RU2319580C2 - Method for producing thin-wall articles or articles with inner cavity of composite material on base of carbide - Google Patents

Abstract

FIELD: powder metallurgy, namely manufacture of thin-wall articles or articles with inner cavity of composite material on base of carbide, possibly manufacture of ball closures, cases for sliding bearing assemblies.

SUBSTANCE: method comprises steps of producing mold with upper opening from refractory material non-reacting chemically with melt of infiltrating metal and having melting temperature higher than infiltration temperature; placing in mold molding mass containing carbide powder and plasticizing agent and performing vibration compaction for making molded piece; removing plasticizing agent and sintering molded piece in non-oxidizing atmosphere; then performing infiltration due to heating in non-oxidizing atmosphere till temperature exceeding liquids temperature of infiltrating metal. Removal of plasticizing agent, sintering and infiltration are realized in the same mold.

EFFECT: simplified manufacturing process for making thin-wall articles or articles with inner cavity at keeping their properties.

11 cl, 5 dwg, 7 ex

Description

The invention relates to the field of powder metallurgy, in particular to the manufacture of wear-resistant thin-walled products or products with an internal cavity of a composite based on carbide, in particular ball valves, bushings for sliding bearings, etc.

A known method of manufacturing products from a composite, including the preparation of a press mass based on titanium carbide powder with the addition of a plasticizer (synthetic rubber, paraffin, zinc stearate) in an amount of up to 15%, pressing it into a mold, removing the mold from the mold, removing the plasticizer and sintering in non-oxidizing environment for transforming the molding into a refractory porous body. Next, the molding is infiltrated with transition metal melts also in a non-oxidizing medium at temperatures of 1400 ... 1600 ° C. The resulting products combine high hardness and wear resistance of a refractory base and the strength of a metal binder [Kieffer R., Benezovsky F. Hard alloys. Translation from German. M. Metallurgy, 1971. - 390 p.].

The disadvantages of the method are the difficulty of obtaining equally porous in volume thin-walled moldings or moldings with an internal cavity due to the poor compressibility of non-plastic carbide particles even when a large volume of plasticizer is subsequently introduced into the press mass, which must subsequently be removed, the difficulty of removing the molding without breaking it from the mold, and the tendency deformation of the molding and the resulting product (preform) during infiltration due to the isolation of molding particles by layers of impregnating metal and violation of its integrity and.

A known method (prototype) of the manufacture of products from a composite, in particular complex matrices, which consists in the manufacture of powders of refractory carbides of a porous molding and its subsequent infiltration with a molten metal. In this method, a malleable mold of silicone rubbers is made according to the model. A plasticizer is added to the refractory powder, the press mass is heated and loaded into the mold in vacuo to remove volatiles from it and the curing of the binder, after which the obtained molding having sufficient strength is removed from the mold. For the purpose of better formability, vibration compaction is used. The flexibility of the form allows to remove complex profiles from it without breaking. Next, the molding is heated to burn the binder and infiltrated with a molten metal [US Patent No. 4,327,156, IPC index B22F 3/00, C22C 1/05, claimed 05/12/1980, published 04/27/1982].

The disadvantages of the prototype and analog are identical - the tendency to deformation of the porous molding and the resulting workpiece during infiltration and the difficulty of obtaining thin-walled products or products with an internal cavity from a carbide composite.

The objective of the invention is to simplify the process of manufacturing thin-walled products or products with an internal cavity of a composite based on carbide while maintaining their quality.

The problem is solved by a method of manufacturing thin-walled products or products with an internal cavity from a carbide-based composite, including preparing a mold with an upper hole, placing a press mass containing carbide powder and a plasticizer in a mold, vibration sealing to form, removing plasticizer, sintering in a non-oxidizing environment , the placement of the impregnating metal and heating in a non-oxidizing medium to a temperature exceeding the liquidus temperature of the impregnating metal and ensuring the infiltration of movki, characterized in that the use form of refractory material that does not react chemically with the melt infiltrant metal and having a melting point higher infiltration temperatures, and the plasticizer removal, sintering and infiltration of the molding is carried out in the same manner.

