JP2012166207A - Molding method for metal and molding die - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve durability of a molding die by suppressing deterioration of the molding die when an amorphous alloy of Zr-base alloy containing a glass transition region not lower than 20 K is molded, in a molding method for metal and the molding die.SOLUTION: By using a die 3 containing a thin film 6 comprising a Ti simple substance, a Ti compound or a mixture of the Ti simple substance and the Ti compound at least at a part of the surface contacting a molten metal, the molten metal of a metal material of the Zr-base alloy becoming the amorphous alloy having the glass transition region not lower than 20 K is charged into the die 3 to cool at a cooling speed not lower than the critical cooling rate of the metal material, to solidify, thus a molded object of the amorphous alloy is formed, by using the molding method for metal.

Description

  The present invention relates to a metal molding method and a molding die.

Conventionally, for example, a metal mold of an amorphous alloy that has a glass transition region of 20K or more and is also referred to as metal glass is filled in a molding die and cooled at a cooling rate that is higher than the critical cooling rate of the metal material. There are known metal forming methods for forming by doing so. Since a metal material that becomes such a metal glass generally has a high melting point, the molten metal also has a high temperature. For example, in forming using a Zr-based alloy, the temperature of the molten metal needs to be about 1000 ° C. or higher, although it depends on the composition of the Zr-based alloy.
Since the molding die used for such molding is repeatedly subjected to thermal shock, deterioration due to heat is likely to proceed.
In addition, since metallic glass has good transferability, it can be easily adhered to a molding die, and the releasability may deteriorate. As a result, the metal glass may be baked or stuck to the molding die.
As described above, in order to protect the molding die and improve the releasability, various thin films are often coated on the surface in contact with the molten metal in the molding die. For example, in Patent Document 1, in a core member for forming a ferrule with various metal glasses, TiN, CrN, Si ₃ N ₄ , BN or the like is coated in order to improve releasability, Al, A technique for forming a film of Cu, Pb, Zn, MoS ₂ or the like is described.

JP 2001-1130 A

However, the conventional metal forming method as described above has the following problems.
The technique described in Patent Document 1 is a technique for improving the releasability of a core member that may be low in life because it is easy and inexpensive to replace, and that any coating film is deteriorated by repeated molding. Is inevitable. For this reason, there is a strong demand for a coating technique that can further improve the life of an expensive mold body.
Patent Document 1 does not disclose any coating technique that is particularly suitable for a Zr-based alloy among metallic glasses.

  The present invention has been made in view of the above-described problems, and suppresses deterioration of a molding die when molding an amorphous alloy of a Zr-based alloy having a glass transition region of 20K or more. An object of the present invention is to provide a metal molding method and a molding die that can improve the durability of the die.

  In order to solve the above-mentioned problems, the metal molding method of the present invention is a thin film layer comprising at least a part of a surface in contact with a molten metal comprising Ti (titanium) alone, a Ti compound, or a mixture of Ti alone and a Ti compound. The metal mold is filled with a molten metal of a Zr (zirconium) -based alloy metal material that becomes an amorphous alloy having a glass transition region of 20K or more. The material is cooled and solidified at a cooling rate equal to or higher than the critical cooling rate of the material to form a molded article of the amorphous alloy.

  In the present invention, it is preferable that at least the surface of the thin film layer has a crystal structure or an amorphous structure different from a crystal structure when the metal material of the Zr-based alloy is crystallized.

In the present invention, the Ti compound is preferably composed of one or more compounds selected from TiN, TiAlN, TiO ₂ , TiC, and TiAlSiCON.

  Further, in the present invention, with the molding die rotated, the molten metal is introduced into the molding die and filled into the molding die by centrifugal force to form the molded product. It is preferable to do.

  The molding die of the present invention is filled with a molten metal material of a Zr-based alloy that becomes an amorphous alloy having a glass transition region of 20K or more to form a molding product of the amorphous alloy. It is a type | mold, Comprising: It is set as the structure which has a thin film layer which consists of a Ti single-piece | unit, Ti compound, or the mixture of a Ti single-piece | unit and Ti compound in at least one part of the surface which contacts a molten metal.

  According to the metal molding method and molding die of the present invention, the molding die having a thin film layer made of Ti alone, a Ti compound, or a mixture of a Ti alone and a Ti compound on at least a part of the surface in contact with the molten metal. Since the mold is used, when forming an amorphous alloy having a glass transition region of 20K or more, there is an effect that the deterioration of the molding die can be suppressed.

