JPS59157235A - Production of aluminum alloy blank material for laser reflection mirror - Google Patents

Abstract

PURPOSE:To obtain a blank material from which a specular surface is immediately obtd. by ultraprecision-cutting using a diamond tool, etc. by specifying the permissible amt. of Mg and impurities in an Al alloy, further removing non- metallic inclusions therefrom to minimize an insoluble metallic compd. and limiting the grain size thereof. CONSTITUTION:A molten Al alloy which contains, by weight, 2-6% Mg, consists of the balance Al, and contains impurities to a permissible limit amt. of total 0.10% including 0.15% iron, 0.05% silicon, 0.25% copper, 0.50% zinc, 1.0% Mn, 0.05% Cr, 0.10% Zr, 0.02% Ti and other impurities, is filtered by a filter medium having <=10mu pore size. The molten metal removed of non-metallic inclusions in such a way is cast so as to solidify at a cooling rate of >=300 deg.C/sec to obtain a cast ingot. The ingot is subjected to a homogenization treatment if necessary and is thereafter hot-rolled and cold-rolled by the conventional method or the ingot is subjected to final annealing after the cold rolling alone. The amt. of the insoluble intermetallic compd. is thus minimized and the grain size thereof is limited to <=2mu.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing an aluminum alloy material for precision mirror finishing used in a laser reflecting mirror.

When using an aluminum alloy material as a laser reflecting mirror such as a rotating polygon mirror for a laser scanner, conventionally, an Al-81-Mg alloy material with excellent corrosion resistance, rigidity and 2 strength is flattened using a precision grinder or a precision cutting lathe. It was made by first applying nickel plating to the surface of the material, and finally applying boring. However, this method requires a very long time for plating and polishing, and the operations are complicated, so there are many chances for surface scratches to occur.

This reduces product yield and causes high costs.

In order to improve the drawbacks of the mirror finishing method, a method has been developed in which a surface protective coating is applied after ultra-precision cutting with a diamond cutting tool to create a boundary surface.

This method is an excellent interface finishing method as it does not require complicated operations such as plating or poling on the surface of the material and can shorten the processing time. as it must act as a reflective surface.

Conventionally used aluminum alloy materials cannot meet the required properties6.
ax) 103 μm or less, a plane accuracy (height of plane waviness) of 0.1 μm or less, and an extremely high reflective function with no local pits or scratches is required.

Furthermore, when this material is used in rotating polygonal reflectors for laser scanners.

Due to the fact that the mirror body rotates at a high speed of tens of thousands of times per minute,
It is necessary to have such strength and regularity that the reflective function will not deteriorate due to elastic or plastic deformation.

The inventor has completed the present invention as a result of repeated research and consideration on a method of manufacturing an aluminum alloy material that can be used as a laser reflecting mirror material immediately after being subjected to ultra-precision turning using a diamond cutting tool, etc. The present invention contains magnesium 2 to 6 parts by weight, and the balance consists of aluminum and impurities, and the permissible content limit amount of impurities is iron Q,
15 width, silicon 0.05%, copper 0.25%, zinc 0.50
Steamed rice cake, manganese toke, 0.05 bite of chrome.

After passing through an aluminum alloy bath containing 10% zirconium cL, titanium Q, 02q6 and other impurities, Q, 10%, through a filter medium with a pore size of 10 μm or less,
An ingot is produced by casting so that solidification occurs at a cooling rate of 0°C/second or more, and this ingot is solution-treated according to a conventional method.
It is characterized by hot rolling, cold rolling or immediate cold rolling to obtain a predetermined thickness, and finally annealing.

In other words, according to a study by the inventors, a solid solution strengthened aluminum-magnesium alloy containing 2 to 6 parts of magnesium is an aluminum alloy system that satisfies the strength, rigidity, and reflection function among the characteristics required for a laser reflecting mirror. It was found to be appropriate.

However, when using a material made from a commercially available aluminum-magnesium alloy and performing ultra-precision cutting using a diamond cutting tool, etc., the processed surface of the material has a high level of smoothness as described above. Various problems have arisen in order to impart the accompanying reflective function.

