JP2011195844A - Method for manufacturing shaft for turbine rotor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a shaft for a turbine rotor, which makes it possible to ensure that the dimensions of a flange, the dimensions of a shaft part, the squareness of the flange with respect to the shaft part, circular runout, and circularity are within a desired accuracy, without the need for a cutting operation.SOLUTION: With respect to target values of a final product, flanges (3a, 3b) have an outer diameter tolerance ranging from +0.0% to +0.6%, and a thickness tolerance ranging from -8% to -0.0%, a shaft part (2) has a diameter tolerance ranging from +0.0% to +0.6%, the circular runout tolerance is 0.5 mm or less, and the squareness tolerance of the flanges with respect to the shaft part is 0.5 mm or less. The method includes a step of pressing a sintered compact having sintered density that is equal to or greater than a relative density of 95%. In the pressing step, the sintered compact is pressed using an upper mold and lower mold having the shape of the shaft for the turbine rotor which has been split into two equal parts along the surface including the axis of rotation. In this case, after a first pressing operation is performed, the phase is shifted through no more than 120° to perform a second pressing operation, after which subsequent pressing operations are performed with the phases being sequentially shifted through no more than 120° till it is rotated by ≥360°.

Description

  The present invention relates to a method for manufacturing a shaft for a turbine rotor incorporated in a turbocharger used in an automobile engine or the like. More specifically, a sintered product obtained by metal powder injection molding (MIM method) is pressed with a mold that corrects the shaft diameter and flange thickness and outer diameter, and the shaft diameter and flange diameter are reduced without cutting. The present invention relates to a method for manufacturing a turbine rotor shaft capable of keeping thickness, outer diameter, roundness, circumferential runout tolerance, and the like within a predetermined range.

  Turbochargers used in automobile engines, etc., amplify the exhaust gas flow rate so that the engine can efficiently obtain output even at low speed rotation, and the exhaust side turbine rotates using this exhaust energy. Therefore, the intake side turbine directly connected to the exhaust side turbine is rotated to forcibly take air into the engine.

  Conventionally, the turbine rotor shaft has been manufactured by cutting. However, the processing time is very long, and it is very inefficient with about 100 to 500 units per day. Since a lot of material is lost by the cutting work, the ratio of the material cost for the product is increased.

The material of the turbine rotor shaft is nickel, chromium, molybdenum steel (SNCM) or heat resistant steel (SUH).
Any material can be heat-treated to increase its hardness and toughness. In particular, heat-resistant steel is excellent in oxidation resistance at 700 ° C. or higher.

Turbine wheels manufactured by casting must maintain a rotational balance after the turbine rotor shaft is attached. The turbine wheel attached with the shaft is rotated at high speed to measure the shaft runout and cut. Therefore, it is necessary to suppress the shake at the time of rotation, and Patent Document 1 describes a method for measuring the shake measurement of the shaft core. Further, Patent Documents 2, 3, and 4 describe methods for brazing a shaft to a turbine wheel with high accuracy.
As described above, cutting is performed to balance the turbine rotor and balance is achieved. However, it is difficult to expand the production quantity because all of these balances need to be checked and cut, and automation is difficult. In order to improve the yield, there is a problem of how to suppress the shake of the shaft core when attaching the turbine wheel and the shaft.

  Many of the current turbochargers have a bearing structure through oil in order to support a shaft that rotates at high speed, and a flange for providing the bearing structure is required on the shaft portion. By providing the bearing, wear of the bearing portion of the shaft is prevented. Therefore, the dimensional accuracy of the shaft is as high as ± several microns, and manufacturing by machining is essential.

The turbine wheel and shaft are joined by laser welding or brazing. To improve the accuracy of the turbine rotor's circumferential runout after joining, the shape of the joint surface, surface roughness, wheel, The shaft runout is an important factor. In particular, in a turbine rotor shaft, it is necessary to devise to reduce the circumferential runout during joining.
JP 2003-302304 A JP 2005-60829 A JP-A-10-118764 JP 2002-235547 A

  Therefore, in order to solve the above problem, an object of the present invention is to provide a method capable of manufacturing a turbine rotor shaft with high dimensional accuracy only by a pressing method without performing a cutting process.