It is a typical system block diagram of the shaping | molding system used for the shaping | molding method of the metal which concerns on embodiment of this invention. It is typical sectional drawing of the metal mold | die used for the shaping | molding method of the metal which concerns on embodiment of this invention. It is a flowchart which shows the process flow of the shaping | molding method of the metal which concerns on embodiment of this invention.

A metal forming method according to an embodiment of the present invention will be described.
FIG. 1 is a schematic system configuration diagram of a molding system used in a metal molding method according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of a molding die used in the metal molding method according to the embodiment of the present invention.

First, the shaping | molding system used for the metal shaping | molding method of this embodiment is demonstrated.
The forming system 1 used in the present embodiment is a method of forming an amorphous alloy of a Zr-based alloy having a glass transition region of 20K or more by quenching and solidifying the molten metal M at a cooling rate higher than the critical cooling rate by centrifugal casting. Forming a product.
The “Zr-based alloy” in the present specification means an alloy having the largest Zr composition in the alloy composition (atm%), that is, an alloy whose main component is Zr.

Metallic glass is an amorphous alloy in which the glass transition point is clearly observed when the temperature rises, and the temperature range of the supercooled liquid region between the glass transition point and the crystallization temperature, that is, the glass transition region is An alloy with 20K or more.
Metallic glass melts a metal base material having a constant composition to form a melt of the base material alloy, and the molten metal is cooled below the critical transition rate of the base material alloy to below the glass transition point of the base material alloy. It is formed by making it amorphous by cooling.
Specific examples of the Zr-based alloy metal glass include, for example, compositions whose composition (atm%) is Zr ₆₅ Al _17.5 Cu _27.5 , Zr ₅₅ Al ₁₀ Cu ₃₀ Ni ₅ or the like. Since these amorphous alloy materials are mainly composed of Zr, they are excellent in mold transferability and can be easily formed into complex shapes. Moreover, in the example which added nickel (Ni), it is excellent also in chemical resistance.
The Zr-based alloys exemplified above are known to have a body-centered cubic structure (bcc) when crystallized.
The crystal structure of other Zr-based alloys varies depending on the specific composition, but the main ones are the hexagonal close-packed structure (hpc) of Zr crystal and the face-centered cubic structure (fcc) of Zr ₂ Ni crystal. Can be mentioned.

As shown in FIG. 1, the schematic configuration of the molding system 1 includes a mold 3 (molding mold), a motor 7 for rotating the mold 3, and a low-pressure atmosphere in which a vacuum or an inert gas is injected. The chamber 2 is adjustable, a high-frequency heating coil 9, a high-frequency power source 10, a rotary pump 12, a turbo pump 13, and an inert gas supply unit 11.
Among these, the mold 3 and the high frequency heating coil 9 are disposed inside the chamber 2, and the motor 7, the high frequency power source 10, the inert gas supply unit 11, the rotary pump 12, and the turbo pump 13 are disposed outside the chamber 2. Has been.
Although not shown, the molding system 1 is a temperature measuring means for the molten metal M formed inside the high-frequency heating coil 9, such as a radiation thermometer, as in the conventional centrifugal casting method using high-frequency heating. It has.

As shown in FIG. 2, the mold 3 is a member that detachably accommodates a mold body 5 that forms a molded product by cooling and solidifying a molten metal inside a mold holder 4. Although not particularly illustrated, the shape of the mold holder 4 in plan view is circular.
Further, as shown in FIG. 1, the upper end of the rotating shaft 7a of the motor 7 fixed to the outside of the bottom of the chamber 2 via a seal 8 is detachably connected to the center of the bottom of the mold 3. . Thus, by rotating the motor 7, the mold 3 can be rotated around its central axis.

As shown in FIG. 2, a molten metal inlet 4 a that is an opening for introducing a molten metal M formed by a high-frequency heating coil 9 described later into the mold 3 is formed at the center of the upper surface of the mold holder 4. ing.
Below the molten metal inlet 4 a, an L-shaped hole that extends in the vertical direction along the central axis of the mold holder 4 and then extends in the horizontal direction along the radial direction of the mold holder 4. A molten metal receiving portion 4b is provided.
A mold main body holding portion 4e that detachably accommodates the mold main body 5 is provided at the radial end of the molten metal receiving portion 4b.

The mold body 5 includes a cavity 5d, which is a hole surrounded by a molding surface 5c for transferring the shape of the molded product, and the diameter of the molten metal receiving part 4b when accommodated in the mold body holding part 4e. This is a block-shaped member in which a molten metal injection hole 5a communicating with the cavity 5d in the horizontal direction is provided on the mold body side surface 5b facing the front end portion in the direction.
Note that FIG. 2 is a schematic diagram, and the mold holder 4 and the mold main body 5 are drawn as a single member, but a plurality of molded articles solidified in the cavity 5d are removed. It can be divided into mold members.

