JP2009262158A - Method for manufacturing metal composite material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a metal composite material having desirable strength, without lowering the strength caused by oxidation of metal staples and without generating the fall-down of the metal staples. <P>SOLUTION: A group of respective metal staples 12 in at least the metal surface layer of a preliminary forming body 2 formed by press-working is pre-combined with a combining agent 16 melted with high molecular polymer and glass particles 17, and a preform 1 is formed by heating to the sintering temperature of the softening point or higher of the glass particles 17 and combining the group of respective metal staples 12 with the glass particles 17 and molten metal 6 is press impregnated into this preform 1 to manufacture the metal composite material 10. Depending on this method, it can be prevented to fall down the respective metal staples 12 with the preliminary forming body 2 and the preform 1. Further, since the group of respective metal staples 12 can be combined with the glass staples 17 without heating to the high temperature, at which the metal staples 12 are sintered, the oxidation of the metal staples 12 can be restrained. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a metal composite material obtained by combining a short metal fiber and a metal base material such as an aluminum alloy in combination.

  For example, automobiles tend to have more parts manufactured from light metals such as aluminum, which are excellent in weight reduction, high durability, low thermal expansion, and the like, in order to improve fuel economy and driving performance. In particular, metal composites made by combining light metals and reinforcing materials such as short ceramic fibers or short metal fibers are applied to those with severe usage environments such as engine parts, which further reduces weight and increases durability. It has become possible to demonstrate sex.

  In the above-mentioned metal composite material, a metal composite material including a metal base material such as a light metal and a short metal fiber is superior in elasticity to a configuration in which a metal base material and a ceramic short fiber are combined. Therefore, it is difficult to break and has high strength. In particular, since it has high strength in a high temperature atmosphere and high fatigue strength, it is applied to the engine parts of automobiles described above. In addition, since the metal base material and the metal short fiber are easy to fit (excellent wettability), they have an advantage that the effect of combining is high.

  As such a metal composite material, for example, Patent Document 1 discloses that a preform is formed by laminating a plurality of sheet-like webs of short metal fibers, pressing them, and sintering them. An article is disclosed in which a reform is impregnated with a molten metal. Here, FeCrSi alloy, stainless steel, or Ni—Cr alloy is used as the short metal fiber.

In addition, when forming a preform from the above-mentioned ceramic short fibers, a method is generally used in which the ceramic short fibers are mixed in water and the moisture is removed, followed by sintering. On the other hand, when using short metal fibers, the short metal fibers are heavier than the short ceramic fibers and cannot be uniformly dispersed in water, and the short metal fibers may rust. A method of forming a preform by forming fibers into a nonwoven fabric and laminating and pressing the fibers has become common.
JP 2007-185705 A

  By the way, when sintering the preform which consists of a metal short fiber, the sintering temperature is 1000 to 1500 degreeC generally with the metal short fiber of steels, such as above-mentioned stainless steel, for example. When sintering at such a high temperature, it is necessary to carry out in vacuum to prevent oxidation of the short metal fibers. Here, the degree of vacuum at the time of sintering needs to be a high vacuum state of 0.1 Pa or less. If the degree of vacuum is lower than this, oxidation of the short metal fibers cannot be sufficiently suppressed. And if a metal short fiber will oxidize in the case of sintering, the intensity | strength of a preform will fall and desired intensity | strength will not be obtained as a metal composite material. However, in order to generate this high vacuum state, a dedicated device is required and a relatively long time is required until the generation, which increases the time and cost for manufacturing, and the engine parts described above. It is not suitable for use in a production line for manufacturing.

  When the sintering temperature is lower than the above-described 1000 ° C., the short metal fibers are not sufficiently sintered, and the short metal fibers are easily dropped when the molten metal is impregnated under pressure. There is concern about problems such as strength reduction.

  In addition, in the state before being sintered after pressing, it is only shaped and held in a predetermined shape by the pressing force of the pressing, so when transferring to a heating furnace for sintering, Short metal fibers may fall off. Similarly, even when the above-mentioned sintering temperature is lower than 1000 ° C., the short metal fibers are not sufficiently sintered, so it is necessary to set the metal melt in a mold for pressure impregnation. In the meantime, the short metal fibers may fall off. When the short metal fibers fall off in this way, for example, there is a concern that the short metal fibers that have fallen out may be mixed with another part to become a foreign substance.

  In the above-mentioned conventional Patent Document 1, it is not disclosed in detail regarding the sintering of the preform, and the above-mentioned problems remain inherent.