Ethyl alcohol can be used as a plasticizer.

Vibration compaction can be accomplished by applying external pressure.

Plasticizer removal, sintering and infiltration can be carried out in one operation.

Plasticizer removal and sintering can be carried out separately from infiltration.

A mold made of steel lined with a layer of refractory oxides that do not chemically interact with the melt of the impregnating metal can be used.

A mold made of refractory oxides may be used.

As carbide powder, titanium carbide powder may be used.

As carbide powder, tungsten carbide powder can be used.

As the impregnating metal, copper alloys, heat-resistant nickel alloys, chromium-nickel steels, tungsten-molybdenum steels can be used.

A mold can be used in the lower part of which a hole is made, closed by a porous lid with through pores of carbide in contact with the bottom of the ceramic crucible from a material that does not chemically interact with the melt of the impregnating metal, while the impregnating metal is placed in the crucible, and molding is infiltrated through cover.

The proposed method is illustrated by drawings:

Figure 1 - steel mold for the manufacture of thin-walled bearing bushings:

1 - steel mold;

2 - refractory layer;

3 - tungsten carbide press mass;

4 - impregnating metal.

Figure 2 - blank thin-walled sleeve of the bearing:

5 - blank thin-walled sleeve.

Figure 3 - ceramic mold of alumina for the manufacture of billet ball valves with a press mass and an impregnating metal:

4 - impregnating metal;

6 - ceramic form;

7 - riser ceramic shape;

8 - press-mass of titanium carbide;

9 - perforated cover;

10 - through holes;

12 - punch.

Figure 4 - carbide billet ball plug:

11 - blank ball plug.

Figure 5 - embodiment of the form with the bottom cover:

4 - impregnating metal;

13 - lower hole of ceramic shape;

14 - a cover;

15 - ceramic crucible;

16 - clearance.

Example 1

An exact blank was prepared for a thin-walled bearing sleeve from a composite based on tungsten carbide in steel mold 1 (Fig. 1). After etching with acids, a ceramic layer was applied to the inner surface of the steel mold by dipping into a suspension based on alumina. After drying and heat treatment at a temperature of 500 ° C, a refractory layer 2 0.3-0.5 mm thick was formed on the inner wall of the mold. Next, a press mass was prepared on the basis of tungsten carbide powder with a particle size of 10-20 μm with the addition of a plasticizer - ethyl alcohol in an amount of 10% by volume. In this case, ethyl alcohol was used to improve the formability of the powder. Press mass 3 was placed in the mold cavity. The form was fixed on a vibrating table and the powder was compacted for 30 s with oscillations with a frequency of 30 Hz and an amplitude of 0.5-0.6 mm. Next, an impregnating metal 4, which is an alloy of copper with 40% nickel by weight, was placed on a powder molding. The form was placed in a chamber of a vacuum electric furnace, evacuated, and heating was turned on. At a temperature of 1000 ° C, an exposure was given for 1.0 h for sintering of carbide powder particles, as a result of which a sintered molding was obtained in the mold cavity with a porosity of 45-47%. Next, the temperature was brought to 1250 ° C, the mold was kept there for 0.5 h to infiltrate the molding with molten metal and the heating was turned off. After cooling and impact on the form of shock loads, a non-porous precise preform of a thin-walled bearing sleeve 5 (Fig. 2) was removed from it from a composite with a tungsten carbide content of approximately 53-55% by volume, the hardness of the material was 50 ... 55 HRC. Subsequently, the steel mold was used repeatedly for the manufacture of bushings from composite.