As a material of the mold 3, an appropriate metal material having a thermal conductivity and a heat capacity capable of cooling the molten metal M at a cooling rate equal to or higher than the critical cooling rate of the metal material can be employed. For example, metal materials such as SKD61, SUS420, and cemented carbide (WC) can be used. As other metal materials, stainless steel, mold steel, tool steel, heat resistant steel, etc. excellent in hardness and heat resistance can be adopted. Specific examples include STAVAX (registered trademark), which is a chromium alloy stainless tool steel, and hot-forging die steel YXR33 (trade name; manufactured by Hitachi Metals, Ltd.).
Further, in the mold 3, a thin film 6 (thin film layer) for improving the releasability of the molded product and protecting the surface of the mold 3 is provided at least at a part where the molten metal M may come into contact. A film is formed. The thin film 6 may be provided on at least a part of the mold surface that the molten metal M is in contact with which it is desired to avoid the deterioration of the mold, and can be provided on, for example, the entire molding surface or a part of the molding surface that is particularly susceptible to degradation. Moreover, it can also provide suitably in the site | part which contacts the molten metal M other than a molding surface. In the present embodiment, in the mold holder 4, the thin film 6 is formed on the receiving portion inner wall surface 4c and the receiving portion bottom surface 4d in the molten metal receiving portion 4b. Further, in the mold main body 5, the film is formed on the mold main body side surface 5b, the molten metal injection hole 5a, and the molding surface 5c facing the molten metal receiving portion 4b.

As a material constituting the thin film 6, a simple Ti, a Ti compound, or a mixture of a simple Ti and a Ti compound can be employed.
The Ti compound is preferably composed of one or more compounds selected from TiN, TiAlN, TiO ₂ , TiC, and TiAlSiCON. However, the Ti compound is not limited to these, and other Ti compounds such as TiCN are also suitable.
Although TiN has the property of being easily oxidized at a high temperature, as described later, in the forming method of the present embodiment, casting of the Zr-based alloy metal glass is performed in a high vacuum or an inert atmosphere such as Ar. Is preferred.

  Since the Ti element is the same group 4 element as the Zr element and has similar chemical properties, the thin film 6 made of simple Ti, Ti compound, or a mixture of simple Ti and Ti compound is a Zr-based alloy. In this molding, it is expected that the deterioration is likely to proceed due to the reactivity with Zr in the Zr-based alloy. However, when the present inventor conducted various experiments, contrary to this expectation, among various metal glasses, Zr is particularly preferred. It has been found that the releasability is good with respect to the base alloy, and the deterioration of the molding die is suppressed.

Zr not only constitutes a crystalline metal with Zr alone, but also has a property of reacting with Cu, Ni, Sb (antimony) and the like to form an intermetallic compound such as ZrCu, ZrNi, ZrSb and the like. Besides, it reacts similarly with Mn (manganese), Cr (chromium), Bi (bismuth), Fe (iron), Al and the like.
On the other hand, it has been found that Ti and Zr do not have such properties and do not react with each other, and there is no diffusion phenomenon in which Zr atoms of molten Zr diffuse into the Ti compound.
Thus, since Zr has a lower reactivity with Ti than other metal atoms such as Cu, it is considered that the reactivity with a simple substance of Ti or a Ti compound is lowered even in a molten metal M of a Zr-based alloy. .

In addition, the present inventor combined various configurations other than the thin film 6 as a protective film for a molding die in a similar experiment. As a result, the amorphous quality of the molded product molded as metal glass was determined as a protective film. It was found to be closely related to the crystal structure of.
That is, if the crystal structure of the protective film is the same as that in the case where the metal material of the Zr-based alloy is crystallized, crystallization is induced in the metal material in contact with the protective film, and a part of the surface of the molded product is It will crystallize. For this reason, characteristics such as high hardness and corrosion resistance of the metal glass as an amorphous alloy are lost in the crystallized portion.
Therefore, it is preferable that the thin film 6 is made of the above-described material, and at least the surface thereof has a crystal structure or an amorphous structure different from the crystal structure when the metal material of the Zr-based alloy is crystallized.

For example, the crystal structure of simple Ti is a hexagonal close-packed structure at normal temperature and pressure, but changes to a body-centered cubic structure at 882 ° C. or higher.
The crystal structure of TiN, TiAlN, TiC, TiCN, and TiAlSiCON can have a face-centered cubic structure.
The crystal structure of TiN can be appropriately selected from tetragonal ε-TiN and cubic δ-TiN by a film forming method.
The crystal structure of TiO ₂ can be selected from tetragonal rutile type or anatase type depending on the film forming conditions.
In addition, any Ti compound can have an amorphous structure by forming the thin film 6 by, for example, sputtering.

