JP2605152B2 - Method for producing elastic member mainly composed of intermetallic compound - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an elastic member such as a spring mainly composed of a Ti—Al intermetallic compound and a method for producing the same.

[Prior art] Conventional springs or elastic members exhibiting properties similar to springs are generally made of metal such as steel or FRP.
And the like. However, recently, attention has been focused on intermetallic compounds that are lightweight and have excellent properties such as heat resistance and oxidation resistance. Examples of the intermetallic _{compound, TiAl, Ti 3 Al, Al} 3 T
i, Ni ₃ Al, TiNi having a shape memory effect, and the like are known. There is an example of coil spring manufacturing by bending in TiNi, but multiple heat treatments (softening annealing) are required in actual forming, although TiNi has better formability among intermetallic compounds It is much more difficult to form a spring than metal. Further, it has been considered that it is difficult to apply other intermetallic compounds to a spring requiring a large bending process such as a coil spring.

It has also been considered that molding is performed in advance at a material stage before forming an intermetallic compound. For example, JP-A-61
As disclosed in JP-A-270353, an intermetallic compound having a desired shape is obtained by hot-pressing a raw material of an intermetallic compound, followed by firing.
As disclosed in Japanese Patent No. 70531, it has been proposed to degas a raw material of an intermetallic compound and then treat it under predetermined molding pressure and temperature conditions.

[Problems to be Solved by the Invention] Even if the pre-forming is performed before forming the intermetallic compound as in the prior art described above, application to a spring requiring large plastic working such as a coil spring is impossible. Met. This is because a three-dimensional object made of an intermetallic compound raw material has poor uniformity before forming an intermetallic compound and contains many pores and defects compared to a normal metal material. This is because when plastic working such as stretching is performed, the deformation tends to be non-uniform, and the working performance is extremely poor.

Further, as described in JP-A-63-247321 and JP-A-62-99425, it has been proposed to perform a heat treatment after performing a process such as pressing or extrusion on a raw material of an intermetallic compound. ing. However, a simple press or extrusion has a small pore reduction rate, and in particular, an effect of almost eliminating pores in the surface layer of the material cannot be expected.

It was also expected that by reducing the porosity of the green compact of the raw material of the intermetallic compound by some means, the formability may be improved when the green compact is bent into a desired shape. . However, the present inventors have conducted enormous research on means for improving formability, and as a result, simply increasing the processing rate by ordinary pressing or forging and reducing the porosity, It was found that improvement in moldability could not be expected.

That is, the factors that affect the formability of the mixed green compact of the raw material of the intermetallic compound are not only related to the voids, but also whether or not there is a reaction at the interface of the mixed green compact and the interface of the mixed green compact. Bonding form (interface shape and interface bonding state),
Or it may depend on the form of mixing of the mixed green compact, etc., and there may be other uncertain factors, and simply increase the processing rate and increase the porosity as seen in the prior art. However, the improvement of moldability was not achieved only by reducing the amount.

Accordingly, an object of the present invention is to provide a manufacturing method capable of manufacturing an elastic member having a desired shape mainly composed of an intermetallic compound without any problem, and obtaining a dense and high-quality elastic member having a low porosity.

Means for Solving the Problems The present inventors have conducted intensive studies on means for improving the formability of an intermetallic compound, and as a result, in a Ti—Al-based intermetallic compound, a mixed pressure containing Ti and Al At the stage before the powder is formed into a desired final product shape, it is possible to perform forging by swaging on the mixed green compact, and in the subsequent step of forming the mixed green compact into a desired shape, a coil is formed. They have found that it is extremely effective in improving the formability of complicated shapes such as springs.

Therefore, the present invention developed to achieve the above object,
Ti mixed in composition ratio to form Ti-Al intermetallic compound
And a raw material containing Al is packed in a wrapping member, and a swaging step of sequentially reducing the cross-sectional area of the raw material from one end side to the other end side by performing preforming by swaging processing to obtain a mixed pressure-bonded body, After forming the mixed pressure-bonded body into a desired elastic member shape after the swaging step,
The treatment is performed under a temperature condition at which a Ti-Al-based intermetallic compound is formed.

Examples of the elastic member include a wound spring, a leaf spring, a torsion bar, and a washer, a fastening member, and the like that exhibit properties similar to a spring. The substance constituting the intermetallic compound may be at least Ti and Al.

