JP2006326630A - Method for manufacturing aluminum composite material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing an aluminum composite material which is formed by casting a ferrous sintered body having high adhesiveness with aluminum. <P>SOLUTION: The method for manufacturing the aluminum composite material comprises a preforming step of forming and sintering ferrous powder so as to obtain a preformed body of a porous ferrous sintered material having 50% to 70% of the ferrous powder by an occupied volume percentage, and a composite material forming step of placing the preformed body, which is preheated at a preheating temperature of 300°C to 400°C in a vacuum, an inert gas atmosphere, a reducing gas atmosphere, or a mixed gas atmosphere of the inert gas and the reducing gas, in a casting mold held at a temperature of 200°C to 400°C, and then press-impregnating the preformed body with a molten aluminum or aluminum alloy to cast it by a two step pressing method comprising a first pressing step and a second pressing step. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing an aluminum composite material obtained by casting an iron sintered body with aluminum.

  Various methods for manufacturing composite materials in which a preform made of a porous sintered material is combined using a metal such as aluminum as a base material have been proposed. As a method for producing such a composite material, for example, a preform preformed with a porous sintered body such as iron is set in a mold, and a high-pressure molten metal is injected into the mold and pressurized, A method for producing a composite material by casting in which a molten metal is infiltrated into a preform to produce a composite material is known.

  In the above-described method for producing a composite material by casting, for example, in a preheating furnace, a preform formed from an iron porous sintered body is preheated to a predetermined temperature of 250 ° C. to 350 ° C.

  However, the closer the preheating temperature of the preform is to the melting temperature of the base metal, the better the permeability of the base metal into the preform. Therefore, a further increase in the preheating temperature is desired.

  When the preform is made of an iron sintered body, if the temperature is 400 ° C. or higher, the surface of the iron sintered body is oxidized and foreign substances such as oxides are deposited on the surface. It is as follows.

  Since the composite material manufacturing method is formed by combining different materials, the adhesion between the materials is one of the important conditions for determining the characteristics of the composite material. Especially when used in parts and manufactured products that are subject to high pressure, if the adhesion between the materials is poor, there is a possibility that problems such as cracking and extension occur due to pressure leaks or pressure applied to areas with poor adhesion. is there.

  Moreover, when the adhesiveness between materials is bad, there exists a possibility that the space | gap containing a foreign material and air may exist in a boundary. In the case where the composite material is used as a material that requires thermal conductivity, it is considered that the thermal conductivity is reduced if there are foreign objects or voids at the boundary.

  This invention is made | formed in view of such a situation, and it aims at providing the manufacturing method of the aluminum composite material which casted the iron sintered compact with higher adhesiveness with aluminum.

  Therefore, the present inventors have intensively studied to solve this problem, and as a result of repeated trial and error, the occupied volume ratio of the iron sintered body is set to 50% or more and 70% or less, and the iron sintered body preform is placed in a vacuum. The preheating temperature is increased to 300 ° C. or more and 400 ° C. or less by preheating in an inert gas atmosphere, a reducing gas atmosphere, or a mixed gas atmosphere of an inert gas and a reducing gas. It is possible to obtain an aluminum composite material having good adhesion by combining a temperature of not lower than 400 ° C. and not higher than 400 ° C. and performing a two-step pressurization of low pressure and high pressure on a method of pressurizing molten aluminum or aluminum alloy. It discovered and came to complete this invention.

That is, in the method for producing an aluminum composite material of the present invention, an iron-based powder is formed so as to have an occupied volume ratio of 50% or more and 70% or less, and in a vacuum, an inert gas atmosphere, a reducing gas atmosphere, or an inert gas. A preform molding step in which a porous iron-based sintered material preform is molded by sintering at a sintering temperature of 1100 ° C. or more and 1300 ° C. or less in a mixed gas atmosphere of a reducing gas and
The preform that has been preheated in a vacuum, in an inert gas atmosphere, in a reducing gas atmosphere, or in a mixed gas atmosphere of an inert gas and a reducing gas at a preheating temperature of 300 ° C. or more and 400 ° C. or less, has a mold temperature of Installed in a casting mold having a temperature of 200 ° C. or more and 400 ° C. or less, and pressurizing molten aluminum or aluminum alloy at a low pressure, and the pressure of the first pressurization step following the first pressurization step And a composite material forming step of casting by impregnating with a two-stage pressurizing method comprising a second pressurizing stage for pressurizing at a high pressure.

