RU2730251C1 - Method of making composite materials - Google Patents

Abstract

FIELD: technological processes.SUBSTANCE: invention relates to production of composite materials with impregnation of a porous carbon-graphite frame, having high electrical conductivity, antifriction properties and resistance to aggressive media. Vibrovacuuming of the porous billet is carried out in a separate vessel for 7–8 minutes in a melt of a matrix copper-phosphate alloy. Workpiece is pre-impregnated before impregnation in cooled to 600 ºC alloy of phosphorous copper on crystallized as a result of cooling surface of copper phosphate alloy, which is preliminarily poured into impregnation device at melt temperature of phosphorous copper 800 ºC per 2/3 of the device volume. Device for impregnation with a molten alloy of phosphorous copper, heated to 800 ºC, is filled. Impregnation of workpiece is carried out due to phase transition of alloy of phosphorous copper from solid state to liquid at heating impregnation device to temperature by 100 ºC higher than liquidus temperature of copper alloy. Then isothermal holding is carried out at the same temperature for 20 minutes to ensure thermal expansion of copper alloy melt.EFFECT: reduced time for composite material production.1 cl, 2 dwg, 1 tbl, 1 ex

Description

The invention relates to the field of metallurgy, namely to a method for producing composite materials with high electrical conductivity, antifriction properties and resistance in aggressive environments, which can be used in mechanical engineering for the manufacture of current collectors, pantograph inserts, electric brushes, seals, plain bearing shells.

A known method of obtaining a composite material by impregnation with simultaneous chemical action. The workpiece is installed on a special graphite platform, heated over the surface of a silicon melt or an alloy based on silicon and copper, having a temperature of 1700-1800 ° C, then gradually, at a speed of no more than 10 cm / min, the workpiece is lowered into a bath with a melt. Thereby, carrying out impregnation with a unidirectional melt flow, propagating by the front along the entire section of the workpiece (RF patent No. 2276631, MPK С04В35 / 52, publ. 02.08.2004).

The disadvantage of this method is the absence in the process of impregnation of the stage of evacuation of both the alloy and the workpiece, as a result of which the melt is oxidized, interacting with air, reducing the quality of the composite material.

A known method of producing a composite material based on a metal matrix and non-metallic fiber, including the preparation of a preform from a non-metallic fiber, sealing the resulting preform with simultaneous removal of water through a perforated bottom in a mold, fixing it, drying, pouring with matrix metal and impregnation with a melt of matrix metal under pressure (RF patent No. 2392090, IPC B22D19 / 14, C22C47 / 00, publ. 20.06.2010).

The disadvantages of this method are the limited nomenclature of matrix alloys that can be used with this manufacturing method, and the high cost of composite materials (CM) due to the high cost of equipment and tooling for impregnation.

There is a known method of impregnating a porous body with metal, in which the porous body is preheated, installed in a special mold, in which there are holes through which the preheated matrix melt is injected using injection molding machines. Injection pressure 20 MPa, exposure for about 3 seconds (US patent No. 6699410, IPC B22D 9/00, publ. 03/02/2004).

The disadvantage of this method is the manufacture of special shapes for each unique workpiece, the high cost of the product, while the porous body is covered with a metal crust with a sprue, which will require additional machining.

The closest in technical essence to the proposed method and the achieved effect is a method of impregnating a porous workpiece with metal, in which the reinforcing porous frame is preheated, then poured with a matrix alloy, vacuum degassing is carried out and impregnated under the influence of an excess pressure of 15 ± 3 MPa on the workpiece due to thermal expansion of the melt in a closed volume of the vessel during heating (RF patent No. 2571295, IPC B22F3 / 26, publ. 20.12.2015).

The disadvantage of this method is the large amount of time spent on heating the tooling and cooling it for degassing the chamber for impregnation.

The objective of the invention is to develop a method for manufacturing composite materials, which makes it possible to effectively use the heating temperature in the process of impregnating graphite carbon.

The technical result of the invention is to reduce the time required to obtain a composite material, which makes it possible to increase the productivity of the method.

The technical result is achieved in a method for manufacturing composite materials, including vacuum degassing of a porous workpiece in a melt of a copper matrix alloy, heating and exposure to excess pressure on the workpiece due to thermal expansion of a copper alloy melt in a closed volume of a sealed device for impregnation while heating the device for impregnation to a temperature of 100 ° C above the liquidus temperature of the copper alloy and subsequent isothermal holding at the same temperature for 20 minutes to ensure thermal expansion of the copper alloy melt, while a phosphorous copper alloy is used as a copper alloy, vacuum degassing of a porous workpiece in a phosphorous copper matrix alloy melt is carried out in a separate container installed on a vibrating table with the provision of vibration vacuumization of the workpiece for 7-8 minutes, before impregnation, the workpiece in the phosphorous copper alloy cooled to 600 ° C is placed on the surface of the alloy crystallized as a result of cooling. sphorous copper, pre-poured into a device for impregnation at a temperature of a phosphorous copper melt of 800 ° C for 2/3 of the volume of the device, after which the device for impregnation with a melt of phosphorous copper alloy heated to 800 ° C is completely filled through a hole in the installed lid, and impregnation of the workpiece carried out due to the phase transition of a phosphorous copper alloy from a solid state to a liquid state.

