JPH02183201A - metal mirror - Google Patents

Abstract

PURPOSE:To obtain the mirror which has high toughness, good workability, good resistance to oxidation and corrosion, and a high reflectivity and low absorption to an optical laser wavelength by forming the mirror of the single crystal of Mo melted by an electron beam. CONSTITUTION:A water-cooled mold 2 which holds a solidified Mo material 5 is disposed perpendicularly below a bar material 1 consisting of Mo as a base material and electron guns 3, 4 are disposed diagonally above the mold 2. The electron beam EB1 is made incident to the front end part 1a of the bar material 1. The Mo liquid drops heated and melted from the front end part 1a of the bar material fall to nearly the central part of the mold 2 to form a molten Mo pool 6. The temp. of the solidified Mo material 5 decreases gradually as the material descends perpendicularly below the mold 2 and the crystal grows perpendicularly downward from a molten part 5a so that the single crystal 10 of a large grain size is obtd. The metallic mirror which has the excellent resistance to oxidation and corrosion, the good workability, the easy workability, and the good reflectivity is obtd. in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a metal mirror, and is applied to a metal mirror that reflects light such as laser light or synchrotron radiation light.

(Prior art) Conventional metal mirrors that reflect laser light are used in low-to-medium power machines, with a Si mirror surface coated with gold, silver, or a dielectric reflective film, and in medium-to-high power machines,
A Cu mirror surface or a Cu mirror surface coated with gold, silver, etc. is often used.

In high-output devices, there is an increasing need for Mo laser beam mirrors. This is because conventional Cu mirrors are prone to rust and scratches in high-temperature, humid environments like Japan, while MO mirrors have lower reflectance than Cu mirrors but are less likely to rust. One of the reasons is that it has excellent properties.

(Problems to be Solved by the Invention) Generally, the characteristics required of a metal mirror include the following points.

(+) High reflectance and low absorption for a wavelength of 10.6 μm; (2) Good thermal conductivity and low coefficient of thermal expansion; (3) High purity, small deformation and scratch resistance; (4) It is chemically and thermally stable and has good oxidation and corrosion resistance. (5) It has excellent workability and reworkability.

When these required characteristics are replaced with the required characteristics of the material, the contents of the required material characteristics are as follows.

(The crystal has no anisotropy and has a single phase structure, (2)
(3) Precipitates, inclusions, pores, and segregation are small; (4) the crystal orientation, grain shape, and grain size are uniform;
) There are few internal strains, lattice defects, disturbances, etc.

In view of the required characteristics of these materials, the present inventor believed that a single crystal of MO would sufficiently satisfy the required characteristics of the metal mirror described above, and thus completed the present invention.

The problem to be solved by the present invention is to provide an MO mirror that has high toughness, good workability, good oxidation resistance and corrosion resistance, and has high reflectance and low absorption at the optical laser wavelength.

(Means for Solving the Problems) The metal mirror of the present invention has an electron beam melting field, and M
It is characterized by being made of a single crystal of O.

The electron beam melting world includes ■Products made by other manufacturing methods,
This is because, compared to, for example, a vacuum arc melting field, powder sintered crystal, etc., the reflectance of the mirror surface to laser light (wavelength of 10.6 μm) is better as shown in the experimental data described later. ■Also, it is possible to produce large single crystals.

Methods for producing single crystals include methods such as secondary recrystallization and seamelting, but these methods have the disadvantage that the size of the single crystal is small. On the other hand, according to the electron beam melting method, the crystal grains are coarsened and a large single crystal is formed by changing the melting conditions, especially adjusting the dissolution rate, for example, by reducing the crystal growth rate to 10 cm/hr or less. This is because it is relatively easy to grow and cut the coarsened single crystal into a mirror of a predetermined size.

The reason for using a Mo single crystal is as follows. If MO is polycrystalline, the grain boundary strength is weak, making plastic working and polishing difficult, and furthermore, when the material is annealed, Na and K concentrate at the grain boundaries, causing grain boundary fractures due to heat shock. Cheap. On the other hand, M.

This is because a single crystal has high toughness, high strength, and viscosity, is relatively easy to plastic work and polish, and does not cause grain boundary fracture. In addition, MO single crystal has a higher reflectance of laser light than MO polycrystal.

(Example) Embodiments of the present invention will be described based on the drawings.

First, the electron beam melting method for manufacturing a Mo single crystal will be explained based on FIGS. 1 and 2.

As shown in FIG. 1, a water-cooled mold 2 holding a Mo solidified material 5 is placed vertically below an MO bar l serving as a base material. An electron beam (EB) is placed diagonally above the water-cooled mold 2.
) is arranged. The electron beam EB1 emitted from the electron gun 3.4 hits the tip 1a of the bar 1.
is incident on the

As a result, the MO droplets heated and melted from the bar tip 1a fall to approximately the center of the cooling mold 2, forming a Mo melting boule 6, as shown in FIG. The electron beam EB is also incident on the molten part 5a within the water-cooled mold 2.

As shown in FIG. 2, the water-cooled mold 2 is made of, for example, Cu, and is cooled by water flowing in from the inlet vibrator 8, absorbs heat from the melting part 5a, the coagulating material 5, etc., and becomes hot water, which is then passed through the outlet vibrator. It is discharged to the outside from 9. The temperature of the Mo solidified material 5 gradually decreases as it descends vertically below the water-cooled mold 2, and a single crystal is produced by crystal growth in the vertically downward direction from the molten part 5a. The crystal growth rate is, for example, 10 cm
By setting the speed to be as low as / hr or less, a single crystal 10 with a large grain size can be produced as shown in FIG.

In the embodiments described above, the electron beam melting method in which the melted base material is sent out in the vertical direction was explained.

As a method for manufacturing the Mo mirror of the present invention, any electron beam melting method can be used as long as it is melted appropriately.

A single crystal is taken out from the obtained solidified material 5 by cutting. A metal mirror-shaped mirror body is obtained from this single crystal by cutting. In this case, since it is a single crystal, plastic working is extremely easy.

The obtained single-crystal Mo mirror was tested to compare the reflectance of various types of light. Comparative examples include Mo polycrystalline electron beam melted products (Comparative Example 1), polycrystalline arc melted products (Comparative Example 2),
This is polycrystalline powder sintered crystal (Comparative Example 3).

The results of the comparative test are shown in Table 1.

(The following is a margin.) As shown in Table 1, according to the single crystal electron beam melted products of the examples, the reflectance to laser light (wavelength 1006 μm) is higher than that of the polycrystalline electron beam melted products (comparative example I) and the arc melted products. (Comparative Example 2) has a larger value than that of the powder sintered crystal (Comparative Example 3), and is superior in terms of reflectance. Furthermore, since it is a single crystal, it has manufacturing advantages of high strength, high toughness, and excellent workability. The reason for the high reflectance is considered to be that the surface roughness of a single crystal is smoother than that of a polycrystal.

(Effects of the Invention) As explained above, the metal mirror of the present invention has excellent oxidation resistance and corrosion resistance because it is constructed from MO single crystal by electron beam melting, which is relatively easy to manufacture. This has the advantage that it is possible to provide a metal mirror that has good workability, is easy to manufacture, and has good reflectance.

FIG. 2 is a schematic diagram showing one embodiment of the electron beam melting method, and FIG. 2 is a schematic diagram showing the growth of a single crystal by the melting method shown in FIG.

...Mo bar material, ...water-cooled mold, ...Electron gun, ...Coagulation material.

Claims (1)

[Claims] (1) A metal mirror that is an electron beam melted product and is made of a single crystal of Mo.