JP2007216237A - Method for manufacturing casting apparatus and mold-surrounding member, and mold-surrounding member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a casting apparatus and a mold-surrounding member, and the mold-surrounding member with which a heat-resistance property can be improved and a manufacturing term can be shortened. <P>SOLUTION: Since a molten metal pouring part constituted member composed of a surface layer made of an intermetallic compound as the base material and a main body part made of a metallic material as the base material is manufactured from a process, in which mixed powder of raw material elements for intermetallic compound are filled up in a master mold having a turning-over shape of the molten metal pouring constituted member, and a process for manufacturing the intermetallic compound surface layer by reacting the filled-up mixed powder in the master mold, especially, a large scaled facility is not necessary and the high melting point intermetallic compound surface layer is simply manufactured in a second unit or a minute unit and further, the main body part of the metallic material as the base material is quickly and efficiently manufactured with overlaying and a high functional mold-surrounding member can be manufactured for extremely short time. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a casting apparatus used for gravity casting, low pressure casting, die casting, or the like, and a pouring part constituting member (hereinafter referred to as a "pouring part constituting member") constituting a path for supplying molten metal to a mold of these casting apparatuses. And the like, and a manufacturing method thereof.

Generally, the following properties are required for a member around a mold such as a pouring member constituting member having a portion that contacts a molten material to be cast in a casting apparatus.
(1) High strength without yielding to high temperatures.
(2) It is difficult for creep deformation due to thermal stress.
(3) Resistant to thermal cycle fatigue accompanying repeated heating and cooling.
(4) Resistant to thermal shock due to contact with molten metal and sudden temperature changes.
(5) Resistant to mechanical damage due to molten metal collision.
(6) Low reactivity with molten metal and strong against erosion.
(7) Excellent oxidation resistance.

Conventionally, the SKD61 material or the like has been used as the material around the mold, and the following problems have been pointed out.
(1) A long time is required for production.
(2) For example, the SKD61 material has problems of creep at high temperatures and thermal fatigue.

  More specifically, for example, a mold pouring sleeve, which is a mold surrounding member, is generally provided with a metal spray layer such as Ni / Cr on the inner wall surface of a steel cylinder and a ceramic layer on the surface thereof. Thus, the impact resistance and the durability against the molten metal were achieved. However, in such a conventional pouring sleeve, when the ceramic layer is easily broken due to repeated heat changes, not only the lower metal spray layer but also the base metal layer is melted, resulting in casting. This causes the inconvenience of not being able to leave things.

  In addition, in the low pressure casting method applied to the manufacture of machine parts made of aluminum or other metals, the molten metal is supplied into the mold from the stalk connected to the gate provided at the lowest position of the lower mold through the gate sleeve. When the casting finally solidifies while the casting is directional solidified, the pressure in the stalk is lowered to separate the casting from the molten metal in the stalk. For this reason, the molten metal circulates frequently in the stalk, so that melting damage is likely to occur.

Furthermore, the following problems have also occurred with respect to the die casting apparatus.
FIG. 45 shows a horizontal casting type cold chamber die casting apparatus which is a die casting apparatus widely applied to manufacture of parts such as automobiles and communication equipment.
As shown in the figure, in this horizontal casting type cold chamber die casting apparatus, molten aluminum alloy at 640 ° C. to 650 ° C. is supplied from the hot water supply port 41 of the plunger sleeve 40 to the plunger hole 42. Thereafter, the plunger tip 43a of the plunger 43 is slid and reciprocated inside the plunger sleeve 40, and the molten aluminum alloy is injected into the cavity through the gate sleeve 45 of the mold 44, thereby performing casting. The tubular plunger sleeve 40 having the plunger hole 42 is generally manufactured by nitriding the SKD-61 of hot tool steel, and its front portion 40c is fixed to the fixed die plate 47 via the bush 46. Supported. On the other hand, the rear portion 40d where the hot water supply port 41 is located is not supported by the fixed die plate 47 but is fixed in a cantilever state.

  The inside of the plunger sleeve 40, particularly the lower part of the plunger hole 42, is heated rapidly by contact with the high-temperature molten metal, and erosion occurs due to the molten metal. The plunger tip 43a cannot slide smoothly inside the plunger sleeve 40. Further, in order to prevent this erosion, when the entire plunger sleeve is made of a brittle ceramic material, there is a problem that it is easily broken and difficult to handle.

Therefore, as a material capable of solving the problems in various casting apparatuses as described above, application of a porous sintered body, particularly, intermetallic compounds typified by TiAl, Ni ₃ Al, FeAl, and MgAl can be studied.
These intermetallic compounds as porous sintered bodies are expected to improve the high temperature strength of the mold periphery member when applied to the mold periphery member because of the property that the high temperature strength is several times higher than room temperature. However, in general, an intermetallic compound has a high melting point, and when an active metal such as Ti or Al is dissolved at a high temperature, it is very easy to oxidize, and measures to prevent reaction with a crucible material are required. Therefore, it is necessary to prepare an ultra-high temperature vacuum furnace for such a melting apparatus, which requires excessive capital investment. Furthermore, Ti and Al, Ni and Al, and Fe and Al also have a difference in specific gravity between them. Gravity segregation and casting segregation also occur, and there is a problem that it is difficult to obtain a homogeneous material. In addition, since it is hard and poor in ductility, machining after casting is difficult, and considerable consideration is required for the processing method, and practically it has been difficult to apply it as a material around a mold.
Specifically, for example, when trying to obtain a cast product of FeAl intermetallic compound, the FeAl intermetallic compound mainly composed of Fe and Al has poor ductility, and in the process where the molten metal solidifies in the mold. Tortoise-shaped cracks occur at the grain boundaries inside the product, making it impossible to obtain a sound casting.

Patent Document 1 exists as a known document that attempts to cast such an intermetallic compound.
In this patent document, the grain boundary of a product is controlled by casting a molten FeAl intermetallic compound in which Al is 37 to 53% in atomic concentration and the remainder is Fe, and controlling the solidification cooling rate to 1000 ° C./hour. It is disclosed that a tortoiseshell-shaped crack is prevented, and an excellent cast product can be obtained as an oxidation-resistant, corrosion-resistant, and wear-resistant part.
However, even when such a casting method is adopted, it is difficult to machine after casting due to the hard and poor ductility of the intermetallic compound. The problem of being difficult is not solved.
JP-A-6-228706

  The present invention has been made in view of the above problems in the prior art, and an object of the present invention is to provide a casting apparatus, a mold rotating member manufacturing method, and a mold rotating member capable of improving heat resistance and shortening the production period.

  The inventors can apply a combustion synthesis method using a thermal explosion reaction of powder, which is known as a method for producing an intermetallic compound, to manufacture a member around a mold made of an intermetallic compound having a high high-temperature strength with extremely high efficiency. I found what I could do and came up with the present invention.

  That is, the casting apparatus of the present invention is characterized by having a mold surrounding member provided with a porous sintered body layer.

  By having a mold-around member having a porous sintered body layer in this way, the casting apparatus of the present invention has a long service life by eliminating the problems of creep and thermal fatigue at high temperatures for the mold-around member. Can do. This mold periphery member is, for example, a pouring portion constituting member that constitutes at least a part of a path for supplying molten metal to the mold.

  The porous sintered body layer can have a corrosion-resistant barrier layer. Thereby, oxidation resistance can be improved.

  A member around the mold is attached to a main body part made of a metal material, and the main body part is made of a metal material, and a first main body part that replenishes the strength of the porous sintered body layer and a metal material. You may make it consist of the 2nd main-body part which is shape-molded and comprises the attachment function part with a casting mechanism.

As described above, the mold-turning member of the casting apparatus of the present invention has a surface layer based on a porous sintered body such as an intermetallic compound as a surface layer that comes into contact with the molten metal to be cast, such as aluminum, and maintains heat retention and resistance to erosion. Give sex. Further, since the strength of the intermetallic compound alone is insufficient, a main body portion using a metal material as a base material is used.
As this metal material, normally used SKD61 and SUS seem to be appropriate, but Ti or Ni-based alloy may be used as necessary.

  Furthermore, the casting apparatus according to the present invention is characterized in that a pouring sleeve for a mold, which is a pouring part constituting member that is installed in a pouring gate of a mold and supplies molten metal to the mold, includes a porous sintered body layer.

  Furthermore, the casting apparatus of the present invention comprises a mold composed of an upper mold and a lower mold, and a gate is provided in the lower mold so as to supply molten metal from below into a space formed between the two molds. A pouring sleeve and / or stalk, which is provided and is a pouring portion constituting member communicating with the pouring gate, includes a porous sintered body layer.

  In addition, the casting apparatus of the present invention is characterized in that a plunger sleeve, which is a pouring part constituting member having an open hot water supply port, has a porous sintered body layer at least in part.