  The present invention proposes a method for producing a metal composite material having a desired strength without causing a decrease in strength due to oxidation of short metal fibers or dropping of the short metal fibers.

  The present invention relates to a press forming step of forming a porous preform formed of short metal fibers by pressing, and a binder having adhesiveness obtained by melting a polymer and predetermined glass particles. From the temporary fixing step of temporarily bonding the short metal fibers of at least the outer surface layer of the preform, and the pre-molded body temporarily bonding the short metal fibers with the binder, the softening point of the glass particles or more By heating at a predetermined sintering temperature, the short metal fibers are bonded to each other by the glass particles of the binder and a porous preform is formed, and the molten metal is pressurized to the preform. And a molten metal impregnation step for impregnating the metal composite material.

  Here, the short metal fibers are those having a fiber length capable of forming a preform with a predetermined shape by pressing, and specifically, those having a fiber length of 10 mm or less are suitable. Further, the high molecular polymer is for causing the adhesiveness of the binder due to its viscoelasticity, and specifically, a polymer having a viscosity of 300 to 1000 cps (molecular weight of 500,000 to 700,000) can be suitably used. And this polymeric polymer can use the thing of the synthetic resin which is organic substance suitably.

  In such a method, the metal short fibers of at least the outer surface layer of the preform formed by press working are temporarily bonded by the adhesiveness of the binder, so that the form of the preform is maintained. Prevents fibers from falling off. Furthermore, by heating the preform at the sintering temperature, at least the short metal fibers on the outer surface layer are bonded to each other with the glass particles of the binder, thereby preventing the short metal fibers from falling off. In this way, it is possible to prevent the short metal fibers from falling off in the preform and the preform, so that the short metal fibers are not dropped before the molten metal is impregnated. It is possible to prevent the occurrence of a problem that it becomes a foreign substance when mixed in.

  In addition, if each short metal fiber of the outer surface layer is temporarily bonded to each other in the preform, it is possible to prevent not only the outer surface layer but also the internal metal short fibers from falling off. Similarly, even in the preform, if the short metal fibers on the outer surface layer are bonded to each other, the short metal fibers inside can be prevented from falling off. In this method, it is preferable that the region temporarily bonded by the binder and the region bonded by the glass particles are as far as possible to the inside. And in the temporary fixing step, at least the outer surface layer of the preform is applied by applying the binder to the outer surface of the preform, spraying it, submerging the preform in the binder, etc. Each short metal fiber can be temporarily bonded with a binder.

  Moreover, in a baking process, each metal short fiber can be firmly couple | bonded by softening and solidifying glass particles. That is, even if it does not sinter metal short fibers directly, since it can couple | bond with a glass particle, it is not necessary to heat to the above-mentioned temperature of 1000 degreeC or more. Therefore, when heated to the sintering temperature, it is not necessary to generate a high vacuum state as described above, and the oxidation of the short metal fibers can be suppressed, so that the strength reduction due to the oxidation can be prevented. And the metal composite material manufactured by this method can exhibit the high intensity | strength and fatigue strength in a high temperature atmosphere, and can be used suitably for an above-described engine component.

  Further, in the present method, as described above, the press molding step for molding the preform includes a step of laminating a non-woven fabric made of metal short fibers and press working, and the metal short fibers in a mold having a predetermined shape. It may be any of the steps of direct press working. In any method, as described above, the short metal fibers can be temporarily fixed with the binder, and the short metal fibers can be bonded with the glass particles of the binder, so that the above-described effects of the present invention can be exhibited. .

  Here, as in the above-described Patent Document 1, in the method of laminating and pressing a nonwoven fabric (web), depending on the form of the preform (preliminary molded body), the metal short fibers are uniformly dispersed. In some cases, it cannot be molded. This is because, for example, if the form of the preform is a locally curved form, wrinkles and the like occur when laminating non-woven fabrics, and local portions with different density of short metal fibers are likely to occur locally. Because. That is, the method of laminating and pressing the nonwoven fabrics has a limit in the degree of freedom of molding, and it is difficult to stably mold the shape according to the shape of the strengthened portion. On the other hand, in the method in which short metal fibers are placed in a press mold and directly pressed, it can be directly molded into a desired product shape using the mold, so it can be easily molded into various forms. It can be done. That is, even when a product having a complicated shape is molded, a preform and a preform in which short metal fibers are uniformly dispersed can be molded without causing wrinkles or the like that are likely to occur when molding with a nonwoven fabric. . Therefore, a metal composite material that reliably and stably exhibits desired mechanical properties can be manufactured relatively easily and stably.