Vacuum degassing of a porous workpiece is carried out in a melt of a matrix alloy of phosphorous copper in a separate container (alundum crucible) installed on a vibrating table with the provision of vibration vacuuming of the workpiece for 7-8 minutes. A phosphorous copper alloy melt is poured into a device for impregnation at a phosphorous copper melt temperature of 800 ° C for 2/3 of the device volume. Further, the workpiece in the phosphorous copper alloy cooled down to 600 ° C (in the volume of which the vibration vacuumization was performed) is placed on the surface of the phosphorous copper alloy crystallized as a result of cooling in the impregnation device. The device is filled with molten phosphorous copper and placed in a heating furnace, where the transition of the matrix alloy from a solid state to a liquid state occurs with an increase in the volume in the device. Excessive pressure is applied to the workpiece due to thermal expansion of the melt in the closed volume of the container and the impregnation of the porous workpiece.

Use a container for impregnation of a material with a minimum coefficient of thermal expansion to provide the required impregnation pressure (with a coefficient of thermal expansion 3 times higher than the coefficient of thermal expansion of the container material) on a porous workpiece immersed in the melt of the matrix alloy.

As a matrix alloy, an alloy of phosphorous copper MF-9 (GOST 4515-93) is used, the melt of which during the impregnation process is heated 100 ° C above the liquidus temperature of the phosphorous copper alloy. Carbon graphite is used as a porous workpiece.

The immersion of a porous workpiece in the melt of a matrix alloy of phosphorous copper, which is in an alundum crucible, during vibration vacuumization of the workpiece, allows simultaneous evacuation and primary (partial) filling of open pores with a liquid matrix alloy. The alloy cooled down to 600 ° C with the workpiece inside goes to the secondary impregnation (in the impregnation device).

Secondary impregnation is carried out due to the transition of the matrix alloy from the solid to the liquid state. This makes it possible to obtain an increase in the volume of phosphorous copper by 5.3% due to the phase transition of a phosphorous copper alloy from a solid state to a liquid state when the device for impregnation is heated to a temperature of 100 ° C above the liquidus temperature of phosphorous copper. Subsequent isothermal holding at the same temperature for 20 minutes provides thermal expansion of the phosphorous copper alloy melt.

Heating up to 100 ° C above the liquidus temperature of a phosphorous copper alloy allows us to take into account the amount of heating required to compensate for the volume of open pores of the reinforcing frame due to thermal expansion of the matrix melt, and ensures the creation of the required impregnation pressure, which makes it possible to obtain a high quality composite material (CM) with high the degree of filling the volume of open pores of the porous workpiece with the matrix melt.

The use of a phosphorous copper alloy as a matrix melt, and carbon graphite as a porous body makes it possible to obtain composite materials widely used in mechanical engineering for the manufacture of current collectors, pantograph inserts, electric brushes, seals, and plain bearing liners.

FIG. 1 shows a device for vibration vacuumization, FIG. 2 shows a device for impregnating a carbon-graphite billet.

The device for vibration vacuumization consists of a vibration table 1, a crucible 2, a vacuum bell 3, which hermetically covers the crucible 2.

In the crucible 2 is placed a carbon-graphite blank 4. In the vibrating table 1, an opening 5 is made, which is connected to a vacuum pump (not shown).

The device for impregnation is made of VT1-0 titanium and consists of a body 6 and a cover 7. The device is 2/3 filled with a molten matrix alloy of phosphorous copper 8 with a crystallized (as a result of cooling) surface. On the crystallized surface of the matrix alloy of phosphorous copper 8, a porous workpiece 9 is installed in the alloy of phosphorous copper cooled to 600 ° C, which has undergone primary impregnation during vibration vacuum. The body 6 of the impregnation device is hermetically closed by a cover 7, into which a plug 10 is inserted, fixed by a wedge 11. The remaining volume of the device is filled with a melt of the matrix alloy.

The method is carried out as follows.

A crucible filled with a molten matrix alloy of phosphorous copper, inside which a porous billet is located, is installed on the vibrating table. For sealing, the crucible is covered with a sealed vacuum bell made of glass and the unit is connected to a vacuum pump. Vibro-vacuumization of a carbon graphite workpiece in a phosphorous copper alloy melt is carried out for 7-8 minutes, at a temperature 30 ^° C higher than the melting temperature of the selected matrix phosphorous copper alloy.

