JPS5921979A - Crucible liner and its manufacture - 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 provides a new and improved crucible liner and a method for making the liner and for promoting deposition of reaction products on the inner surface of the liner during injection of molten metal from the liner. and the liner manufacturing method used.

Nickel-chromium superalloys are commonly used to form blades used in gas turbine engines.

When the cononickel chromium alloy is melted in the crucible, it reacts with the refractory properties of the crucible liner. This reaction results in reaction products or waste products. When pouring molten metal from the crucible, these reaction products tend to flow into the mold with the molten metal. This reaction product tends to cause defects in the casting.

The present invention provides a new and improved crucible liner that promotes strong adhesion of a relatively thick reactive layer on the inside of the liner during pouring and pouring of nickel chromium alloys. The liner is made of refractory and impregnated with alkaline earth. The refractory liner can be impregnated with alkaline earths by rapidly pouring and pouring an aqueous alkaline earth solution into the liner.

When a nickel-chromium alloy is melted in a crucible liner -
This alloy is co-reactive with the alkaline earths and the refractory material of the liner. The alloy, alkaline earth, and refractory interact to form a relatively thick layer of reaction products on the inside of the liner. The layer of reaction products adheres firmly to the surface of the liner. This prevents reaction products from entering the mold.

It is therefore a dual object of the present invention to provide a new and improved method of making refractory liners for crucibles by impregnating the inside of the liner with alkaline earth metals.

Another object of the present invention is to provide a new and improved crucible liner formed by wetting the inside of the refractory liner with alkaline earth solution.

Another object of the present invention is to create an interaction between the 11H nickel chromium alloy, the alkaline earth metal and the refractory material of the crucible liner during pouring of the molten alloy so that the inner surface of the liner is relatively thick. It is an object of the present invention to provide a new and improved method involving retaining a layer of reaction products.

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

New and improved Liner 10 wins U.S. T1 permit No. 3
, 401,227. In use, the generally cylindrical cavity 12 within the refractory liner 10 is partially filled with a nickel chromium alloy. This alloy is melted in a known manner by means of an induction coil.

The molten nickel-chromium alloy is then poured from the crucible into a mold to cast the gas turbine component.

According to one feature of the invention, when the nickel chromium alloy is melted in the crucible f-chie 10, the alloy reacts with both the refractory of the liner and the alkaline earth impregnated in the liner. The reaction products are deposited inside the liner. While the molten nickel-chromium alloy is being poured from the crucible, a reaction product 'sticks' adheres to the inner surface 11 of the proboscis inner 10, forming a relatively thick reaction layer. This prevents reaction products from entering the mold. By reducing the amount of impurities entering the mold, defects in the casting are greatly reduced. The crucible liner 10 has a cylindrical refractory sidewall 1 extending upwardly from a circular bottom 18 to an annular lip 20.
6. If desired, the lip 20 can be shaped to facilitate pouring molten metal onto that particular portion. Crucible liner 10 has a generally cylindrical shape, but could have a different shape if desired.

The crucible liner 10 is formed from a material such as fused silica, zircon, or other materials, or both or all thereof, in combination with a suitable binder. The crucible liner 10 is formed by encasing a mold in a slurry of ceramic mold material. It is made by soaking. Types of Slurries That Can Be Used - One exemplary slurry combines fused silica-zircon and other refractory materials with a binder. If desired, chemical binders such as ethyl silicate, sodium silicate, and colloidal silica can be used. Yet again. The slurry may contain suitable film-forming elements such as alginates to control viscosity and wetting agents to control flow properties and mold wettability.

A crucible liner 10 was formed by making a cylindrical aluminum plug tip covered with a "filter" to form a mold according to known methods. The mold was given an initial slurry coating. This slurry coating contained finely ground refractory particles to provide a precise surface finish. This initial slurry coating also contained a colloidal silica suspension, zirconium d, and a small amount of wetting agent.

After the initial slurry coating was applied, one surface was given a heavy coat of dry powder. After the tack coat, the coating was dried, dipped again, and tightly coated. After this thick coat, the coating was dried, dipped again, and thick coated. The mold was repeatedly dipped and dried until the desired thickness of ceramic mold coating was obtained. This method is described in U.S. Patent No. 6,401,2
It is similar to the one described in No. 27 No. 1. After forming a coating of desired thickness, the mold is removed from the liner. Next, the lychees are baked for one hour to a temperature of about 1,500 to 1,800 degrees below, the remaining mold filter 5 is removed, and the outer shell is strengthened.

If desired, the remaining mold filter 5 can be removed without firing the liner. This allows residual mold filler 5 to be removed from the green or unbaked mold with known solvents such as trichlorethylene, which are used to dissolve residual mold wax.

According to one feature of the invention, liner 10 is impregnated with alkaline earth metals. For this purpose.

Preference is given to using aqueous alkaline earth solutions.

