JP2003049658A - Manufacturing method for preform of variable vane in vgs(variable geometry system) type turbocharger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new manufacturing method actually providing a preform of a variable vane into a near net shape by a precise casting and a metal injection molding method. SOLUTION: When the preform of the variable vane 1 is formed by the precise casting, it is characterized in that a blank material using a heat-resistant metal as a primary base metal is applied thereto and various contents of C, Si, and O contained in the blank material are optimized so as to improve fluidity of molten metal. When the preform of the variable vane 1 is formed by the a metal injection molding method, it is characterized in that burning is performed so as to finely and uniformly product independent bubbles and the injection molded preform is treated by hot hydrostatic pressure pressing so as to heighten the density of the preform.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a turbocharger used in an automobile engine or the like,
In particular, when manufacturing a prototype (form material) of a variable blade to be incorporated in this product, the present invention relates to a novel manufacturing method capable of finishing a so-called near net shape, which is closer to the actual product in shape and size.

[0002]

BACKGROUND OF THE INVENTION A turbocharger is known as a supercharger used as a means for increasing the output and improving the performance of an automobile engine. This turbocharger drives a turbine by the exhaust energy of the engine, It is a device that rotates the compressor by the output and brings the engine into a supercharged state that is higher than natural intake. By the way, in this turbocharger, when the engine is rotating at a low speed, the exhaust turbine hardly works due to a decrease in the exhaust flow rate, and therefore, in the case of an engine that can rotate up to a high rotation range, the turbine has a feeling of rattling until it rotates efficiently, It was inevitable that the so-called turbo lag, etc., required for the subsequent blowing up of the air all at once. Also, the diesel engine, which has a low engine speed, has a drawback that it is difficult to obtain a turbo effect.

For this reason, a VGS type turbocharger has been developed which operates efficiently even in a low rotation range. This is a device in which a small exhaust flow rate is narrowed down by variable blades (blades), the speed of exhaust is increased, and the work of the exhaust turbine is increased, so that high output can be exhibited even at low speed rotation. Therefore, the VGS type turbocharger requires a variable blade variable mechanism and the like, and the peripheral components also have to be more complicated in shape and the like than the conventional ones. When manufacturing a variable blade for a VGS type turbocharger, first, a metal material (a raw material that is a prototype of the variable blade) in which a blade portion and a shaft portion are integrally formed is formed. Is appropriately cut to finish it into a desired shape and size.

Incidentally, in forming the above-mentioned variable blade material, there are methods such as a precision casting method typified by lost wax casting and a metal injection molding method. And by using such a method, if the raw material is finished in a so-called near net shape that is closer to the finished product in both shape and size, post-processing becomes extremely easy, and the efficiency of processing and the reduction of the number of steps are reduced. It can be achieved. In other words, by finishing the material to the net shape as much as possible,
For example, if the shaft portion of the blank is then rolled to a desired diameter, the rolling allowance is small, and the axial elongation associated with the rolling is suppressed as much as possible to correct the axial elongation. It is also possible to eliminate the cutting process. Furthermore, it becomes possible to mass-produce variable blades while maintaining a high quality level and dimensional accuracy level.

However, the following problems have been encountered in forming the variable blade material by the precision casting method or the metal injection molding method. First, when obtaining a base material by the precision casting method, there is a problem that the dimensional accuracy of the base material is not good and varies because, for example, it is difficult to maintain good molten metal flowability of the molten metal to be cast. . Also, when the cast molten metal solidifies, its crystal grains grow or expand, and during post-processing such as rolling, sharp edges (the rolling of the shaft causes plastic flow of the metal material on the surface of the shaft, There is a problem that it is easy to form an acute angle portion formed in a protruding state from the tip of the shaft. On the other hand, in obtaining the base material by the metal injection molding method, there is a problem that a relatively large number of fine voids are present as compared with the solid material and the porosity is high. In particular, heat-resistant high alloys have an insufficient bulk density, which causes a problem of low high-temperature rotary bending fatigue resistance.

