JPH1052733A - Method for casting beryllium alloy, mold and core therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a cast product high in quality by coating a core with coating film selected to make the core substantially inactive or non-reactive during casting process. SOLUTION: The core constituted of a stainless steel tube is e.g. pasma- coated with Al2 O3 havng 100μm thickness and set to the inside of inner cavity of a ceramic shell mold. The ceramic shell is preheated to 900-1250 deg.C, for example, and thereafter, molten aluminum-beryllium (40:60) alloy of 1200-1470 deg.C is poured to fill the inner cavity, i.e., the surrounding of the tube coasted with Al2 O3 . Argon gas atmosphere is held during casting and cooling. At the time of cooling the cast product, this cast product is obtained by being cleaned in the same condition as the ordinary product of an aluminum cast product and a magnesium cast product.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION In preparing beryllium alloys, particularly beryllium-aluminum alloy castings,
Many alloys have been found to be reactive with the core (and, in some cases, mold) materials, leading to core degradation and poor grade castings. It has been found that it is possible to protect the core (and the mold, if necessary) by selecting a coating that sufficiently suppresses reactions that adversely affect the core (mold) during the casting process.

[0002]

BACKGROUND OF THE INVENTION Castings of aluminum and magnesium alloys have desirable properties for various applications where light weight, good corrosion resistance and moderate strength are important. Various alloys of these metals have been developed to improve strength and high temperature properties. Certain beryllium alloys, particularly beryllium-aluminum alloys, have high toughness, low density and high melting point that provide the desired combination of properties. When casting these alloys, the high casting temperatures and corrosiveness of these alloys can result in virtually unacceptable core degradation and poor metallurgical casting integrity. I understood. The reaction products formed from the casting alloy and the core create harmful defects during casting.

[0003] Beryllium-aluminum alloys are difficult to cast, mutual insolubility and wide solidification temperatures result in excessive microporosity and a coarse microstructure results in reduced strength and ductility. In order to reduce these effects, various ternary, quaternary and even multi-element alloys have been developed to include additives such as silicon, copper, nickel or cobalt. Alternatively or additionally, powder metallurgy has been applied to these alloys in an attempt to reduce these difficulties. However, reactivity issues with core (and certain mold) materials still exist in multi-component alloys when casting the melt. Typical ternary and even multi-component alloys are 199
U.S. Pat. No. 5,417,778, May 23, 5, 1;
No. 5,421,916, June 6, 995, both issued to Nachtrab et al. Grensing et al., Application number PCT / WO95, dated October 12, 1995.
No./27088 discloses certain aluminum alloys containing beryllium and the shaping and casting precision casting of these alloys.

[0004] During casting, it is desired to make cores that can withstand the effects of these molten alloys, so that high quality castings can be obtained and mold release is possible, and in some cases, the cores are re-used. It is desirable to use it.

[0005]

The core material (and optionally the mold) is applied to the core (and optionally the mold) by applying a coating selected to be substantially inert or non-reactive during the casting process. And susceptible mold materials) can be protected during the casting of the beryllium alloy. Substantially inert or non-reactive means that it does not react with either the core or the casting during the casting process to have a detrimental effect.

[0006] It is an object of the present invention to provide an improvement in the molding or core material in a method of casting a beryllium alloy that is significantly reactive with the molten alloy, ie, substantially non-reactive during the casting process. The use of at least one of a mold or a core coated with a protective coating selected to achieve this. Further, the present invention relates to a method for casting a beryllium alloy, comprising the steps of:
mold or core or combination thereof, the mold and / or core having a protective coating selected to be substantially non-reactive with the beryllium alloy being cast throughout the casting process.

[0007] More particularly, the present invention relates to a method for producing a composition comprising:
A method of casting a beryllium-aluminum alloy containing about 80% beryllium, i.e., providing a casting mold and at least one core to produce the desired shape, oxides, borides selected to be inert with the alloy. Coating the core and optionally the mold with at least one of the group consisting of: nitride, cermet, casting the alloy into and around the mold during melting, cooling and removing the mold. , And collecting the cast part.