  As a result of intensive studies to solve the above-mentioned problems, the present inventor prepared a sintered product having a shape approximate to that of the final product, having a certain relationship with the desired final product, and rotated. Turbine rotor shaft with desired dimensional accuracy without cutting by rotating the sintered product multiple times with the upper die and lower die that have the shape that bisects the final product on the surface including the shaft Succeeded in manufacturing the above-mentioned problems.

That is, the present invention
A method of manufacturing a shaft for a turbine rotor having a cylindrical shaft portion and a flange,
Including a step of pressing a sintered product having a shape close to a desired final product with the same mold a plurality of times,
The sintered product is an integrally formed product of a flange and a shaft. The outer diameter of the flange is + 0.0% to + 0.6% and the thickness of the flange is -0.8% with respect to the target value of the final product. ~ -0.0%, shaft diameter is + 0.0% to + 0.6%, circumferential runout tolerance is within 0.5mm, squareness tolerance of flange to shaft is within 0.5mm, and firing The consolidation density is 95% or higher relative density,
The mold is composed of an upper mold and a lower mold having a mold having a shape obtained by dividing the final product into two equal parts in parallel to the axial direction;
In the pressing step, after the sintered product is pressed by the mold, the sintered body is rotated 360 ° by repeating the next press by rotating the sintered body at an angle of 120 ° or less. The press is performed until it rotates as described above.

When performing the pressing process, the sintered product to be pressed is the flange outer diameter, flange thickness, shaft diameter, circumferential runout tolerance, and perpendicularity of the flange with respect to the shaft portion, with respect to the desired final product dimensions. The outer diameter of the flange is compressed by pressing the final product with a die having a shape that is divided into two equal parts in parallel to the axial direction using a sintered product having a tolerance within the above range. Therefore, the flange thickness follows the mold shape, and the desired flange outer diameter, flange thickness, and flange spacing can be achieved. At the same time, the circumferential runout, squareness, and roundness are adjusted by pressing the outer diameter of the entire shaft portion.
Further, after pressing the sintered product, the phase is changed within 120 ° and the next press is performed. Thereafter, the phase is changed within 120 ° and the total rotation is rotated 360 degrees or more to perform the press. Circularity and circumferential runout can be set to desired dimensional accuracy.
In addition, by using a sintered product having a relative density of 95% or more, a shaft for turbine rotor that can fit the dimensional accuracy after pressing into the desired dimensional accuracy and has mechanical strength that can withstand high-temperature use is manufactured. be able to.

  The pressing is preferably performed three times at a rotation angle of 120 ° or four times at a rotation angle of 90 °.

  The sintered product is more preferably a sintered product having a relative density of 98% or more.

  Furthermore, in the manufacturing process of the sintered product, after producing a primary sintered product having a relative density of 94% or more, the relative density is preferably made 98% or more by a hot isostatic pressing method.

  According to the present invention, a turbine rotor shaft with high dimensional accuracy can be manufactured by only pressing a sintered product without performing machining.

  As shown in FIG. 1, a turbine rotor shaft 1 used in a turbocharger has a joint 4 for joining with a turbine wheel 5 and a flange for providing a bearing. Moreover, it has a shape for joining a low temperature turbine wheel to the opposite part of a high temperature turbine wheel. The cross section of the shaft including the flange portion and the shaft portion 2 (surface orthogonal to the rotation axis direction) is circular. As shown in FIG. 1, a joint 4 for joining to a high-temperature turbine wheel is provided at the top of the shaft, and a plurality of flanges (3a, 3b) are usually located just below the joint 4 (usually 2-3). Provided).

  In the manufacture of a shaft for a turbine rotor, it is necessary to first manufacture a sintered product having a shape close to that of a desired final product. This is necessary for the use of powdered metal as a raw material. Using a molding material obtained by adding an amount of an organic binder, a molded body is prepared by molding in advance with a mold in consideration of the shrinkage rate after sintering of the product.

In order to produce a sintered product used in the pressing process,
In the method of adding an organic binder to the metal powder and heating and mixing, then pulverizing or pelletizing to obtain an injection molding material, producing a molded body by injection molding the molding material, and heating and degreasing the obtained molded body,
As the metal material, it is desirable to use a metal material composed of SUH and SNCM having excellent heat resistance, and it is desirable to use a metal powder having an average particle diameter of 1 to 20 μm and a tap density of 3.5 g / m ³ or more.
As the organic binder, thermoplastic resin, paraffin wax, fatty acid-based lubricant, phthalic acid diameter plasticizer is appropriately added according to the shape of the product, the addition ratio is changed, and by heating and mixing with the metal powder, a molding material is obtained, By subjecting this to injection molding, degreasing, and sintering, a sintered product suitable for manufacturing the turbine rotor shaft can be obtained.

