JP2005248238A - Method for manufacturing aluminum matrix composite - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve a production efficiency of an aluminum matrix composite, by placing crucibles used for manufacturing the aluminum matrix composite at maximum density in a heating furnace used for manufacturing the aluminum matrix composite. <P>SOLUTION: The method for manufacturing the aluminum matrix composite comprises: the first step of placing an aluminum alloy 82 on a powder 81 in the crucible 25; the second step of accommodating magnesium in the furnace along with the crucible; and the third step of obtaining the aluminum matrix composite by making the molten metal of an aluminum alloy penetrate into gaps among the powders by heating the inside of the furnace and reducing the pressure in the furnace at a predetermined timing. The third step includes, by using a heat source 23 consisting of an upper heat source 43 located above the crucible and a lower heat source 44 located below it, setting the output of the lower heat source higher than that of the upper heat source before a reduction reaction is completed, and the output of the upper heat source higher than that of the lower heat source after the reduction reaction has been completed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing an aluminum-based composite material.

The aluminum-based composite material is made of aluminum and oxide ceramics, and alumina (Al ₂ O ₃ ) is used as the oxide ceramics, for example. The outline of the method for producing such an aluminum-based composite material is as follows. First, a porous molded body made of an oxide-based ceramic is heated in a furnace and the porous molded body is reduced with magnesium nitride.

Subsequently, aluminum dissolved in the reduced porous molded body is infiltrated to obtain an aluminum-based composite material. At that time, a method for producing an aluminum-based composite material that performs depressurization or pressurization is known (for example, see Patent Document 1).
Japanese Patent Laid-Open No. 2002-30361 (page 6, FIG. 3)

Patent document 1 is demonstrated based on the following figure.
7A and 7B are diagrams for explaining the basic principle of the conventional technique.
In (a), the aluminum-based composite material manufacturing apparatus 101 includes an atmosphere furnace 102, an argon gas supply unit 103, a nitrogen gas supply unit 104, and a vacuum pump 105.

The outline of the manufacturing process of the composite material manufactured by the manufacturing apparatus 101 will be described below.
First, a porous molded body 107, a porous partition body 108 made of alumina (Al ₂ O ₃ ) powder, and an aluminum alloy 109 are placed in a crucible 106. The porous molded body 107 is made by containing magnesium in porous alumina (alumina 111).

In (b), argon gas (Ar) is subsequently put into the atmosphere furnace 102 from the argon gas supply means 103 and replaced, and heating is started. After a predetermined time, nitrogen gas (N ₂ ) is supplied from the nitrogen gas supply means 104 to the atmosphere furnace 101, the atmosphere furnace 101 is set under reduced pressure, and the pressure is increased after a predetermined time has elapsed from the start of the pressure reduction.

  In the atmosphere furnace 102 that has undergone such a process, the magnesium 112 and the nitrogen gas 113 react with each other to produce magnesium nitride 114 by heating, and the magnesium nitride 114 reduces the alumina of the porous molded body 107 under reduced pressure. The dissolved aluminum alloy penetrates into the reduced porous molded body 107 under pressure. Therefore, the poor penetration portion can be eliminated.

  However, in the method for producing an aluminum-based composite material disclosed in Patent Document 1, the aluminum alloy 109 may begin to dissolve before magnesium nitride is generated, and a sound composite may not occur. For this reason, wetting due to the reducing action of magnesium nitride is insufficient, and bonding may be insufficient. In particular, when the crucible 106 is placed at the maximum density in the atmosphere furnace 102 and heated at the fastest heating rate, the aluminum alloy 109 placed on the top is easily melted by the rise of the air flow, and as a result, the aluminum-based composite material Yield was bad and production efficiency was low.

  An object of the present invention is to place a crucible used for producing an aluminum matrix composite at a maximum density in a heating furnace for producing the aluminum matrix composite to improve the production efficiency of the aluminum matrix composite.

  The invention according to claim 1 is a first step of placing a porous molded body or powder made of an oxide-based ceramic in a crucible and placing an aluminum alloy on the porous molded body or powder, and generation of magnesium or magnesium together with the crucible. The second step of placing the source in the furnace, and heating the furnace in a nitrogen atmosphere and heating to produce magnesium nitride, reducing the porous molded body or powder by the action of magnesium nitride, and reducing the pressure in the furnace A third step of obtaining an aluminum matrix composite by infiltrating a molten aluminum alloy into the reduced porous molded body or powder, and in the method of manufacturing an aluminum matrix composite, Reduction using a heat source that consists of an upper heat source located below and a lower heat source located below, and which can control these upper and lower heat sources separately. Until completion from the output of the upper heat source, to increase the output of the lower heat source, after reduction from the output of the lower heat source, characterized by increasing the output of the upper heat source.