  In addition, another method for producing an aluminum composite material of the present invention includes preheating at 300 ° C. to 400 ° C. in vacuum, in an inert gas atmosphere, in a reducing gas atmosphere, or in a mixed gas atmosphere of an inert gas and a reducing gas. A porous iron-based sintered material preform having an iron-based powder preheated at a temperature of 50% to 70% is placed in a casting mold having a mold temperature of 200 ° C. to 400 ° C., Two stages comprising a first pressurizing stage for pressurizing molten aluminum or aluminum alloy at a low pressure and a second pressurizing stage for pressurizing at a pressure higher than the pressure of the first pressurizing stage following the first pressurizing stage. It has the composite material formation process which carries out pressure impregnation by the pressurization method of this, and casts.

  The aluminum composite manufactured by this manufacturing method has improved adhesion at the boundary between aluminum or an aluminum alloy and an iron sintered body.

  The preheating temperature is more preferably 350 ° C. or higher and 400 ° C. or lower.

  The mold temperature is more preferably 200 ° C. or higher and 250 ° C. or lower.

  Preforms are preheated in vacuum, in an inert gas atmosphere, in a reducing gas atmosphere, or in a mixed gas atmosphere of an inert gas and a reducing gas. It is possible to raise the temperature to over 300 ° C. without depositing foreign matters such as the like on the boundary.

  As the preheating temperature of the preform is closer to the molten metal temperature of aluminum or aluminum alloy, the impregnation of the iron sintered body with aluminum or aluminum alloy is improved, and the adhesion between the two materials is improved.

  The upper limit of the preform preheating temperature is 400 ° C. or less. The preheating temperature should be as close as possible to the molten metal temperature of aluminum or aluminum alloy as described above, but as the temperature rises, intermetallic compounds and oxides are generated, so poor adhesion between the iron sintered body and aluminum or aluminum alloy. Occurs.

  The mold temperature of the casting mold is preferably equal to or lower than the preform preheating temperature. The reason for this is not clear, but since the thermal expansion coefficient of aluminum is larger than that of iron, the iron-based sintered material of aluminum or aluminum alloy is impregnated by lowering the casting mold temperature below the preform preheating temperature. Is thought to improve.

  The two-stage pressurizing method includes a first pressurizing step of pressurizing at a low pressure of 20 MPa or more and 30 MPa or less for 5 seconds or more and 15 seconds or less, and a high pressure of 70 MPa or more and 100 MPa or less following the first pressurizing method. It is preferable that it is the 2nd pressurization step which pressurizes from 5 minutes or more to 5 minutes or less.

  The voids in the preform of the iron sintered body are crushed by pressurization. Therefore, first, the molten aluminum or aluminum alloy is impregnated into the voids of the iron sintered body without crushing the voids of the preform at a low pressure, and then the molten aluminum or aluminum alloy is impregnated at the required pressure. By using the above two-stage pressurization method, it is possible to impregnate the molten iron or aluminum alloy without crushing the voids in the sintered iron body, so the adhesion at the boundary between the two materials is improved due to the physical anchor effect. To do.

  The occupied volume ratio of the iron-based powder is more preferably 55% or more and 65% or less.

  When the occupation volume ratio of the iron-based powder in the porous preform sintered body is within the above range, the iron sintered body is preferably impregnated with aluminum or an aluminum alloy.

  The iron-based powder preferably has a particle size of 45 μm or more and 200 μm or less.

  When the particle size of the iron-based powder is within the above range, the occupied volume ratio of the iron-based powder can be adjusted by the particle size of the iron-based powder.