[0008] Optionally, the mold can be used to further form a casting. If the core is removed intact from the casting, the core can also be reused. Some core coatings can serve as release agents to facilitate core removal. It is another object of the present invention to provide a method for casting a beryllium alloy, wherein the surface of the mold that reacts upon contact with the molten metal is coated as well as the surface of the core. This advantage reduces reactivity with the molten metal and improves casting quality. The preferred embodiment is that the coatings serve as a release agent as well as a protective barrier, i.e., those coatings that have been found to have release agent properties that facilitate removal of both the mold and the core, have a Mg
O, ZrO ₂ , TiN and Al ₂ O ₃ . Release agent added Particularly preferred protective chemical barrier coating as a combination is ZrO ₂ or Al ₂ O _3.

Preferably, the beryllium alloy is a beryllium-aluminum alloy containing about 20 to about 80% by weight beryllium and contains additives to improve microstructure, strength and ductility. More preferably, the alloy can contain about 50 to about 70% beryllium.

[0010]

SUMMARY OF THE INVENTION Cast alloys can contain up to about 80% beryllium by weight. Beryllium alloy, which is easy to cast, has a weight
About 80% beryllium, about 20% to about 75% aluminum by weight, and the balance silicon, silver, magnesium, copper,
An alloy containing additives and impurities selected from nickel and cobalt. All of these alloys have about 115
Melts at temperatures above 0 ° C. (Beryllium melts at 1277 ° C.).

A casting technique involving a molten beryllium alloy,
And molds or cores that are susceptible to reaction can be solved by the present invention, and investment casting
casting, shape casting, sand casting, permanent mold and mold casting. Generally, a vacuum or inert gas atmosphere (eg, argon, helium) is maintained during casting.

[0012] Thus, the general molding materials used in the casting technique include binders with sand, ceramics such as alumina (along with the binder), silica, alumina-silicate mixtures, zircon, sodium and potassium silicates, zirconia ( (With binders), gypsum, graphite, and magnesium / iron silicate. Any of the known methods of molding a mold can be used. Many of these mold materials react with the molten beryllium alloy and can be coated as well as the core to prevent reaction.

The core may be a) a suitable metal (or alloy) that melts above the casting temperature, b) a suitable ceramic, such as an alumina / binder or silica-based ceramic, and c) a mixture thereof. Can be made. Such mixtures include, for example, stainless steel + silica-based ceramics, titanium + Al ₂ O ₃ + binders, and mixed ceramics. Often, alumina has been used with a binder of a predetermined shape, and the binder has been found to be reactive with the molten alloy. Examples of metals useful for making cores include various stainless steels such as 304, 316 and 321, titanium and Ti6
Ti-based alloys such as Al4V, nickel and IN-10
0 is a Ni-based alloy. This core was found to react with the beryllium alloy during casting.

The core body can be formed by known metallurgical techniques (for metals) or ceramic molding techniques (for ceramics and mixtures). The core can be hollow, for example, a metal tube or a slip-cast fired ceramic.
as in s) or substantially solid, such as, for example, metal rods or sintered ceramic powder. When the core is removed from the finished part, the core material must be either chemically dissolvable or mechanically destructible. These mechanical demolding processes include vibration, drilling, abrasion, and / or polishing. Depending on the method, residual core coating material can remain during casting without damage. Also, if the protective coating acts as a release agent, it is possible to remove the core into units or several parts.

It has been found that the selected coating is substantially non-reactive during casting and is capable of protecting the mold and / or core from molten beryllium alloy. As coatings, the oxides are, for example, alumina, magnesia, beryllia, thoria, titania and zirconia, the borides are, for example, beryllium boride, aluminum boride and titanium boride, and the nitrides are, for example, nitrides. Beryllium, boron nitride, aluminum nitride and titanium nitride. Cermets can also be used, for example, Be + beryllia, Be + alumina,
Be + zirconia, Mo + alumina, Ta + alumina and Ta + zirconia. Intermetallic oxides or borides or nitrides or cermets can also be used,
For example, Be-Ti boride, Be-Al nitride, beryllia-zirconia, alumina-tria.