  In the third step of the invention according to claim 1, the upper heat source located above the crucible and the lower heat source located below are used and a heat source capable of separately controlling these upper and lower heat sources is used to complete the reduction. Since the output of the lower heat source is higher than the output of the upper heat source, and the output of the upper heat source is higher than the output of the lower heat source after reduction, the temperature of the crucible is higher than that of the aluminum alloy located above the crucible. The temperature rise rate of the porous molded body or powder located in the lower portion is increased, and the temperature of the porous molded body or powder is increased in advance without dissolving the aluminum alloy. The temperature of magnesium can be raised in advance. As a result, the difference in reduction completion timing between the crucible far from the heat source and the crucible close to the heat source can be shortened, and the variation in the reduction completion timing due to the crucible arrangement is reduced. Therefore, there is an advantage that the production efficiency of the aluminum-based composite material can be improved by placing the crucible at the maximum density in the heating furnace.

The best mode for carrying out the present invention will be described below with reference to the accompanying drawings. The drawings are viewed in the direction of the reference numerals.
FIG. 1 is a cross-sectional view of an apparatus for producing an aluminum matrix composite used in the production method of the present invention. The aluminum matrix composite manufacturing apparatus 11 includes a heating furnace 12, a gas supply apparatus 13 connected to the heating furnace 12 for supplying gas, a vacuum pump 14 for reducing the pressure in the heating furnace 12, and the heating furnace 12. And a control device 15 for controlling the gas supply device 13 and the vacuum pump 14. Reduced pressure means a pressure lower than atmospheric pressure.

  In the heating furnace 12, a heat insulating means 22 is attached in the pressure vessel 21, a heating means 23 as a heat source is disposed inside the heat insulating means 22, a tight box 24 is provided inside the heating means 23, and the tight box 24 This is a furnace in which a mounting table 26 on which the crucible 25 is placed is arranged.

  In the pressure vessel 21, first and second heads 31 and 32 are attached to both ends of the main body portion 28 via an opening / closing mechanism (not shown), and mounts 33 and 33 are attached to the lower portion of the main body portion 28. The first nozzle 34 (... indicates a plurality; the same applies hereinafter), the second nozzles 35, 35, and the third nozzle 36 are attached to the main body 28, and the workpiece is placed under a predetermined reduced pressure or pressure. To process.

  In addition, depending on what is processed, it is also possible to weld (overlay) stainless steel for preventing corrosion of the inner surface to the entire inner surface of the pressure vessel 21. Moreover, you may form a larger or smaller nozzle in the pressure vessel 21 as needed.

  The heating means 23 is an electric heater (including a carbon heater), and includes an upper heat source 43 located above the crucible 25, a lower heat source 44 located below the crucible 25, a thermocouple 45 disposed above the crucible 25, and a lower part. And a thermocouple 46 disposed in the.

The gas supply device 13 includes an inert gas supply means 47, a nitrogen supply means (nitrogen gas supply means) 48, a switching valve 49, and a pipe 51 connected to the second nozzles 35, 35. Then, an inert gas or nitrogen gas (N ₂ ) is supplied.

The switching valve 49 guides the inert gas inlet 52 or the nitrogen inlet 53 to the outlet 54 based on the information of the control device 15 and closes the inert gas inlet 52 and the nitrogen inlet 53 as necessary.
The nitrogen gas supply means 48 includes a gas preheating chamber 56 provided near the heat source (heating means) 23 in the heating furnace 12, and a nozzle 57 that is attached to the gas preheating chamber 56 and supplies gas into the crucible 25. And comprising.

  2 is a cross-sectional view taken along the line 2-2 of FIG. 1, and shows a heating furnace 12, a gas supply device 13, a vacuum pump 14, a control device 15, a heating means 23 disposed in the heating furnace 12, and a gas. A preheating chamber 56 is shown.

The heating means 23 includes the upper heat source 43 and the lower heat source 44 as already described.
The upper heat source 43 is obtained by attaching the first heaters 61, 61 to the first nozzles 34, 34, and the control device 15 controls the first heaters 61, 61 under the same conditions.