Example 2

An accurate preparation of a Du50 ball valve (a hollow ball with an external diameter of 90, a wall thickness of 5, inlet and outlet diameters of 50 mm) was made of a composite by infiltration of a titanium carbide molding placed in a refractory form of aluminum oxide with a ZhS6U nickel heat-resistant alloy (Fig. .3). The mold was made by repeatedly applying ceramic layers to the fusible model by dipping it into a suspension of fine-ground electrocorundum (aluminum oxide) and sprinkling it with electrocorundum sand in a "pseudo-boiling" layer, followed by vacuum-ammonia drying. After obtaining a sufficient shell thickness, removing the model from it, drying and sintering in a chamber furnace at a temperature of 980 ° C, a refractory form of aluminum oxide was obtained.

In the prepared form 6 with a riser 7, a press mass of titanium carbide powder 8 of a fraction of 63/10 μm in the amount of 0.25 kg with the addition of ethyl alcohol was placed. After fixing the form on the vibrating table, the press was compacted with vibration with an oscillation frequency of 30 Hz and their amplitude of 0.6 mm. The result was molding with a porosity of 45% and an average pore size of 35 μm. The molding was closed from above with a perforated lid 9 of sintered aluminum oxide with through holes 10. Measured pieces of metal 4 — ZhS6U alloy weighing 0.30 kg, were placed on the lid. with a certain excess in weight to guarantee the filling of the entire pore volume of the carbide molding.

The process of molten metal molding was carried out in a OKB-8086 model vacuum furnace, the temperature was controlled by a tungsten-tungsten fusion thermocouple. The prepared mold with molding and metal was placed in an electric furnace chamber, it was sealed, and after it reached a residual pressure of not more than 1.0 Pa, heating was switched on. The forms were heated stepwise according to the regime:

- heating to a temperature of 1300 ± 10 ° C and sintering of the molding at this temperature for 2.0 hours;

- heating to a temperature of 1500 ± 10 ° C and holding at this temperature for 0.5 h to melt the impregnating metal and completely infiltrate the sintered molding through a perforated lid;

- cooling the mold when the heating is off.

As a result, a non-porous billet ball billet 11 was obtained from a hard alloy based on titanium carbide with a bunch of ZhS6U alloy (Fig. 4). The workpiece was removed from the mold by breaking it and processed with an abrasive tool to obtain the finished part. The volume content of the carbide base in the composite was 54-56%, the hardness of the composite was 60 ... 63 HRC.

Example 3

An accurate billet ball shutter was prepared as in Example 2. In this case, the molding was pressed with a steel punch 12 (Fig. 3) with a polished end surface to create a static load on titanium carbide powder. After vibration compaction, the punch was removed, and the molding was closed from above with a perforated cover. Further, the process was carried out as in example 2.

The volumetric content of the carbide base in the composite was 60-62%, the hardness of the composite was 63 ... 66 HRC.

Example 4

An exact billet of the ball valve was made according to Example 3. In this case, after vibration compaction, the molding was sintered in vacuum at a temperature of 1500 ± 10 C for 2.0 h, after which spontaneous cooling was performed with heating turned off. After depressurization and opening the chamber, the molding was closed with a perforated lid, metal 4 was placed on it, the chamber was closed, evacuated, the mold was heated to a temperature of 1500 ± 10 ° C and held there for 0.5 h. The volume content of the carbide base in the composite was 64-67% , the hardness of the composite was 65 ... 68 HRC.

Example 5

A ball valve blank was prepared according to Example 2. In this case, steel 12Kh18N10T with a weight of 0.28 kg was taken as the metal. The temperature of infiltration was kept equal to 1550 ± 10 ° С.

As a result of the process, a non-porous billet billet from a hard alloy based on titanium carbide with a steel binder was obtained. The volume content of the carbide base in the composite was 54-56%, the hardness of the composite was 58 ... 61 HRC.

Example 6

A ball valve blank was prepared according to Example 2. In this case, tungsten-molybdenum steel grade P6M5 weighing 0.30 kg was taken as metal. The temperature of infiltration was maintained equal to 1550 ± 10 ° C.

As a result of the process, a non-porous ball valve blank was prepared from a composite based on titanium carbide with a steel binder. The volume content of the carbide base in the composite was 54-56%, the hardness of the composite was 63 ... 65 HRC.

