US 3895671 A
A method of manufacturing a thin sheet of beryllium or an alloy thereof which comprises depositing beryllium or an alloy thereof on a substrate bearing a prescribed shape, in vacuum and separating the deposited thin sheet of beryllium from the substrate.
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Description (OCR text may contain errors)
United States Patent Suzuki July 22, 1975  METHOD OF MANUFACTURING A THIN 3,390,026 6/1968 Cerych et a1. 117/107 X 3,631,745 1/1972 Walkey CI a] 164/46 X THEREOF FOREIGN PATENTS OR APPLICATIONS [751 Invent flamamatsu' Japan 513,244 11/1971 Switzerland I64/l3l  Assignee: Nippon Gakki Seizo Kabushiki Kalsha Hamamatsu Japan Primary Examiner--Francis S. l-lusar Filed: 1973 Assistant Examiner.lohn E. Roethel Attorney, Agent, or Firml(emon, Palmer & [211 App]. No.. 415,417 Estabrook Foreign Application Priority Data Nov. 15, 1972 Japan 47-114561  ABSTRACT  U.S. Cl 164/46; 164/131 A method of manufacturing a thin sheet of beryllium  Int. Cl. B22D 23/00 or an alloy thereof which comprises depositing beryl 1 Field of Search 1, lium or an alloy thereof on a substrate bearing a pre- 164/50, 250, 65, 258; 1 17/107, R scribed shape, in vacuum and separating the deposited thin sheet of beryllium from the substrate.  References Cited UNITED STATES PATENTS 9/1939 Reid 164/46 13 Claims, No Drawings METHOD OF MANUFACTURING A THIN SHEET OF BERYLLIUM OR AN ALLOY THEREOF This invention relates to a method of manufacturing a thin sheet of metal, particularly, that of beryllium or an alloy thereof.
A diaphragm used with a loudspeaker, particularly a high-pitched sound loudspeaker is desired to consist of such material as has a large Youngs modulus of elasticity and a small mass. However, a prior art alloy mainly consisting of aluminum or titanium which has hitherto been used to this end has a small Youngs'modulus of elasticity E and a high density (Al:E 7.05 X 10 N/m and p 2.7X l kg/m and Ti:E 11.9 X N/m and p 4.54 X 10 kg/m failing to meet the above-mentioned requirements. The present inventor has made experiments to search for a material fully satisfying said requirements, and discovered that beryllium'(Be) or an alloy thereof is adapted for the abovementioned application. The reason is that beryllium is conveniently provided with properties meeting the aforesaid requisites because of E 30.8 X 10 N/m and p 1.85 X 10 kg/m. Particularly suitable among beryllium alloys are Be-Cu alloy [Cu 0.5 to 5.0%, (E 30.0 to 32.0 X 10 N/m and p 1.89 to 2.20 X 10 kg/m")]; Be-Al alloy [Al to 40%, (E= 28.0 to 30.0 X 10 N/m and p,= 2.02 to 2.19 X 10 kg/m and Be-Ti alloy [Ti =0.5 to 5.0%, (E 27.2 to 27.9 X 10 N/m and p 1.86 to 1.98 X 10 kg/m A sheet of beryllium or an alloy thereof has also been found suitable for various applications including not only a loudspeaker diaphragm, but also, for example, a tone arm cantilever by being rolled up into a cylindrical form.
Though a thin sheet of beryllium or an alloy thereof is of great use, the prior art of manufacturing the sheet has been accompanied with numerous shortcomings, for example, that the product is of low quality, and expensive and that the manufacturing process is complicated. One of the conventional processes consists in forging or pressing a lump of beryllium into a thin strip and thereafter mechanically cutting out a far thinner piece from said strip. However, this process gives rise to a large amount of scrap at the time of machining, utilizing the material very inefficiently. According to another known process, forged beryllium is hot rolled into a thin sheet, which is later hot pressed or drawn into a desired form. Yet, the latter process has the drawbacks that rolled thickness is difficult to control and the work piece of beryllium has to be rolled in a state wrapped in a thin sheet of stainless steel in order to save beryllium from oxidation. Further disadvantage of said process is that the pressing or drawing step should be carried out inconveniently at high temperature to prevent the cracking of beryllium.
It is accordingly the object of this invention to provide a method free from the above-mentioned difficulties and capable of manufacturing a good quality thin sheet of beryllium or an alloy thereof with great ease and at low cost.
The above object of this invention is attained by preparing a substrate bearing a prescribed shape, depositing a thin sheet of beryllium or an alloy thereof on the substrate in vacuum, and finally separating the deposited thin sheet from the substrate.