The alkaline earth solution is quickly injected into the liner 10. The solution is immediately poured out of the liner without allowing time for it to soak through. If the remaining mold filter 5 is removed from the liner by baking, the liner will not be green when the mono-alkaline earth solution is poured into or poured from the liner. However - if a solvent is used to remove the residual mold wax, the liner will be green when the alkaline earth solution is poured into or poured from the liner.

The wet refractory liner is then at least partially dried. After drying, the alkaline earth treated liner 10 is fired. This may be done during the first or second firing of the liner, depending on how the remaining mold 5 is removed.

The fired liner 10 is ready for use in an alkaline earth impregnated crucible.

In one particular example, liner 10 was treated with supra-alkaline calcium. Therefore, aqueous solution of calcium nitrate) was made. This calcium nitrate solution contains 1.71 hydrated calcium nitrate (Ca(NO)3)2/cc of solvent.
4H20). This solution was made by gradually adding 4 oocc of distilled water to 15 lbs of aqueous calcium nitrate. If the solution is dirty, i.e. - if it is contaminated with dirty foreign matter, the bath liquid? Pass through a 11 sieve through a 65 mesh or finer sieve. The criterion for determining whether a solution can be reused is its dirtiness.

Therefore, the solution after processing several liners:
It is preferable that it passes >=5.

An aqueous solution of calcium nitrate was injected into the fired liner 10 over a period of about 5 to 7 seconds to remove the remaining mold filtration 5. The solution was then immediately poured out of the liner without allowing any soaking time. The total time required to pour the alkaline earth solution into and out of the liner was less than 2 minutes.

When pouring the solution from the liner 10, the solution was poured over the entire area of the lip 20 of the liner. This was done by rotating the liner 10 as the solution was poured out of the liner. When pouring molten metal from the liner by pouring the solution over the entire area of the lip 20 of the liner 10, the metal always flows to a portion of the alkaline earth-impregnated lip.

After pouring out the aqueous alkaline solution from the liner 10, the liner was turned upside down and dried for 15 minutes or more.

One batch or group of treated liners 1o
, 500 to 1,800'F. liner to 1,500'F for approximately 1 hour.
A second firing was performed at the above temperature. This firing formed an alkaline earth oxide, ie, calcium oxide, inside each liner. After the liner was removed from the furnace and allowed to cool, the liner was ready for use in a crucible.

Although described and illustrated above in connection with impregnating the crucible liner with alkaline earth calcium, alkaline earth magnesium can also be used. however.

When nickel chromium containing hafnium is melted in a crucible, it is preferable to impregnate a refractory crucible liner with calcium oxide. In the foregoing description, a refractory inner was impregnated with calcium oxide by rapidly pouring and pouring an aqueous alkaline earth solution into the liner. However, other methods can be used to impregnate liner 1o with alkaline earths if desired.

The treated and fired refractory liner 1o is described in U.S. Patent No. 5. d
Place in a crucible in a manner similar to that described in No. 01,227. The crucible liner 10 is then partially filled with nickel chromium alloy. An induction coil surrounding crucible liner 10 is energized to melt the nickel-chromium alloy.

The molten alloy is exposed together with the refractory slag forming the base of the liner and the alkaline earth deposited on the refractory. Therefore, the molten alloy can react with the refractory liner and the alkaline earth. The reaction products remain at the reaction site, ie at the surface 11 of the liner 1o. Transfer the molten metal to liner 1
During pouring out of the liner 100, the reaction product clings to the surface 11 of the liner 100, resulting in the formation of a relatively thick layer of reaction product on the inside of the liner. Maintaining a relatively thick reactive layer inside the liner during pouring of molten metal prevents impurities from entering the mold and causing defects in the produced casting.

If the refractory crucible liner 10 is not treated with alkaline earths - after the nickel-chromium alloy is poured from the liner, the untreated liner is left with a relatively thin, partially deposited, discontinuous layer of reaction products. . Nickel chromium alloy P
This thin layer of reaction product remaining on the bed treatment liner after pouring out WA I A 22 (Mar-M200+Hafnim) is schematically shown in FIG. The surface 11 of the refractory base 24 of the untreated liner is substantially, but not completely, covered by a relatively thin layer 26 of reaction products' proboscis.

In one particular example, shown in FIG. 2, this thin layer 26 of one reaction product was about 5 inches thick.

The reaction product layer 26 formed on the untreated refractory base 24 of the liner in FIG. Reacts with refractories to produce significant amounts of reaction products. Layer 2 is a layer 26 of reaction product that is loosely adhered to the liner or refractory base 24.
The space between the portions 6 and 24 of the base 24 is indicated by the space 28. Some of these reaction products, which were partially deposited, were poured into the mold when the molten nickel chromium alloy was poured from the liner. Because the layer 26 of reaction product did not adhere tightly to the base 24, further reaction may occur between the molten metal and the base. Yet again. Loosely adhering layer 2
A portion of 6 washes off the surface of the liner during pouring of the molten metal.