  In such a method, the press molding step is a method in which the metal short fiber put in the mold is stirred and pressed by vibrating the mold for press working. You can also. This is a method in which short metal fibers are put into a predetermined mold and pressed, and the short metal fibers are uniformly dispersed in the mold by vibrating the mold. In the preform formed by this press molding process, the short metal fibers are uniformly dispersed as a whole, and the short metal fibers are uniformly dispersed in the metal composite produced from the preform through the preform. Thus, the desired strength can be exhibited more stably.

  In the present method, borate glass particles, silicate glass particles, borosilicate glass particles, alkali glass particles and the like can be suitably used as the glass particles.

  In the method for manufacturing a metal composite described above, a method is proposed in which the predetermined glass particles of the binder used in the temporary fixing step have a particle size of 100 μm or less.

  In such a method, by using glass particles having a particle size of 100 μm or less, the glass particles easily enter between the respective short metal fibers, so that they are easy to disperse and stabilize each short metal fiber temporarily fixed with a binder. Can be combined. For example, in the temporary fixing process, when the binder is applied to the outer surface of the preform or sprayed, the glass particles also easily enter as the binder penetrates from the outer surface to the inside. Can be dispersed.

  The glass particles preferably have a particle size of 80 μm or less, and more preferably have a particle size of 50 μm or less so that the above-described effects can be more easily and stably exhibited. Moreover, since it will become difficult to couple | bond each metal short fiber when a particle size is too small, a thing with a particle size of 1 micrometer or more is suitable. And since the glass particle | grains which can be obtained stably and comparatively cheaply on manufacture are preferable, a particle size of 0.3 micrometer or more can be used conveniently.

  In the metal composite manufacturing method described above, before the heating step is heated to a predetermined sintering temperature, the polymer polymer of the binder is burned out by heating to a predetermined temperature lower than the softening point of the glass particles. A method to do so is proposed.

  In such a method, the high molecular weight polymer of the binder is burned out before heating to the sintering temperature, so that the glass particles remaining between the short metal fibers are stably softened at the sintering temperature. And each metal short fiber can be couple | bonded. Therefore, the metal short fibers bonded by the glass particles are bonded more firmly and stably. As a result, the effect of preventing the metal short fibers from dropping off during the transfer to the molten metal impregnation step is further improved, and the effect of maintaining the form of the preform can be maintained even by high pressure when the molten metal is pressure impregnated. improves.

  In the above-described method for producing a metal composite material, a method is proposed in which the polymer polymer of the binder used in the temporary fixing step is polyvinyl alcohol.

  In such a method, the binder exhibits desired tackiness due to the viscoelasticity of polyvinyl alcohol. And each metal short fiber of a preforming body is temporarily adhere | attached with the adhesiveness of a binder, and the effect of this invention mentioned above can be exhibited appropriately. Furthermore, since polyvinyl alcohol has a very high hydrophilicity and is easily dissolved in warm water, it has an excellent advantage that a binder having desired adhesiveness can be easily obtained.

  In the metal composite manufacturing method described above, a method is proposed in which the predetermined glass particles of the binder used in the temporary fixing step have a softening point of 400 ° C. or higher and 700 ° C. or lower.

  As a short metal fiber, steels such as the above-described stainless steel generally promote oxidation when exceeding 700 ° C., and the brittleness also becomes prominent. By using glass particles having a softening point, the firing step can be performed at a sintering temperature not exceeding 700 ° C. In this method, by heating to a sintering temperature not exceeding 700 ° C., the short metal fibers can be bonded to each other by the glass particles, and oxidation and embrittlement (occurrence of brittleness) of the short metal fibers can be sufficiently suppressed. Therefore, a metal composite material that can exhibit a desired strength can be manufactured.

  In addition, when the softening point is lower than the temperature of the molten metal and the temperature difference between them is large, the metal short fiber is easily softened by the heat of the molten metal when impregnated with the molten metal. Bonds between each other are easily broken. Therefore, by using glass particles having a softening point of 400 ° C. or higher, the bond between the short metal fibers is prevented from being broken by the heat of the molten metal. In addition, as glass particles, those having a softening point of 450 ° C. or higher and 600 ° C. or lower have a higher suppression effect on oxidation and embrittlement of short metal fibers, and further suppress the breakage of bonds between short metal fibers. Since the action is further improved, it can be suitably used.