The method of the invention is entirely different from the conventional concept of machining a lump of beryllium into a desired form, namely, utilizes the deposition of fine particles of raw beryllium in vacuum. Accordingly, the present method enables a good quality thin sheet of beryllium or an alloy thereof to be easily manufactured with a uniform thickness in a desired shape, and very efficiently utilizes raw beryllium. because little waste arises during manufacture.
There will now be detailed the various steps of manufacturing a thin sheet of beryllium or an alloy thereof according to the method of this invention.
I. PREPARATION OF A SUBSTRATE A substrate is prepared to match the desired shape of an article to be produced, for example, a loudspeaker diaphragm. The substrate consists of such material as has different chemical or physical properties from those of beryllium or an alloy thereof to facilitate the later described separating step. A first type of substrate is made of material easily soluble in nitric acid, preferably copper or magnesium. A second type of substrate is prepared from material having a very low thermal expansion coefficient, preferably quartz glass. A third type of substrate is formed of metal, particularly a fusible alloy having a lower melting point than beryllium or an alloy thereof. Copper and magnesium can be easily pressed into a desired form and the fusible alloy can also be readily forged into a proper shape. The quartz glass is worked by ultrasonic wave machining.
II. DEPOSITION OF A THIN SHEET OF BERYLLIUM OR AN ALLOY THEREOF Deposition of raw beryllium is carried out by vacuum evaporation or ion plating. No detailed description is herein given of a vacuum evaporator which is already known. A source of vacuum evaporation is, for example, beryllium itself or a beryllium alloy such as Be-Cu alloy (Cu 0.5 to 5.0%), Be-Al alloy (Al 20 to 40%) or Be-Ti alloy (Ti 0.5 to 5.0%) which has already been melted, for example, by high frequency induction heating in vacuum. The source of vacuum evaporation is melted again by electron beams in the vacuum evaporator in order to prevent the oxidation of beryllium or an alloy thereof.
In the case of vacuum evaporation, the degree of vacuum is chosen to be 6 X 10 to 2 X 10' Torr, and the substrate is heated to such a temperature as facilitates the deposition of a thin sheet of beryllium or an alloy thereof, for example, 350 to 650C when the substrate consists of copper, 350 to 400C when the substrate is formed of magnesium and 350 to 700C or preferably 600C when the substrate is prepared from quartz glass. Where the substrate is made of a fusiblealloy, the substrate is heated to a lower temperature than the melting point of the alloy.
In the case of ion plating, the degree of vacuum is set at 10 to 10 Torr. The atmosphere in which this plating is carried out may consist of inert gas, such as argon. Further, the substrate is heated to a temperature ranging between the atmospheric and 200C, regardless of the kind of raw material of which the substrate is formed. High DC. voltage is impressed across the substrate (negative electrode) and the source of evaporation for the growth of glow discharge. When the substrate is made of a non-metallic material, a separate electrode is placed just behind the substrate with respect to the source of evaporation. Other conditions than described above under which a thin sheet of beryllium or an alloy thereof is deposited on the substrate may be defined according to the customary practice of vacuum evaporation or ion plating.
The deposition step included in the method of this invention causes fine particles of beryllium or an alloy thereof to settle on'the substrate at the rate at which a compact, uniform layer is deposited on the substrate with a thickness of 1.5 microns per minute. A thin sheet thus formed has a thickness of 25 to 35 microns for use with a tweeter type loudspeaker and a thickness of 50 to 80 microns for use with a squawker type loudspeaker.
lll. REMOVAL OF A THIN SHEET FROM THE SUBSTRATE Removal of a thin sheet of beryllium or an alloy thereof is effected by drawing upon the different chemical or physical properties of the raw material constituting the substrate and beryllium or an alloy thereof.
Beryllium or an alloy thereof does not substantially react with nitric acid, whereas copper or magnesium is readily dissolved in the acid. When, therefore, a copper or magnesium substrate coated with a thin sheet of beryllium or an alloy thereof is dipped in an aqueous solution of nitric acid, the substrate dissolves itself, leaving said thin sheet. Where the substrate consists of quartz glass, a thin sheet of beryllium or an alloy thereof is removed therefrom due to the different thermal expansion coefficients between beryllium and quartz glass. As is well known, beryllium has a relatively large thermal expansion coefficient of 12.3 X deg, while quartz glass has as small a thermal expansion coefficient as 5.5 to 5.8 X 10 deg. When, therefore, the
quartz glass substrate bearing a thin sheet of beryllium or an alloy thereof is heated to a temperature ranging between 500 and l200C, the thin sheet very easily comes off the quartz glass substrate ln this case, the
quartz glass substrate has the advantageof being repeatedly used. Where the substrate isformed of a fusible alloy, at thin-sheet of beryllium or alloy thereof is removed from the substrate due to different melting points between beryllium and the fusible alloy (beryl- EXAMPLE 2 A substrate was formed over 96% pure magnesium in the same manner as in Example 1. In this case, annealing was carried out at 200C. The magnesium substrate thus prepared was placed in an ion plating device evacuated to an extent of 5 X 10 Torr. Also placed in the ion plating device was an already melted berylliumaluminum alloy (A1 30%) in a state received in a crucible at a point 15 cm apart from the substrate. While the beryllium-aluminum alloy was melted again by electron beams, DC. voltage of 5 kv was impressed across the crucible and substrate. A thin sheet of beryllium-aluminum alloy 60 microns thick settled on the substrate inabout minutes. The thin sheet was dipped in an aqueous solution of nitric acid as in Example l to remove the thin sheet from the substrate, followed by aging or sintering for, one hour at 800C.