  Such a casting apparatus can be a casting apparatus having a plunger sleeve for die casting having a plunger hole and a cylindrical plunger sleeve having a hot water supply port for pouring at the upper part on the rear end side.

  Each casting apparatus of the present invention described above can prevent erosion due to the molten metal by providing the molten metal pouring sleeve and the pouring sleeve and / or the stalk, the plunger sleeve as the pouring part constituting member with the porous sintered body layer, A casting apparatus having excellent durability and low cost can be obtained.

  In addition, by making the porous sintered body layer of each of the above-described casting apparatuses of the present invention have a corrosion-resistant barrier layer, for example, in a casting apparatus having a plunger sleeve for die casting, the reciprocating movement of the plunger tip of the plunger can be performed. It is possible to prevent erosion caused by the molten metal at the lower portion of the hot water outlet of the plunger sleeve, which becomes an impediment factor, and the durability can be further improved.

  In the casting apparatus of the present invention, an erosion preventing member formed of a porous sintered body can be fitted into a fitting portion provided in a part of the plunger sleeve. With this configuration, it is possible to provide an erosion prevention member formed of a porous sintered body having excellent heat resistance and wear resistance in a portion where the erosion is struck directly by the molten metal supplied from the hot water supply port, and smooth sliding of the plunger Reciprocating motion can be maintained for a long time. Also, the porous sintered body can be made into a handling plunger sleeve by forming the whole as a relatively small part and making the other part as a whole with an easy-to-handle material such as metal.

In addition, the method for producing a mold turning member of the present invention is a mixed powder of raw material elements of a porous sintered body in a graphite master mold having a reversal shape with respect to the contact surface shape of the mold turning member with the molten metal, particularly between metals. A step of filling a mixed powder of raw material elements of the compound and a step of producing a porous sintered body layer, that is, an intermetallic compound layer, by reacting the filled mixed powder in a master mold. To do.
In filling the mixed powder into the graphite master mold, a uniaxial pressurization or a CIP (hydrostatic pressurization) method can be applied.

  The mixing ratio of the raw material element mixed powder of the porous sintered body, especially the mixed powder of the intermetallic compound raw material element, is adjusted based on the desired porous sintered body, particularly the stoichiometric composition of the intermetallic compound. can do. Furthermore, the mixing ratio of the mixed powder of the raw material elements of the porous sintered body, in particular, the mixed powder of the raw material elements of the intermetallic compound can be adjusted so that the required raw material elements are excessive with respect to the stoichiometric composition. Furthermore, in addition to the mixed powder of the raw material elements of the target porous sintered body, particularly the mixed powder of the raw material elements of the intermetallic compound, a metallic element powder serving as an auxiliary agent may be added. In this case, the additive amount of the metal element powder as an auxiliary is preferably 0.01% to 10%, more preferably 0.1 to 8%, and most preferably 0.3 to 6%. It is good to do.

To react the mixed powder filled in the master mold, the master mold filled with the mixed powder is heated, and a porous sintered body, especially an intermetallic compound, is synthesized on the master mold by a thermal explosion reaction of the mixed powder. be able to. In this case, the heating temperature is higher than the melting point by 50 ° C. above the melting point of the porous sintered body, in particular, the melting point of the intermetallic compound raw material element and auxiliary metal element having the lowest melting point. The temperature is preferably lower than the temperature, more preferably higher than the melting point by 5 ° C to 40 ° C, most preferably higher than the melting point by 10 ° C to 30 ° C.
In the above, it is desirable that the heating temperature be controlled so that a slight liquid phase is formed. When the liquid phase is excessive, the mixed powders lose their connection with each other and the shape cannot be easily maintained due to meltdown. When melted down, it becomes droplets due to the problem of wettability with the graphite master, and powder formability is lost.
Therefore, it is desirable that the mixed powder is brought into a so-called semi-molten state by controlling the heating temperature at which a small amount of liquid phase is generated between the powders to sinter the powder.

The heating atmosphere at that time may be an inert gas or a vacuum atmosphere, and in addition, an auxiliary heat source such as induction heating or pulse application energization may be used. Furthermore, it is possible to perform heating of the master mold filled with the mixed powder under pressure. A well-known HIP method or the like can be applied as a method of heating under pressure. A stable reaction can be promoted by sealing the pores on the back side of the master mold and cooling.
In addition, an HP (hot press) method and an electric current sintering method can also be applied.

  Furthermore, in the method for producing a mold periphery member of the present invention, a build-up weld layer is formed on the porous sintered body synthesized on the master mold, particularly on the intermetallic compound layer. As a result, the mold surrounding member is attached to the main body having the metal material as the base material. That is, the build-up weld layer constitutes the main body portion of the mold surrounding member, and the porous sintered body, particularly the intermetallic compound surface layer, is supported by the mold surrounding member main body portion.

  The relative density with respect to the theoretical true density of the porous sintered body of the mold periphery member, particularly the intermetallic compound layer, produced by the above method for producing a mold periphery member of the present invention is about 50 to 97%, preferably 75. % Or more, and most preferably 85% or more.

  A corrosion-resistant barrier layer can be provided on the surface of the mold surrounding member of the present invention, and this corrosion-resistant barrier layer is a porous sintered body, particularly an oxide film or porous sintered body formed on the surface of the intermetallic compound layer, particularly Can be a corrosion-resistant layer and / or a release layer formed by thermal spraying on the surface of the intermetallic compound layer.

  In general, a porous material has features such as weight reduction of a structural material, filtration action, heat exchange action, and impact resistance, and is currently widely used. There are gas injection method and gas sealing method as a method for producing porous materials. However, it is difficult to produce ultra-light materials due to variations in material characteristics due to variations in the size of bubbles, or due to limitations in relative density. There is also a problem such as.

As a method for producing a porous sintered body constituting the member around the mold of the present invention, particularly an intermetallic compound, a rapid production method using a thermal explosion reaction of powder is known. According to this rapid production method, that is, the combustion synthesis method, a high melting point compound can be produced efficiently, and a large-scale facility such as an ultrahigh temperature furnace is not required. Furthermore, since the porous material can be produced efficiently and is a kind of powder metallurgy technique, it is possible to control the structure of the porous material as the surface layer of the mold surrounding member.
By combining the advantages of the combustion synthesis method that takes advantage of the rapid thermal explosion reaction of such powder and the high-temperature strength characteristics of porous sintered bodies, particularly intermetallic compounds, the production of the casting apparatus and the mold surrounding members of the present invention A method and a mold surrounding member were established.

Hereinafter, the principle of combustion synthesis and the adiabatic combustion temperature used by the method for producing a mold-around member of the present invention will be described.
In combustion synthesis, a powder reaction is adiabatically generated, and the reaction is accelerated and explosively generated to synthesize the compound while sintering the powder.
This is explained by taking Ni ₃ Al as an example. When 3/4 mol of Ni powder and 1/4 mol of Al powder are reacted to generate a total of 1 mol of Ni ₃ Al (Ni ₃ Al is represented by the formula Since 3 mol and 1 mol of Al are contained, 1 / 4Ni ₃ Al becomes 1 mol of compound.) 42.9 kJ of heat is generated.
3 / 4Ni + 1 / 4Al = 1 / 4Ni ₃ Al + 42.9 kJ / mol
In this case, if the Ni powder and the Al powder are simply reacted, the reaction heat is dissipated outside the system, so that combustion synthesis does not occur. However, when the powder is closely packed and the reaction is carried out in an insulated container, the heat of reaction stays in the system, resulting in a temperature rise due to the heat of reaction. Synthesis and powder sintering occur in a short time. This phenomenon is called combustion synthesis.
The theoretical combustion temperature at that time is calculated by a temperature enthalpy diagram. The temperature enthalpy diagram in this case is shown in FIG.
In the figure, the upper solid line is the internal energy (enthalpy) of the Ni + Al powder, and the lower solid line and the broken line are the internal energy of Ni ₃ Al.
In general, the reaction between the metals in the solid state hardly occurs because the diffusion of the metal element is slow. For this reason, combustion and reaction do not occur even if the powder is simply mixed at room temperature. However, when Ni + Al powder is heated in a furnace to trigger the melting of Al, active diffusion of metal elements occurs and the reaction starts.
When the Ni + Al mixed powder is heated to 933 K (the melting point of Al) and an adiabatic reaction is caused, the reaction heat is all consumed for temperature rise, and the powder is 1668 K (the melting point of Ni ₃ Al from the law of energy immortality). ) Until heated. Using this high temperature, compound synthesis and powder sintering can be performed.
The principle is the same for TiAl and FeAl, and the reaction heat is 1/2 Ti + 1/2 Al = 1/2 TiAl + 41.8 kJ, respectively.
1 / 2Fe + 1 / 2Al = 1 / 2FeAl + 31.0kJ
9 and FIG. 10, the adiabatic combustion temperature is 1733 K (melting point of TiAl), the adiabatic combustion temperature of FeAl is 1538 K (melting point of FeAl), Become.