From the above, it is extremely difficult to finish the material of the variable blade into a near net shape by the precision casting method, the metal injection molding method, etc. until the variable blade is actually mass-produced at a stable and high level. At present, the stage has not been reached, and there has been a demand for overcoming the above problems in order to realize mass production. In recent years, particularly in diesel vehicles, the exhaust gas discharged into the atmosphere is strongly regulated from the viewpoint of environmental protection and the like, and NO _x and particulate matter ( It has been earnestly desired to mass-produce a VGS type turbocharger that can improve the efficiency of the engine even in a low rotation range in order to reduce PM).

[0007]

The present invention has been made in view of such a background, and it solves the problems of the precision casting method and the metal injection molding method described above. This is an attempt to develop a new manufacturing method that can actually obtain a variable wing element in a near net shape.

[0008]

That is, in the method for manufacturing the variable blade material in the VGS type turbocharger according to the first aspect of the present invention, the shaft portion serving as the center of rotation and the flow rate of the exhaust gas are substantially adjusted. With a wing part, the relatively small amount of exhaust gas exhausted from the engine is appropriately narrowed down, the speed of the exhaust gas is amplified, the exhaust turbine is rotated by the energy of the exhaust gas, and the compressor directly connected to this exhaust turbine is used for more than natural intake. VG that sends the air of the engine to the engine so that the engine can show high output even at low speed rotation.
When manufacturing variable blades to be incorporated in an S type turbocharger, the process of obtaining the raw material that is the prototype of the variable blade by integrally having the blade and the shaft portion realizes the raw material with high accuracy. It is performed by the precision casting method to be obtained. In casting, a virgin material containing heat-resistant steel (alloy) as a main base material is applied, and C, Si, and O contained in this virgin material are applied.
% By weight of 0.05-0.5%, 0.5-1.5
%, 0.01 to 0.1% to improve the molten metal flowability of the molten metal cast into the mold. According to the present invention, when a variable blade material is obtained by precision casting, the amount of C (carbon), Si (silicon) and O (oxygen) contained in the virgin material is adjusted and cast into a mold. Since the molten metal flowability of the raw material is improved, it is possible to obtain a precise shaped material due to its shape and size, and it is possible to suppress the variation of individual shaped materials within a smaller range.

According to a second aspect of the present invention, in addition to the requirements of the first aspect, in the method for producing a variable blade element for a VGS type turbocharger, in the casting, either a mold or an element is used. One or both of them is cooled to shorten the time from casting the molten metal to crushing the mold, and refining the solidified structure of the raw material. According to the present invention, since a shaped material having fine crystal grains can be obtained, for example, when the shaft portion of the shaped material is subsequently subjected to rolling processing, a sharp edge is less likely to occur, and the shape and size are more accurate. Highly shaped materials and variable blades as a finished product can be realized.

According to the third aspect of the present invention, in addition to the requirements of the first or second aspect of the present invention, in the method for producing a variable blade element material for a VGS type turbocharger, in the casting, the molten metal cast into the die is used. 1 out of Pb, Se, Te
One or more species are added, and a large amount of O and S is contained within the range in which the presence of non-metallic inclusions is not a problem. According to this invention, Pb (lead), Se (selenium), Te (tellurium)
It is possible to improve the rolling property and the machinability of the material (the cutting here means polishing mainly performed in the post-processing) and the like by appropriately adding the above. Further, it is possible to improve the flowability of molten metal in casting by intentionally adding non-metallic inclusions such as O (oxygen) and S (sulfur), which are generally preferred to be less in steel materials.

According to a fourth aspect of the present invention, in addition to the requirements of the first, second or third aspect of the present invention, the method for producing a variable blade component in a VGS type turbocharger is characterized in that, in the casting, a molten metal cast into a die. Is higher than the melting point, and is cast in a state where the viscosity is lower than the melting point temperature. According to the present invention, the molten metal to be cast into the mold is heated to a temperature equal to or higher than the melting point and is cast in a state where the viscosity is lowered, so that the flowability of the raw material can be further improved. The viscosity of the molten metal has a high temperature dependency near the melting point, and the higher the temperature, the lower the viscosity.
For example, in a high temperature range of about 30 ° C. or higher from the melting point, the temperature dependence is low, and even if heated, the viscosity does not decrease so much. Therefore, in the present embodiment, the effect of decreasing the viscosity and the heating cost are increased. In consideration of the above, as an example, from the melting point to about 30 ° C.,
It is cast at a high temperature.