  Moreover, when the particle size is in the above range, desired excellent castability can be ensured and desired strength can be ensured.

  The method for producing an aluminum composite material in which the iron sintered body of the present invention is cast with aluminum can improve the adhesion at the boundary between the aluminum or aluminum alloy and the iron sintered body by having the above-described production steps. . For example, it is possible to prevent problems such as pressure leakage, crack generation, crack extension, and decrease in conductivity, which have conventionally occurred due to poor adhesion at the boundary.

  In particular, when used as a material used under high pressure, the effect of improving adhesion becomes more remarkable.

  The best mode for carrying out the method for producing a composite material of the present invention will be described below.

  The method for producing an aluminum composite material of the present invention includes a preform molding step for molding a porous iron-based sintered material preform, and a composite material forming step for casting the molten aluminum or aluminum alloy by pressure impregnation. It consists of.

  In the preform molding process, the iron-based powder is molded so as to have an occupied volume ratio of 50% or more and 70% or less and mixed in a vacuum, in an inert gas atmosphere, in a reducing gas atmosphere, or in an inert gas and a reducing gas. It is a step of forming a porous iron-based sintered material preform by sintering at a sintering temperature of 1100 ° C. or higher and 1300 ° C. or lower in a gas atmosphere.

  The shape of the porous iron-based sintered material preform is not particularly limited as long as it is a target shape. A desired preform can be molded by putting an iron-based powder in a mold having a desired shape and sintering it by heating under pressure.

  At that time, the occupied volume ratio of iron is desirably 50% or more and 70% or less. Here, the occupied volume ratio is expressed as VF (abbreviation of Volume Fraction) and expressed in%.

  VF can be controlled by controlling the particle size, amount and pressure of the iron-based powder during preform molding.

  If VF is 70% or less, the porosity of the porous iron-based sintered material preform becomes 30% or more, and the iron-based sintered material is preferably impregnated with aluminum or an aluminum alloy.

  In particular, the VF of the iron-based powder is desirably 55% or more and 65% or less. By using an iron-based sintered material preform having a VF in this range, an aluminum composite material having excellent strength and adhesion can be obtained.

  The iron-based powder is not particularly limited as long as it is a powder containing iron. For example, powders such as pure iron, iron containing copper, iron containing copper and carbon, iron containing copper, carbon and nickel, or iron containing chromium and / or molybdenum can be used.

  The particle size of the iron-based powder is preferably 45 μm or more and 200 μm or less. By using the iron-based powder having a particle size in this range, desired excellent castability can be ensured and desired strength can be ensured.

  Sintering can be carried out by maintaining at a high temperature below the melting point of the raw materials used in a vacuum, in an inert gas atmosphere, in a reducing gas atmosphere, or in a mixed gas atmosphere of an inert gas and a reducing gas.

  For example, sintering is performed at a sintering temperature of 1100 ° C. or more and 1200 ° C. or less for 45 minutes. The cooling rate after sintering is desirably 30 ° C. to 40 ° C./min or less.

  Further, after sintering, post-treatment such as carburizing, nitriding, quenching, tempering, normalizing, annealing, and steam treatment may be performed.

  In addition to the iron-based powder, a lubricant or the like may be added as a porous iron-based sintered material preform raw material.

  The preform is preheated at a preheating temperature of 300 ° C. to 400 ° C. in a vacuum, in an inert gas atmosphere, in a reducing gas atmosphere, or in a mixed gas atmosphere of an inert gas and a reducing gas. Is placed in a casting mold having a mold temperature of 200 ° C. or more and 400 ° C. or less, and molten aluminum or aluminum alloy is press-impregnated by a two-stage pressurizing method for casting.

  As the inert gas, nitrogen, argon or the like can be used.

  As the reducing gas, hydrogen, carbon monoxide, ammonia or the like can be used. Preheating may be performed by putting the preform in a heating furnace or by high frequency heating. In order to prevent oxidation of the surface of the preform, preheating is preferably performed in a short time.