The metal used in the turbine rotor shaft has corrosion resistance and is made of a heat-resistant steel metal material. SNCM and SUH are preferable metal materials for producing a sintered product. Especially in SNCM, Cr: 0.6-1.0, Ni: 1.6-2.0, Mo: 0.15-0.3, Mn: 0.6-0.9, C: 0.36-0.43, SUH: Cr: 7.50-9.50, Si: 1.0-2.0, C: 0.45 SNCM439 and SUH11 consisting of ~ 0.55 are mainly used.
As a metal powder made of such a metal material, an alloy powder manufactured by a water atomizing method or a gas atomizing method is usually used. In addition to a powder alloy powder produced by the atomizing method, an alloy component is used during sintering. The element powder may be adjusted and added according to the composition. In general, water atomized powder can be produced in a larger amount than gas atomized powder, so the manufacturing cost is also low, but because the powder shape tends to be irregular, the tap density tends to be low, and The amount of oxygen also increases. On the other hand, although the manufacturing cost of the gas atomized powder is increased, it is easy to obtain a spherical powder and the tap density is increased. For this reason, the water atomized powder and the gas atomized powder may be mixed and used in consideration of the cost and the tap density.

  The average particle size of the metal powder is preferably 1 to 20 μm. When the average particle size is less than 1 μm, the amount of binder added increases as the surface area of the powder increases, and deformation during degreasing increases. In addition, when the amount of the binder is increased, the shrinkage rate at the time of sintering is increased, the dimensional variation after sintering is increased, and it is difficult to obtain a sintered product with high dimensional accuracy in a subsequent pressing step. When the powder particle diameter exceeds 20 μm, it becomes difficult to stably obtain a sintered density (relative density) of 95% or more, the strength is remarkably lowered, and it cannot be used as a product. A more preferable average particle diameter is 5 to 12 μm, and more desirably 8 to 10 μm. In the present invention, the average particle diameter means an average diameter of 50% cumulative weight measured using a particle size distribution measuring apparatus using a laser diffraction / scattering method. As a particle size distribution measuring apparatus, SALD-2000 type manufactured by Shimadzu Corporation can be used.

Further, as the organic binder, thermoplastic resins such as polyethylene, polypropylene, polyacetal, polystyrene, amorphous polyolefin, ethylene vinyl acetate copolymer, acrylic resin, polyvinyl butyral resin, glycidyl methacrylate resin, and the like are used. Fatty acid ester, fatty acid amide, phthalic acid ester, paraffin wax, microcrystalline wax, polyethylene wax, polypropylene wax, carnauba wax, montan wax, urethanized wax, maleic anhydride to provide fluidity and improve degreasing Modified waxes and polyglycol compounds are used. Particularly preferred materials include paraffin wax, fatty acid ester, and polypropylene wax.
The organic binder and metal powder having the above ratio are heated and kneaded at about 160 to 180 ° C. for about 2 hours to completely disperse and mix the metal powder with the organic binder. Then, it is taken out and formed into a pellet having a diameter of about 5 mm by an extruder or a pulverizer, and used as a molding material.

In the sintered product, the outer diameter of the flange is + 0.0% to + 0.6%, the flange thickness is -0.8% to -0.0%, and the shaft diameter is + 0.0% to + 0.6%, circumferential runout tolerance (circular runout tolerance of the whole shaft): within 0.5mm, perpendicularity tolerance of flange to shaft part: within 0.5mm There is. When there are a plurality of flanges, the outer diameter and diameter of each flange must be in the above range.
And in shaping | molding, it is necessary to determine a metal mold | die shape in consideration of the dimension after sintering. These dimensions are dimensions obtained after sintering or by the hot isostatic pressing method, and the dimensions differ depending on the sintering density. Therefore, it is necessary to sufficiently consider the subsequent dimensional changes in the mold design. For this reason, it is necessary to design the dimensions of the mold in consideration of the above dimensional accuracy, and it is necessary to calculate the shrinkage ratio from molding to sintering in advance.