The casting apparatus and the mold surrounding member of the present invention include a porous sintered body, particularly an intermetallic compound layer, and the porous sintered body, particularly the intermetallic compound has high high-temperature strength, high hardness, and chemically stable. From the nature
(1) High strength without yielding to high temperatures.
(2) It is difficult for creep deformation due to thermal stress.
(3) Resistant to mechanical damage due to molten metal collision.
(4) Excellent oxidation resistance.
It has the advantage of.
In addition, the method for producing a mold turning member of the present invention for producing such a mold turning member is a mixed powder of raw material elements of a porous sintered body in a master die having a reversal shape with respect to a contact surface shape of the mold turning member with molten metal, in particular, Has a step of filling a mixed powder of raw material elements of intermetallic compound and a step of producing a porous sintered body, particularly an intermetallic compound surface layer, by reacting the filled mixed powder in a master mold. Therefore, it does not require large-scale equipment, and efficiently manufactures a high-melting-point porous sintered body, especially an intermetallic compound layer, and further overlays the main body using a metal material as a base material. As a result, it is possible to produce a high-functional mold-turning member in a very short time by molding quickly and efficiently.

  In general, when a plurality of materials having different linear expansion coefficients are heated, cracking and distortion due to stress occur due to the difference in expansion amount between adjacent and closely contacting materials. Also in the manufacturing method of the mold periphery member of the present invention, due to the difference between the linear expansion of the master type and the linear expansion of the intermetallic compound, after the expansion by heating in the manufacturing process, through slow cooling and demolding of the master type As for the shape of the mold surrounding member to be obtained, the shape of the master mold is not accurately transferred as it is, and a shape transferred in a substantially similar shape is obtained. However, the mold surrounding member itself does not function as a mold for casting a molten metal to create a product shape, and the shape of the master mold does not need to be accurately transferred like the mold itself. That is, in the manufacturing method of the mold periphery member of the present invention, the shape error between the master mold and the mold periphery member due to the difference between the linear expansion of the master mold and the intermetallic compound is estimated in advance based on calculation or actual measurement data. Therefore, it is possible to manufacture a mold-around member that can be used to a practical extent and can be applied to an actual casting apparatus.

  In the following, an embodiment of a pouring sleeve for a mold, which is a member around a mold of the present invention, which is used when a molten metal is supplied to a mold installed in a pouring gate of the mold will be described.

  FIG. 1 is a cross-sectional view showing a use state of a casting apparatus according to the present invention, and FIG. 2 is a cross-sectional view of a mold pouring sleeve of the casting apparatus according to the present invention.

  FIG. 1 shows a casting apparatus 11 for a motorcycle wheel. A casting space 11 </ b> A of the casting apparatus 11 is formed by the main lower mold 12, the first auxiliary lower mold 13, the second auxiliary lower mold 14, the insert 15, the horizontal mold 16, and the main upper mold 17. An annular auxiliary upper mold 18 for casting the upper surface of the hub portion of the wheel, which is a cast product obtained by casting in the casting space 11A, is fitted into the inner periphery of the main upper mold 17, and the shaft of the auxiliary upper mold 18 is inserted. A spout 19 is provided in the heart. A pouring sleeve 11 </ b> B is fitted into the pouring gate 19 of the auxiliary upper mold 18 and extends upward, and an upper end portion thereof is fixed to the substrate 20.

  As shown in FIG. 2, a pouring sleeve 11 </ b> B that also functions as a feeder is attached to a cylindrical body 21 that expands toward the casting space 11 </ b> A, and is attached to the casting apparatus 11 via the cylindrical body 21. The pouring sleeve 11B is composed of a main body portion 22 having a porous sintered body as a base material and an oxide film formed on the surface of the main body portion 22 made of the porous sintered body, but also a corrosion-resistant barrier layer 23. In addition, the thermal expansion coefficient of the main-body part 22 which uses a porous sintered compact as a base material shall be approximated to the cylindrical body 21 made from metal.

  The casting pouring sleeve 11B for a casting apparatus according to the present invention shown in FIGS. 1 and 2 is a main body having a porous sintered body as a base material on the inner wall surface of a cylindrical body 21 which is an attachment portion to the casting apparatus 11. While providing the part 22, this main-body part 22 has the corrosion-resistant barrier layer 23 which is an oxide film. The thermal expansion coefficient of the main body 22 based on the porous sintered body approximates the expansion coefficient of the base material of the cylindrical body 21, and the main body due to the difference in expansion coefficient between the cylindrical body 21 and the main body 22. The portion 22 is hardly damaged. Further, the presence of the corrosion-resistant barrier layer 23 does not cause melting of the main body 22 having the porous sintered body as a base material.

FIG. 3 is a schematic sectional view of a gravity casting apparatus which is another casting apparatus according to the present invention.
In the casting apparatus shown in FIG. 3, a casting space 24 </ b> A of the casting apparatus 24 is formed by a lower mold 25, a core 26, and an upper mold 27. In addition, a runner 28a is provided in the runway 28 that leads to the casting space 24A. Further, a spout cup 29 for injecting molten metal into the runner 28 is attached. On the other hand, a feeder cup 30 having a function as a feeder that leads to the casting space 24 </ b> A is attached to the upper mold 27.

  In the casting apparatus according to the present invention shown in FIG. 3, the main body portion having the porous sintered body as a base material is the runner insert 28, the spout cup 29, and the feeder cup 30 as the mold surrounding members of the present invention. And an oxide film as a corrosion-resistant barrier layer formed on the surface of the main body made of the porous sintered body. The mold surrounding members, such as the runway insert 28, the sprue cup 29, and the feeder cup 30, are formed with a corrosion-resistant barrier layer, which is a surface portion formed on the main body made of the porous sintered body. Contact but not eroded by molten metal.

Hereinafter, a gate sleeve (weir insert) and stalk of a low pressure casting apparatus configured as a mold surrounding member of the present invention will be described with reference to FIGS. 4 and 5.
The low-pressure casting apparatus includes an upper mold 31 and a lower mold 32. The lower mold 32 is provided with a gate sleeve 33 so as to supply molten metal from below into a space formed between the two molds. Further, a substantially vertical stalk 34 communicating with the gate sleeve 33 is provided, and the molten metal 35 is supplied between the upper mold 31 and the lower mold 32 clamped to each other via the stalk 34 and the gate sleeve 33. .

  As shown in FIG. 5, the sprue sleeve 33 is formed by forming an oxide film 33b as a corrosion-resistant barrier layer on a main body 33a having a porous sintered body as a base material, while the stalk 34 is formed of a porous sintered body. An oxide film 34b as a corrosion-resistant barrier layer is formed on a main body 34a having a base material. As shown in FIG. 4, the lower mold 32 is placed on a fixed plate 37 on the heating and holding furnace 36 in which the molten metal 35 is accumulated.

In the low-pressure casting apparatus configured as described above, the inside of the heating and holding furnace 36 is in a state where the upper mold 31 is placed on the lower mold 32 and pressed (clamped) by the mold pressurizing cylinder 38. When the compressed air from the air pressure supply port 39 is supplied to the molten metal 35, the molten metal 35 rises in the stalk 34 against gravity and is supplied into the mold space via the molten metal sleeve 33.
Thereafter, when the molten metal 35 starts to solidify and the supply of compressed air from the air pressure supply port 39 to the heating and holding furnace 36 is stopped, the molten metal 35 pushed up into the stalk 34 is brought into the heating and holding furnace 36 by gravity. Returned to

  Typical components constituting the engine of automobiles and motorcycles manufactured by applying the above-described low pressure casting are a cylinder head and a cylinder block. This cylinder head is positioned as the most important safety part having the function of (i) supplying mixed gasoline to the combustion chamber and (ii) taking out exhaust gas after combustion. The manufacturing method uses low pressure casting in which molten aluminum is injected into the upper mold 31 and the lower mold 32 from the bottom upward. Since the aluminum casting made by this method receives heat generated when gasoline burns, it is characterized by having a structure with less air entrainment so that it is hard to break even at high temperatures. In the present invention, the low pressure casting apparatus according to the present invention has a gate sleeve 33 (weir insert) which becomes a passage when being poured into the upper mold 31 and the lower mold 32 from the holding furnace 36 for maintaining the molten aluminum at a constant temperature. ), A porous intermetallic compound (porous sintered body) having the characteristics (i) to (iii) of (i) resistance to erosion, (ii) heat insulation, and (iii) constant strength is applied. An oxide film 33b as a corrosion-resistant barrier layer is formed on the main body 33a made of an intermetallic compound (porous sintered body).