The above-mentioned raw material needs to be mainly composed of a metal material, but may partially contain an intermetallic compound. Further, for the purpose of improving various properties as an elastic member or facilitating molding, an appropriate element or compound may be added. The raw material need not be a lump of pure metal, but may be a solid solution or a composite made by plating or the like. The form of the raw material before mixing is powder, flake, wire, foil or the like.

When the raw materials are in the form of powder or flakes, for example, they are mixed with a V-type mixer, a ball mill, a mixer, or the like. When the raw material is linear, for example, the wires are bundled or twisted. In the case of a foil-like raw material, for example, foil is stacked and wound.

The mixed raw material is packed in an appropriate wrapping member such as a metal or a synthetic resin, and forged by a swaging machine until a predetermined working degree is obtained. The degree of processing referred to in this specification refers to the ratio of the cross-sectional area of the mixed material before processing to the cross-sectional area of the mixed press-bonded body after processing. When the raw material is linear, the wires can be twisted, and when the raw material is foil, a strong mixture can be obtained by, for example, overlapping and winding, so that the above-mentioned covering member is not necessarily required. In order to increase the strength of these mixtures, if the raw material is linear, the mixture is drawn, and if the raw material is a foil, such as by rolling, the mixture is preliminarily compressed. Good.

Similarly, when the raw material is in the form of powder or flakes, the mixture may be preliminarily compressed by hydrostatic pressing, uniaxial pressing, extrusion, swaging, rolling, or the like to improve the strength of the mixture. In such a case, it is not always necessary to provide a wrapping member in which the mixed raw material is pre-packed before forging or drawing to a predetermined working degree by the swaging machine.

[Operation] In order to reduce the number of pores in the mixed raw material and press the raw materials together as strongly as possible, it is preferable to apply as much deformation as possible to the mixed raw material. From this point, it is easy for the swaging machine to increase the working degree, and the swaging machine meets the object of the present invention. In addition, the swaging process has an effect of sufficiently crushing the mixed raw material when the cross-sectional area is reduced, so that the contact area of the mixed raw material can be increased, and a good pressing force (adhesive force) can be obtained. This leads to an improvement in processing performance when forming into a desired elastic member shape, and a fine structure can be obtained, so that a high-strength Ti-Al-based intermetallic compound spring can be obtained. When the mixed raw material subjected to the swaging process is fed into the die of the swaging machine, deaeration is promoted while the cross-sectional area is sequentially reduced from one end side to the other end side, and at the same time pores are sufficiently crushed. .

In the present invention, at the stage before the mixed green compact is formed into a desired final product shape, the above-mentioned swaging is performed on the mixed green compact, and the swaging process forms the mixed green compact into a desired shape. There is a point that the cause is not clear about the effect on the formability when forming into a shape, but in any case, compared to conventional processing such as simple press, forging or extrusion, the raw material of the intermetallic compound is The moldability when molding the mixed green compact into a desired product shape has been remarkably improved.

The degree of processing by the swaging machine is determined according to the shape, size, filling rate, and the like of the mixed raw material. As a guide of the degree of processing, it is preferable to perform processing until the porosity of the mixed press-bonded body after the cross-sectional area is reduced to 5% or less by volume. As the degree of processing increases, the degree of rubbing and crushing of the mixed raw materials increases, so that the contact force increases, the contact area increases, and the processing performance when forming into a spring shape improves.

In addition, even if the porosity is the same, the processing performance deteriorates if there are large pores. Therefore, the distribution of the pore diameter together with the porosity is also an important factor for the processing performance. Therefore, it is necessary to evaluate the pore diameter in addition to the porosity, but as the degree of processing is increased, the porosity is reduced and the porosity is reduced, and since there is a positive correlation that the porosity is reduced, the management is easy. There is no practical problem even if the working ratio is determined based on the porosity.

The swaging process sequentially reduces the cross-sectional area in the longitudinal direction of the material while strongly hammering the material surface with a die, and thus has an effect of particularly crushing pores in the surface layer. That is, the porosity of the surface portion tends to be smaller than the porosity of the central portion, and when a porosity of 5% or less is obtained, almost no porosity exists in the surface portion. Conversely, if the working ratio is such that the porosity exceeds 5%, the mixed raw material is not sufficiently crushed or adhered, and not only the porosity is high but also large pores are present, which is not preferable.