Refractory base 6 of liner 10 treated with alkaline earths
2 and a relatively thin reactive layer 26 is shown schematically in FIG. The molten nickel chromium alloy PWA in liner 10 was exposed to the refractory base material 62 of the liner and the calcium deposited on the refractory base using an aqueous solution in the manner described above. The molten nickel chromium alloy reacted with the refractory base 32 and the alkaline earth to form reaction products that were deposited on the inner surface of the liner 10.

During pouring of the molten nickel chromium alloy from the liner 10, these reaction products adhere firmly to the inner surface of the liner, resulting in the formation of a thick layer 34 of reaction products.

In the particular example shown in FIG. 6, one reaction layer 26 is about 0.00
It had a thickness of 0.05 inches. The reaction layer 26 firmly attached to the treated base filter 2 of FIG. 6 is ten times thicker than the reaction layer 26 attached to the untreated base 24 of FIG. Experiments have shown that the reactive layer remaining on the alkaline earth impregnated refractory liner is at least twice as thick as the reactive layer remaining on the untreated crucible liner.

Of course, the specific thickness of the reaction layer remaining on the sidewalls of the treated crucible liner after pouring the molten nickel chromium alloy from the crucible will vary depending on the purity and composition of the alloy.

According to the present invention, the nickel-chromium alloy melted in a Luppolar fner treated with alkaline earth metals is certified as
260,505 for casting articles used under severe service conditions, such as blades for gas turbine generators. In one particular example, 10 molds with a total of 12 vanes were each cast from IT nickel chromium alloy.

The blades were JT9D-7R two-stage blades. All ten molds were cast from the same alloy. The alloy is manufactured by United 5 Chikunolose Corporation (UnitedT).
echnologj,es Corporation
pWAI A 55, which has a composition approximately equivalent to the hafnium-containing B1900 alloy according to the specifications of ). 1
The molten nickel chromium alloy (particularly -PWA1455) for 5 of the 0 molds was poured from the calcium treated refractory liner by the method described above. other 5
The molds were filled with the same alloy poured from a refractory liner having the same composition but without calcium impregnation. The results obtained by pouring are as follows.

Items inspected 60 pieces 60 particles and raw visual yield 97'! o 9
8% 1st FPI yield 9royu 88%
Overall FPI yield 98% 92% Overall yield 88% 77% Therefore -
The overall yield from a mold filled with molten nickel-chromium alloy from a calcium-impregnated liner 10 is greater than that from a mold filled with the same alloy from a similar liner not treated with calcium - also impregnated with calcium. JT9D-7A 2-stage vane and JT9 using the liner
D-7R46 stage vanes were cast from PWA1d55 nickel chromium alloy. In either case, immediate yield results are obtained. If the vanes are cast from a nickel-chromium alloy that does not contain nickel, the refractory crucible liner can be impregnated with magnesium instead of calcium. In one particular example, a nickel-chromium alloy 716G was injected into a mold from a magnesium-impregnated crucible liner to cast jet engine parts. Results of the test - Using a liner 10 impregnated with an alkali, it was equally better than a columnar grained casting.
It has been proven that cast products have higher yields.

However, when using a liner impregnated with monoalkaline soil, a columnar rough surface is formed.
Rained) Castings and) Production11 We are confident that it will increase the paternity rate.

In view of the foregoing, the present invention provides a new and improved method for facilitating the deposition of a relatively thick reaction layer 34 on the inside of the lychee during pouring of nickel chromium alloys such as pwAia5s. is clear. Liner 10 is made of refractory material and impregnated with alkaline earth. The liner 10 is made by injecting or pouring an alkaline earth aqueous solution into it before firing it! It can be impregnated with alkaline earths such as calcium oxide or magnesium oxide.

When the nickel-chromium alloy is melted in the crucible 10--the alloy reacts with the alkalis and the refractory material of the liner.

During pouring and pouring of the molten alloy - the alkaline earth and refractory maintain a relatively thick reactive layer 34 on the inner surface 11 of the liner 10 .

This prevents reaction products from entering the mold and also prevents defects from occurring in the cast product.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a refractory liner for a crucible; FIG. 2 is a highly enlarged partial cross-sectional view schematically showing the thickness of the reaction layer deposited on the inside of a refractory liner that is not impregnated with alkaline earths; The figure is a highly enlarged cross-sectional partial view schematically illustrating the thickness of a reactive layer deposited on the inside of an alkaline earth impregnated refractory liner according to the present invention. 10...Liner, 11...One rule for liner. 26... Reaction product layer. Patent Applicant: T.R.W. Incorporated 1-S (4 others)

Claims (2)

[Claims] (1) A method of manufacturing a refractory liner for a crucible that promotes the deposition of a relatively thick layer of reaction products on the inside of the crucible during pouring and pouring of molten nickel-chromium alloy. providing a solution containing an alkaline earth and dissolving the alkaline earth inside the refractory liner and the refractory liner reacting with the molten nickel chromium into the liner during pouring and pouring of the alloy; Impregnating to form a relatively thick layer of reaction product that can be retained. (2) A crucible liner comprising a liner made of a refractory material and an alkaline earth metal provided inside the liner, and the liner is fired.