  In particular, the gate sleeve 33 (weir insert) is formed in the holding furnace 36 by releasing the pushing-up pressure from below necessary for pushing up the molten aluminum that has not yet solidified into the upper mold 31 and the lower mold 32. It is made relatively thin so as to be surely pulled from the unsolidified molten aluminum returned to the product and the product part where solidification proceeds. Thus, by making it thin, the temperature difference of the product part which solidification advances and the molten aluminum part by the side of the holding furnace 36 can be enlarged. For this purpose, the gate sleeve 33 (weir insert) has been conventionally made as a single piece using SKD61 as its material.

  On the other hand, a wire mesh is attached to the product side portion of the weir for the purpose of removing the oxide film during casting. As a result of frequent desorption of the wire mesh, the weir insert is melted due to scratches caused by the wire mesh on the product side portion of the wire mesh insert. Therefore, the boundary between the tip of the gate sleeve 33 (the weir insert) (the portion in contact with the lower mold 32), the portion that solidifies when taken out and pulled by the product, and the portion that is returned to the holding furnace 36 during decompression is included. There are attempts to ceramicize only the part. However, when the base material of the lower mold insert and the spigot sleeve (weir insert) 33 is a metal, and the base material expands greatly, the ceramic spout sleeve (weir insert) is used, resulting in a difference in thermal expansion. The resulting cracking occurs.

  In this respect, the sprue sleeve (weir insert) 33 in the casting apparatus of the present invention uses an intermetallic compound (porous sintered body), and is corrosion-resistant to the main body 33a made of the intermetallic compound (porous sintered body). The formation of the oxide film 33b as a barrier layer is effective, and the linear expansion coefficient of the gate sleeve 33 (weir insert) is very close to the linear expansion coefficient of SKD61 (13.6 × 10−6 when the operating temperature is 500 to 600 ° C.). It is possible to prevent damage caused by the difference in expansion.

  Next, an embodiment of a die casting apparatus as a casting apparatus of the present invention will be described with reference to the drawings. As shown in the schematic cross-sectional view of FIG. 6, the plunger sleeve 40 according to the present invention is formed on a main body portion 40a formed of an intermetallic compound member that is a porous sintered body and an inner surface of the main body portion 40a. And a surface barrier layer 40b which is an oxide film. According to this plunger sleeve 40, when molten metal is poured into the plunger hole 42 from the hot water supply port 41, the molten metal is formed on the inner surface of the main body portion 40a and the main body portion 40a formed of an intermetallic compound member that is resistant to corrosion. Since it can be received by the surface barrier layer 40b which is the formed oxide film, erosion inside the plunger sleeve 40 can be prevented.

Furthermore, Fig.7 (a), (b) shows other embodiment of the die-casting apparatus as a casting apparatus of this invention.
The plunger sleeve 40 according to this embodiment includes a cylindrical body 48 and an erosion preventing member 49. This cylindrical body 48 can be manufactured using SKD-61 which is a nitriding hot tool steel. In addition, a fitting concave portion 48 a that is a fitting portion into which a semicylindrical erosion preventing member 49 is fitted is provided in a lower portion on the rear end side of the cylindrical body 48.

  The erosion preventing member 49 is formed in a semi-cylindrical shape with the inner side being in sliding contact with the plunger 43, and is disposed in the fitting recess 48 a of the tubular body 48. The erosion preventing member 49 includes a main body portion 49a formed of an intermetallic compound member that is a porous sintered body, and a surface barrier layer 49b that is an oxide film formed on the surface of the main body portion 49a.

  According to the plunger sleeve 40 in the die casting apparatus of the above embodiment, when molten metal is injected into the plunger hole 42 from the hot water supply port 41, this molten metal is provided in the lower portion of the hot water supply port 41 and is resistant to corrosion. Since it can be received by the main body 49a formed of an intermetallic compound member which is a porous sintered body of the member 49 and the surface barrier layer 49b which is an oxide film formed on the surface thereof, Erosion of the side portions can be prevented, and smooth sliding reciprocation of the plunger tip 43a of the plunger 43 can be maintained for a long period of time. The intermetallic compound material of the main body 49a has a low coefficient of thermal expansion, is not easily deformed by heat, and is excellent in heat resistance and wear resistance. Therefore, even if the temperature changes due to pouring, the plunger tip 43a slides. Is not disturbed.

  In addition, in this embodiment, the erosion preventing member 49 using the intermetallic compound member is made into a small semi-cylindrical part, so that the cost can be reduced. Moreover, since the whole plunger sleeve 40 is manufactured using SKD-61 etc., it can also handle easily.

Next, a typical porous sintered body, particularly an intermetallic compound, applied to the mold surrounding member of each casting apparatus of the present invention will be described.
Examples of the porous sintered body, particularly those shown in Table 1 as intermetallic compounds.

Using the intermetallic compound which is the porous sintered body described above, in the present invention, the mold-around member is manufactured as follows.
1. Mixing of starting material and powder A graphite master mold having the inverted shape of the target mold member is filled with a mixed powder of elements constituting an intermetallic compound. For example, in the case of manufacturing a TiAl intermetallic compound mold member, a mixed powder of Ti and Al is filled. Ni ₃ Al is filled with Ni and Al powder, and FeAl is filled with mixed powder of Fe and Al. The mixing ratio of the element powder is blended so as to be the stoichiometric composition of the target intermetallic compound. For example, in TiAl, the atomic ratio is Ti: Al = 1: 1, in Ni ₃ Al, the atomic ratio is Ni: Al = 3: 1, and in FeAl, the atomic ratio is Fe: Al = 1: 1.

If you want to control the composition of the metal compound for the purpose of adjusting the strength of the parts around the mold and the material structure, change the powder mixing ratio from Ti: Al = 1: 1 to Ti rich (Ti excess) or Al rich (Al excess). ). By doing so, in addition to the TiAl phase, a Ti ₃ Al phase and a TiAl ₃ phase are also synthesized, and a composite material of these compounds is obtained.
When adjusting the degree of bonding of the intermetallic compound particles to be synthesized, in addition to the mixed powder of Ti and Al as a raw material, a small amount is added with a mixed powder of Co and Al, a mixed powder of Ni and Al, etc. as an auxiliary agent .
The addition amount may be very small and is about 0.5% to 10%. The auxiliary agent supplements the heat of reaction for generating the intermetallic compound, and also generates a small amount of melt during the reaction, thereby promoting the bonding between the particles. The mixed powder prepared as described above is reacted in a graphite master mold to produce a member around the intermetallic compound mold.
In the case where HIP or HP (hot press) is used in this step, the degree of particle bonding can be controlled and adjusted by controlling the temperature and pressure.

2. Synthesis of intermetallic compounds by thermal explosion reaction of powder (a) Principle of thermal explosion reaction of powder Ti powder + Al powder = TiAl + heat of reaction (1)
3Ni powder + Al powder = Ni ₃ Al + reaction heat (2)
Fe powder + Al powder = FeAl + heat of reaction (3)
(B) By using the thermal explosion reaction of the intermetallic compound as described above, it becomes possible to rapidly manufacture the mold-around member.

  The graphite master mold filled with the mixed powder is heated in an electric furnace to cause the reactions (1) to (3) above. In the case of the above intermetallic compound, the heating temperature is required to be a melting point of Al of 660 ° C. or higher. It is desirable that the temperature in the furnace be 700 ° C. or more in consideration of unevenness in the furnace temperature. The heating atmosphere is an inert gas atmosphere such as Ar, He, Ne, or a vacuum atmosphere in order to prevent oxidation of the powder. In the thermal explosion reaction of the powder, the Al powder of the mixed powder is first melted by heating and penetrates around the Ti, Ni, and Fe particles. This molten and permeated Al is absorbed by Ti particles, Ni particles, and Fe particles, and the reactions (1) to (3) are started. Due to the heat of reaction, the temperature of the powder rises, and the reaction is further promoted by the temperature rise. This is repeated in a chain, and the reaction proceeds rapidly and explosively, and finally an intermetallic compound is obtained. The relative density of the intermetallic compound to be synthesized is about 50 to 97% although it depends on the conditions. This relative density depends on the mixing ratio of the powder, the particle size, the heating conditions, the presence or absence of an auxiliary agent, and the amount added. The higher the relative density of the intermetallic compound is preferable as the mold surrounding member, but if the density is increased, the sintering shrinkage of the powder is superior to the expansion of the powder due to the reaction, and the graphite master mold is satisfied. It becomes insufficient. Therefore, the relative density in the intermetallic compound is adjusted so that the inside of the master mold is filled. Depending on the shape of the mold-around member and the amount of powder, the heat is lost to the graphite, resulting in insufficient heat, poor reaction, and insufficient corner corner filling. In such a case, an auxiliary heat source such as induction heating or pulse application energization is used, and pressurization such as hot pressing is also used to prevent reaction failure and filling failure in the graphite master mold.