In the present invention, the flange outer diameter is + 0.0% to + 0.6% relative to the target value of the final product, the flange thickness is -0.8% to -0.0%, and the shaft diameter is Is in the range of + 0.0% to + 0.6% when the final product and the sintered product (having a shape similar to the final product) are measured at corresponding locations, the difference is within the above range. It means that there is. The outer diameter, thickness, and shaft diameter of the flange can be measured by a three-dimensional measuring device and a projector.
Regarding the circumferential runout and the perpendicularity of the flange with respect to the shaft part, if they vary depending on the measurement location, the difference between the final product and the sintered product when measured at the corresponding locations is the same as above. Means that it is within. Usually, the circumferential runout is measured with reference to both ends of the shaft. In the present invention, the circumferential runout means the runout of the entire shaft in the sintered product or the final product.
Circumferential run-out can be measured with a roundness / cylindrical measuring machine, and the perpendicularity of the flange with respect to the shaft can be measured with a measuring microscope.

  Molds are mounted on an injection molding machine and molded, but the number of molded products obtained should be from 1 to 8 with a single mold, taking into account the size and mass production quantity of the product. Can do. The capacity of the injection molding machine is appropriately adjusted according to the number of molds to be taken and the size of the product. In general, molding is performed using a molding machine having a clamping force of about 50 to 100 tons. The injection speed and pressure are adjusted so that defects such as bubbles and cracks do not occur in the molded body, and the mold is provided with a gas escape to effectively release the air in the mold and the gas generated from the molding material. There is a need. If there is no effective gas escape, air or gas generated from the molding material is taken into the molded body, and bubbles are generated in the molded body.

  The obtained molded body is put into a degreasing furnace, and the added organic binder is removed. The degreasing furnace for removing the organic binder is performed using any one of a reduced pressure inert gas atmosphere, an atmospheric pressure inert gas atmosphere, and an atmospheric pressure hydrogen gas atmosphere. In the case of a sintering apparatus having a degreasing function, the degreasing sintering is performed. Can be done consistently. As the degreasing furnace, a batch type degreasing furnace or a continuous (belt type, pusher type, walking beam type) degreasing furnace can be used. In particular, it is effective to perform degreasing using a jig having a shape along the shape of the molded body so as to prevent deformation to a minimum in view of the fact that the amount of deformation increases during degreasing.

The degreasing atmosphere is performed at any one of a reduced pressure inert gas atmosphere, an atmospheric pressure inert gas atmosphere, and an atmospheric pressure hydrogen atmosphere at a maximum temperature of 800 ° C. or less.
When the degreasing atmosphere is in the air, the powder is oxidized at 300 ° C. or higher, and the amount of oxygen after sintering increases, which greatly affects the strength of the sintered product. Therefore, a depressurized inert gas atmosphere, an atmospheric pressure inert gas atmosphere, and an atmospheric pressure hydrogen atmosphere are used as the degreasing atmosphere. Nitrogen or argon is used as the inert gas, but it is desirable to use nitrogen gas in consideration of cost. In addition, the temperature rising rate during degreasing is preferably 50 ° C./hr from room temperature to 400 ° C. in consideration of deformation during degreasing. Moreover, the deformation | transformation at the time of degreasing of a molded object can be suppressed by using the jig | tool which considered the deformation | transformation of a molded object at the time of degreasing.
The degreasing temperature is 800 ° C. or lower. However, when the temperature is about 300 ° C., the organic binder tends to remain about 30%, and when the temperature is 600 ° C. or higher, the organic binder is easily removed completely. There exists a possibility that it may collapse | crumble, and a more preferable degreasing temperature is 400 to 500 degreeC at maximum. Moreover, it is effective to use a sintering furnace having a degreasing function as a method for preventing the collapse of these molded products, and it is possible to shift to sintering without lowering the temperature even after the degreasing. In addition, by connecting a continuous (belt, pusher, walking beam) sintering furnace as well as a continuous (belt, pusher, walking beam) degreasing furnace, sintering is not interrupted by degreasing. Processing can be performed continuously.