A method of manufacturing a variable blade material for a VGS type turbocharger according to a fifth aspect of the present invention includes a shaft portion that serves as a center of rotation and a blade portion that substantially adjusts the flow rate of exhaust gas. The relatively small amount of exhaust gas discharged from the engine is appropriately narrowed down, the speed of the exhaust gas is amplified, the exhaust turbine is rotated by the energy of the exhaust gas, and air that is more than naturally aspirated is sent to the engine by the compressor directly connected to this exhaust turbine. When manufacturing a variable blade that is incorporated in a VGS type turbocharger that enables the engine to exhibit high output even at low speed rotation, it has a blade portion and a shaft portion integrally, and has the original shape of the variable blade. The step of obtaining the shaped material is performed by a metal injection molding method in which metal powder having plasticity is injected into a mold to be solidified,
In injection molding, sintering is carried out so that closed bubbles, which are spherical gaps between metal particles, are finely and uniformly generated, and then hot isostatic pressing is performed on the injection-molded material. (HIP treatment) is performed to increase the density of the base material. According to this invention, the porosity of the metal material obtained by metal injection molding is reduced, and the strength of the raw material can be increased. That is, the high porosity, which is one of the drawbacks of metal injection molding, can be improved, and the material formed by injection molding can be actually applied. Further, due to the reduced porosity, the dimensional accuracy is improved, and the shaped material to be molded can have a near net shape closer to the target variable blade. Therefore, the rolling allowance in the post-processing can be further suppressed, and simplification of the rolling process can be achieved.

Further, in the method for manufacturing a variable blade material for a VGS type turbocharger according to a sixth aspect, in addition to the requirements according to the fifth aspect, in the metal injection molding, the shape of a metal powder as a raw material is changed. It is characterized in that it is made spherical and fine, and the high temperature rotary bending fatigue property of the base material is improved. According to this invention, the high temperature rotary bending fatigue of the metal material obtained by injection molding is improved. That is, it is possible to overcome high-temperature rotary bending fatigue, which is one of the drawbacks of metal injection molding, and to make a method for forming a blank by injection molding a reality.

According to a seventh aspect of the present invention, in addition to the requirements of the fifth or sixth aspect of the present invention, the method for producing a variable blade component in a VGS type turbocharger is characterized in that, in the metal injection molding, a raw material is used before sintering. It is characterized by reducing the particle surface of the metal powder. According to this invention, the surface of the metal particles is reduced and the oxide on the surface of the particles is removed before sintering, so that the sinterability is improved. Further, the effect of the hot isostatic pressing treatment is increased, which greatly contributes to the reduction of the porosity of the raw material.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below based on the illustrated embodiments. In the description, while explaining the exhaust guide assembly A in the VGS type turbocharger to which the variable vane 1 which is the object of the present invention is applied, the variable vane 1 will also be described, and then the variable vane of the present invention will be described. The manufacturing method of the blank 1 will be described. The exhaust guide assembly A adjusts the exhaust gas flow rate by appropriately narrowing the exhaust gas G when the engine is rotating at a low speed. As an example, as shown in FIG.
A plurality of variable blades 1 provided on the outer periphery of the exhaust turbine T for substantially setting the exhaust flow rate, a turbine frame 2 for rotatably holding the variable blade 1, and a variable blade for appropriately setting the flow rate of the exhaust gas G. It comprises a variable mechanism 3 for rotating 1 at a constant angle. Each component will be described below.

First, the variable blade 1 will be described. As an example, as shown in FIG. 1, a plurality of these are arranged in an arc shape along the outer periphery of the exhaust turbine T (one exhaust guide assembly A
Approximately ten to fifteen of them are disposed, and each of them is rotated by approximately the same degree to appropriately adjust the exhaust gas flow rate. Each variable blade 1 comprises a blade portion 11 and a shaft portion 12. The blade portion 11 is formed so as to have a constant width mainly according to the width dimension of the exhaust turbine T, the cross-section in the width direction thereof is formed into a substantially blade shape, and the exhaust gas G is effectively exhaust turbine. It is configured to go to T. Here, the width dimension of the blade portion 11 is referred to as a blade height h for convenience. In addition, the shaft portion 12 is formed so as to be continuous with the wing portion 11 integrally, and is a portion corresponding to a rotating shaft when the wing portion 11 is moved.