3. Improvement of corrosion resistance, construction of member body around mold When porous sintered body, especially intermetallic compound, comes into direct contact with molten Al, there is a possibility of causing reaction or defect. As a countermeasure,
(I) The contact surface with hot water is heated in the air and oxidized to form an oxide film. For example, Al ₂ O ₃ or TiO ₂ generated by high-temperature oxidation of TiAl is used as the corrosion resistant barrier.
(Ii) Thermally spraying Al ₂ O ₃ or the like having high corrosion resistance on the surface as a corrosion-resistant layer or a release layer.
On the back side, pores are sealed with a brazing material or the like, a water channel is provided, and cooling is performed. Alternatively, a water-cooled pipe is joined. Or the member which has a water cooling structure is joined by welding or brazing. Alternatively, the water-cooled member itself can be constructed directly by welding overlay.

FIG. 11 is a conceptual diagram of the mold-around member of the present invention.
As shown in the figure, a porous sintered body, in particular, a porous sintered body via a shape offset portion 3 made of an intermetallic compound is formed on a master 2 having a reversal shape with respect to the contact surface shape of the mold surrounding member 1 with the molten metal. A body, in particular, a main body portion 5 and a surface layer portion 4 having a wedge function made of an intermetallic compound are formed. The shape offset portion 3 disappears when released from the master 2, and the surface layer portion 4 is exposed as the surface layer portion of the mold surrounding member 1, and since it is made of a porous sintered body, particularly an intermetallic compound, it is heat resistant. Good breathability. Furthermore, the main body 6 and the first main body 5 having a function of replenishing the strength of the surface layer portion 4 made of an intermetallic compound and having a wedge function are formed of a metal material. Further, the second main body portion 7 is made of a metal material through a uniform mold temperature balance layer 6 for absorbing thermal deformation of the first main body portion 5. The homogenizing layer 6 has a second body portion 7 and a wedge function. The second main body portion 7 incorporates a water cooling jacket for cooling and constitutes an attachment function portion with a casting machine such as a die casting machine.
As described above, on the back side of the surface layer portion 4, a main body portion formed by welding overlay is arranged, and when the main body portion is created, the selection of a good heat transfer material as a function for equalizing the temperature balance and the external amount of heat A water channel for discharge can also be provided to provide a heat exchange function.

In the above, the first main body 5, the mold temperature balance uniformizing layer 6, and the second main body 7 are made high by performing overlay welding on the surface layer portion 4 made of an intermetallic compound formed on the master 2. Can be molded efficiently. At that time, the first main body 5, the mold temperature balancing uniform layer 6, and the second main body 7 can be molded according to their functions by different welding materials and welding methods.
For example, the first main body 5 is ensured in material continuity due to the progress of diffusion with the surface layer portion 4 made of an intermetallic compound, and warps, strains, and the like are generated due to uneven thermal expansion and contraction. The welding material and method are determined so that the degree is suppressed.

  In addition, in the above, depending on the structure of the target mold surrounding member, it is possible to configure the mold surrounding member only by the intermetallic compound layer. For example, a relatively simple core or the like is composed of the intermetallic compound as a whole. It is possible to mold as a base material.

  In the mold surrounding member 1 of the present invention described above, the surface layer portion 4 forms a molten metal contact surface, and the molten metal contact surface is polished as necessary, and the functional portion on the opposite surface (for interlocking with functional parts) Part) is formed by the second body 7.

Examples of the present invention will be described below.
Example 1
Raw material powders were mixed so as to have a stoichiometric composition of Ni ₃ Al, TiAl, and FeAl compounds, and the temperature change of the powder during combustion synthesis was measured by inserting a thermocouple into the mixed powder compact.

  FIG. 12 is an example of temperature measurement at the time of reaction shown in the above (1), that is, Ti powder + Al powder = TiAl + reaction heat during combustion synthesis. The mixing ratio of Ti powder and Al powder was atomic ratio Ti: Al = 1: 1. As shown in the figure, the temperature rises to almost the adiabatic combustion temperature at each particle size of the Ti powder. In this case, a part of the heat is generated and becomes slightly lower than the adiabatic temperature. Further, as the particle size of the Ti powder increases to 15 μm, 45 μm, and 150 μm, the temperature rise time becomes longer as the reaction energy decreases per unit time due to the decrease in the particle surface area.

FIG. 13 is an example of temperature measurement at the time of reaction shown in (2), 3Ni powder + Al powder = Ni ₃ Al + reaction heat during combustion synthesis. The mixing ratio of Ni powder and Al powder was atomic ratio Ni: Al = 3: 1. As shown in the figure, the temperature rises to approximately the adiabatic combustion temperature at each particle size of the Ni powder. In this case, a part of the heat is generated and becomes slightly lower than the adiabatic temperature. Further, even if the particle size of the Ni powder is changed slightly to 42 μm, 56 μm, and 72 μm, the temperature rise time does not change greatly. The ignition temperature was 910K.

FIG. 14 is an example of temperature measurement during the reaction shown in the above (3), that is, Fe powder + Al powder = FeAl + reaction heat during combustion synthesis. The mixing ratio of Fe powder and Al powder was Ti: Al = 1: 1 in atomic ratio. As shown in the figure, the temperature rises to almost the adiabatic combustion temperature at each particle size of the Fe powder. In this case, a part of the heat is generated and becomes slightly lower than the adiabatic temperature. Further, even if the particle size of the Fe powder is changed to 30 μm, 70 μm, or 110 μm, there is no significant change in the temperature rise time. The ignition temperature was 926K.
Since it is impossible to create a complete adiabatic state in each of the above cases, the implementation data itself shows a slightly low value, but it can be seen that both are heated to near the theoretical adiabatic combustion temperature.
It can also be seen that the temperature rise is as short as 10 seconds. By using this high temperature state and a high temperature rise, the porous sintered body mold member and the intermetallic compound mold member can be rapidly manufactured.

FIG. 15 is a photograph of a structure obtained by rapidly cooling a powder mixed sample of Ni ₃ Al combustion synthesis and examining its structure.
(A) is before the start of the reaction, (b) is a sample that is rapidly cooled in the early stage of combustion synthesis, (c) is a sample that is synthesized in the middle period of combustion synthesis, and (d) is a combustion synthesis body. In FIG. 15A, white particles are Ni particles, gray particles are Al particles, and black portions are pores between the particles. From this figure, it can be confirmed that Ni and Al particles are mixed before the reaction starts. When the powder mixed sample is heated in the furnace as shown in FIG. 15B, the Al particles first melt at around 933 K (the melting point of Al) and permeate around the Ni particles. Next, as shown in FIG. 15 (c), when the combustion synthesis further proceeds, a compound formation reaction occurs between the molten Al and Ni particles, and an intermetallic compound phase is formed around the Ni particles, and combustion occurs. Synthesis proceeds. That is, a compound layer is formed as if molten Al is absorbed by Ni particles. Further, as shown in FIG. 15D, finally, all of Al and Ni react to form an intermetallic compound phase as a whole.

FIG. 16 schematically shows this state.
As shown in FIG. 16 (a), Ni and Al particles are in a mixed state before the start of the reaction. However, when the reaction is started, the Al particles are melted as shown in FIG. Penetrate to the surroundings. Thereafter, as shown in FIG. 16C, the molten Al is absorbed by the Ni particles, and an intermetallic compound layer starts to be formed between the Ni particles (around Ni). Finally, as shown in FIG. 16D, the molten Al and Ni particles all react to synthesize an intermetallic compound phase.
The above is a systematic change when the combustion synthesis of Ni ₃ Al is viewed microscopically. Other than this example, TiAl combustion synthesis and FeAl combustion synthesis also synthesize compounds by similar reactions.

FIG. 17 shows the result of X-ray diffraction analysis of the synthesized product thus synthesized. FIG. 17A shows the analysis result of the Ni + Al mixed powder sample, and FIG. 17B shows the X-ray diffraction analysis result of the composite. In the composite shown in FIG. 17B, the Ni and Al peaks seen in FIG. 17A disappear, and the Ni ₃ Al peak appears instead. That is, it can be seen that the compound was synthesized from Ni and Al raw material powders by combustion synthesis.
When the X-ray analysis of the combustion composite is performed on the Ti + Al mixed powder, TiAl and Ti ₃ Al phases are detected. That is, it can be seen that an intermetallic compound phase was synthesized by combustion synthesis. For the Fe + Al mixed powder, the FeAl phase is similarly detected when X-ray analysis of the combustion composite is performed.