As a film forming method of the thin film 6, an appropriate film forming method can be adopted according to the material of the thin film 6 and the target crystal structure. For example, chemical vapor deposition (CVD), physical vapor deposition (PVD), or the like can be employed. According to CVD, a specific crystal structure can be realized depending on film forming conditions. Moreover, according to PVD, an amorphous structure can be realized.
The film thickness of the thin film 6 can be appropriately set in consideration of durability according to the material. For example, the thickness is preferably 0.5 μm to 50 μm, and more preferably 1 μm to 6 μm.
Such a film thickness range is sufficiently thinner than ± 0.03 mm (30 μm), which is a typical example of a dimensional tolerance required for precision machine parts such as an endoscope front frame. . Therefore, when molding such a precision machine part, since the molding surface 5c can be processed without considering the shape change caused by the thin film 6, the mold body 5 can be easily manufactured. .
Moreover, since the film thickness of the thin film 6 can be reduced in this way, the thermal resistance can be reduced. For this reason, cooling of the molten metal M becomes difficult to be hindered, which is particularly suitable for metal glass casting.
Moreover, if the film thickness of the thin film 6 becomes too thick, the durability deteriorates due to the influence of film stress due to thermal expansion. Therefore, it is preferable not to exceed 50 μm as described above.
On the other hand, since a thin film of a Ti and Ti compound system has high hardness, it is assumed that followability to deformation of the base material is slightly poor and film stress is increased. Therefore, since there is a concern that the film is likely to crack when the film thickness is too thin, the film thickness is preferably not less than 0.5 μm.

As shown in FIG. 1, the high-frequency heating coil 9 is for obtaining a molten metal M by electromagnetic induction heating of a metal material for centrifugal casting. It is a coil formed by the formed metal tube. In this embodiment, in order to induce and float the molten metal M, the upper half portion and the lower half portion have opposite winding directions, and the winding diameter is reduced toward the upper end and the lower end, respectively.
Metal tubes 9 a and 9 b extending from the upper end and the lower end of the high-frequency heating coil 9 are led to the outside of the chamber 2 and connected to a refrigerant supply line (not shown) and electrically connected to the high-frequency power source 10. It is connected to the.
The high-frequency heating coil 9 is disposed above the center portion of the mold 3 so that the center of the opening on the lower end side of the high-frequency heating coil 9 is located on the vertical axis passing through the center of the molten metal inlet 4 a in the mold 3. ing.

The rotary pump 12 is a vacuum pump for roughing the atmosphere in the chamber 2 and reducing the pressure to about 10 Pa, for example, and is connected to the chamber 2 via a suction line 14.
The turbo pump 13 depressurizes the chamber 2 with the rotary pump 12 and then pulls the atmosphere in the chamber 2 into a vacuum degree of, for example, about 1.0 × 10 ⁻² Pa to 1.0 × 10 ⁻⁴ Pa. It is a vacuum pump consisting of a turbo molecular pump for reducing the pressure. The turbo pump 13 is provided at an intermediate portion of the suction pipe line 15 provided between the chamber 2 and the rotary pump 12.

The inert gas supply unit 11 supplies an inert gas such as argon (Ar) or nitrogen (N ₂ ) into the chamber 2 after the vacuum degree of the chamber 2 is increased by the turbo pump 13. The gas supply line 16 is connected to the chamber 2.

Next, the metal forming method of this embodiment will be described.
FIG. 3 is a flowchart showing a process flow of the metal forming method according to the embodiment of the present invention.

The metal forming method of the present embodiment is a method of forming a metal glass molded product by solidifying the molten metal M using the mold 3 having the thin film 6 on at least a part of the surface in contact with the molten metal M.
The means for solidifying the molten metal M is not particularly limited as long as it can be solidified by cooling at a cooling rate equal to or higher than the critical cooling rate of the metal material of the molten metal M so that the molten metal M becomes metallic glass. Appropriate means similar to the molding method can be employed.
In the present embodiment, an example in the case of solidification by the centrifugal casting method using the molding system 1 will be described.
As shown in FIG. 3, the metal forming method of the present embodiment is a method of performing a mold installation step S1, a vacuum replacement step S2, a forming step S3, and a molded product taking out step S4.

  The mold installation step S <b> 1 is a process for installing the mold 3 inside the chamber 2. In this step, the mold body 5 is accommodated in the mold holder 4 to assemble the mold 3 and fixed to the upper end of the rotating shaft 7a in the chamber 2 opened to the atmosphere.