  In the manufacturing method of the metal composite material described above, a method is proposed in which the short metal fibers are stainless steel having magnetism. Here, as stainless steel, ferritic stainless steel or martensitic stainless steel can be suitably used.

  In this method, since the short metal fibers have magnetism, a preform formed from the short metal fibers can be magnetized and transferred by a magnet. Therefore, for example, when the preform is positioned and set in the mold in the molten metal impregnation step, the preform is magnetically attached to the magnet disposed in the mold, thereby making the preform accurate. Good and stable positioning is possible. Further, even when material separation is performed at the time of recycling, since it can be easily separated using a magnet, it has an advantage of excellent recyclability. In addition, since the short metal fibers are stainless steel, for example, even when a water-soluble binder is used, there is an excellent advantage that the short metal fibers can be prevented from rusting.

  In the present invention, as described above, the short metal fibers of at least the outer surface layer of the preform formed by press working are temporarily bonded to each other with a binder in which a polymer polymer and glass particles are melted. By heating the molded body at a sintering temperature equal to or higher than the softening point of the glass particles, the metal short fibers are bonded to each other by the glass particles to form a preform, and the preform is pressure-impregnated with a molten metal. This is a method for producing a metal composite material. According to this method, since the short metal fibers constituting the preform and the preform can be prevented from falling off, the short metal fibers dropped off are mixed into other parts as in the conventional configuration described above. There is no problem of becoming a foreign object. In addition, since the short metal fibers are bonded to each other with the glass particles, it is not necessary to heat the above-described 1000 ° C. or more, and the oxidation of the short metal fibers can be suppressed. It can exhibit high strength and fatigue strength in the atmosphere.

  In the method for producing a metal composite material described above, when the predetermined glass particles of the binder used in the temporary fixing step are those having a particle size of 100 μm or less, the glass particles are each short metal fiber. Since it is easy to enter, it is easy to disperse, and it is possible to stably bond the short metal fibers in the firing step.

  In the above-described method for producing a metal composite material, before the baking step is heated to a predetermined sintering temperature, the polymer polymer of the binder is burned down by heating to a predetermined temperature lower than the softening point of the glass particles. In the case of the method, the short polymer fibers are burned off and then heated to the sintering temperature, so that the short metal fibers can be bonded to each other more firmly and stably by the glass particles. Therefore, the above-described operational effects of the present invention can be more appropriately exhibited.

  In the method for producing a metal composite material described above, when the polymer polymer of the binder used in the temporary fixing step is polyvinyl alcohol, the polyvinyl alcohol is highly hydrophilic and soluble in hot water. Therefore, a desired binder can be easily obtained, and the above-described effects of the present invention can be appropriately and easily exhibited by the binder.

  In the manufacturing method of the metal composite material described above, when the predetermined glass particles of the binder used in the temporary fixing step have a softening point of 400 ° C. or higher and 700 ° C. or lower, It is possible to produce a metal composite material that can sufficiently suppress the oxidation and embrittlement of the short fibers and can exhibit a desired strength.

  In the above-described method for producing a metal composite material, when the metal short fiber is made of stainless steel having magnetism, a melt impregnation step is performed by magnetizing a preform made of the metal short fiber with a magnet. Therefore, accurate and stable positioning in the mold can be easily performed. Also, when material separation is performed at the time of recycling, it can be easily separated using a magnet, and excellent recyclability is achieved.

Embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 shows a process of forming a porous preform 1 made of short metal fibers 12, and FIG. 2 forms a metal composite 10 by impregnating the preform 1 with a molten aluminum alloy 6. The process is shown. The process for molding the preform 1 and the process for molding the metal composite material 10 constitute a method for producing a metal composite material according to the present invention. Hereinafter, each process will be described in detail.

  FIG. 1A shows a press molding process for molding a preform 2 having a predetermined shape, which is performed by a mold 21 including an upper punch 22 and a lower die 23. Here, the die 23 includes a bottomed cylindrical pressing hole 24, and the punch 22 is fitted into the pressing hole 24 to press the pressed object disposed in the pressing hole 24. That is, a predetermined amount of the short metal fibers 12 are filled in the pressing holes 24 of the die 23 and pressed by the punch 22, thereby pressing the short metal fibers 12 in the pressing holes 24 to form a cylindrical preform. Get 2. The preform 2 is formed by pressing a large amount of short metal fibers 12 and is porous.