At the connecting portion between the blade portion 11 and the shaft portion 12, there is provided a taper portion 13 that narrows from the shaft portion 12 toward the blade portion 11, and a flange portion 14 having a diameter slightly larger than that of the shaft portion 12. Are formed to be continuous. The bottom surface of the collar portion 14 is formed substantially on the same plane as the end surface of the blade portion 11 on the shaft portion 12 side, and this plane serves as a sliding surface when the variable blade 1 is attached to the turbine frame 2, The smooth rotating state of the blade 1 is ensured. Furthermore, at the tip of the shaft 12,
A reference surface 15 is formed which serves as a reference for the mounting state of the variable blade 1. The reference surface 15 is a portion fixed to the variable mechanism 3 described later by crimping or the like, and as an example, FIG.
As shown in FIG. 2, the plane in which the shaft portion 12 is cut out in a facing manner is formed with a substantially constant inclination with respect to the blade portion 11.

Next, the turbine frame 2 will be described. This is configured as a frame member that rotatably holds a plurality of variable blades 1. As an example, as shown in FIG. 1, the variable blade 1 is sandwiched by a frame segment 21 and a holding member 22. Is configured as follows. The frame segment 21 is provided with a flange portion 23 that receives the shaft portion 12 of the variable blade 1 and a boss portion 24 that fits the variable mechanism 3 described later on the outer circumference. Due to such a structure, the flange portion 23 is formed with the same number of receiving holes 25 as the variable blades 1 at the peripheral portion at equal intervals. Further, the holding member 22 is formed in a disk shape having an opening in the central portion as shown in FIG. The dimension of the variable blade 1 sandwiched between the frame segment 21 and the holding member 22 is substantially constant (generally, the blade width of the variable blade 1 is approximately constant so that the blade portion 11 of the variable blade 1 can always be smoothly rotated. The caulking pins 26 are provided at four places on the outer peripheral portion of the receiving hole 25 as an example.
The dimension between both members is maintained by. Here, the holes formed in the frame segment 21 and the holding member 22 to receive the crimping pins 26 are referred to as pin holes 27.

In this embodiment, the flange portion 23 of the frame segment 21 has two flange portions, that is, a flange portion 23A having substantially the same diameter as the holding member 22 and a flange portion 23B having a diameter slightly larger than the holding member 22. , Which are made of the same material,
In the case where processing with the same member becomes complicated, it is also possible to form two flange portions having different diameters by dividing them and then to join them by caulking or brazing.

Next, the variable mechanism 3 will be described. This is provided on the outer peripheral side of the boss portion 24 of the turbine frame 2 and rotates the variable blade 1 in order to adjust the exhaust flow rate. As an example, as shown in FIG. The variable blade 1 includes a rotating member 31 that causes the variable blade 1 to rotate, and a transmission member 32 that transmits the rotation to the variable blade 1. The rotating member 31 is formed in a substantially disc shape with an opening in the central portion as shown in the figure, and the same number of transmitting members 32 as the variable blades 1 are provided at equal intervals on the peripheral portion thereof. The transmission member 32 includes a drive element 32A rotatably attached to the rotating member 31 and the variable blade 1.
Element 32 fixedly mounted on the reference plane 15 of the
B is included, and the rotation is transmitted in a state where the drive element 32A and the passive element 32B are connected. Specifically, a rectangular piece-shaped drive element 32A is rotatably pinned to the rotating member 31, and a passive element 32B formed in a substantially U shape so as to receive the drive element 32A is variable. Fixed to the reference surface 15 at the tip of the wing 1, and the square-piece-shaped drive element 32A is replaced by the U-shaped passive element 32.
The rotation member 31 is fitted in the B and is engaged with both.
Is attached to the boss portion 24.