The swaging process may be performed cold, but may be performed warm by heating the processing step by an appropriate method in order to reduce the deformation resistance during the processing and enhance the effect. When forming in a warm state, the temperature is preferably equal to or lower than the temperature at which an intermetallic compound is formed. The molding may be performed at a temperature equal to or higher than a certain temperature.

Rod (linear) obtained by the above swaging process
Is formed into a desired shape such as a coil spring. Then, it is heated to a temperature at which a Ti-Al-based intermetallic compound is formed. This heat treatment causes diffusion or self-combustion sintering to form an intermetallic compound. The heating temperature is a temperature range below the solidus of the intermetallic compound. To end the formation of the intermetallic compound, it is necessary to maintain the above temperature for a certain period of time. Lower temperatures take longer. Further, for the purpose of further reducing pores, heating may be performed at a temperature higher than a temperature at which an intermetallic compound is formed in a pressurized state.

After the intermetallic compound is formed, a heat treatment after the formation of the intermetallic compound may be performed, if necessary. By performing this heat treatment, pores can be further reduced, the uniformity of the structure can be promoted, and impurities can be diffused or removed. The treatment temperature is in a temperature range below the solidus of the intermetallic compound. This heat treatment may be performed in the air, but more preferable results may be obtained when performed in an inert gas or vacuum atmosphere. Also,
These atmospheres may be combined. Depending on the material, the heat treatment may be performed in a state where the heat treatment is performed by using an appropriate pressurizing unit.

Example An example of the present invention will be described below with reference to the drawings. An example of the manufacturing process shown in FIG. 1 includes a raw material mixing process 1, a mixed pressure bonding body manufacturing process (swinging process) 2 by a swaging machine, a pre-forming heat treatment process 3 performed as necessary, and a necessary process. A pre-processing step 4 such as a deformed cross-section processing, a forming step 5 for forming into a desired spring shape, a heat treatment step 6 for heating to a forming temperature of an intermetallic compound, and a compound formation performed as necessary It comprises a heat treatment step 7 and a finishing step 8 later.

In the mixing step 1 of the raw materials, the Al powder having a size of 350 mesh or less and the sponge Ti powder having a size of 350 mesh or less produced by the gas atomization method were substituted with Ar gas so that the ratio by weight was Ti: Al = 37.17: 62.83. Mix using a dry ball mill.

Next, in the manufacturing process 2 of the mixed pressure-bonded body, the mixed powder is an outer diameter φ20 mm, an inner diameter φ19 mm as an example of a covering member,
The pipe is packed in a stainless steel pipe having a thickness of 0.5 mm, and first swaging is performed using a rotary swaging machine 9 shown in FIG. 2 as an example to reduce the outer diameter to 8 mm. Thereafter, the pipe is scraped off by a cutting process to obtain a rod-shaped mixed pressure-bonded body A. The material of the pipe may be other than stainless steel, and may be other than metal. In short, any material that can withstand the swaging process may be used.

When the raw material is linear, the wires are twisted, and when the raw material is foil, a strong mixture can be obtained by, for example, overlapping and winding, so that the metal pipe is not necessarily required. In order to increase the strength of these mixtures, the mixture may be compressed by drawing the mixture when the raw material is linear, or rolling it when the raw material is foil.

Similarly, when the raw material is in the form of powder or flake, the strength of the mixture is improved by compressing the mixture by hydrostatic pressing, uniaxial pressing, extrusion, swaging, rolling, or the like. In such a case, a pipe for packing the mixed raw material when the cross-sectional area is reduced by the rotary swaging machine is not always necessary.

An example of the structure of the rotary swaging machine 9 is such that a divided die pair is provided inside a group of rollers arranged in the circumferential direction, and this die pair is rotated at a high speed by a spindle. When the outer end is hammered by a group of rollers, the material is plastically deformed to reduce the diameter.

After performing the first swaging, the mixed pressure-bonded body A is reduced to an outer diameter φ1 mm by the second swaging. The porosity was 1% or less.

FIGS. 5 to 10 show micrographs of the metal structure of the mixed pressure-bonded body A on which the above-described swaging process was performed. Fig. 5 (400x magnification) and Fig. 6 (1000x magnification)
Are the structures when the cross-sectional area is reduced from the outer diameter of φ19 mm to φ18 mm. The degree of processing is 1.1. In this photograph, Al looks white, Ti is gray, and pores look black.