  Furthermore, in this embodiment, when the metal short fiber 12 is filled in the pressing hole 24 of the die 23, the metal short fiber in the pressing hole 24 is vibrated by vibrating the die 23 in the vertical direction or the horizontal direction. The fibers 12 are stirred. As a result, the short metal fibers 12 are uniformly dispersed in the pressing hole 24 of the die 23. Then, as described above, the preform 22 having a uniform volume ratio is formed by pressing with the punch 22 and pressing.

  In this embodiment, SUS430, which is a ferritic stainless steel, is used as the short metal fiber 12. The short metal fibers 12 have an average fiber diameter of 60 μm and an average fiber length of 6 mm. The average fiber diameter and the average fiber length are average values of the fiber diameter and the fiber length, respectively, and have variations.

  Next, as shown in FIG. 1B, a temporary fixing step of applying the binder 16 to the preform 2 is performed. Here, the binder 16 is an aqueous solution having adhesiveness in which polyvinyl alcohol is dissolved with warm water, and glass particles 17 (see FIG. 4) are added thereto and mixed so as to be uniformly dispersed. Here, the density | concentration of polyvinyl alcohol is set so that it may become 1 weight%-10 weight%, and is set to about 2 weight% in a present Example. On the other hand, the glass particles 17 are borosilicate glass particles in this embodiment, and have an average particle size of 30 μm and a softening point of about 480 ° C. The borosilicate glass particles 17 are set so that the content in the binder 16 is 5 wt% to 20 wt%. In this embodiment, the borosilicate glass particles 17 are set to about 9 wt%.

  In the temporary fixing step of this embodiment, the binder 16 is sprayed on the outer surface of the preform 2. As a result, the binder 16 penetrates from the outer surface of the porous preform 2 to the inside and adheres to at least each metal short fiber 12 constituting the outer surface layer of the preform 2. Here, since the binder 16 has adhesiveness with polyvinyl alcohol, the adjacent metal short fibers 12 on the outer surface layer of the preform 2 are temporarily bonded to each other by the binder 16. Furthermore, since the borosilicate glass particles 17 are uniformly dispersed in the binder 16 as described above, the borosilicate glass particles 17 are attached to each short metal fiber 12 to which the binder 16 is attached. .

  As described above, the short metal fibers 12 constituting the outer surface layer of the preform 2 are temporarily bonded to each other by the temporary fixing step. Thereby, it is possible to prevent the short metal fibers 12 from falling off in the process of transferring the preform 2. Therefore, the metal short fibers that have fallen are mixed in another molded product, or in a molten metal impregnation process that will be described later, and mixed in a portion where the preform 2 is not placed in the mold. Can be prevented from becoming mixed.

  Next, the baking process which couple | bonds the preforming body 2 temporarily adhere | attached with the binder 16 is performed. In this firing step, first, as shown in FIG. 1 (C), it is placed in a heating furnace 30 and heated to about 250 ° C. to be dried. Thereby, while removing the water | moisture content of the binder 16 adhering to the preform 2, the polyvinyl alcohol component is burned out. By this heat treatment, the polyvinyl alcohol component can be completely burned out, so that impurities can be prevented from remaining due to burning. Here, since the borosilicate glass particles 17 are dispersed and adhered to the short metal fibers 12 constituting the outer surface layer of the preform 2 as described above, the borosilicate is obtained by burning off polyvinyl alcohol. The glass particles 17 are arranged between the short metal fibers 12.

  Then, it heats to sintering temperature 600 degreeC, hold | maintains for 30 minutes, and cools. Thereby, the borosilicate glass particles 17 are softened and solidified, and adjacent metal short fibers 12 to which the borosilicate glass particles 17 are attached are bonded to each other. Thus, the short metal fibers 12 on the outer surface layer of the preform 2 are bonded together by the borosilicate glass particles 17 to form the preform 1. Since the preform 1 is bonded by the borosilicate glass particles 17, the metal short fibers 12 on the outer surface layer are bonded relatively firmly, and the metal short fibers 12 fall off during transfer or the like. Can be prevented.

  Furthermore, since the preform 1 described above is molded by heating to 600 ° C., the oxidation of the short metal fibers 12 can be sufficiently suppressed and the brittleness of the short metal fibers 12 is generated and proceeds remarkably. This can also be suppressed. Therefore, the metal short fiber 12 of the preform 1 does not cause a decrease in strength due to oxidation or embrittlement, and can exhibit its original strength. Therefore, the preform 1 also has sufficient strength. That is, in this example, the short metal fibers 12 are bonded to each other by the borosilicate glass particles 17 without being heated to 1000 ° C. or higher, so that the short metal fibers 12 are oxidized and embrittled. The short metal fibers 12 can be bonded relatively firmly without being generated.