The coating may be formed by any suitable technique, for example,
Plasma spray, evaporation, immersion, electrodeposition, spray around core body
Out, brushing, spraying, impregnating, plating and flowing
Or formed on the core by gravity or cascade coating
Done. Evaporation temperature, melting temperature and firing temperature are required.
Achieved during film formation. The thickness of the coating
Must be selected to constitute an effective diffusion barrier
It is necessary. Generally, the thickness is about 20-1000 microns,
Preferably it is in the range of about 50-200 microns. Many
Layer coatings can be used, for example, ZrO _TwoA under
l_TwoO_ThreeAnd TiO_TwoAl below_TwoO_Threeincluding.

A preferred coating is plasma sprayed or physical vapor deposited alumina having a thickness of about 50-100 microns. Another preferred coating is ZrO _2. The cast product was found to be improved to a shape such as smooth, defect-free detail passages, pockets and cavities (when using these coated molds and / or cores).

If it can be completely released, the coated mold and core can be reused. The coating layer is recoated if necessary. The following examples are exemplary and are not intended to be limiting or complete.

[0019]

【Example】

Example 1 A core composed of a stainless steel tube (321) was plasma-coated with Al ₂ O ₃ having a thickness of 100 μm. The core was placed inside the internal cavity of the ceramic shell mold by using techniques known in the investment casting industry. The ceramic shell is heated to 900 ° C to 1250 ° C (preferably 12 ° C
(00 ° C. to 1250 ° C.).
00 to 1470 ° C (preferably 1400 ° C to 1450
° C) molten aluminum-beryllium 40:60
The alloy is cast and the internal cavity or Al ₂ O ₃
Around the tube covered with. An argon gas atmosphere was maintained during casting and cooling. When the casting was cooled, the casting was provided in a cleaned condition similar to conventional aluminum and magnesium castings. It has been found that a tube coated with Al ₂ O ₃ is resistant to this molten alloy and gives a very high quality cast product. Example 2 Except that the core was immersed in a ceramic slurry (aqueous slurry of beryllium oxide) to coat and then fired,
All methods were the same as in Example 1. The beryllia coated tubing was found to be resistant to this molten alloy and to produce high quality castings. Example 3 All procedures were similar to Example 1 except that the core was made of a tube of titanium-based metal and was coated with aluminum boride by plasma spraying. It has been found that the boride coated tube is resistant to this molten alloy and gives a high quality cast. Example 4 All coatings were the same as in Example 1 except that the coating was plasma sprayed with thotia. A high quality cast product was obtained. Example 5 All procedures were the same as in Example 1, except that the coating was deposited with alumina-zirconia. It has been found that a core coated with alumina-zirconia is resistant to this molten alloy and a high-quality cast product can be obtained. Example 6 The method of Example 1 was repeated except that the ceramic shell mold was coated with 100 μm plasma spray alumina on all surfaces exposed to the molten alloy. Very high quality castings were obtained when the mold and core were removed. Example 7 A 50 μm thick Al ₂ O _{3 was} prepared by using a SiO ₂ -based ceramic core
Covered. Plasma spray, which creates a reliable and chemically inert barrier, was used to apply the layers. The coated ceramic core is placed in the internal cavity of the ceramic shell to be cast and precision cast so that the core component is exposed to the casting. 900 ceramic shell
Preheated to a temperature in the range of
A molten aluminum-beryllium alloy of 65% beryllium at a temperature in the range of １４1450 ° C. was cast into the shell and filled around the inner cavity or Al ₂ O ₃ coated tube. Once the casting was cooled, it was cooled and provided in a manner similar to known aluminum and magnesium castings. Thereafter, the exposed ceramic core was removed by filtration in a solution of borohydride. Very high quality castings were obtained. Example 8 Except that the coating was plasma sprayed with magnesia
All methods were the same as in Example 7. The magnesia-coated core was resistant to the molten alloy and produced a high-grade casting. Example 9 The core coating was made of the following ceramic, ThO ₂ , ZrO ₂ , M
gO, except _{TiO 2, AlN, BeN, BN} , that is made of TiN, the method was the same as in Example 7. In each case, the coated core was resistant to the molten alloy, producing a high quality casting. Example 10 The method is the same as in Example 7, except that the coating is made from at least two layers of alumina and zirconia of different ceramic materials. An excellent quality cast product was obtained. Example 11 The procedure was the same as in Example 7, except that the coating was made from Cermet Be + Alumina. An excellent quality cast product was obtained.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various improvements can be made within the scope of the present invention. It does not depart from the essence.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Fritz Glenning, United States, 43551, Perrysburg, Indian Wells Lane 632 (72) Inventor, Robert Tombury, Canada Quebec H9B2P9, Doralde Olmoux, Hilton Drive 153 (72) Inventor Stephen Kenner Nectect Quebec H. 7R 1 Canada 1 B3, Laval sur Le Lac, Les Hélable 629