Next, the vacuum replacement process S2 is performed. This step is a step of vacuum replacement of the atmosphere in the chamber 2 in which the mold 3 is placed. Here, “vacuum replacement” refers to replacement in which the atmosphere in the chamber 2 is evacuated to form a high-vacuum atmosphere having a pressure of 0.1 Pa or less, more preferably 1.0 × 10 ⁻³ Pa or less. It means that an inert gas atmosphere is formed by introducing an inert gas after forming a high vacuum atmosphere.
In the present embodiment, first, the atmosphere in the chamber 2 is roughly drawn by the rotary pump 12 and the pressure in the chamber 2 is reduced to about 10 Pa. Next, the turbo pump 13 is further driven from this state to perform main pulling, and the degree of vacuum in the chamber 2 is increased. In the present embodiment, the pressure is reduced so that the degree of vacuum is 1.0 × 10 ⁻³ Pa.
By performing the vacuum replacement in this way, the amount of oxygen remaining in the chamber 2 is extremely reduced. Moreover, since the molten metal receiving part 4b and the cavity 5d communicate with the chamber 2, the oxygen concentration in the molten metal receiving part 4b and the cavity 5d is also reduced to a similar level.

Next, in this embodiment, Ar gas having a purity of 99.9999% is supplied from the inert gas supply unit 11 into the chamber 2, and an Ar gas atmosphere of about atmospheric pressure is formed in the chamber 2.
After forming a high-vacuum atmosphere in the chamber 2 as described above, Ar gas is further supplied to the chamber 2 while maintaining a pressure close to atmospheric pressure by replacing Ar gas with a higher purity. Compared with the case where gas replacement is performed, the oxygen concentration remaining in the chamber 2 can be significantly reduced.

Next, the molding step S3 is performed. This step is a step of forming metallic glass by centrifugal casting.
First, a metal material in an amount necessary for forming is placed inside the high-frequency heating coil 9, and a high-frequency current is passed through the high-frequency heating coil 9 while cooling the high-frequency heating coil 9 by flowing a coolant through the high-frequency heating coil 9.
Thereby, a magnetic field is generated around the high-frequency heating coil 9, the metal material is induction-heated, and the molten metal M is formed.
In the high-frequency heating coil 9, the coil winding directions are opposite in the upper half and the lower half, and thus magnetic fields in opposite directions are generated in the upper half and the lower half, respectively. Upon receiving the repulsive force, it is inductively floated inside the high-frequency heating coil 9.

On the other hand, before the molten metal M reaches a predetermined molding start temperature, the operator starts rotation of the motor 7 so as to reach a predetermined rotational speed at which a predetermined centrifugal casting is performed.
Next, the operator cuts off the high-frequency current to the high-frequency heating coil 9 when the temperature of the molten metal M measured by a temperature measuring means (not shown) reaches the molding start temperature.
Thereby, the magnetic field by the high frequency heating coil 9 lose | disappears, and the molten metal M which lost buoyancy falls freely.

The molten metal M passes through the inside of the coil on the lower end side of the high-frequency heating coil 9, and falls into the molten metal receiving part 4b from the molten metal inlet 4a vertically below.
The molten metal M that has fallen to the molten metal receiving portion 4b is urged radially outward by centrifugal force, proceeds radially outward in the molten metal receiving portion 4b, and is filled into the cavity 5d through the molten metal injection hole 5a.
During this time, the molten metal M comes into contact with the mold holder 4 and the mold main body 5 and is cooled at a cooling rate higher than the critical cooling rate, for example, a cooling rate of 10 K / s or higher, and follows the shape of the molding surface 5c in the cavity 5d. Solidify.
Thereby, a molded product in which the shape of the molding surface 5c is transferred is formed in the cavity 5d.
Thus, the molding step S3 is completed.

Next, a molded product removal step S4 is performed. This step is a step of taking out the molded product formed in the cavity 5d.
First, the motor 7 is stopped, the chamber 2 is opened, and the mold 3 is taken out of the chamber 2. Then, the molded product in the cavity 5d is removed by disassembling the mold 3 or the like.
In this embodiment, since the thin film 6 is formed on the surfaces of the receiving portion inner wall surface 4c, the receiving portion bottom surface 4d, the mold main body side surface 5b, the molten metal injection hole 5a, and the molding surface 5c, the seizure to the mold 3, etc. Is unlikely to occur. For this reason, the metal piece and molded product solidified at each position can be easily released.
The centrifugal casting by the molding system 1 is thus completed.
Furthermore, when continuing shaping | molding, the metal mold | die 3 after mold removal is assembled, and said each process is repeated.