In the sintering process, any one of a reduced pressure inert gas atmosphere, an atmospheric pressure inert gas atmosphere, and a pressurized inert gas atmosphere is used as the sintering atmosphere. As the inert gas, a stainless material is often used as a material during sintering. Therefore, it is preferable to use argon gas in consideration of nitriding of the material.
The sintering temperature is 1000 ° C. or higher and 1500 ° C. or lower. However, if the sintering temperature is lower than 1000 ° C., the sintering is insufficient. In order for the sintered density to be 95% or more, 1200 to 1400 ° C is desirable, and further 1250 to 1380 ° C is desirable.
In addition, it is desirable to maintain the maximum temperature for about 2 to 4 hours in consideration of improvement of the sintering density during sintering and dimensional variation during sintering. As in the degreasing process, deformation occurs at high temperatures in the sintering process, so it is effective to use a jig for preventing deformation of the sintered product.

In degreasing and sintering, considering the production volume, batch type degreasing furnaces and sintering furnaces are used for small quantities of various products, and degreasing and sintering are performed by pusher type continuous furnaces and walking when the number increases. By using a continuous process using a beam-type continuous furnace and a belt-type continuous furnace, production can be dramatically improved.
Further, by performing degreasing and sintering by using a V-shaped setter as appropriate, hanging or standing the product, deformation of the product after sintering can be prevented during degreasing.

By setting the density of the sintered product to 95% or more in terms of relative density, the mechanical strength and hardness at high temperatures can be maintained. If the relative density is less than 95%, the mechanical strength at high temperatures, particularly the elongation and hardness, are lowered, and continuous use at high temperatures is difficult.
The relative density of the sintered product can be measured by the Archimedes method.

  The obtained sintered product is further subjected to a hot isostatic pressing method (HIP method) in order to further increase the sintered density to improve the mechanical strength and to improve the reliability of the mechanical strength in a high temperature range. It is effective to be treated at a low temperature of about 10 ° C. to 100 ° C. lower than the sintering temperature and at a high pressure of about 10 MPa to 180 MPa, so that there is no pinhole inside and a relative density of 98% or more. A sintered product can be obtained stably. In addition, by using a sintered HIP apparatus that can perform a pressure treatment of up to about 6 MPa during the sintering process, a sintered product having a relative density of 98% or more can be obtained without using the HIP method in the subsequent process.

When the hardness of the sintered product after sintering or after the HIP process is high, annealing is appropriately performed. Then, as shown in FIG. 2, the shaft can be processed into a desired shape by rotating and pressing the shaft by 120 degrees or less (preferably 90 degrees or 120 degrees) for each pressing step.
The pressed product is appropriately heat-treated according to the material to obtain the required hardness and strength.
Hereinafter, the pressing process will be described in more detail.

In the pressing process, the mold includes a surface that includes the shaft rotation axis in order to simultaneously define the outer diameter of the flange, the thickness of the flange, the roundness of the shaft, the circumferential runout, and the perpendicularity of the flange with respect to the shaft. It consists of an upper mold and a lower mold that have a shape that divides the final product into two equal parts. By pressing the upper mold toward the lower mold, the flange outer diameter is compressed while the flange portion is compressed downward. As the thickness of the flange swells and deforms, the side part follows the mold shape, and the outer diameter of the shaft part is compressed, and the squareness, circumferential runout, roundness, and the whole shaft part are It is corrected following the mold shape.
Since the desired squareness, circumferential runout, and roundness cannot be satisfied with only one press from above and below, as shown in FIG. Press the part rotated by changing the phase within / 3 (within 120 °). This process is repeated 3 times for 120 ° and 4 times for 90 °, for example, so that the overall dimensions of the turbine rotor shaft (flange outer diameter, flange thickness, perpendicularity to the flange shaft, circumferential runout) , Roundness, etc.) can be set to a desired dimensional accuracy. In terms of cost, 120 ° × 3 times, 90 ° × 4 times, 72 ° × 5 times, etc. 360 ° may be rotated by an angle divided by an integer of 3 or more, but 100 ° × 4 times, etc. You may rotate beyond 360 degree | times. Further, the rotation angle does not need to be the same between the presses, and the press may be repeated so that the rotation angle is within 360 degrees and the total rotation angle is 360 degrees or more. The press pressure and press time in each press may be appropriately adjusted according to the shape of the product (shaft outer diameter, flange shape). Usually, the press pressure ranges from 25 to 100 tons, and the press time is one time. 0.3 to 3 seconds per press is appropriate.

  As described above, a desired turbine rotor shaft can be obtained without performing cutting by rotating and rotating the phase within 120 °. Die steel, high-speed steel, and cemented carbide are used as the die material used for the press in consideration of the life. The press process uses a parts feeder and a progressive feed device to save labor, so that the processing capacity per hour can be greatly improved compared to conventional machining, and the processing capacity per hour is 500-1000. It can be increased to about one.