Example 7

A ball valve blank was prepared according to Example 2. In this case, a hole 13 (Fig. 5) was made in the lower part of the mold, which was closed with a cover 14 before placing the press mass. The lower cover was made by known technology by pressing titanium carbide powder with a particle size of fraction 63 / 10 μm and its sintering at a temperature of 1550 ± 10 ° С with obtaining in it an open porosity of 45% and an average diameter of through pores of approximately 30 μm.

The mold was placed in a prefabricated ceramic crucible 15 so that the lid 14 was in contact with the bottom of the crucible with the entire bottom end surface. The crucible was made of refractory material, such as electrocorundum, which does not chemically interact with the molten metal. A metal sample 4 of a mass of 0.34 kg was placed in the crucible. Between the bottom of the ceramic crucible and the shell mold, a gap 16 was provided for the molten metal to enter the lid 14. Infiltration was carried out through the lower lid of the mold. The molten metal infiltrated the bottom cover and through it a sintered titanium carbide molding.

As a result of the process, a non-porous ball valve blank was prepared from a titanium carbide composite. The volume content of the carbide base in the composite was 54-56%, the hardness of the composite was 60 ... 63 HRC.

Example 8

According to the prototype technology, a washer with a diameter of 30 mm and a height of 10 mm was made (due to the impossibility of manufacturing thin-walled and with internal cavities of products similar to the invention). From a press-mass based on titanium carbide with the addition of granular paraffin (5% by weight) in a flexible silicone rubber mold using vibration, a molding was obtained that was removed from the mold and sintered in a vacuum oven at a temperature of 1500 ± 10 ° C for 0, 5 hours. The obtained sintered molding, a washer with a porosity of about 45%, was infiltrated with ZhS6U alloy at a temperature of 1500 ± 10 ° C for 0.5 hours. As a result, a non-porous article was obtained from a composite with a hardness of 60-63 HRC.

Thus, the method of the present invention allows to simplify the manufacturing process of thin-walled products or products with internal cavities from a carbide-based composite with high hardness and the absence of their deformation.

Claims (11)

1. A method of manufacturing thin-walled products or products with an internal cavity from a carbide-based composite, comprising preparing a mold with an upper hole, placing in the form of a press mass containing carbide powder and plasticizer, vibration sealing to form, removing plasticizer, sintering in a non-oxidizing environment, the placement of the impregnating metal and heating in a non-oxidizing medium to a temperature exceeding the liquidus temperature of the impregnating metal and providing molding infiltration, characterized in that polzujut form of refractory material that does not react chemically with the melt infiltrant metal and having a melting point higher infiltration temperatures, and the plasticizer removal, sintering and infiltration of the molding is carried out in the same manner. 2. The method according to claim 1, characterized in that ethanol is used as a plasticizer. 3. The method according to claim 1, characterized in that the vibration compaction is carried out with the application of external pressure. 4. The method according to claim 1, characterized in that the removal of the plasticizer, sintering and infiltration is carried out in one operation. 5. The method according to claim 1, characterized in that the removal of the plasticizer and sintering is carried out separately from the infiltration. 6. The method according to claim 1, characterized in that they use a mold made of steel lined with a layer of refractory oxides that do not chemically interact with the melt of the impregnating metal. 7. The method according to claim 1, characterized in that they use a mold made of refractory oxides. 8. The method according to claim 1, characterized in that titanium carbide powder is used as carbide powder. 9. The method according to claim 1, characterized in that the tungsten carbide powder is used as carbide powder. 10. The method according to claim 1, characterized in that as the impregnating metal, copper alloys, nickel heat-resistant alloys, chromium-nickel steels, tungsten-molybdenum steels are used. 11. The method according to claim 1, characterized in that a mold is used in the lower part of which a hole is made, closed with a porous lid with through pores of carbide in contact with the bottom of the ceramic crucible from a material that does not chemically interact with the melt of the impregnating metal, while impregnating metal is placed in the crucible, and molding infiltration is carried out through the lid.

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