When the crystal structure of the thin film 6 is the same as the crystal structure in the case where the metal material of the molten metal M is crystallized, crystallization may be induced in a part of the surface of the molded article, but it remains in a part of the surface. As a bulk, a molded product having the properties of metallic glass is obtained.
If the crystallized portion cannot be allowed depending on the usage of the molded product, the crystallized portion may be removed by performing secondary processing such as cutting.
However, if a thin film 6 having a crystal structure or an amorphous structure different from the crystal structure when the molten metal M is crystallized, crystallization is not induced, and such secondary processing becomes unnecessary. For example, when the Zr-based alloy is crystallized to have a body-centered cubic structure, other thin crystal structures such as a body-centered cubic structure, a rutile crystal structure, a hexagonal crystal, or the like are formed. Can be adopted.

Next, the metal forming method of this embodiment will be described based on specific examples.
[Example 1]
In Example 1, SKD61 was adopted as the material of the mold 3. As the thin film 6, a TiAlN film was formed by plasma CVD.
However, since the TiAlN film does not have good adhesion to the SKD 61 as a base material, a TiN film was provided as a base layer. The thickness of the TiAlN film was 6 μm, and TiN was 1 μm.
In the thin film 6, the crystal structure of the TiAlN film as the outermost layer was made to be a face-centered cubic structure by appropriately setting the conditions of plasma CVD.
Using such a mold 3, centrifugal casting was performed by the molding system 1 using a Zr-based alloy having a composition of Zr ₆₅ Al _7.5 Cu _27.5 as a metal material for molding.
As a result, casting could be carried out continuously without the occurrence of seizure on the mold.
Further, when the crystallinity of the molded product was analyzed by XRD (X-ray diffractometer), no crystallization was observed.

Thus, by forming the TiAlN film, which is a compound of Ti having low reactivity with Zr, on the outermost layer of the thin film 6 in contact with the molten metal M, the mold release property of the molded product is improved and the mold 3 The base material SKD61 was protected and could be continuously cast without damaging the base material due to seizure or the like. For this reason, according to the shaping | molding method like a present Example, durability of the metal mold | die 3 can be improved.
Further, in this example, when Zr ₆₅ Al _7.5 Cu _27.5 crystallizes, it becomes a body-centered cubic structure, whereas the outermost TiAlN film of the thin film 6 has a face-centered cubic structure. Therefore, it has an effect of not inducing crystallization of ZrCu having a body-centered cubic structure. For this reason, it is thought that crystallization of the molded product was prevented.

  In addition, the TiAlN film in the thin film 6 of this embodiment is a high-hardness and dense protective film, and if the base material to be formed is a soft material, peeling or cracking of the film is likely to occur. However, in this embodiment, since SKD61, which is a steel material having a sufficiently high hardness, is adopted as the base material of the mold 3, the deterioration of the thin film 6 with time due to the flexibility of the base material is suppressed. be able to.

Further, since the TiAlN film used for the thin film 6 contains Ti, it has been found that the wettability of the Zr-based alloy to the molten metal M is small. And it turned out that a frictional resistance becomes small by this property, and since the slipperiness with the molten metal M becomes favorable at the time of casting, the flow resistance in the thin film 6 becomes small.
Therefore, the structure of the present embodiment provides good filling properties to the mold 3 even in a casting method in which the filling pressure is low compared to injection molding such as centrifugal casting. For this reason, it is suitable as a molding method of a molded product having a product shape having a thin portion or a complicated shape.

  In this embodiment, as an example, the thickness of the TiAlN film is 6 μm, but the thickness can be further increased. If the film thickness is increased, even if the surface of the thin film 6 is further deteriorated, it takes more time for the damage to reach the base, so that the number of durable shots of the mold 3 can be improved.

[Example 2]
In Example 2, SUS420 was adopted as the material of the mold 3. As the thin film 6, a TiO ₂ film was formed by CVD. The crystal structure of the thin film 6 was mainly a rutile structure. The film thickness of the TiO ₂ film was 1 μm.
Using such a mold 3, composition as the metal material for forming the Zr-based alloy of _{Zr 55 Al 10 Cu 30 Ni 5} , it was subjected to centrifugal casting by the molding system 1.
As a result, casting could be carried out continuously without the occurrence of seizure on the mold.
Further, when the crystallinity of the molded product was analyzed by XRD, no crystallization was observed.