In the initial state in which a plurality of variable vanes 1 are attached, in order to align them in a circumferential shape, each variable vane 1 and the passive element 32B need to be attached at a substantially constant angle. In the above embodiment, the reference surface 15 of the variable vane 1 mainly plays this role. Further, when the rotating member 31 is simply fitted in the boss portion 24, when the rotating member 31 is slightly separated from the turbine frame 2,
Since there is concern that the engagement of the transmission member 32 may be released, in order to prevent this, a ring 33 or the like is provided so as to sandwich the rotating member 31 from the opposite side of the turbine frame 2,
The rotation member 31 is given a tendency to be pressed toward the turbine frame 2 side. With such a configuration, when the engine rotates at a low speed, the rotating member 31 of the variable mechanism 3 is appropriately rotated, and the shaft portion 12 is moved through the transmission member 32.
And the variable blade 1 is rotated as shown in FIG. 1, the exhaust gas G is appropriately narrowed, and the exhaust flow rate is adjusted.

An example of the exhaust guide assembly A to which the variable vane 1 which is the object of the present invention is applied is constituted as described above, and hereinafter, a method for manufacturing a raw material which is a prototype of the variable vane 1 will be described. Will be described. It should be noted that this raw material is a metal material that integrally has the blade portion 11 and the shaft portion 12 in a state before completion, and is appropriately subjected to rolling processing, polishing processing, and the like to obtain the target variable blade. 1 to form 1. Further, as the material of the base material, a metal material having heat resistance such as SUS310S is applied. Here, in the present invention, a raw material is obtained by a precision casting method or a metal injection molding method. Hereinafter, regarding the manufacturing method, the precision casting method will be described in [Embodiment 1] and the metal injection molding method will be described in [Embodiment 1]. 2].

[First Embodiment] Precision Casting Method The precision casting method is generally a method capable of realizing a cast product (form material) with high accuracy, and the lost wax method is applied here as an example. In the lost wax method, a wax model prototype having the same shape as that of the product to be cast is generally formed first, a refractory coating layer is formed around this wax model prototype, and then the whole is heated to leave only the wax model. Start melting
A mold (coating layer) is produced, and a mold faithful to the intended product is obtained by such a method, and the cast product is reproduced with high accuracy.

In addition to the lost wax method described above, the precision casting method includes the show process method and the CADIC method, and these methods are also applicable. By the way, the show process method is to knead a liquid alkyl silicate binder and a powdery refractory material to form a raw mold, and rapidly dry the raw mold to prevent cracks caused by the drying. It is a method that is generated as invisible fine hair cracks to prevent overall shrinkage and deformation of the mold.

As described above, in the precision casting method, a mold is formed so as to have a shape and a size that are substantially the same as a target product (here, the variable blade 1), and a cast product (material that is extremely faithful to the target product). Shaped material) can be reproduced with high accuracy. However, even with such a precision casting method, it is difficult to finish the raw material into a near net shape as it is,
In order to obtain the variable blade 1 having the desired shape and accuracy, there is a defect that the dimensional accuracy of the cast blank is still insufficient and varies. In addition, there is also a drawback that sharp edges are easily formed when post-processing such as rolling is performed on the material. Therefore, in the present invention, the following technical innovations are appropriately applied during casting.

First, in order to improve the molten metal flowability of the molten metal cast into the mold, a virgin material containing a heat-resistant metal as a main base material is applied, and C (carbon) and S contained in this virgin material are applied.
Optimize i (silicon) and O (oxygen) amounts. Specifically, a material (virgin material) made by direct reduction from iron sand or iron ore is applied without passing through a scraping process, and the amount of each of C, Si, and O is 0. 05-0.5
%, 0.5-1.5%, 0.01-0.1% (respectively by weight) to improve the flowability of molten metal and the shape and dimensional accuracy of the base material, and roll it. It also aims to improve the sex. Incidentally, the amount of each element is adjusted while monitoring the amount of analytical variation in the electric furnace.