  For example, high-frequency heating can be used in an inert gas atmosphere.

  The mold temperature of the casting mold is preferably equal to or lower than the preform preheating temperature. Preheating may be performed in a heating furnace by placing a casting mold in a heating furnace, or high-frequency heating may be performed.

  The preheating of the preform and the casting mold may be performed simultaneously at the same place or at different times at different times. For example, in the case of high-frequency heating, preheating for the preform and preheating for the casting mold can be performed simultaneously at different temperature settings in the casting mold.

  The aluminum alloy is not particularly limited as long as it is an alloy containing aluminum. For example, an aluminum alloy containing Mg, Cu, Zn, Si, Mn, Fe, Cr, Ti, or the like can be given.

  The two-stage pressurization method includes a first pressurization stage in which pressurization is performed at a low pressure and a second pressurization stage in which pressurization is performed at a pressure higher than the pressure in the first pressurization stage following the first pressurization stage.

  The pressurization may be performed using a feeder pressure or by another method. The pressurization is particularly preferably performed using a feeder pressure from the viewpoint of preventing the shrinkage of the casting and the generation of voids caused by the removal of gas in the mold, cooling and solidification.

  In the case of the feeder pressure, a pressure comparable to that of die casting (for example, several tens of MPa to one hundred MPa) may be applied.

  The aluminum composite material after casting may be air-cooled while being put in the casting mold after releasing the pressure, or may be taken out from the casting mold and air-cooled.

  Another method for producing an aluminum composite material of the present invention comprises a composite material forming step in which a porous iron-based sintered material preform is impregnated with molten aluminum or an aluminum alloy and cast.

  This manufacturing method is the same as the above-described method except that a porous iron-based sintered material preform having an occupied volume ratio of iron-based powder formed by any method that is not particularly limited is 50% to 70%. Since there is, description is abbreviate | omitted.

  Below, one Embodiment of the manufacturing method of the aluminum composite material of this invention is described using FIG. 1, FIG.

  FIG. 1 is an explanatory diagram of the preform molding process. (A) is a schematic diagram of a state in which a molding die is filled with iron-based powder or the like and pressed, and (b) is a state in which the molded preform is sintered in a sintering furnace. It is a schematic diagram.

  The preform molding process will be described with reference to FIG. The mold 1 as a molding die is cylindrical and is configured to be disassembled into a plurality of molding die constituent pieces. As the material of the mold 1, for example, high carbon steel (carbon concentration: 0.1% to 0.6%) such as S25C is used.

  A raw material such as iron-based powder is put into the mold 1 and is pressed by the pressing dies 2 and 3 so that the VF of the iron-based powder in the mold 1 is 50% or more and 70% or less. For the pressurization, an appropriate pressure is used depending on the particle size and amount of the iron-based powder.

  The formed iron-based powder 4 is put into a sintering furnace 5 and sintered in a vacuum, in an inert gas atmosphere, in a reducing gas atmosphere, or in a mixed gas atmosphere of an inert gas and a reducing gas. Sintering is performed by holding at a high temperature below the melting point of the iron-based powder or the like.

  Next, the preform sintered body after sintering is cooled by cooling the temperature of the sintering furnace.

  In addition, when higher dimensional accuracy is required, the sintered body may be pressed again to perform dimensional correction. For other purposes, for example, induction hardening, carburizing quenching, steam treatment, or the like may be performed.

  In FIG. 1, the shape of the iron sintered body is a cylindrical shape, but by using the mold 1 having a shape that matches the shape of the target composite material, an iron sintered body having a desired shape is formed. The

  Next, the composite material forming process will be described with reference to FIG.

  FIG. 2 is an explanatory diagram of the composite material forming step. (A) is a schematic diagram of an iron sintered compact preform, (b) is a schematic diagram of the state which installed the iron sintered compact preform in the casting metal mold | die, (c) is after casting. It is a schematic diagram of an aluminum composite material.