Thus, by using the TiO ₂ film, which is a compound of Ti having low reactivity with Zr, as the thin film 6 in contact with the molten metal M, the releasability of the molded product is improved and the base material of the mold 3 can be improved. A certain SUS420 was protected and could be continuously cast without damaging the base metal due to seizure or the like. For this reason, according to the shaping | molding method like a present Example, durability of the metal mold | die 3 can be improved.
Further, in this _embodiment, when the Zr ₅₅ Al _{10 Cu} 30 Ni ₅ crystallizes, whereas becomes a face-centered cubic structure of ZrNi crystal, TiO ₂ film of the thin film 6, rutile tetragonal Since it is a structure, it has an effect of not inducing crystallization of ZrNi having a face-centered cubic structure. For this reason, it is thought that crystallization of the molded product was prevented.

In addition, the TiO ₂ film in the thin film 6 of this embodiment is a high-hardness and dense protective film, and if the base material to be formed is a soft material, peeling or cracking of the film is likely to occur. However, in the present embodiment, SUS420, which is a steel material having a sufficiently high hardness, is adopted as the base material of the mold 3, and thus the deterioration with time of the thin film 6 due to the flexibility of the base material is suppressed. be able to.

Further, since the TiO ₂ film used for the thin film 6 contains Ti, the wettability of the Zr-based alloy with respect to the molten metal M is the same as that of the TiAlN film of the first embodiment. Therefore, even in this embodiment, even in a casting method in which the filling pressure is lower than that of injection molding such as centrifugal casting, the filling property to the mold 3 is improved, and a product shape having a thin part or a complicated shape is formed. It is suitable as a molding method for products.

[Examples 3 to 5]
Next, based on Table 1 below, the results of Examples 3 to 5 other than Examples 1 and 2 and the results of Comparative Examples 1 to 3 will be briefly described.

In Table 1, the material of the “thin film layer” indicates the material of the outermost layer of the thin film 6 (a protective film in the case of the comparative example).
“Bcc” represents a body-centered cubic structure, and “fcc” represents a face-centered cubic structure. “Rutyl type” is an abbreviation for a rutile crystal structure, and “amorphous” is an abbreviation for an amorphous structure.
In addition, the “mold durability” was evaluated by the number of shots capable of forming a good molded product for the life of the mold 3. “◎” represents 500 shots or more, “◯” represents 100 shots or more and less than 500 shots, “Δ” represents 50 shots or more and less than 100 shots, and “X” represents less than 50 shots.
“Amorphous” is evaluated using XRD, “◎” indicates good amorphous property, “◯” indicates a practical level, “△” indicates a crystallized region on the very surface, and “-” evaluation. Represents out of scope. In the evaluation of the amorphous property, “◎”, “◯”, and “Δ” indicate that the material is amorphous enough to be recognized as a metallic glass. A level that was not recognized as a metallic glass because it was entirely crystallized was not found in these Examples and Comparative Examples.
In Comparative Example 3, since the mold durability is extremely poor, the amorphous property is not evaluated.

Example 3 is an example in which the Zr-based alloy of Example 2 was molded using the mold 3 of Example 1.
Example 4 is an example in which the Zr-based alloy of Example 1 was formed using a mold 3 having a thin film 6 having a thin film layer (film thickness 5 μm) sputtered with TiN as the outermost layer. TiN has an amorphous structure by sputtering.
In Example 5, the Zr-based alloy of Example 1 was formed by using a mold 3 on which a thin film 6 having a thin film layer (film thickness 5 μm) composed of a mixed film of Ti alone and TiN was formed as the outermost layer by CVD. This is an example of molding. TiN has a body-centered cubic structure, and Ti alone has a body-centered cubic structure when a Zr-based alloy is formed.
In both cases, the material of the mold 3 is SKD61.

Comparative Example 1 is an example in which AlN is sputtered on a mold having the same shape as the mold 3 to form the outermost layer (film thickness: 5 μm) of the protective film, and the Zr-based alloy of Example 2 is formed. AlN is hexagonal.
Comparative Example 2 is an example in which the outermost layer (film thickness 5 μm) of the protective film made of SiC is formed on a mold having the same shape as the mold 3 by using plasma CVD, and the Zr-based alloy of Example 2 is molded. It is. SiC has a face-centered cubic structure.
In both cases, the material of the mold 3 is SKD61.
In Comparative Example 3, the SKD61 mold having the same shape as the mold 3 was used, and only the surface nitriding treatment was performed without providing a protective film on the molding surface, and the Zr-based alloy of Example 2 was molded. It is an example.