In other words, in commercial standard aluminum alloy materials, there are insoluble intermetallic compound particles based on various impurity metal elements and nonmetallic inclusion particles that are mixed in during the process, and many of these inclusions are separated from the alloy matrix. Because it is hard, inclusion particles may remain as protrusions on the surface after finishing, or may fall off during cutting, resulting in pits or scratches. This causes scattering of the projected light in these areas, making it difficult to accurately It was extremely difficult to see the clear reflected image.

The inventors conducted a detailed study on the influence of these inclusions contained in the alloy material on the laser beam reflection function after finishing the material surface, and found that the size of the insoluble intermetallic compound particles was 2 μm or less. If so, it is possible to form a good reflective surface as a laser reflecting mirror. In other words, the molten metal of the two alloys is filtered once or several times through a filter material with a pore size of 10 μm or less to not only remove nonmetallic inclusions, but also remove insoluble metal inclusions. Insoluble intermetallic compounds contained in the material can be removed by restricting the presence of elements that produce intermetallic compounds to a limited amount and casting the molten metal after filtration to solidify at a cooling rate of 300°C/second or more. The amount is kept small and the particle size is 2 μm.
The alloy material obtained by the present invention has excellent rigidity by diamond cutting, has a good smoothness of the cut surface, and has a reflectance of X:';'as or higher. In addition, since the reflected image has high clarity, it has excellent performance as a laser reflecting mirror, especially as a rotating polygon for a laser scanner.

In the present invention, the amount of magnesium as an alloying element is 2 to 6.
The reason for this is that if the magnesium content is less than 2%, sufficient strength and good stiffness by diamond bite cannot be achieved, and if it exceeds 6%, βAl-Mg intermetallic compounds are formed in the alloy structure.

This reduces the workability of the alloy, and this compound
The particles become coarser and reduce the reflective function of the mirror surface.

As mentioned above, in the present invention, it is especially important to control the content of non-metallic elements that cause insoluble intermetallic compounds in the alloy. That is, these metal elements include iron, silicon, chromium, manganese, zirconium, and titanium.

The maximum allowable content of these elements is 0.15% iron and 0 silicon.
．． Section 05, Chrome [105q6. The reason for limiting the amounts of manganese to O, zirconium to α10, and titanium to 0.02 is because if each element exceeds the above-mentioned limits, even if the molten metal is cooled and solidified at a cooling rate of 300°C/sec or more, insoluble intermetallic compound particles will be formed. This is because if the size exceeds 2 μm, the function as a laser reflecting mirror cannot be achieved.

In the present invention, a molten aluminum-magnesium alloy having the above composition is passed through a filter having a pore size of 10 μm,
After removing non-metallic inclusions.

The ingot is cast to solidify at a cooling rate of 300%. When the molten alloy is solidified at such a high cooling rate, the ingot is cooled extremely rapidly, the amount of insoluble intermetallic compounds precipitated is small, and the particle size can be kept at 2 μm or less.

The ingot thus obtained is either immediately cold-rolled to a predetermined thickness or annealed at 400-550°C for 2-24 hours and then hot-rolled and cold-rolled to a desired thickness. After making a plate, it is finally heated to 300-550℃ by 0.5-5
It is subjected to time annealing to remove distortion and then used as a material for a laser reflecting mirror.

In addition, when the annealing temperature is 500 to 550°C during final annealing, and the cooling rate to 250°C after annealing is 100°C/min or more, the material reflectance is further increased by 2 to 6 qb.
It is preferable because it can be improved.

Next, examples of the present invention will be described.

Example 1 The molten aluminum-magnesium alloys of sample numbers 1 to 14 having the alloy composition shown in Table 1 were filtered through a porous graphite filter with a pore size of 10 μm, and then solidified at a cooling rate of 650°C/sec to obtain a thick After casting into a plate-shaped ingot with a diameter of 8 μm, it was cold-rolled to a thickness of 6 plates.
Annealing was performed at 20°C for 4 hours.