  First, the porous iron sintered body preform 6 is preheated at a preheating temperature exceeding 300 ° C. in a vacuum, in an inert gas atmosphere, in a reducing gas atmosphere, or in a mixed gas atmosphere of an inert gas and a reducing gas. Preheating may be performed in a heating furnace, or high-frequency heating may be performed. Further, high-frequency heating may be performed in a state where the preform is set in the casting mold 7 for fixing the preform.

  The preheated porous iron sintered body preform 6 is placed in a casting mold 7 for fixing the preform. The casting molds 7 and 8 are preheated to a temperature lower than the preheating temperature of the preform 6. Next, a molten aluminum or aluminum alloy is poured into a casting mold 8 in which the preform 6 is installed.

  Then pressurize in two stages. Two-stage pressurization is performed for several seconds at a low pressure and then for several minutes at a high pressure.

  After releasing the pressure, the entire casting mold is cooled by air cooling. The finished aluminum composite material 9 is taken out from the casting mold.

  Below, the Example of the manufacturing method of the aluminum composite material of this invention is described.

  The iron powder removed by sieving the particle size of 45 μm or less, lithium stearate as a lubricant, and carbon powder were mixed using a mixer. The mixing ratio was 100% by weight as a whole, 98.3% by weight of iron powder, 0.7% by weight of carbon powder, and 1% by weight of lithium stearate.

  Next, an iron preform mold was prepared. The mixed raw material powder was put into a preform mold and pressurized so that VF would be 60% or 70%. In order to make VF 60%, it was pressed and molded at about 150 MPa. The shape of the preform was a cylindrical shape.

The pressed iron powder was put into a sintering furnace and sintered at 1150 ° C. for 45 minutes under AX gas (N ₂ -75% H ₂ ). The cooling rate of the sintering furnace after sintering was 30 to 40 ° C./min.

  A cylindrical porous iron sintered material preform having a height of 150 mm, an outer diameter of 120 mmφ, and an inner diameter of 100 mmφ was obtained.

  The porous iron sintered material preform cooled to near room temperature was put in a heating furnace and preheated in an argon atmosphere. The preheating temperature was 300 ° C. or 400 ° C.

  The porous iron sintered material preform preheated from the heating furnace was taken out and placed in a casting mold preheated to 200 ° C. or 250 ° C. in another heating furnace.

  A molten metal of 750 to 800 ° C. of aluminum alloy ADC12 was poured from the opening of the casting mold. The molten metal was poured to almost fill the casting mold and melt pressure was applied.

  The molten metal pressure was 80 MPa for 4 minutes from the beginning (pressurization method 1), and 20 MPa for 10 seconds and then 100 MPa for 4 minutes (pressurization method 2).

  Finally, the pressure was released and the casting mold was air-cooled.

  Then, it was taken out from the casting mold and the inner peripheral surface of the cylinder was cut.

  A cylindrical aluminum composite material having a height of 150 mm, an outer diameter of 200 mmφ, and an inner diameter of 90 to 100 mmφ was obtained.

  The production conditions for each example are listed in Table 1.

  The obtained aluminum composite materials of Examples 1 and 2 were milled on the upper end face and processed in cross section.

  FIG. 3 shows a schematic cross-sectional view of the aluminum composite material subjected to cross-section processing.

  An aluminum composite material 9 in which an aluminum alloy 11 is cast around a porous iron sintered material preform 10 is shown. The boundary between the preform 10 and the aluminum alloy is represented by a boundary 12.

  Using the processed cross sections of Examples 1 and 2, a solution penetration test was conducted.

  In the solution penetrant test, a red penetrant containing a fatty acid ester, a high boiling point hydrocarbon, and a red dye is sprayed on the cross section by spray, and after 5 minutes, the developer aerosol is applied using the spray. The cross section is observed visually.

  The red penetrant enters the gap between the porous iron sintered material and the aluminum alloy, and the boundary can be visually observed.

  In the cross-sectional observation results using the aluminum composite materials of Example 1 and Example 2, no red color change portion was visually observed at the boundary between the porous sintered material and the aluminum alloy.