  In the present embodiment, the firing step is performed by bonding (sintering) at a sintering temperature of 600 ° C. after heating to 250 ° C. as described above. Thus, the polyvinyl alcohol component of the binder 16 can be completely burned out before the borosilicate glass particles 17 are softened, so that the borosilicate glass particles 17 can be softened reliably and stably when heated to the sintering temperature. , The binding by the borosilicate glass particles 17 can be generated stably.

  Next, the metal composite material 10 is formed by performing a molten metal impregnation step in which the above-described preform 1 is combined with an aluminum alloy by the die casting forming apparatus 33 shown in FIGS. As shown in FIG. 2, the die casting apparatus 33 includes a mold 34 composed of a fixed mold 34a and a movable mold 34b. The movable mold 34b is opened (see FIG. 2A) and closed (see FIG. 2). 2 (see (B)), and a cylindrical cavity 35 is formed at the closed position. Here, a sleeve 37 is connected to the lower portion of the fixed die 34 a, and a gate 36 is formed on the tip side of the sleeve 37. The sleeve 37 is provided with a plunger tip 38 that moves forward and backward. Further, an inlet 39 for injecting the molten metal 6 into the sleeve 37 is provided at the rear portion of the sleeve 37.

  In a state where the fixed mold 34a and the movable mold 34b are closed, a hot water passage 40 that connects the cavity 35 and the gate 36 is formed (see FIG. 2B). That is, when the plunger tip 38 is advanced while the movable die 34b is held in the closed position, the molten metal 6 put in the sleeve 37 flows into the cavity 35 from the gate 36 through the hot water passage 40 (FIG. 3 (A)). The runner 40 is formed with a cross-sectional area smaller than the respective cross-sectional areas of the sleeve 37 and the gate 36, and the injection speed of the molten metal 6 is made faster than the operating speed of the plunger tip 38. Yes.

  The movable die 34b includes an extrusion pin that is converted into a holding position (see FIG. 2) that is uniform with the inner surface of the cavity 35 and a protruding position (see FIG. 3B) that protrudes into the cavity 35. 41 is provided. The operation of changing the position of the push pin 41, the opening / closing operation of the movable die 34b, and the advance / retreat operation of the plunger tip 38 are controlled by a control device (not shown). Further, the die casting apparatus 33 is provided with a handle rod 42 (see FIG. 2B) for flowing a predetermined amount of the molten metal 6 into the sleeve 37. The handle rod 42 is also operated by a control device (not shown). I try to control it.

  Here, in the present embodiment, an aluminum alloy of ADC 12 (JIS standard) is used, and the preform 1 is impregnated with the molten aluminum alloy 6 by the die casting apparatus 33 described above. ing.

The melt impregnation step by the die casting apparatus 33 is performed in the following order.
First, the preform 1 is preheated at about 500 ° C., and the mold 34 is held at about 100 ° C. As shown in FIG. 2 (A), after the preheated preform 1 is disposed at a predetermined position in the cavity 35 of the movable mold 34b in the open position, the movable mold 34b is closed as shown in FIG. 2 (B). Move to position and close cavity 35. Thereby, the preform 1 is accommodated in the cavity 35.

  Here, when the preform 1 is set in the cavity 35, the preform 1 is accurately attached by magnetizing the preform 1 on a magnet (not shown) embedded in the cavity 35 of the movable die 34b. Good and stable positioning can be achieved. Moreover, since the metal short fiber 12 of the outer surface layer is couple | bonded by the borosilicate glass particle 17, the metal short fiber 12 does not drop out of the preform 1. Therefore, the short metal fibers 12 do not fall off during the transfer until the preform 1 is placed in the cavity 35, and the short metal fibers 12 exist only in the preform 1 in the cavity 35.

  In FIG. 2, the plunger tip 38 is set at the retracted position and is kept waiting behind the inlet 39 in the sleeve 37. After the movable die 34b is in the closed position as described above, a predetermined amount of the molten aluminum alloy 6 maintained at about 680 ° C. is injected by the handle rod 42 as shown in FIG. Then, as shown in FIG. 3A, the plunger tip 38 is driven to advance from the retracted position at a predetermined driving speed, and the molten metal 6 in the sleeve 37 is injected into the cavity 35. Here, since the cross-sectional area of the hot water passage 40 is set to be relatively small as described above, the injection speed of the molten metal 6 injected into the cavity 35 is higher than the driving speed of the plunger tip 38. Speed up. In this embodiment, when the driving speed of the plunger tip 38 is 2 m / s, the injection speed is 30 m / s.