In the casting, either one or both of the mold and the base material is rapidly cooled to shorten the time until the crushing of the mold and to make the solidified structure of the base material fine. Specifically, for example, before and after casting, water is sprayed on the mold to cool it, and the time required for crushing the mold is shortened to, for example, 1 hour or less (normal air cooling takes 1 to 4 hours). At this time, only the mold is cooled in the pre-cooling before the casting, and both the mold and the base material are cooled in the cooling after the casting. Needless to say, the quenching is performed within a range in which the mold does not cause thermal stress cracking. If it is not necessary to cool before and after casting, either one may be used, or if it is desired to further enhance the cooling effect, in addition to cooling both before and after casting, the material removed from the mold It is also possible to spray cooling water on.

By the technical device (rapid cooling) as described above, the solidification structure of the base material is, for example, 50 to 200.
Can be miniaturized to μm (approx. 100-500μ with normal air cooling)
(m solidified particles of m) and subsequent processing such as rolling, it is difficult to generate a sharp edge due to the effect of uniform deformation strain, and rolling processing is facilitated.

Furthermore, the molten metal cast in the mold contains Pb.
One or more of (lead), Se (selenium), and Te (tellurium) are added, and a large amount of O (oxygen) and S (sulfur) is contained as long as the presence of nonmetallic inclusions does not interfere. It is what makes me. Specifically, Pb is 0.01 to
0.1%, Se 0.01-0.1%, Te 0.01
.About.0.1% (each by weight), O is 0.02 to 0.1%, and S is 0.005 to
The amount of the components is 0.5% (each weight%). The addition of Pb, Se, Te, etc. is to improve the rolling property and machinability (mainly showing polishing) of the base material, and the addition of O, S, etc. is for hot water. This is to improve the flowability. By the way, regarding the melt flowability, it has been confirmed by the present applicant that the viscous flowability of the Stokes flow is improved by at least 20 to 40%.

Further, in casting, the molten metal is to be cast into a mold while being heated to a temperature higher than the melting point and having a viscosity lower than the melting point temperature.
Taking a (iron) -based heat-resistant material as an example, FIG. 3 shows the relationship between temperature (displayed by the heating condition relative to the melting point) and viscosity. The molten metal flowability (standard value) described in this figure indicates the fluidity of the molten metal, and corresponds to the viscosity. From this figure, it can be seen that the viscosity of the molten metal has a high temperature dependence near the melting point, and the higher the temperature of the material, the lower the viscosity. It can be seen that the temperature dependence of the viscosity is weakened and the viscosity does not decrease so much even when heated. Therefore, in the present embodiment, considering the effect of decreasing the viscosity and the cost of heating,
As an example, the material is cast at a high temperature of about 30 ° C. from the melting point.

[Embodiment 2] Metal Injection Molding Method Metal injection molding is substantially the same as the conventionally known general synthetic resin (plastic) injection molding. For example, metal powder such as iron or titanium. A binder (mainly an additive for binding metal powders together, which is a mixture of polyethylene resin, wax, and phthalate ester as an example) is kneaded with (material) to impart plasticity. Then, the material to which the plasticity is imparted is injected into a mold, hardened into an appropriate shape, the binder is removed, and then sintered to obtain a raw material having a desired shape.

As described above, the metal injection molding can obtain a molded product (form material) that is almost faithful to the target product (the variable blade 1 here) as in the precision casting method. However, the porosity of the formed raw material is higher than that of the solid material, and particularly in the case of heat-resistant and high-alloy materials, there are drawbacks such as insufficient bulk density and poor high-temperature bending fatigue resistance. It was Here, the vacancy is a kind of cavity (a large number of aggregates of point defects, which are integrated to form fine cracks) in a crystal of a metal material, etc. If this ratio is too high, the metal It has a negative effect on the material. For this reason, in the present invention, the following technical ideas are appropriately applied in metal injection molding.

First, in order to make the closed cells (spherical gaps between metal particles) small and uniform, sintering is performed for a long time. Specifically, for example, the melting point is 1500 ° C.
When SUS310S is applied, it is 1300 ℃
The sintering is performed for a relatively long time of about 2 hours. By performing such sintering, the porosity of the raw material is reduced,
Although the bulk density can be improved, HIP treatment (Hot Isostatic) is applied to the injection-molded material.
Abbreviation of Pressing; hot isostatic pressing treatment) is performed to further improve the bulk density. Specifically, while heating the molding material to, for example, about 1300 ° C., a pressure of about 100 MPa (1000 atmospheric pressure) is isotropically applied to the molding material.

