JPH011399A - Magnesium thin plate for speakers - 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 The present invention relates to a thin magnesium plate for a diaphragm of a speaker. More specifically, the present invention relates to a thin magnesium plate for speakers produced by rolling a unidirectionally solidified ingot, which is produced by a heated mold continuous casting method.

Speakers come in a variety of sizes, including those for audio, televisions, telephone handsets, and earphones, but all of them emit sound through the vibration of a diaphragm made of metal, glass, or paper. . In order to reproduce delicate sounds, it has been considered important that the diaphragm be thin and light. In particular, the diaphragms of small earphones and telephone receivers must be made from light, extremely thin materials with high rigidity.

Magnesium has a specific gravity of 1.7, making it the lightest metal in practical use. Ti, which has been commonly used for speaker diaphragms, has a specific gravity of 4.5, and magbusium is a much lighter metal suitable for speaker diaphragms. However, since magnesium has a crystal structure consisting of a close-packed hexagonal lattice, it has poor workability and is difficult to roll into a plate, making it impossible to make a pure magnesium speaker diaphragm.

Conventionally, metal ingots, which are processed materials, have been cast using cooling molds. Therefore, the ingot is made of polycrystalline material including equiaxed products, and there are columnar crystal bands with poor workability on the outer periphery of the ingot, and! Casting defects such as J voids, air bubbles, and segregation of impurities often occurred. Roll such an ingot to make ultra-thin foil! When manufacturing, the occurrence of pinholes due to these casting defects and the occurrence of edge cracks during processing are unavoidable problems. Furthermore, it was impossible to move around a speaker diaphragm made of pure magnesium, which has a dense hexagonal lattice structure, and which is extremely thin.

Conventionally, in order to give workability to magnesium, zinc and manganese were added to make a magnesium alloy ingot, and 250
After hot working at temperatures above ℃, the plates were assembled and used as diaphragms for speakers.

However, even if such elements are added, the
In order to make a thin whistle with a thickness of , it is easy to cause edge cracks in the foil during rolling, and cracks at primary grain boundaries, that is, solidified grain boundaries, that remain inside the foil as a history of casting m weave. , the yield rate of sound foil was extremely low.

Therefore, ultra-thin foils of magnesium alloys were extremely expensive and were not used except in specialized speakers.

Also, adding elements with high specific gravity such as zinc or manganese to magnesium will increase the weight of the diaphragm.
There has been a strong desire for a method for producing a thin and light pure magnesium diaphragm without the addition of such elements.

The present inventor has conducted many experiments on a method for obtaining ultra-thin speaker diaphragms with excellent rigidity using pure magnesium without adding heavy elements such as zinc or manganese to magnesium. The heated mold continuous casting method is characterized by keeping the temperature of the inner wall of the mold above the solidification temperature of the cast metal and cooling the ingot only outside the mold.
Patent No. 1049146), by casting a thin single-crystal plate-shaped ingot and rolling it, a healthy O. We have discovered that an extremely thin magnesium diaphragm like this can be made extremely easily.

That is, a horizontal graphite mold with a hollow cross section of 1.00 mm in width and 1 to 10 mm in height was placed at an inner wall temperature of 251°C.
The mold was heated as above. Continuous casting of magnesium strip ingots with a diameter of 1 to 10 mm was carried out by supplying molten magnesium to a mold and cooling the ingot using water only outside the mold. The area near the solidified end of these ingots was made up of polycrystals, but as casting progressed, the number of crystals decreased as a result of competitive growth of crystals, and finally a single crystal was obtained. It has been found that rolling can be carried out at the above various temperatures to a thickness of 0.01 mm without cracking.

Moreover, by changing the thickness of the ingot, which is the processing material, the degree of processing of the plate, and by appropriately selecting the processing temperature, it is possible to easily obtain any hardness, such as hard or soft. We discovered that diaphragms for various sound qualities can be made from lightweight pure magnesium.

The present invention provides a pure magnesium diaphragm for speakers, which could not be obtained by processing ingots obtained by conventional cooling molds, and will greatly contribute to the development of audio equipment. It seems to be.

Claims (1)

[Claims] Magnesium thin plate for speakers, characterized in that it is made by processing an ingot obtained by a heated mold continuous casting method.