  When the molten metal 6 is filled in the cavity 35, the plunger tip 38 stops and the injection of the molten metal 6 stops, and after cooling, the movable die 34b is set to the open position as shown in FIG. The metal composite material 10 is taken out of the movable die 34b by moving the push pin 41 of the movable die 34b from the holding position (see FIG. 2) to the protruding position. Thereafter, the metal composite material 10 is formed into a predetermined cylindrical shape by cutting and removing a portion (aluminum alloy 6 ') formed by the gate 36 and the water passage 40 (not shown).

  As a result of cross-sectional observation of the outer surface layer portion of the metal composite material 10 thus formed, the metal short fibers 12 are dispersed in the aluminum alloy 6 ′ (metal base material) as shown in FIG. It can be confirmed that 12 are bonded together by the borosilicate glass particles 17. As a result, the short metal fibers 12 are relatively strongly bonded to each other by the borosilicate glass particles 17, and even when the molten aluminum alloy 6 is impregnated at a relatively high speed, the bonded state is maintained and the metal base material 12 is maintained. It turns out that it is compounded in a dispersed state. Further, as described above, the preform 1 is obtained by firmly bonding the short metal fibers 12 on the outer surface layer, and since the form is firm, the preform 1 is impregnated at a relatively high speed. However, the preform 1 is not deformed, and the metal composite material 10 in which the short metal fibers 12 are dispersed in the base material of the aluminum alloy 6 ′ can be obtained.

  In this embodiment, since the short metal fiber 12 is SUS430 of ferritic stainless steel, it can be accurately and stably positioned in the cavity 35 of the die casting apparatus 33 as described above. Furthermore, the metal composite material 10 molded by the present manufacturing method is also easily demanded for the environmental resistance, which has been strongly demanded in recent years, because the short metal fibers 12 have magnetism as described above. Therefore, it has excellent recyclability.

Next, the result of having conducted the test which measures the intensity | strength of the metal composite material 10 of a present Example mentioned above is demonstrated.
Here, in the present Example, the tensile test is performed and the tensile strength is measured. The tensile test is performed according to JIS Z2241. As a test piece for the tensile test, a round bar-shaped test piece having a predetermined size is cut out from the cylindrical metal composite material 10 described above.

  In addition, as a comparative example of the metal composite material 10 of the present example, a structure in which a preform sintered at a high temperature of 1000 ° C. or higher was impregnated with an aluminum alloy and only an aluminum alloy were prepared, and a similar tensile test was performed. Tensile strength was measured. Here, the configuration of the former comparative example is the same as in the above-described embodiment. After the preform 2 is molded by the press molding process, the preform 2 is placed in the heating furnace 25 and a vacuum pump (shown in the figure). (Omitted) is operated to bring the inside of the heating furnace 25 into a vacuum state of about 0.4 Pa. And this vacuum state is maintained, it heats to 1150 degreeC and hold | maintains for 60 minutes. As a result, the preform 2 is sintered to form a preform. This preform is impregnated with the molten aluminum alloy 6 by the die casting apparatus 33 in the same manner as in the above-described embodiment to obtain a metal composite material of a comparative example. This comparative example is manufactured in the same manner as in the example except that no binder is used and sintering is performed at a high temperature of 1000 ° C. or higher in a vacuum.

  The result of the tensile test is shown in FIG. The metal composite material 10 of the present example has a higher tensile strength than the configuration of the comparative example described above. In particular, it can be confirmed that the metal composite material 10 of the present example exhibits higher tensile strength than the tensile strength of a metal material made of only an aluminum alloy, and high strength can be achieved by combining. In comparison, the comparative example sintered at a high temperature of 1000 ° C. or higher has a significantly lower tensile strength than a metal material made of only an aluminum alloy. This is presumably because the short metal fibers were not oxidized and embrittled when sintered at a high temperature of 1000 ° C. or higher, so that the inherent strength of the short metal fibers could not be exhibited. And when sintering at a high temperature of 1000 ° C. or higher, even if sintering is performed in a vacuum of about 0.4 Pa, oxidation and embrittlement of the short metal fibers cannot be suppressed. For this reason, if the sintering is performed at 1000 ° C. or higher, a higher vacuum state is required. Therefore, a dedicated machine is required, which increases the manufacturing time and the manufacturing cost. . This causes a problem that the market competitiveness decreases.