By the above-mentioned sintering or HIP treatment, the closed cells, which were about 100 μm before sintering, become about 10 μm after sintering, and the bulk density is improved by about 5%.
Confirmed by the applicant. And by improving this bulk density, it is possible to increase the strength of the raw material,
The dimensional accuracy is improved, and a near net shape material can be obtained. In addition, when sintering the metal powder, for precipitation-hardening heat-resistant materials such as SUH660, γ '
(It is called gamma prime and represents an intermetallic compound of Ni ₃ (Al, Ti)) By rapid heating, it suppresses the growth and miniaturizes it. This is to suppress the overaging phenomenon in a high temperature environment, and the rapid heating method at this time is preferably induction heating in which a heating current is generated by electromagnetic induction.

Further, in the present embodiment, a technical device for making the metal powder for injection molding spherical and fine and improving the high temperature rotary bending fatigue resistance of the molded blank is also taken.
Here, in making the metal powder spherical and fine, for example, molten metal is ejected from a nozzle, and a high-speed fluid such as air or water is made to act on this, and the metal is divided into a large number of droplets by the impact force of the high-speed fluid. Then, a so-called air atomizing method or water atomizing method, in which the metal powder is obtained by cooling and solidifying, is applied. And in such an atomizing method, by appropriately changing the shape and diameter of the nozzle for ejecting the molten metal, the discharge rate of air or water acting on the molten metal, the cooling rate, etc., the metal of the desired size can be obtained. A powder is obtained. By the way, SUS310
It has been confirmed by the applicant of the present invention that when the metal powder of S is pulverized to about 200 μm and sintered, the high temperature rotary bending fatigue property is improved by about 20%.

Furthermore, in performing metal injection molding, the surface of the metal material before sintering is reduced, and specifically, a gas such as hydrogen, ammonia, carbon monoxide, etc., which brings about a reducing atmosphere, is added to the metal particles. It is reduced by flowing it on the surface of and contacting it. This removes oxides on the surface of the metal particles, improves the sinterability, and increases the effect of hot isostatic pressing,
It greatly contributes to the reduction of porosity.

[0037]

According to the first aspect of the present invention, when precision casting is performed, a virgin material having an appropriate content of C, Si and O is applied, so that the flowability of molten metal is improved and A net shape element can be formed.

According to the second aspect of the present invention, the solidified particles of the base material are made extremely fine, and the shaft portion 1 of the base material is later formed.
When 2 is rolled, sharp edges are less likely to occur,
It facilitates the rolling process.

Further, according to the invention of claim 3, since Pb, Se, Te, O, and S are appropriately added to the raw material to be cast, the flowability of the molten metal is improved and the raw material Rollability and machinability (polishing) can be improved.

Further, according to the invention of claim 4, the raw material is heated to a temperature equal to or higher than the melting point and cast in a state where the viscosity is lower than the melting point temperature, so that the flowability of the molten metal can be further improved.

Further, according to the invention of claim 5, in the shaped material sintered after metal injection molding, the pores between the metal particles are effectively reduced and spherical independent bubbles are formed.
By the P treatment, such pores can be further reduced, and a higher density of the raw material can be achieved.

According to the sixth aspect of the invention, since the particles of the metal powder to be injection-molded are spherical and fine, the high-temperature rotary bending fatigue property of the raw material to be a molded product is remarkably improved. .

Further, according to the invention of claim 7, the surface of the metal particles as a raw material is reduced in the stage before the molding to remove the oxide on the surface of the particles, so that the sinterability is improved and the HIP treatment is carried out. The effect of is increased and contributes greatly to the reduction of the porosity of the raw material.

[Brief description of drawings]

FIG. 1 is a perspective view (a) showing a VGS type turbocharger incorporating a variable vane according to the present invention, and an exploded perspective view (b) showing an exhaust guide assembly.

FIG. 2 is a front view and a left side view showing a variable vane according to the present invention.