Claims (17)

[Claims] 1. A method for casting a beryllium alloy, wherein the mold material or the core material is reactive with the molten beryllium alloy to a significant extent, wherein the beryllium alloy is substantially non-reactive during the casting process. A method of casting a beryllium alloy using at least one of a mold and a core having a selected protective coating. 2. The method of claim 1 wherein said alloy comprises sufficient beryllium to react with up to about 80% by weight of said mold material and said core material. 3. The method of claim 1 wherein said core is formed of a material selected from the group consisting of metals, ceramics and mixtures thereof, is reactive with molten metal and is solid at the casting temperature. 4. The coating of claim 1 wherein said coating is formed of a material selected from the group comprising oxides, borides, nitrides, and mixtures thereof, and is solid at the temperature of said molten alloy.
The described method. 5. The core material comprises stainless steel or silica-based ceramic, and the material of the coating is at least two of alumina, beryllium oxide, thorium oxide, magnesium oxide, titanium oxide, zirconium oxide or the oxide. The method of claim 1, comprising a mixture of species. 6. A molded mold or core for a method of casting a beryllium alloy, wherein the mold or core is reactive with the alloy.
And a mold or core having a protective coating selected to be substantially non-reactive with the alloy cast at the casting temperature. 7. The core according to claim 6, wherein the core material comprises a metal selected from stainless steel, titanium, a Ti-based alloy, nickel and a Ni-based alloy. 8. The core according to claim 6, wherein the core material comprises a ceramic selected from silica-based ceramics. 9. The mold or core of claim 6, wherein said coating comprises an oxide, boride, nitride or cermet that is solid at said molten beryllium alloy temperature. 10. The mold or core according to claim 9, wherein the coating comprises at least one of alumina, beryllium oxide, thorium oxide, zirconium oxide, titanium oxide, and magnesium oxide. 11. The mold or core according to claim 9, comprising an intermetallic compound of boron or nitrogen. 12. A combination of the mold of claim 6 and a core as a unit. 13. The combination of claim 12, wherein both the surface of both the mold and the core exposed to the alloy are coated with the protective coating. 14. A method of casting a beryllium-aluminum alloy having about 20 to about 80% beryllium by weight, comprising: providing a casting mold to obtain a predetermined shape and at least one core; Coating said core and optionally said mold with at least one selected from the group consisting of oxides, borides, nitrides and cermets selected to be active, and surrounding said alloy during melting with said mold and said core Casting a beryllium-aluminum alloy comprising cooling the mold and optionally the core and removing the cast part. 15. The method of claim 14, wherein the mold and the core are recovered, optionally recoated, and returned to the casting process for use to form a casting. 16. The method of claim 14, wherein the surface of the mold exposed to the molten alloy is reactive with the molten alloy and is coated like the core prior to casting. 17. The method of claim 14, wherein said coating is selected to also have a release agent effect.