The lower heat source 44 is obtained by attaching the second heaters 62 and 62 to the first nozzles 34 and 34 in the lower part of the figure, and the control device 15 controls the second heaters 62 and 62 under the same conditions. That is, the heat source can control the upper and lower heat sources 43 and 44 separately.
Both the first and second heaters 61 and 62 have the same structure, and existing ones were used.

3A and 3B are explanatory views of the first step of the manufacturing method of the present invention.
(A): First, a powder 81 made of an oxide ceramic is placed in the crucible 25, and an aluminum alloy 82 is placed on the powder 81.
Here, a porous partition body 85 is further interposed between the powder 81 and the aluminum alloy 82.

The powder 81 is a mixed powder obtained by mixing alumina (Al ₂ O ₃ ) and magnesium (Mg). The porous partition 85 is a sheet in which an alumina (Al ₂ O ₃ ) powder 86 has a thickness of 0.5 mm to 2.0 mm, and the average particle size of the powder 86 is desirably 50 μm to 100 μm.

The aluminum alloy 82 is, for example, JIS-A6061 which is a kind of Al—Mg—Si alloy.
In addition, although the powder 81 which consists of oxide type ceramics was used, you may use the porous molded object which consists of oxide type ceramics.
Moreover, although the porous partition body 85 employ | adopted the sheet | seat, what deposited the powder may be used.

(B): Next, the crucible 25... Containing the powder 81, the porous partition 85, and the aluminum alloy 82 is conveyed to the heating furnace 12 of FIG.
Since magnesium (Mg) has already been dispersed in the powder 81, a container containing magnesium is not prepared. Prepare a container containing magnesium.

Magnesium is stored in the heating furnace 12 of the aluminum-based composite material manufacturing apparatus 11 together with the crucibles 25. In the example shown here, since magnesium has already been included in the powder 81, the operation of storing magnesium in the heating furnace 12 is omitted.
The first head 31 of the heating furnace 12 in FIG. 1 is opened, 16 crucibles 25... Are placed at predetermined positions on the mounting table 26, and the first head 31 is closed.

FIG. 4 is an explanatory view (No. 1) of the third step of the manufacturing method of the present invention, in which the tight box 24 (see FIG. 2) is omitted. The action is schematically shown.
Magnesium nitride (Mg ₃ N ₂ ) is generated by heating and heating the heating furnace 12 under a nitrogen atmosphere. Specifically, in order to remove oxygen in the heating furnace 12, the inside of the heating furnace 12 is evacuated by a vacuum pump 14 (see FIG. 1), and when a certain degree of vacuum is reached, the vacuum pump 14 is stopped and the switching valve is turned off. 49 (see FIG. 1), an inert gas (for example, argon gas (Ar)) is arrowed from the inert gas supply means 47 (see FIG. 1) to the gas preheating chamber 56 (see FIG. 1) of the heating furnace 12. Then, heating of the powder 81 (including magnesium (Mg)) and the aluminum alloy 82 is started by the heating means 23.

More specifically, the output Wb of the lower heat source 44 is made higher than the output Wt of the upper heat source 43 until the reduction is completed.
The reduction completion information is the heating elapsed time th, and the heating elapsed time th is counted by a timer not shown in the diagram of the control device 15 (see FIG. 1). That is, the timing of the output Wt of the upper heat source 43 and the output Wb of the lower heat source 44 is controlled based on the information of the timer of the control device 15.

  The heating elapsed time th is a time from when the switch for the heating means 23 of the control device 15 (see FIG. 1) is turned “ON” until the reduction of alumina is completed, and is a statistically calculated time.

  While detecting the temperature of the atmosphere heated by the upper heat source 43 with a thermocouple 45 (see FIG. 2), the temperature of the atmosphere heated by the lower heat source 44 is detected while detecting with the thermocouple 46 (see FIG. 2) ( Auto). In the process of reaching a predetermined temperature (for example, about 750 ° C. to about 900 ° C.), since the inside of the heating furnace 12 is in an inert gas atmosphere, the aluminum alloy 82 and magnesium (Mg) 32 are not oxidized.

  Here, since the output Wb of the lower heat source 44 is made higher than the output Wt of the upper heat source 43, the temperature increase rate of the powder 81 located in the lower part is faster than the temperature increase rate of the aluminum alloy 82 located in the upper part. The temperature of the powder 81 can be increased without dissolving the aluminum alloy 82, and at the same time, the temperature of magnesium in the powder 81 can be increased.