FIG. 3 is a graph showing the relationship between temperature and viscosity in Ni-based heat-resistant materials and Fe-based heat-resistant materials.

[Explanation of symbols]

1 variable wings 2 turbine frame 3 variable mechanism 11 wings 12 Shaft 13 Tapered part 14 Tsubabe 15 Reference plane 21 frame segments 22 Holding member 23 Flange 23A Flange (small) 23B Flange (large) 24 Boss 25 receiving hole 26 Caulking pins 27 pin hole 31 Rotating member 32 transmission member 32A drive element 32B passive element 33 ring A Exhaust guide assembly G exhaust gas h blade height T exhaust turbine

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yukio Takahashi             4-38-2 Fukuodai, Sodegaura-shi, Chiba Cosmo             Sodegaura No. 106 F-term (reference) 3G005 EA15 FA43 GB25 KA03 KA07                       KA09

Claims (7)

[Claims] 1. A shaft having a center of rotation and a wing that substantially adjusts a flow rate of exhaust gas, and appropriately narrows a relatively small amount of exhaust gas discharged from an engine to amplify the speed of the exhaust gas. VGS type that rotates the exhaust turbine with the energy of the exhaust gas, and sends the air more than naturally aspirated to the engine by the compressor directly connected to this exhaust turbine, so that the engine can exhibit high output even at low speed rotation. In manufacturing variable blades to be incorporated into the turbocharger, the process of obtaining the raw material that is the prototype of the variable blade by integrating the blade and the shaft is a precision process that can realize the raw material with high accuracy. It is performed by the casting method. When casting, a virgin material containing heat-resistant steel (alloy) as a main base material is applied, and C contained in this virgin material is
The weight% of each of Si and O is 0.05 to 0.5%, 0.5
To 1.5% and 0.01 to 0.1% so as to improve the flowability of the molten metal cast into the mold, and to manufacture the variable blade component in the VGS type turbocharger. Method. 2. In the casting, either one or both of the mold and the raw material is cooled to shorten the time from the casting of the molten metal to the crushing of the die, and the solidification structure of the raw material. The method for manufacturing a variable blade element material in a VGS type turbocharger according to claim 1, characterized in that: 3. In the casting, one or more kinds of Pb, Se, and Te are added to the molten metal to be cast in the mold, and O and S are increased to the extent that non-metallic inclusions may exist. 3. The method for manufacturing a profile material of a variable blade in a VGS type turbocharger according to claim 1 or 2, characterized in that 4. The casting according to claim 1, wherein the molten metal to be cast into the mold is raised to a temperature equal to or higher than the melting point and the viscosity is lowered below the melting point temperature.
Alternatively, the method of manufacturing a variable blade element material in the VGS type turbocharger according to the item 3. 5. An exhaust gas velocity is amplified by appropriately squeezing a relatively small amount of exhaust gas emitted from an engine, comprising a shaft portion that is a center of rotation and a blade portion that substantially adjusts the flow rate of exhaust gas. VGS type that rotates the exhaust turbine with the energy of the exhaust gas, and sends the air more than naturally aspirated to the engine by the compressor directly connected to this exhaust turbine, so that the engine can exhibit high output even at low speed rotation. In manufacturing variable blades to be incorporated into the turbocharger of, the process of obtaining the raw material that is the prototype of the variable blades by integrally forming the variable blades in the mold has metal blades with plasticity added in the mold. It is carried out by a metal injection molding method of injecting and solidifying, and in the injection molding, baking is performed so that independent bubbles that are spherical gaps between metal particles are finely and uniformly generated. VGS type turbocharger characterized by subjecting the injection-molded material to hot isostatic pressing (HIP processing) to increase the density of the material. Method for manufacturing variable blade in. 6. The metal injection molding according to claim 5, wherein the shape of the metal powder as a raw material is made spherical and fine so as to improve the high temperature rotary bending fatigue property of the raw material. A method of manufacturing a variable blade material in a VGS type turbocharger. 7. The material for forming a variable blade in a VGS type turbocharger according to claim 5, wherein in the metal injection molding, the particle surface of the metal powder as a raw material is reduced before sintering. Manufacturing method.