JPH0252683B2 - - Google Patents

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 aluminum alloy material as a laser reflecting mirror such as a rotating polygon mirror for a laser scanner,
In the past, materials with excellent corrosion resistance, machinability, strength, etc.
It was made by flattening an Al-Si-Mg alloy material using a precision grinder or precision cutting lathe, then applying nickel plating to the surface of the material, and finally polishing. However, with this method, plating and polishing take a very long time, and the operations are complicated, so there are many chances for surface scratches to occur, which reduces product yield and causes high costs. It's summery. In order to improve the drawbacks of such mirror finishing methods, a method has been developed in which ultra-precision cutting is performed using a diamond cutting tool and then a surface protective coating is applied to create a mirror finish. This method does not require complicated operations such as plating or polishing on the surface of the material, and it also shortens processing time, making it an excellent mirror finishing method.However, the finished material surface directly reflects the laser beam. Since it must function as a surface, conventionally used aluminum alloy materials cannot meet the required characteristics. In other words, the mirror surface of a laser reflecting mirror is required to have a surface roughness (Rmax) of 0.03 μm or less, a flatness accuracy (height of plane waviness) of 0.1 μm or less, and an extremely high level of reflection function with no local bits or scratches. . Furthermore, when this material is used in rotating polygonal reflectors for laser scanners, the mirror body is rotated at high speeds of tens of thousands of times per minute, so the reflective function is affected by elastic or plastic deformation. It is necessary to have such strength and rigidity that the material does not deteriorate. The inventors have completed the present invention as a result of repeated research and study on a method of manufacturing an aluminum alloy material that can be immediately used as a laser reflecting mirror material after ultra-precision turning with a diamond cutting tool or the like. The present invention uses magnesium 2 by weight.
~6%, the balance consists of aluminum and impurities, and the permissible impurity content limit is 0.15% iron, 0.05% silicon, 0.25% copper, 0.50% zinc, and 1.0 manganese.
%, 0.05% chromium, 0.10% zirconium, 0.02% titanium, and 0.10% in total of other impurities. After passing through a pore diameter of 10 μm or less, the molten aluminum alloy is solidified at a cooling rate of 300°C/sec or more. An ingot is produced by casting, and this ingot is solution-treated, hot-rolled, cold-rolled, or immediately cold-rolled to a specified thickness according to conventional methods, and finally It is characterized by being annealed. That is, according to the inventors' study, a solid solution strengthened aluminum-magnesium alloy containing 2 to 6% magnesium is an aluminum alloy system that satisfies the strength, rigidity, and reflective function among the various properties required for a laser reflecting mirror. It was found to be appropriate. However, when precision cutting is performed using a diamond cutting tool or the like using a material made from a general commercially available aluminum-magnesium alloy, 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 harder than the alloy matrix. Because of this, inclusion particles may remain as protrusions on the surface after finishing, or they may fall off during cutting, resulting in pits or scratches, resulting in scattering of the projected light in these areas, resulting in accurate and clear images. It was extremely difficult to obtain a clear reflection image. The inventors conducted a detailed study on the effect that these inclusions contained in the alloy material have on the laser beam reflection function after mirror finishing the material, and found that even if the size of the insoluble intermetallic compound particles is 2 μm or less, In other words, it is possible to form a good reflective surface as a laser reflecting mirror, that is, by passing the molten alloy through a pass material with a pore size of 10 μm or less once or several times, not only can nonmetallic inclusions be removed, but also insoluble intermetallic compounds can be removed. The amount of insoluble intermetallic compounds contained in the material can be reduced by limiting the abundance of elements that produce We succeeded in reducing the particle size to 2 μm or less. The alloy material obtained by the present invention has excellent machinability with a diamond cutting tool, the smoothness of the cut surface is also good, the reflectance can be increased to approximately 90% or more, and the reflected image is Because of its high clarity, it has excellent performance as a laser reflecting mirror, especially as a rotating polygon mirror for laser scanners. The reason for setting magnesium as an alloying element in the present invention at 2 to 6% is that if magnesium is less than 2%, sufficient strength and good machinability with a diamond bite cannot be obtained, and if it exceeds 6%, the alloy structure A βAl-Mg intermetallic compound is produced, which reduces the workability of the alloy, and this compound becomes coarse grains of 2 μm or more, reducing the reflective function of the mirror surface. As mentioned above, in the present invention, it is particularly important to control the content of metal impurity elements that cause insoluble intermetallic compounds in the alloy. In other words, these metal elements include iron, silicon, chromium, manganese, zirconium, and titanium, but the maximum allowable content of these elements is 0.15% iron, 0.05% silicon, 0.05% chromium, 1.0% manganese, and zirconium. 0.10
%, and titanium to 0.02%.The reason for limiting the amount of each element to above limits is that even if the molten metal is cooled and solidified at a cooling rate of 300℃/second or more, the size of the insoluble intermetallic compound particles will exceed 2μm in the laser reflector. This is because it will no longer be possible to fulfill its functions. 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 to remove nonmetallic inclusions, and then
It is cast into an ingot so that it is solidified at a cooling rate of ℃/second or higher. 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 to 2 μm or less. The ingot thus obtained can be immediately cold-rolled to a desired thickness, or it can be annealed at 400-550°C for 2-24 hours and then hot-rolled and cold-rolled to a desired thickness. After making the plate, the final temperature is 300~550℃.
The material is annealed for 0.5 to 5 hours to remove distortion, and then used as a material for a laser reflecting mirror. In addition, during final annealing, the annealing temperature is 500 to 550℃.
When cooling to 250℃ after annealing is performed at a cooling rate of 100℃/min or more, the material reflectance is further increased by 2.
This is more preferable since it can be improved by ~3%. Next, examples of the present invention will be described. Example 1 Sample numbers 1 to 14 having the alloy composition shown in Table 1
After passing the molten aluminum-magnesium alloy through a porous graphite filter with a pore size of 10 μm,
After solidifying at a cooling rate of 350°C/sec and casting into a plate-like ingot with a thickness of 8 μm, it was cold-rolled to a thickness of 6mm, and then this cold-rolled plate was annealed at 420°C for 4 hours. Mechanical properties, crystal grain size, and particle size of insoluble intermetallic compounds were measured for the material thus obtained. Furthermore, this material is precision cut using a diamond cutting tool to give it a mirror finish, and the surface roughness, the presence of marks such as cutting edge marks, scratches, etc., the 60° reflectance for laser incident light, and the clarity of the reflected image. The suitability of the mirror as a laser reflector was evaluated by measuring its strength. These results are summarized in Table 2. In addition, during proper evaluation, the presence or absence of crystallized substances and inclusions of 2 μm or more, cutting edge marks, and surface scratches are measured using a microscope (400x magnification), and the surface roughness is measured using a stylus type surface roughness meter. The reflectance was measured by measuring the 60° reflectance and the shape of the reflected image by irradiating with 2 mW visible light range laser light (He-Ne laser: λ = 632.8 nm).