FIG. 5 is an explanatory diagram (part 2) of the third step of the production method of the present invention, schematically showing.
The powder 81 is reduced by the action of magnesium nitride (Mg ₃ N ₂ ) and the inside of the heating furnace 12 is reduced in pressure. Specifically, the operation of the switching valve 49 in FIG. 1 supplies nitrogen gas from the nitrogen gas supply means 48 to the gas preheating chamber 56 of the heating furnace 12, and at the same time, the inert gas is extracted by the vacuum pump 14, The atmosphere is replaced with nitrogen gas. When the inside of the heating furnace 12 is in an atmosphere of nitrogen gas, the nitrogen gas reacts with magnesium to generate magnesium nitride (Mg ₃ N ₂ ). Magnesium nitride reduces the alumina of the powder 81 and the alumina of the porous partition 85, so that the wettability of alumina is improved.

  After reducing the alumina, the supply of nitrogen gas is stopped, and the gas in the heating furnace 12 is evacuated by the vacuum pump 14 (see FIG. 1) to obtain a predetermined degree of vacuum. At that time, the gas in the gap between the powders 81 (in the case of a molded body, in the pores) and the gas in the gap of the porous partition 85 are sucked, and the degree of vacuum is the same as in the heating furnace 12.

  Based on the information of the timer of the control device 15 (see FIG. 1) informing that the predetermined heating elapsed time th has been reached, the output Wt of the upper heat source 43 is made higher than the output Wb of the lower heat source 44 after reduction. Then, the melting of the aluminum alloy 82 is promoted.

FIG. 6 is an explanatory view (No. 3) of the third step of the manufacturing method of the present invention, which is schematically shown.
A molten aluminum alloy 82 is infiltrated into the reduced powder 81 to obtain an aluminum-based composite material. Specifically, after the reduction, the output Wt of the upper heat source 43 is made higher than the output Wb of the lower heat source 44, so that the aluminum alloy 82 is actively melted, and the molten aluminum alloy 82 becomes the upper surface of the porous partition 85. The molten metal seals the top surface.

  Subsequently, an inert gas is supplied to the heating furnace 12 of FIG. Then, when the pressure in the heating furnace 12 is raised to a desired pressure and pressurized, the melted aluminum alloy 82 is pushed and begins to enter a large amount into each gap of the porous partition 85, and penetrates between the powders 81 in a reduced pressure state. To do. The aluminum alloy solidifies and the aluminum matrix composite is completed.

  The method for producing an aluminum-based composite material according to the present invention is suitable for producing a composite material whose base material is an aluminum alloy (including aluminum).

Sectional drawing of the manufacturing apparatus of the aluminum matrix composite material used for the manufacturing method of this invention 2-2 sectional view of FIG. Explanatory drawing of the 1st process of the manufacturing method of this invention Explanatory drawing of the 3rd process of the manufacturing method of this invention (the 1) Explanatory drawing of the 3rd process of the manufacturing method of this invention (the 2) Explanatory drawing of the 3rd process of the manufacturing method of this invention (the 3) Diagram explaining the basic principle of conventional technology

Explanation of symbols

  DESCRIPTION OF SYMBOLS 12 ... Furnace (heating furnace), 23 ... Heat source (heating means), 25 ... Crucible, 43 ... Upper heat source, 44 ... Lower heat source, 81 ... Powder, 82 ... Aluminum alloy

Claims (1)

A first step of placing a porous molded body or powder made of an oxide-based ceramic in a crucible, and placing an aluminum alloy on the porous molded body or powder;
A second step of storing magnesium or a magnesium source in the furnace together with the crucible;
By heating the furnace under a nitrogen atmosphere and heating, magnesium nitride is generated, and the porous molded body or powder is reduced by the action of magnesium nitride, and the inside of the furnace is reduced in pressure to form the reduced porous molded body or powder. A third step of obtaining an aluminum matrix composite by infiltrating a molten aluminum alloy;
In the third step, a heat source that is composed of an upper heat source located above the crucible and a lower heat source located below is used and the upper and lower heat sources can be controlled separately, and from the output of the upper heat source until the reduction is completed. A method for producing an aluminum-based composite material, wherein the output of the lower heat source is increased, and the output of the upper heat source is made higher than the output of the lower heat source after reduction.

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