FIG. 7 (400 × magnification) and FIG. 8 (1000 × magnification) show the metal structures when the cross-sectional area was reduced to an outer diameter of φ4 mm. The porosity is about 2%. The processing degree is 22.6.

Further, the metal structures reduced to an outer diameter of φ1 mm are shown in FIG. 9 (400 × magnification) and FIG. 10 (1000 × magnification). The porosity is about 1% or less, which indicates that the gray Ti particles are fine. The processing degree is 361.

By performing the above-described swaging, the porosity is greatly reduced, and particularly, the pores hardly exist in the surface layer portion, the raw materials are sufficiently crushed, and a strong adhesion state is obtained. Among them, regarding the most important bending workability when forming a spring, a mixed pressure-bonded body by a conventional processing method (extrusion, rolling, drawing, etc.) cannot provide a sufficient adhesion force and includes many defects such as pores. Whereas
By performing the swaging process of the present embodiment, it is possible to provide excellent workability not found in the conventional material for an intermetallic compound. In other words, given a large plastic working that was conventionally considered difficult to manufacture
Ti-Al based intermetallic compound springs can be easily manufactured, and application to coil springs and the like has become possible.

A heat treatment step 3 before molding is applied to the mixed pressure-bonded body A obtained in the mixed pressure-bonded body manufacturing step (swinging step) 2.
May be implemented. This step 3 is, for example, annealing performed in a vacuum, which is effective for removing the processing strain generated when the mixed pressure-bonded body A is manufactured, and reduces the deformation resistance during molding in the molding step 5 described later. Can be done. Moreover, the crimping surface of the mixed crimping body A becomes strong due to diffusion, and the strength can be improved. Further, there is also an effect of removing the impurity component of the mixed pressure-bonded body A. This step 3
Is performed in the air, an inert gas, a vacuum atmosphere, or a combination of these atmospheres. The processing temperature is generally lower than the temperature at which the intermetallic compound is formed,
If the heating is performed for such a short time that an intermetallic compound is formed on a part of the pressure-bonded surface, the temperature may be lower than the temperature at which the intermetallic compound is formed. This heat treatment is performed before or during swaging, or before pre-processing,
It may be performed before forming the spring. In the pre-processing step 4, molding for obtaining a desired cross-sectional shape can be added to the mixed press-bonded body A by forging, machining, or the like.

In the forming step 5 for giving a desired spring shape, as an example, coiling of the mixed press-bonded body A is performed using a forming apparatus 10 as shown in FIG. This device 10
It comprises a core 11, a roller 13, a chuck 14 and the like. The roller 13 has a function of pressing the mixed pressure-bonded body A against the core metal 11 to bend and a function of applying a predetermined compressive force P. As an example, in FIG. 3, a spiral groove 15 corresponding to the pitch and curvature of the coil spring molded body A 'to be molded is provided in the outer peripheral portion of the cored bar 11.

The pre-processing step 4 and the forming step 5 may be performed in a cold state, but may be performed in a warm state in order to reduce deformation resistance during forming. When forming in a warm state, it is preferable that the temperature is equal to or lower than the temperature at which an intermetallic compound is formed.
The molding may be performed at a temperature higher than the temperature at which the intermetallic compound is formed.

Coiled molded product A 'obtained in molding step 5 above
Is placed in a heating device 20 illustrated in FIG. 4 in a heat treatment step 6, and heated to a temperature at which an intermetallic compound is formed. The heating device 20 includes a pressure-resistant stainless steel pot 22 filled with silica sand 21, a coil-shaped resistance heating element built in the pot 22, a Kanthal heater 23, a thermocouple 24 for temperature detection, and a stainless steel pot. Made of lid 25 and this lid 25
And a pressure means 26 such as a hydraulic cylinder for pressurizing the pressure.

The coil-shaped molded body A 'was set inside the heater 23 housed in the pot 22, and was pressed at 200 kgf / c by the pressing means 26.
Apply m ² pseudo isotropic pressure. And 700 by heater 23
Heat to ° C. At this time, the temperature of the coil-shaped compact A 'is measured by the thermocouple 24. When the coil-shaped compact A 'was heated to the above-mentioned temperature, heat generation due to intermetallic compound formation by self-combustion sintering was observed. The gas may be pressurized using gas, powder or liquid by HIP or HP, or may be mechanically pressurized.