【table】

[Table] From the results in Table 2, the alloy materials according to the present invention shown in sample numbers 1 to 7 have a maximum grain size of intermetallic compound particles of 2 μm or less, and also have good machinability with a diamond cutting tool, such as cutting edge marks and surface No scratches left, and the 60° reflectance from laser light is 88-91.
While the clarity of the reflected image is also extremely good,
The comparative materials shown in sample numbers 8 to 14 have poor machinability, such as the maximum particle size of intermetallic compound particles of 2 μm or more, and the presence of cutting edge marks and surface scratches from cutting with a diamond cutting tool. It can be seen that it is inferior in all respects, such as low reflectance and low clarity of reflected images. Example 2 The molten alloy of the alloy according to the present invention (Sample No. 2 in Table 1) used in Example 1 was overtreated in the same manner as in Example 1, and the cooling rate during solidification was 15° C./sec (Sample No. 2). -1), 200℃/sec (sample number 2-2),
and 400℃/sec (sample numbers 2-3 and 2-
4) It was cast into a plate-shaped ingot with a thickness of 8 mm. Next, the ingot was homogenized at 480°C for 8 hours, hot rolled to 6 mm, further cold rolled to 4 mm, final annealed at 340°C for 1 hour, and naturally cooled to room temperature. . For sample number 2-4, final annealing was performed for sample number 2-3.
It was heated at 520°C for 1 hour and cooled to 250°C at a cooling rate of 150°C/min. Table 3 shows the evaluation test results.

[Table] From the results in Table 3, 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 bite was poor, and the 60° reflectance and reflection image clarity with laser light were also poor, whereas the materials according to the present invention (sample numbers 2-3 and 2-4) were good in all points of reflection performance evaluation. It turns out that it is excellent.

Claims (1)

[Claims] 1 Contains 2 to 6% magnesium by weight, the balance consists of aluminum and impurities, and the permissible content limit amount of impurities is 0.15% iron, 0.05% silicon, 0.25% copper,
After passing molten aluminum alloy containing 0.50% zinc, 1.0% manganese, 0.05% chromium, 0.10% zirconium, 0.02% titanium and a total of 0.10% other impurities through an overmetal with a pore size of 10 μm or less, it was heated at 300℃/
An ingot is made by casting to solidify at a cooling rate of seconds or more, and after homogenization treatment if necessary, hot rolling and cold rolling, or only cold rolling are carried out by conventional methods, and final annealing is carried out. A method for manufacturing an aluminum alloy material for laser reflecting mirrors, which is characterized by applying 2. Production of an aluminum alloy material for a laser reflecting mirror according to claim 1, wherein the final annealing is performed by heating and holding at 500 to 550°C for 30 minutes to 5 hours, and then cooling at a temperature of 100°C/min or more. Law.