FIG. 2 shows a preform molding process in an embodiment of the present invention, wherein (a) is a schematic view showing a state where a molding die is filled with iron-based powder or the like and pressed, and (b) is a diagram illustrating a process in which the molded preform is baked. It is a schematic diagram of the state sintered in the sintering furnace. The composite material formation process in embodiment of this invention is shown, (a) is a schematic diagram of an iron sintered compact preform, (b) is a schematic diagram of the state which installed the iron sintered compact preform in the casting metal mold | die. (C) is a schematic diagram of an aluminum composite material after casting. The cross-sectional schematic diagram of the aluminum composite material by which the cross-section process in the Example of this invention was represented.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, Mold 2, 3, Push mold 4, Iron-based powder 5, Sintering furnace 6, Porous iron sintered material preform, 7, Casting mold for preform fixation, 8, Casting mold , 9, aluminum composite material, 10, porous iron sintered material preform, 11, aluminum alloy, 12, boundary

Claims (8)

The iron-based powder is molded to have an occupied volume ratio of 50% or more and 70% or less, and is baked in a vacuum, in an inert gas atmosphere, in a reducing gas atmosphere, or in a mixed gas atmosphere of an inert gas and a reducing gas. A preform forming step of forming a porous iron-based sintered material preform by sintering at a sintering temperature of 1100 ° C. or higher and 1300 ° C. or lower;
The preform that has been preheated in a vacuum, in an inert gas atmosphere, in a reducing gas atmosphere, or in a mixed gas atmosphere of an inert gas and a reducing gas at a preheating temperature of 300 ° C. or more and 400 ° C. or less, has a mold temperature of Installed in a casting mold having a temperature of 200 ° C. or more and 400 ° C. or less, and pressurizing molten aluminum or aluminum alloy at a low pressure, and the pressure of the first pressurization step following the first pressurization step A composite material forming step of casting by impregnating with a two-stage pressurizing method comprising a second pressurizing stage for pressurizing at a high pressure; and
The manufacturing method of the aluminum composite material characterized by having.   The method for producing an aluminum composite material according to claim 1, wherein the occupied volume ratio is 55% or more and 65% or less.   The method for producing an aluminum composite material according to claim 1, wherein the preheating temperature is 350 ° C. or higher and 400 ° C. or lower.   The method for producing an aluminum composite material according to any one of claims 1 to 3, wherein the mold temperature is 200 ° C or higher and 250 ° C or lower.   The two-stage pressurization method includes a first pressurization stage in which pressurization is performed at a low pressure of 20 MPa or more and 30 MPa or less for 5 seconds or more and 15 seconds or less, and a high pressure of 70 MPa or more and 100 MPa or less following the first pressurization method. The manufacturing method of the aluminum composite material in any one of Claims 1-4 which consists of a 2nd pressurization step pressurized from 5 minutes or more for 5 minutes or more.   The method for producing an aluminum composite material according to claim 1, wherein the iron-based powder has a particle size of 45 μm or more and 200 μm or less.   The method for producing an aluminum composite material according to any one of claims 1 to 6, wherein a mold temperature of the casting mold is equal to or lower than the preform preheating temperature.   50% occupied volume ratio of iron-based powder preheated at a preheating temperature of 300 ° C. or more and 400 ° C. or less in a vacuum, an inert gas atmosphere, a reducing gas atmosphere, or a mixed gas atmosphere of an inert gas and a reducing gas. A porous iron-based sintered material preform having a mold temperature of not less than 70% and not more than 70% is placed in a casting mold having a mold temperature of not less than 200 ° C. and not more than 400 ° C., and the molten aluminum or aluminum alloy is pressurized at a low pressure. A composite material that is cast by being impregnated by a two-stage pressurization method comprising a pressurization stage and a second pressurization stage that is pressurized at a pressure higher than the pressure of the first pressurization stage following the first pressurization stage. The manufacturing method of the aluminum composite material characterized by having a formation process.

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