After the intermetallic compound is formed, the compact A 'is maintained at 900 ° C. while maintaining the above pressure, and the heat treatment step 7 is performed for 2 hours. By performing this heat treatment step 7, the pores contained in the compact A 'can be further reduced, the uniformity of the structure can be promoted, and the impurity can be diffused or removed.

Through the above series of steps, the wire diameter is 1 mm and the average coil diameter is 12
A coil spring mainly composed of an intermetallic compound having a diameter of 10 mm and a winding number of 10 was obtained. Coil springs, from the results of X-ray analysis of the Al ₃ Ti Ti
-It was found that it was composed of an Al-based intermetallic compound. This coil spring completely maintained its original shape even after unloading after being subjected to a compression deformation of 5 mm at 700 ° C., and it was confirmed that the coil spring exerted a good spring action.

The finishing step 8 may be performed on the coil spring obtained through the above manufacturing steps. For example, the surface of the spring is made smooth by barrel processing. Alternatively, the surface of the spring is polished by machining, or the shape is corrected by removing or cutting or grinding a surface flaw or surface layer. Further, by performing shot peening to generate a compressive residual stress in the surface layer portion of the spring, the durability of the spring can be further increased.

[Effect of the Invention] According to the present invention, an elastic member mainly composed of a Ti-Al-based intermetallic compound, which has conventionally been considered difficult or impossible to manufacture, is easily and accurately formed into a desired shape. Therefore, application to a spring shape that requires large plastic working such as a coil spring, for example, is also facilitated.

In addition, a dense Ti-Al-based intermetallic compound having a low porosity and having almost no pores in the surface layer can be obtained. In particular, regarding the most important bending workability when forming a spring, a mixed pressure-bonded body obtained by a conventional processing method (extrusion, rolling, drawing, etc.) did not provide sufficient adhesion and contained many defects such as pores. On the other hand, in the present invention, by performing preforming by swaging processing, it becomes possible to impart excellent workability not found in conventional intermetallic compound materials, and application to coil springs and the like is also possible. It is now possible.

[Brief description of the drawings]

FIG. 1 is a process explanatory view showing one embodiment of the method of the present invention, and FIG.
The figure is a perspective view showing an example of a swaging machine, FIG. 3 is a perspective view of an apparatus for coiling a mixed press-bonded body, FIG. 4 is a cross-sectional view of a heating apparatus, and FIG. 5 is a cross-sectional area having an outer diameter of φ19 mm to φ18 mm. Reduce the microstructure of the reduced mixed crimp body with a microscope 400
FIG. 6 is a photograph of the same metal structure as in FIG. 5 magnified 1000 times with a microscope, FIG. 7 is a photograph of a metal structure reduced to φ4 mm with a microscope 400 times magnified, 8
The figure is a photograph of the same metal structure as in FIG. 7 magnified 1000 times with a microscope, FIG. 9 is a photograph of a metal structure reduced in diameter to φ1 mm 400 times with a microscope, and FIG. 10 is the same as FIG. It is a photograph which expanded the metal structure by 1000 times with a microscope. A: mixed pressure-bonded body, A ': molded body, 9: swaging machine, 10: molding device, 20: heating device.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor: Toyoyuki Higashino 1 Shinisogocho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture, Nikka Group Research Institute, Inc. (56) References JP-A-63-247321 (JP, A) JP-A-62-99425 (JP, A) JP-A-61-270353 (JP, A) JP-A-52-69293 (JP, A) JP-A-48-103407 (JP, A) JP-A-52-33811 (JP, A) Japanese Patent Publication No. 57-10526 (JP, B2)

Claims (2)

(57) [Claims] A wrapping member is filled with a raw material containing Ti and Al mixed at a composition ratio to form a Ti-Al-based intermetallic compound, and the raw material is preformed by swaging to thereby reduce the raw material from one end side. A swaging step of sequentially reducing the cross-sectional area toward the other end to obtain a mixed pressure-bonded body, and after the swaging step, the mixed pressure-bonded body is formed into a desired shape, and then a Ti-Al-based intermetallic compound is formed. A method for producing an elastic member mainly comprising an intermetallic compound, wherein the elastic member is treated under a temperature condition. 2. The Ti-Al based intermetallic compound according to claim 1, wherein the cross-sectional area of the mixed pressure-bonded body is reduced by swaging until the porosity of the mixed pressure-bonded body becomes 5% or less. A method for manufacturing an elastic member.