  In addition, also from the result of the above-described tensile test, even if the metal composite material 10 of the present embodiment is molded by a die casting method in which the preform 1 is impregnated with the molten metal at a relatively high speed, the molten metal is sufficiently impregnated. In addition, it is clear that the preform 1 is not deformed or broken, and it can be seen that the short metal fibers 12 are firmly bonded to each other by the borosilicate glass particles 17.

  In the manufacturing method of the above-described embodiment, ferritic stainless steel SUS430 is used as the short metal fiber 12, but martensitic stainless steel SUS410 can also be used. Even in this martensitic stainless steel, since it has magnetism like ferritic stainless steel, it can be accurately positioned in the cavity 35 of the die casting apparatus 33 as described above. It has the effect of being excellent in recyclability. In addition, as the short metal fibers 12, other stainless steel, mild steel, or the like can be used, and further, short fibers of copper, brass, or aluminum alloy can be used. And it is preferable to set it as 10 mm or less as the short metal fiber 12 if the fiber length considers applying to press work. A fiber length of 3 mm to 7 mm can be suitably used as the fiber length.

  In the above-described embodiments, a molten aluminum alloy is used as the molten metal, but a molten metal such as a magnesium alloy can also be suitably used.

  Further, as the binder, a high molecular polymer that is an organic synthetic resin such as polyacrylamide can be used instead of polyvinyl alcohol. In addition to borosilicate glass particles, borate glass particles or silicate glass particles can also be used as the glass particles of the binder.

  In the embodiment described above, the baking step is heated to 250 ° C. and then to a sintering temperature of 600 ° C. However, it is also possible to heat only to the sintering temperature of 600 ° C. By heating to 600 ° C., the moisture of the binder and the polyvinyl alcohol component can be burned out, so that the short metal fibers 12 can be bonded to each other by the borosilicate glass particles 17.

  In the embodiment described above, a metal composite material that locally includes a portion to be combined by a preform can be formed in the molten metal impregnation step. In this metal composite material, a composite portion where the preform and the metal base material are combined and a metal portion made of only the metal base material are integrally cast. Even when such a metal composite material is formed, the above-described effects of the present invention are exhibited. In the molten metal impregnation step, even when the preform is disposed at a predetermined location in the cavity of the mold, the metal short fiber of the preform does not fall off. It will not be mixed as.

  In this invention, it is not limited to the Example mentioned above, About another structure, it can change suitably within the range of the meaning of this invention.

It is explanatory drawing showing the process of shape | molding the preform 1 of an Example. It is explanatory drawing showing the molten metal impregnation process by the die-casting apparatus 33. FIG. It is explanatory drawing showing the molten metal impregnation process continuous from FIG. It is a cross-sectional enlarged photograph of the metal composite material 10 of a present Example. It is a graph which shows the measurement result of the tensile strength of the metal composite material 10 of a present Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Preform 2 Preformed object 6 Molten metal of aluminum alloy (molten metal)
6 'Aluminum alloy (metal base material)
DESCRIPTION OF SYMBOLS 10 Metal composite material 12 Short metal fiber 16 Binder 17 Glass particle (borosilicate glass particle)

Claims (6)

A press forming step of forming a porous preform formed of short metal fibers by pressing; and
A temporary fixing step of temporarily adhering the short metal fibers of at least the outer surface layer of the preform with a binder having adhesiveness obtained by melting a polymer and predetermined glass particles;
By heating the preform in which the short metal fibers are temporarily bonded with the binder at a predetermined sintering temperature equal to or higher than the softening point of the glass particles, the short metal fibers are bonded with the glass particles of the binder. A firing step of forming a porous preform;
A method for producing a metal composite material, comprising: a melt impregnation step in which the preform is impregnated with a molten metal under pressure.   The method for producing a metal composite according to claim 1, wherein the predetermined glass particles of the binder used in the temporary fixing step have a particle size of 100 µm or less.   The high molecular polymer of the binder is burned down by heating to a predetermined temperature lower than the softening point of the glass particles before the baking step is heated to a predetermined sintering temperature. The manufacturing method of the metal composite material of Claim 1 or Claim 2.   The method for producing a metal composite according to any one of claims 1 to 3, wherein the polymer polymer of the binder used in the temporary fixing step is polyvinyl alcohol.   The predetermined glass particles of the binder used in the temporary fixing step have a softening point of 400 ° C or higher and 700 ° C or lower, according to any one of claims 1 to 4. A method for producing a metal composite.   The method for producing a metal composite according to any one of claims 1 to 5, wherein the short metal fibers are stainless steel having magnetism.