As shown in Table 1, in Examples 1 to 5, the evaluation of mold durability was ◎, whereas the evaluations of Comparative Examples 1 to 3 were x, Δ, and x, respectively. It can be seen that the durability can be improved by including Ti alone or a Ti compound in the outermost layer.
In addition, regarding the evaluation of the amorphous property, in Examples 1 to 4, it was ◎, in Comparative Examples 1 and 2, it was ◯, while in Example 5, it was Δ. In Examples 1 to 3 and Comparative Examples 1 and 2, the material of the outermost layer of the thin film 6 or the protective film has a different crystal structure from the crystal structure at the time of crystallization of the metal material used for forming. On the other hand, it is considered that the thin film 6 of Example 5 has the same body-centered cubic structure as the crystal structure at the time of crystallization of the metal material used for forming. Moreover, according to the result of Example 4, even if the outermost surface layer of the thin film 6 is an amorphous structure which does not have a crystal structure, it turns out that it has the same effect as the case where it has a different crystal structure.

  As described above, according to the metal molding method and the molding die of the present embodiment, since the die 3 having the thin film 6 is used as the molding die, the amorphous Zr-based alloy having a glass transition region of 20K or more is used. When forming a high quality alloy, deterioration of the molding die can be suppressed and the durability of the molding die can be improved.

  In the above description of the embodiment, an example in which the vacuum replacement step S2 is provided between the mold installation step S1 and the molding step S3 has been described. However, the atmosphere in the chamber 2 when starting the molding step S3 is such that the molded product, the thin film 6 and the mold 3 are not deteriorated due to oxidation of the molten metal M, the thin film 6 and the mold 3 by the heat of the molten metal M. Any vacuum atmosphere or inert gas atmosphere may be formed. For this reason, depending on the material and molding temperature of the molten metal M, the thin film 6 and the mold 3, a vacuum atmosphere with a lower degree of vacuum (a higher pressure), or an inert gas replacement performed at atmospheric pressure or a lower degree of vacuum. It can be an active gas atmosphere.

In the description of the above embodiment, the example in which the centrifugal casting method is employed has been described. However, the present invention is not limited to the centrifugal casting method. For example, if the cavity 5d can be filled even at a low pressure, such as when the shape of the cavity 5d is simple, a gravity casting method can be employed.
Further, when the life of the thin film 6 with respect to the filling pressure is acceptable, an injection molding method can be adopted.

  In the description of the above embodiment, the example in which the metal material of the molten metal M is a Zr-based alloy has been described. However, since the Zr-based alloy only needs to be formed when the molten metal M is formed, the Zr-based alloy is formed. Alternatively, the molten metal M may be formed by melting a material obtained by mixing particles of individual metal materials.

  In the description of the above embodiment, the example of the case where the molten metal M is formed by induction floating heating with the high frequency heating coil 9 has been described. However, high frequency heating may be performed without induction floating, or other than high frequency heating. The molten metal M may be formed by the heating source.

  Moreover, all the components described in the above embodiment can be implemented by being appropriately combined or deleted within the scope of the technical idea of the present invention.

1 Molding system 2 Chamber 3 Mold (molding mold)
4 Mold holder 4b Melt receiving portion 4c Receiving portion inner wall surface 4d Receiving portion bottom surface 5 Mold body 5a Molten injection hole 5b Mold body side surface 5c Molding surface 5d Cavity 6 Thin film (thin film layer)
9 High-frequency heating coil M Molten metal 11 Inert gas supply part S1 Mold installation process S2 Vacuum replacement process S3 Molding process S4 Molded article taking-out process

Claims (5)

Using a molding die having a thin film layer made of Ti (titanium) alone, a Ti compound, or a mixture of Ti alone and a Ti compound on at least a part of the surface in contact with the molten metal,
By filling a metal mold of a Zr (zirconium) -based alloy, which is an amorphous alloy having a glass transition region of 20K or more, into the molding die, the cooling rate is higher than the critical cooling rate of the metal material. A method for forming a metal, comprising cooling and solidifying to form a molded article of the amorphous alloy. 2. The metal forming method according to claim 1, wherein at least a surface of the thin film layer has a crystal structure or an amorphous structure different from a crystal structure when the metal material of the Zr-based alloy is crystallized. . The metal forming method according to claim 1, wherein the Ti compound is composed of one or more compounds selected from TiN, TiAlN, TiO ₂ , TiC, and TiAlSiCON. The molded product is formed by introducing the molten metal into the molding die in a state where the molding die is rotated and filling the molding die by centrifugal force. Item 3. A metal forming method according to Item 1 or 2. A molding die for filling a molten metal material of a Zr (zirconium) base alloy that becomes an amorphous alloy having a glass transition region of 20K or more to form a molded article of the amorphous alloy,
A molding die having a thin film layer made of Ti (titanium) alone, a Ti compound, or a mixture of a Ti simple substance and a Ti compound on at least a part of a surface in contact with the molten metal.

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