecting mirror was evaluated.

These results are summarized in Table 2, and it can be seen that the alloys with the composition of the present invention (alloy numbers 1 to 5) have superior machinability with a diamond tool compared to the comparative alloys (alloy numbers 6 to 14). In addition to obtaining a surface roughness of R,...0.02 μm or less, the number of inclusions and crystallized substances present on the cut surface is extremely small, and it is possible to obtain a high reflectance of 90% or more. Its excellent suitability as a laser reflector was confirmed.

[Example 2] In Example 2, an alloy material having the composition of the present invention was used and an alloy material for a laser reflector was manufactured under the conditions of the present invention and other conditions. This shows the difference in performance.

That is, the alloys having the composition of the present invention used in Example 1, that is, the alloys of alloy numbers 2 and 5, were melted as the alloys used, and the results were as follows: filtration with a filter with a pore size of 10 μm or less, hot rolling temperature, and cold rolling rate. The effects of various factors such as these on the crystal grain size of the alloy plate and the surface condition of the cut surface by a diamond cutting tool were investigated. (Condition of the present invention: material number 2-
2 and 5-2, comparison conditions: other material numbers)
In this case, the ingot was heat treated at 480°C for 16 hours, and the cold rolled plate was annealed at 380°C for 1 hour.

The results are shown in Table 3. As can be seen from Table 3, the material (
Material numbers 2-2 and 5-2), that is, filtration is performed with a filter of LO μm or less, and the hot rolling end temperature is 40
For alloy materials manufactured under conditions of 0°C or lower and a cold rolling rate of 30% or higher, the crystal grain size, surface roughness of the cut surface by a diamond cutting tool, presence of inclusions and crystallized substances, cutting edge marks, and Excellent results were obtained in all measurements and evaluations of scratches, 60° reflectance, etc., and it can be seen that the alloy material according to the present invention has excellent properties as a material for a laser reflecting mirror.

[Effects of the Invention] As described above, when using the manufacturing method of the present invention, that is, using an aluminum alloy having a specific alloy composition and performing stretching processing under specific heat treatment and processing conditions, the resulting laser mirror The aluminum alloy material has excellent cutting performance through ultra-precision cutting using a diamond cutting tool, and has extremely good performance in terms of surface roughness, cutting edge marks, surface scratches, 60° reflectance, presence of inclusions and crystallization, etc. In addition to the high mechanical strength and rigidity, this invention can be said to be an excellent method for producing aluminum alloy materials for laser reflectors.

Patent applicant: Nippon Light Metal Co., Ltd.

Claims (1)

[Claims] Mg2.0-6.0% by weight as essential elements, Be0
．． 001~0.01%, further Cu0.02~0
．． 25%, Zn0.02 to 0.5%, or both, the remainder consists of Al and inevitable impurities, and Mn and Cr as impurities are each 0.03%.
Hereinafter, a molten aluminum alloy containing 0.05% or less of Fe and Si, 0.02% or less of Ti, and a total of 0.1% or less of impurities other than the above is used as a filter material with a pore size of 10 μm or less. After passing through the ingot, it is cast into a predetermined ingot, and then this ingot is heated in a temperature range of 400 to 550℃ for 2 hours.
After heat treatment for ~24 hours, hot working is performed so that the temperature at the end of hot working is 400°C or less, and then cold working is performed so that the degree of working is 30% or more. , and then annealed to have an average grain size of 100 μm.
A method for producing an aluminum alloy material for a laser mirror, characterized by using the following materials.