18 and 19 are structural photographs of the composite. FIG. 18 shows the structure of the Ni ₃ Al combustion composite, and FIG. 19 is a structural photograph of the TiAl combustion composite.
The white part of the figure is an intermetallic compound, and the black part is a void. The structure of the combustion composite is a porous body.
In using an intermetallic compound as a structural material, the composite needs to be dense in terms of strength. However, when an intermetallic compound is used as a member around the mold of a casting apparatus, a porous material is more preferable as a member around the mold in order to quickly release the gas during casting from the casting.

That is, a large amount of gas dissolves in the molten metal when the metal is melted during casting production, and is released from the metal during solidification. Further, during pouring, gas is caught in the mold, and these are brought into the mold together with hot water. These gases are confined inside the mold, which not only degrades the finished product but also causes casting defects. For this reason, in casting, a mold with air permeability is sometimes used, and a typical example is a sand mold.
From this point, if a porous intermetallic compound is used as a structural material for the mold surrounding member as well, it is possible to more efficiently degas the molten metal during solidification, thereby improving the degassing efficiency of the entire casting apparatus. it can.

  As described above, the mold periphery member using the intermetallic compound produced by the present combustion synthesis has a porous structure having air permeability, and is effective in preventing casting defects. Also, by making the sintered body, especially intermetallic compounds porous (for example, relative density of about 50 to 97%), the thermal shock during pouring can be mitigated, and the life of the mold surrounding member can be extended. effective. The thermal shock resistance of industrial bricks is largely due to the porous nature. Furthermore, in castings, mold release often becomes a problem due to heat shrinkage of the solidified metal. However, by making the intermetallic compound porous (for example, a relative density of about 50 to 97%), for example, a part of the molten metal during solidification is used. In the low pressure casting spout sleeve in contact with the mold, the Young's modulus of the mold surrounding member can be lowered to prevent biting due to thermal contraction and to improve the releasability.

As described above, it is important to make the material porous and ensure air permeability in manufacturing a mold-around member having an intermetallic compound layer. It is controlled by the amount of the agent or the press pressure and CIP pressure when filling the mold with the powder. Further, in the case of using HIP and hot press together, the HIP pressure, hot press pressure, temperature and the like are also controlled.
FIG. 20 shows the density of the intermetallic compound synthesized by changing the particle size of the raw material powder during the Ni ₃ Al combustion synthesis.
It can be seen that the composite density of the intermetallic compound can be controlled by changing the Ni powder particle size and the Al powder particle size. Considering the strength of the members around the mold, it is preferable that the density is high. However, it is desirable to select conditions under which the composite density is about 50% to 97% in consideration of air permeability and thermal shock resistance.

FIG. 21 shows the TiAl combustion composition density when the Ti particle size and the Al particle size are changed. However, if the particle size of the raw material powder is controlled just like TiAl, the density of the composite is nearly 40%, and the appropriate density may not be 50% to 97%. In such a case, in addition to Ti + Al powder, Ni + Al powder (Ni: Al = 1: 1) or Co + Al powder (Co: Al = 1: 1) auxiliary agent (combustion agent) is added.
FIG. 22 shows the result of measuring the composite density by adding Ni + Al auxiliary to the Ti + Al raw material powder. FIG. 23 shows the density of a composite obtained by adding a Co + Al auxiliary agent to Ti + Al raw material powder.
As apparent from FIGS. 22 and 23, by adding Ni + Al auxiliary agent and Co + Al auxiliary agent to the Ti + Al raw material powder, the density of the composite can be controlled, and an appropriate density of 50% to 97% can be obtained.
FIG. 24 and FIG. 25 show structural changes when Ni + Al auxiliary (Ni: Al = 1: 1) and Co + Al powder (Co: Al = 1: 1) auxiliary are added to Ti + Al raw material powder.
It can be seen that by adding the Ni + Al auxiliary agent and the Co + Al auxiliary agent, the composite density can be controlled even when viewed from the microscopic structure. As shown in both figures, when the amount of auxiliary agent is large, the density certainly increases and the residual pores decrease. However, since the pores are completely closed pores, the air permeability of the members around the mold is lost, and the thermal shock resistance is also lowered. In the case of TiAl, there are residual pores in the amounts of Ni + Al auxiliary agent and Co + Al auxiliary agent. About 1 to 6% obtained is appropriate. When pressure sintering such as HIP or hot press is used in combination during combustion synthesis, it is not always necessary to rely on Ni + Al auxiliary agent or Co + Al auxiliary agent. The composite density can also be controlled by controlling the HIP pressure and temperature.

Example 2
l Ti powder having an average particle size of 17, 24, 42, and 128 μm and Al powder having an average particle size of 5, 4, 12, 30, and 60 μm were used as the raw material powder. These raw material powders were mixed in a mortar and pressed with a mold to produce a green compact.
At that time, the Ti: Al ratio was 10: 0 to 0:10, and the molding pressure was controlled at 50 to 150 MPa. The procedure was as follows: the green compact was placed in a quartz tube and evacuated with a vacuum pump. Then, it heated with the electric furnace and made the combustion synthesis reaction react with the powder of Ti and Al. The heating pattern at that time was heated from room temperature to 700 ° C. at a rate of 10 ° C./min, held at 700 ° C. for 10 minutes, and then gradually cooled to room temperature at 10 ° C./min. The obtained porous body was examined for expansion coefficient, and X-ray diffraction, cross-sectional structure observation, picker hardness measurement, and strength test were performed.

2. Preparation conditions of porous body Green compacts were prepared by combining various powders, combustion synthesis was performed, and the diameter expansion coefficient and volume expansion coefficient were investigated. FIG. 26 shows the result of changing the powder particle diameter under the conditions of φ8, molding pressure 100 MPa, and mixing ratio 5: 5. FIG. 26A shows a case where the Al particle size is fixed and the Ti particle size is changed, and FIG. 26B shows a case where the Ti particle size is fixed and the Al particle size is changed. It can be seen that the expansion coefficient increases as the grain sizes of Ti and Al are increased. In the case where the expansion coefficient is the largest, in (a), the diameter expansion coefficient increases by about 20%, the volume expansion coefficient increases by about 70%, and in (b), the diameter expansion coefficient increases by about 20%, the volume expansion coefficient Increased by about 70%.

FIG. 27 shows the result of changing the molding pressure. It can be seen that the expansion coefficient increases as the molding pressure is increased. When the molding pressure was the highest at 150 MPa, the diameter expansion coefficient increased by about 20% and the volume expansion coefficient increased by about 60%, both of which were maximum.
FIG. 28 shows the result of changing the diameter of the green compact. It can be seen that the expansion coefficient increases as the diameter of the green compact increases. The maximum diameter expansion coefficient increased by about 20%, and the volume expansion coefficient increased by about 70%. However, the change in the expansion coefficient due to the diameter of the green compact was small, and no significant change was observed.

  FIG. 29 shows the result of changing the mixing ratio of Ti: Al. When the expansion coefficient was Ti: Al = 5: 5, the expansion coefficient was maximum, and the expansion coefficient at that time was about 20% increase and the volume expansion coefficient was about 60%. However, the expansion rate decreases when Ti rich or Al rich. Further, when Al was rich, the composite was dissolved and a porous trade body could not be produced. Therefore, from this result, the range in which the porous body can be produced by this method is the range where the Al ratio is 10 to 70%.

3 Characteristics of Porous Material FIG. 30 shows the results of X-ray diffraction. In the composite, the peak of the raw material powder disappears, and it can be seen that Ti ₃ Al and TiAl ₃ are synthesized instead. Further, when the Ti: Al ratio was changed, the TiAl phase was composed of a TiAl phase and an αTi phase, and the Al rich layer was composed of a TiAl ₃ phase and an Al phase.

FIG. 31 shows a cross-sectional structure of the porous body. It can be seen that when the green compact is burned and synthesized, Al melts and is absorbed by Ti and voids are generated. Further, when the Ti: Al ratio was changed, the vacancies tended to increase as the Al ratio increased. However, when Ti: Al = 2: 8 or later, vacancies were reduced. This is considered to be because Ti could not be absorbed because the amount of Al dissolved increased, and the composite was dissolved.
FIG. 32 shows the hardness of the composite. Hardness was 100-350. When the mixing ratio was changed, the maximum was obtained at Ti: Al = 5: 5, and when the mixture ratio was Ti-rich and Al-rich, it decreased. This is probably because the heat of reaction is highest at Ti: Al = 5: 5. Further, when Ti rich and Al rich, the reaction heat is decreased, the surroundings of the particles react, and the Ti and Al are unreacted in the central portion.

FIG. 33 shows the relationship between the mixing ratio and the strength. When the mixing ratio was changed, the strength decreased as the Al ratio increased. The strength of Ti: Al = 4: 6 to 5: 5 was minimized, and a tendency to be parabolic was observed. This is because the expansion coefficient is large in the vicinity of 4: 6 to 5: 5, and the density decreases. The 3: strength at 7, but was low, compound phase to be TiAl _3, also it is because poor is connected between particles within the tissue.