EXAMPLE 3 A piece of transparent quartz glass was machined by ultrasonic waves into a prescribed form, followed by the grinding of the machined surface of the glass The substrate thus prepared was washed in the same mannet as in Example l.- A beryllium-copper alloy (Cu 7 sheet of beryllium-copper alloy about 30 microns thick wasdeposited on the substrate in about 20 minutes. when heated to 650C, the
lium has a melting point of l'28-5C and the fusiblealloy generally has a lower melting point'than"230 C). Ac-
cordingly, heating of the substrateto' a temperature ranging between 230 and l285Cattains the-separation of a thin sheet of beryllium or anialloy. thereof. I 1
If necessary, athin sheet-of beryllium or an alloy thereof removed from the substrate maybe subjected to aging or sintering at a temperature of 200 to 1200C, or preferably 800C. Where, however; the thin sheet has a considerably small thickness, this heating should advisably be avoided to prevent the deformation of the thin sheet.
This invention will be more fully understood from the examples which follow.
EXAMPLE 1 .substrate.
3.0%) once melted was again melted in the vacuum evaporator in the same manner as inExample l. A thin thin sheet peeled off the i -l .'A method for manufacturing a thin sheet of metal selected from a group consisting'of beryllium and beryllium alloy which comprises the steps of fabricating a substrate of a' predetermined shape .made' of material selected from a group consisting of-copper and ma gne-- siumfdepositing the thin sheet of said metal on said substrate, and removing the thin sheet from the. substrate by dissolving the latter in nitric acid.
2.The method of claim 1 wherein said metal is deposited on said substrate by vacuum evaporation.
3. The method of claim 1 wherein said metal is deposited on said substrate by ion plating.
4. A method according to claim 1 wherein said beryllium alloy is selected from a group consisting of Be-Cu alloy (Cu=0.5 to 5%), Be-Al alloy (Al=20 to 40%) and Be-Ti alloy (Ti=0.5 to 5%).
5. A method according to claim 4 vhereinsaid nitric acid is employed in the form of an aqueous solution consisting of one part of water and three parts of 60% nitric acid.
6. A method according to claim 4 wherein said thin sheet of the deposited metal, after removal from the' substrate, is subjected to heat-treatment at a temperature of 200 to 1200C.
7. A method according to claim 1 wherein said nitric acid is employed in the form of an aqueous solution consisting of one part of water and three parts of 60% nitric acid.
8. A method according to claim 1 wherein said thin sheet of the deposited metal after removal from the substrate, is subjected to heat-treatment at a temperature of 200 to 1200C 9. A method for manufacturing a thin sheet of metal selected from the group consisting of beryllium and beryllium alloy which comprises the steps of fabricating a substrate of quartz glass into a prescribed form, depositing a thin sheet of the metal on the substrate, and heating the combination to separate the thin sheet from the substrate due to different thermal expansion coefficients between the metal and the quartz glass.
10. A method according to claim 9 wherein said combination is heated at a temperature ranging from 500 to l200C when the thin sheet is separated from the substrate.
11. A method according to claim 9 wherein said metal is deposited on the substrate by vacuum evaporation.
12. A method according to claim 9 wherein said metal is deposited on the substrate by ion plating.
13. A method according to claim 9 wherein said beryllium alloy is selected from the group consisting of Be-Cu alloy (Cu=0.5 to 5%). Be-Al alloy (Al=20 to 40%) and Be-Ti alloy (Ti=0.5 to 5%).
UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. 3,895,671
DATED July 22, 1975 |NVENTOR(S) Kunio Suzuki It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:
"  Foreign Application Priority Data Nov. 15, 1972 Japan....... .47-114561 Insert -Dec. 29, 1972 Japan .2778/73 Signed and Scaled this twenty-eight Day of October 1975 [SI EAL] Arrest:
RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner uj'Palents and Trademarks