After vibration vacuumization, the cooled content of the crucible with the porous workpiece is placed on the crystallized surface of the copper-phosphorous alloy by 2/3 of the filling device for impregnation. After that, the heated lid is taken out of the furnace and the body of the device is covered, the device is completely filled with a melt of matrix alloy of phosphorous copper through the hole in the lid (until the alloy appears on the surface of the cone) and this hole is closed with a heated stopper, and then cottered with a cold wedge.

Table

Carbon-graphite composite material - copper According to the proposed method at the temperature of the workpiece By prototype 600 ° C 20 ° C Temperature of the alloy in contact with the workpiece, ° С at the beginning of impregnation 650 550 680-700 at the end of impregnation 800 800 780 Impregnation pressure, MPa 15 15 12 Pressure holding time, min. 20 20 20 The degree of filling open pores,% 77 ± 2 77 ± 2 72 ± 2 Compressive strength of CM, MPa 48.0 ± 2 48.0 ± 2 44.6 ± 2 Evacuation, min. 7 7 15-20 Results of metallographic studies Some microscopic pores are not filled Some microscopic pores are not filled

Next, the device for impregnation is placed in a furnace, the temperature in which is 800 ° C, and, when the melt of the matrix alloy reaches a temperature of 100 ° C above the liquidus temperature of phosphorous copper, the specified temperature is maintained for 20 minutes. After this CM is removed from the melt and cooled in air.

The resulting CM was tested for compressive strength, the degree of filling of open pores (impregnation density). The degree of pore filling was estimated from the specific gravity of CM before and after impregnation, the CM structure was estimated from the results of metallographic studies. The results of CM tests are shown in the table.

The claimed method of manufacturing composite materials does not require large expenditures of time for heating the tooling as in the case of degassing in the device for impregnation and makes it possible to effectively use the heating temperature, carrying out degassing to the preparatory stage of processing the porous frame and performing vibration vacuuming with a small amount of the impregnating alloy. This eliminates the repeated heating-cooling cycle of the impregnation device, which makes it possible to reduce the time for obtaining CM.

In addition, after the degassing process, a semi-finished product is obtained - the result of primary impregnation (carbon graphite in a solidified alloy of phosphorous copper), which can be used for delayed impregnation. In this case, the time for a single heating of the impregnation device will increase by 3-5 minutes. In general, these stages allow to reduce the time of CM manufacturing by 50%, which allows increasing the productivity of the process by reducing the time for CM production.

Thus, a method for manufacturing a composite material, including vibro-evacuation of a porous workpiece in a separate container for 7-8 minutes in a melt of a matrix alloy of phosphorous copper, installing a workpiece before impregnation in a phosphorous copper alloy cooled to 600 ° C on the surface of a phosphorous copper alloy crystallized as a result of cooling pre-poured into a device for impregnation at a temperature of a molten phosphorous copper of 800 ° C for 2/3 of the volume of the device, filling the device for impregnation with a melt of a phosphorous copper alloy heated to 800 ° C, heating and exposure to excess pressure on the workpiece due to the phase transition of a phosphorous alloy copper from a solid state to a liquid state, due to thermal expansion of a copper alloy melt in a closed volume of a sealed device for impregnation when the device for impregnation is heated to a temperature of 100 ° C higher than the liquidus temperature of the copper alloy and subsequent isothermal holding at the same temperature for 20 minutes to ensure the thermal expansion of the copper alloy melt., provides a reduction in the time to obtain a composite material, which increases the productivity of the method.

Claims (1)

A method of manufacturing a composite material, including vacuum degassing of a porous carbon-graphite workpiece in a melt of a copper matrix alloy, heating and exposure to excess pressure on the workpiece due to thermal expansion of a copper alloy melt in a closed volume of a sealed device for impregnation while heating the device for impregnation to a temperature of 100 ° C higher liquidus temperature of the copper alloy and subsequent isothermal holding at the same temperature for 20 minutes to ensure thermal expansion of the copper alloy melt, characterized in that a phosphorous copper alloy is used as a copper alloy, vacuum degassing of a porous billet in a phosphorous copper matrix alloy melt is carried out in a separate a container installed on a vibration table with the provision of vibration vacuumization of the workpiece for 7-8 minutes, before impregnation, the workpiece in the phosphorous copper alloy cooled to 600 ° C is placed on the surface of the phosphorous alloy crystallized as a result of cooling copper, pre-poured into the device for impregnation at a temperature of phosphorous copper melt of 800 ° C for 2/3 of the volume of the device, after which the device for impregnation with a melt of phosphorous copper alloy heated to 800 ° C is completely filled through the hole in the installed cover, and the workpiece is impregnated due to the phase transition of a phosphorous copper alloy from a solid to a liquid state.

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