FIG. 34 shows the relationship between particle size and strength. There was a tendency for the strength to decrease as the Ti grain size was increased and as the Al grain size was increased.
FIG. 35 and FIG. 36 attempt to fill the graphite master mold 8 using green compacts with different mixing ratios. The porous sintered body 9 and the graphite master mold 8 obtained as a result are shown in FIGS. Show. FIG. 35 shows a state molded by combustion synthesis after filling, and FIG. 36 shows a state where the porous sintered body 9 is released from the graphite master die 8.
As shown in the figure, the graphite master mold 8 can sufficiently withstand the heat of combustion synthesis, and a porous sintered body 9 in which the shape of the graphite master mold 8 is transferred is obtained.

In this example, production of a porous material on a graphite master mold was attempted by a combustion synthesis method, and the production conditions were examined.
・ Expansion coefficient is higher when the compacting pressure of the green compact is increased. The composition ratio is high when the mixing ratio is Ti: Al = 5: 5. And the range which can produce a porous body is a range whose Al ratio is 10 to 70%.
・ The larger the particle size of the raw material powder, the higher the expansion rate, but the lower the strength. When the Ti particle size is 17 to 50 μm and the Al particle size is 5 to 30 μm, the expansion rate is not so high, but the strength is high. In view of the balance between strength and expansion rate, the raw material powder preferably has a Ti particle diameter of 24 to 50 μm and an Al ablation of 12 to 30 μm.

Example 3
FIG. 37 shows the results of examining the expansion coefficient of the Mg—Al porous sintered body. The plot in the figure shows the volume expansion coefficient. Partially melted samples are indicated by black marks. In this system, there was no volume change and no expansion was observed at Al compositions of 0 to 0.4, but expansion was observed at 0.5 to 0.9. It can be said that the ratio of Al is related to expansion. At the heating temperature, little expansion is observed at 700K. Although expansion was observed at 800K, melting occurred at a composition of 0.5 to 0.7. Up to about 140% expansion was observed at 750K. From this result, a heating temperature of about 750K is appropriate.

  38, 39, and 40 show the results of examining the volume expansion coefficient of the Fe—Al sintered body. FIG. 38 shows the results when the mixing ratio of Fe and Al is controlled, FIG. 39 shows the results when the Al particle size is changed, and FIG. 40 shows the results when the Fe particle size is changed. With regard to the mixing ratio, in this system, except for the Fe: Al ratio of 0.2: 0.8, all the samples showed a large volume expansion of 150% or more. At 0.2: 0.8, the volume expansion coefficient is low, but this is because the sample melted due to the Al-rich composition. Regarding the effect of the particle size, when the Al particle size was changed, the influence of the particle size was not so much observed at any ratio. When the particle size of Fe is changed, the effect of particle size is not observed when the Fe: Al ratio is 0.5: 0.5 and 0.8: 0.2, but the Fe: Al ratio is 0.2. : When 0.8, the larger the particle size, the greater the expansion.

FIG. 41 shows the structure of the Mg—Al sintered body. In this system, sintering is not observed when the Mg: Al ratio is 0.8: 0.2. This is thought to be because Mg is easily oxidized, and reaction with Al hardly occurs. Regarding the difference depending on the heating temperature, when the structure of the sintered body at 700 K is seen, the powders of the raw material Mg and Al are observed, and the sample is hardly sintered. At 800K, the Mg and Al powders disappeared and sintering started. However, the expansion rate is low due to sintering shrinkage. Sintering shrinkage as high as 800K was suppressed at 750K, which was found to be optimal for obtaining a porous body. 42, 43, and 44 show the structure of the Fe-Al sintered body. 42 shows a case where the Fe: Al ratio is changed, FIG. 43 shows a case where the Al particle size is changed, and FIG. 44 shows a case where the Fe particle size is changed. In each sample, Fe and Al particles disappeared, and it was confirmed that FeAl compound particles were generated instead. When the effect of the Fe: Al ratio was examined, there was a tendency that fine particles were generated when the amount of Fe was large, and particles having a large bonding portion were formed when the amount of Al was large. This is presumably because if the amount of Al is large, the melting point decreases, and the reaction and the sintering easily proceed due to the generation of the liquid phase. Expansion occurs even when the Fe: Al ratio is 0.8: 0.2, but the obtained sample is inappropriate because the particles are fine and the sintered body is brittle. As for the particle size, when the particle size of Al was changed, in the case of 12 μm Al and 30 μm Al, a fine compound was obtained. On the other hand, at 60 μm, a sample with a large binding portion was obtained. In a fine compound such as 12 μm Al and 30 μm Al, the sintered body is fragile and inappropriate. With 60 μm Al, the bonded portion was large and a firm sintered body was obtained.
When the particle size of Fe is changed, the expansion coefficient is affected by the particle diameter, and it is recognized that the expansion coefficient increases when the particle diameter is increased. However, when the structure was examined, it was found that when the particle size was increased, the bonded portion was reduced and the sintered body became brittle.

From the above experimental results, conditions for expansion and internal structure were confirmed, and based on this, a porous metal was produced in a graphite master mold.
A porous sintered body filling the graphite master mold can be obtained by expansion during sintering, and a filler can be obtained by devising the size of the green compact even in the case of Mg-Al.

  INDUSTRIAL APPLICABILITY The present invention is applied to a casting apparatus used for gravity casting, low pressure casting, die casting, a method for producing a mold surrounding member, and a mold surrounding member. Can be used. Furthermore, the present invention can be widely applied to casting technology such as a casting apparatus for manufacturing a gear box that accommodates a transmission of an automobile.