Mechanical properties, crystal grain size, and particle size of insoluble intermetallic compounds were measured for the material obtained as in C.

Furthermore, this material is precision cut using a diamond cutting tool to give it a mirror finish.

The suitability as a laser reflector was evaluated by measuring the surface roughness, the presence or absence of streaks such as cutting edge marks, scratches, etc., the 60° reflectance of human laser radiation, and the sharpness of the reflected image.

These results are summarized in Table 2. For proper evaluation, the presence or absence of crystallized substances and inclusions of 2 μm or more, and the presence or absence of blade edge marks and surface scratches were examined using a microscope (
400x magnification), and 2 for surface roughness measurements using a stylus type surface roughness meter, and 2 for reflectivity measurements.
r, w Laser light in the visible light region (He-He laser;
600 reflectance and the shape of the reflected image were measured by irradiation with λ=632.8 nm).

The alloy materials according to the present invention, shown as sample numbers 1 to 7 in Table 2, have a maximum grain size of intermetallic compound particles of 2 μm or less, and also have good machinability with a diamond cutting tool, and are free from cutting edge marks and surface scratches. Also, the laser beam does not leave any residue.
The 0° reflectance is 88-91 and the clarity of the reflected image is also extremely good, whereas the comparative materials shown in sample numbers 8-14 have intermetallic compound particles with a maximum particle size of 2 μm or more and have reeds and diamonds. It can be seen that it is inferior in all respects, such as poor cutting performance, such as the presence of cutting edge marks and surface scratches due to cutting with a cutting tool, and low reflectance and clarity of reflected images by laser light.

Example 2 Alloy according to the invention used in Example 1 (Table 1 Sample No. 2)
) After subjecting the molten metal to the same filtration treatment as in Example 1,
# Simultaneous cooling rate of 15°C/sec (sample number 2-1), 2
00°C/sec (sample number 2-2), and 400°C/sec (
Sample numbers 2-6 and 2-4) were cast into a plate-shaped ingot with a thickness of 8 plates.

Next, the ingot was homogenized at 480°C for 8 hours, hot rolled to 5ml, further cold rolled to 4mm, final annealed at 640°C for 1 hour, and naturally cooled to room temperature. Regarding sample number 2-4, the final annealing was performed at 520°C for 1 hour with respect to sample number 2-6.
It was cooled down to 0°C at a cooling rate of 150°C/min.

Table 3 shows the evaluation test results.

The results in Table 3 show that even though the alloys have the same composition, intermetallic compound particles of 2 μm or more are generated in the alloy materials of sample numbers 2-1 and 2-2, which are not manufactured under the conditions of the present invention. :
The machinability with a diamond cutting tool was also poor, and the sharpness of the 60° reflectance 9 reflection image with a laser beam was also not good, whereas the materials according to the present invention (sample numbers 2-6 and 2-4) failed in all of the reflection performance evaluations. It can be seen that the points are off.

Patent applicant: Nippon Light Metal Co., Ltd.

Claims (2)

[Claims] (1) Contains 2 to 6 inches of magnesium by weight, the balance is aluminum and impurities, and the permissible limit content of impurities is 15 degrees of iron α and 0.05 inches of silicon. Copper 0.25 yen, zinc 0.50%, manganese 1.0 yen. Chromium α05, zirconium α10, titanium 0.0
The molten aluminum alloy containing 296 and other impurities must be passed through a filter medium with a total pore diameter of 10 μm or less, and then cast to solidify at a cooling rate of 600°C/sec or more to form an ingot. Manufacture of an aluminum alloy material for a laser reflecting mirror, which is characterized by subjecting it to homogenization treatment if necessary, followed by multi-hot rolling and cold rolling, or only cold rolling, and final annealing. Law. (2) Final annealing is performed by heating and holding at 500 to 550°C for 60 minutes to 5 hours, and then cooling at a temperature of 100°C/min or more. Manufacturing method for alloy materials.