FIG. 1 is a sectional view of a casting pouring sleeve for a casting apparatus according to the present invention in use. FIG. 2 is a cross-sectional view of the mold pouring sleeve of the casting apparatus according to the present invention. FIG. 3 is a schematic cross-sectional view of the gravity casting apparatus according to the present invention. Sectional drawing which shows the structure of the casting apparatus of embodiment of this invention. The expanded sectional view of the gate part of the casting apparatus of embodiment of this invention. It is sectional drawing of the plunger sleeve of the casting apparatus of embodiment of this invention. (A) It is sectional drawing of the plunger sleeve of the casting apparatus of other embodiment of this invention. (B) FIG. 7 (a) is a cross-sectional view taken along the line AA. Temperature enthalpy diagram for calculating theoretical combustion temperature in combustion synthesis of Ni powder and Al powder Temperature enthalpy diagram for calculating theoretical combustion temperature in combustion synthesis of Ti powder and Al powder Temperature enthalpy diagram for calculating theoretical combustion temperature in combustion synthesis of Fe powder and Al powder Conceptual diagram of the mold surrounding member of the present invention The figure which shows the example of temperature measurement at the time of the combustion synthesis reaction of Ti powder + Al powder = TiAl + reaction heat Shows the temperature measurement example during combustion synthesis reaction that 3Ni powder + Al powder = _Ni 3 Al + reaction heat The figure which shows the example of temperature measurement at the time of the combustion synthesis reaction of Fe powder + Al powder = FeAl + reaction heat FIG. 15 (a) shows a structure before starting the reaction, in which a powder mixed sample of Ni ₃ Al intermetallic compound combustion synthesis in Example 1 of the present invention was rapidly cooled and its structure was examined. FIG. 15 (b) shows the structure of the sample rapidly cooled in the early stage of combustion synthesis. FIG. 15C shows the structure of a sample synthesized in the middle of combustion synthesis. FIG. 15 (d) shows the structure of the combustion composite. It is the figure which showed typically the mode of the structure | tissue change shown to Fig.15 (a)-FIG.15 (d), and shows the structure | tissue before reaction of Fig.16 (a). FIG. 16 (b) shows the structure of a sample that was rapidly cooled in the early stage of combustion synthesis. FIG. 16C shows the structure of the sample synthesized in the middle of combustion synthesis. FIG. 16 (d) shows the structure of the intermetallic compound phase. It is a figure which shows the result of having performed X-ray diffraction analysis in Example 1 of this invention, FIG.17 (a) shows the result of having performed X-ray diffraction analysis of Ni + Al mixed powder, FIG.17 (b) is a combustion synthesis | combination. It is a figure which shows the X-ray-diffraction analysis result of a body. In Example 1 of the present invention is a structural photograph of Ni 3 _Al combustion composite. It is a structure | tissue photograph of the TiAl combustion synthetic | combination body in Example 1 of this invention. In Example 1 of the present invention alter the particle size of the raw material powder during the Ni 3 _Al intermetallic compound combustion synthesis diagrams of examining the density of the intermetallic compound to be synthesized. The figure which shows the density of each TiAl combustion synthetic | combination body obtained by changing Ti particle size and Al particle size in Example 1 of this invention. The figure which shows the result of having measured the density of the combustion synthetic | combination body obtained by adding Ni + Al adjuvant to Ti + Al raw material powder in Example 1 of this invention. The figure which shows the result of having measured the density of the combustion synthetic | combination body obtained by adding Co + Al adjuvant to Ti + Al raw material powder in Example 1 of this invention. The figure which shows the structure | tissue change of the combustion synthetic | combination body at the time of adding Ni + Al adjuvant (Ni: Al = 1: 1) to Ti + Al raw material powder in Example 1 of this invention. The figure which shows the structure | tissue change of a combustion synthetic | combination body when the adjuvant of Co + Al powder (Co: Al = 1: 1) is added to Ti + Al raw material powder in Example 1 of this invention. It is a figure which shows the preparation conditions when the combustion synthesis | combination of the porous body is carried out in Example 2 of this invention and the diameter expansion coefficient and the volume expansion coefficient were investigated, and its result, Fig.26 (a) fixes Al particle size. When the Ti particle size is changed, FIG. 26B shows the case where the Ti particle size is fixed and the Al particle size is changed. The figure which shows the result of having changed the shaping | molding pressure at the time of shaping | molding of mixed powder in Example 2 of this invention. The figure which shows the result of having changed the diameter of the green compact in Example 2 of this invention. The figure which shows the result of having changed the mixing ratio of Ti: Al in Example 2 of this invention. The figure which shows the result of having performed the X-ray-diffraction test in Example 2 of this invention. The figure which shows the cross-sectional structure | tissue of the porous body obtained in Example 2 of this invention. The figure which shows the hardness of the combustion synthetic | combination body obtained in Example 2 of this invention. The figure which shows the relationship between the mixing ratio of a raw material powder and the intensity | strength of the combustion synthetic | combination body obtained in Example 2 of this invention. The figure which shows the relationship between the particle size of raw material powder and the intensity | strength of the combustion synthetic | combination body obtained in Example 2 of this invention. Photograph of porous sintered body and graphite master mold obtained in Example 2 of the present invention Photograph of porous sintered body and graphite master mold obtained in Example 2 of the present invention The figure which shows the result of having investigated the expansion coefficient about the Mg-Al sintered compact in Example 3 of this invention. The figure which shows the result of having investigated the expansion coefficient about the Fe-Al sintered compact, when the mixing ratio of Fe and Al was controlled in Example 3 of this invention. The figure which shows the result of having investigated the expansion coefficient about the Fe-Al sintered compact when changing Al particle diameter in Example 3 of this invention. The figure which shows the result of having investigated the expansion coefficient about the Fe-Al sintered compact when changing the Fe particle size in Example 3 of this invention. The figure which shows the structure | tissue of the Mg-Al sintered compact obtained in Example 3 of this invention. The figure which shows the structure | tissue of the Fe-Al sintered compact at the time of changing Fe: Al ratio obtained in Example 3 of this invention. The figure which shows the structure | tissue of the Fe-Al sintered compact at the time of changing the Al particle diameter obtained in Example 3 of this invention. The figure which shows the structure | tissue of the Fe-Al sintered compact at the time of changing the Fe particle size obtained in Example 3 of this invention. It is a schematic sectional drawing which shows a die-casting apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Mold surrounding member, 2 ... Master, 3 ... Shape offset part, 4 ... Surface layer part, 5 ... 1st main-body part, 6 ... Uniformation layer, 7 ... -2nd main-body part, 8 ... graphite master type | mold, 9 ... combustion synthetic intermetallic compound, 11 ... casting apparatus, 11A ... casting space, 11B ... pouring for gravity casting molds Sleeve ... 19 ... Spout, 21 ... Cylinder, 22 ... Body, 23 ... Corrosion-resistant barrier layer, 31 ... Upper mold, 32 ... Lower mold, 33 ... Spout sleeve, 34 ... Stoke, 35 ... Molten metal, 36 ... Heating and holding furnace, 37 ... Fixed plate, 39 ... Air pressure supply port, 38 ... Cylinder for pressurizing mold.

Claims (30)

A casting apparatus comprising a mold periphery member provided with a porous sintered body layer. The casting apparatus according to claim 1, wherein the porous sintered body layer has a corrosion-resistant barrier layer. The casting apparatus according to claim 1, wherein the mold surrounding member is a pouring part constituting member constituting at least a part of a path for supplying the molten metal to the mold. The casting apparatus according to claim 1, wherein the mold-around member is attached to a main body having a metal material as a base material. The casting apparatus according to claim 4, wherein the main body portion made of a metal material is formed of a weld metal. A first main body portion made of a metal material to replenish the strength of the porous sintered body layer; a second main body portion made of a metal material and constituting an attachment function portion with a casting mechanism; The casting apparatus according to claim 4 comprising: The casting apparatus according to claim 6, wherein a temperature uniformizing layer is provided between the first main body portion and the second main body portion. The casting apparatus according to claim 1, wherein the porous sintered body is an intermetallic compound. A casting apparatus, wherein a pouring sleeve for a mold, which is a pouring part constituting member that is installed at a pouring gate of a mold and supplies molten metal to the mold, includes a porous sintered body layer. A mold comprising an upper mold and a lower mold is provided, and a pouring gate is provided in the lower mold so as to supply molten metal from below into a space formed between the two molds, and communicates with the pouring gate. A casting apparatus, wherein a pouring sleeve and / or stalk, which is a pouring part constituting member, includes a porous sintered body layer. A casting apparatus characterized in that a plunger sleeve, which is a pouring part constituting member having a hot water supply opening for pouring, is provided with a porous sintered body layer at least in part. The casting apparatus according to claim 11, wherein an erosion preventing member formed of a porous sintered body is fitted and disposed in a fitting portion provided in a part of the plunger sleeve. The process of filling the mixed powder of the raw material elements of the porous sintered body into the master mold having a reversal shape with respect to the contact surface shape with the molten metal of the mold surrounding member, and reacting the filled mixed powder in the master mold to make the porous A method for producing a mold surrounding member comprising a step of producing a sintered body layer. The method according to claim 13, wherein the porous sintered body is an intermetallic compound. The method for producing a mold-around member according to claim 13, wherein the mixing ratio of the raw material element mixed powder of the porous sintered body is adjusted based on the stoichiometric composition of the target porous sintered body. 14. The method for producing a mold-surrounding member according to claim 13, wherein the mixing ratio of the raw material element mixed powder of the porous sintered body is adjusted so that the required raw material element is excessive with respect to the stoichiometric composition. The manufacturing method of the mold periphery member as described in any one of Claims 13-16 which adds the element powder used as an adjuvant to the mixed powder of the raw material element of the target porous sintered compact. The method for producing a mold-turning member according to claim 13, wherein the additive amount of the element powder as an auxiliary agent is 0.5% to 10%. The manufacturing method of the mold periphery member as described in any one of Claims 13-18 which heats the master type | mold filled with mixed powder, and synthesize | combines a porous sintered compact on a master type | mold by thermal explosion reaction of mixed powder. The heating temperature of the mold periphery member according to claim 19, wherein the heating temperature is higher by 10 ° C to 50 ° C or more than the melting point of the material having the lowest melting point among the porous sintered body raw material element and the auxiliary metal element. Production method. 21. The method for producing a mold periphery member according to claim 20, wherein a small amount of liquid phase is generated between the powders to sinter the powders. The manufacturing method of the mold periphery member according to any one of claims 13 to 21, wherein the heating atmosphere is an inert gas or a vacuum atmosphere. The method for producing a mold-around member according to any one of claims 13 to 22, wherein an auxiliary heat source such as induction heating or pulse application energization is used. The manufacturing method of the mold periphery member as described in any one of Claims 13-22 which heats the master type | mold filled with mixed powder under pressure. The method for producing a mold-turning member according to any one of claims 13 to 24, wherein pores on the back side of the master mold are sealed and cooled. The manufacturing method of the mold periphery member as described in any one of Claims 13-24 which forms a build-up welding layer on the porous sintered compact layer synthesize | combined on the master type | mold. The mold periphery member obtained by the manufacturing method according to any one of claims 13 to 26, wherein the relative density of the synthesized porous sintered body is about 50 to 97%. The mold turning member according to claim 27, further comprising a corrosion-resistant barrier layer. The mold-turning member according to claim 28, wherein the corrosion-resistant barrier layer is an oxide film formed on the surface of the porous sintered body layer. 30. The mold periphery member according to claim 29, wherein the corrosion-resistant barrier layer is a corrosion-resistant layer and / or a release layer formed on the surface of the porous sintered body layer by thermal spraying.