  In order to further save labor in the pressing process, by using a multi-forming machine capable of press bending from the 360-degree direction in the pressing process, the pressing process can be continuously performed, and the labor saving of the process becomes possible. In the cutting process, the processing capacity of about 10 to 50 per hour can be dramatically improved to about 1500 to 3000 per hour.

  Furthermore, the surface roughness of the product after pressing can be improved by barrel polishing and electrolytic polishing as needed, and burrs can be removed.

  According to the present invention, by using a sintered product whose dimensional accuracy is controlled in advance as a raw material, the machining and cutting steps by machining are not performed in post-processing, and the shaft for a turbine rotor having a desired shape with excellent dimensional accuracy is obtained. Can be manufactured. In particular, by adopting the MIM method for the production of sintered products, the production loss of materials can be suppressed to 5% or less compared to conventional cutting, so the cost reduction effect is high and automation processing by press Therefore, the manufacturing efficiency is 5 to 10 times or more compared with the conventional machining method. Further, by adopting the MIM method, it becomes possible to mass-produce a turbine rotor shaft having a complicated shape.

A sintered product according to the present invention was produced. The molding material, heat-kneading conditions, injection molding conditions, degreasing conditions, sintering conditions, etc. were as follows. 100 compacts were molded, degreased and sintered, and dimensional variations were measured.
・ Metal powder: SUH11 Average particle size 9.2μm Tap density 4.2g / m ³
・ Organic binder composition: Polyacetal 15Vol%, Polypropylene 25Vol%, Amorphous polyolefin 10Vol%, Paraffin wax 35Vol%, Acrylic resin 10Vol%, Fatty acid ester 5Vol%
・ Metal powder: 60Vol% Organic binder 40Vol%
・ Heat kneading: 180 ℃ for 2 hours ・ Injection molding conditions: 180 ℃ Mold temperature: 40 ℃
Degreasing conditions: Maximum temperature 500 ° C (nitrogen) held for 2 hours Total time 24 hours Sintering conditions: Maximum temperature 1350 ° C (argon, reduced pressure atmosphere) held for 2 hours

One mold for injection molding was taken, and the shape of the turbine rotor shaft (total length 92 mm) shown in FIG. 3 was used. The desired final product dimensions are as follows: The measurement location is shown in FIG. A is the outer diameter of the first flange 3a, B is the thickness of the first flange 3a, C is the outer diameter of the second flange 3b, D is the thickness of the second flange 3b, and E is the diameter of the shaft portion.
Desired final product dimension A: 14.50mm (target value) ± 0.05mm (14.45mm to 14.55mm)
B: 0.9mm (target value) ± 0.05mm (0.85mm to 0.95mm)
C: 14.50mm (target value) ± 0.05mm (14.45mm-14.55mm)
D: 0.9mm (target value) ± 0.05mm (0.85mm to 0.95mm)
E: 7.5mm (target value) ± 0.002mm (7.498mm-7.502mm)
Tolerance of circumferential runout: Within 0.005mm, Squareness tolerance of flange to shaft: Within 0.005mm Roundness tolerance: Within 0.005mm

As the molding machine, a molding machine having a clamping pressure of 50 tons was used. The dimensions of the manufactured sintered product were as follows. The dimension measurement was performed using a tool microscope. Circumferential run-out tolerance measurement and roundness tolerance measurement were performed using a roundness / cylindrical shape measuring machine (Taylor Hobson Co., Ltd. Model: Talirond 300). It was measured). The perpendicularity tolerance of the flange with respect to the shaft portion was measured using a high-precision measuring microscope (Mitutoyo Corporation model: MF).
Dimension A of the manufactured sintered product : 14.535mm to 14.572mm (target value + 0.24% to + 0.50%)
B: 0.895mm to 0.898mm (Target value -0.56% to -0.22%)
C: 14.539mm ~ 14.577mm (target value + 0.27% ~ + 0.53%)
D: 0.894mm to 0.897mm (Target value -0.67% to -0.33%)
E: 7.525mm to 7.539mm (Target value + 0.33% to + 0.52%)
Circumferential runout tolerance: 0.37 mm, Flange squareness tolerance to the shaft: 0.32 mm, Roundness tolerance: 0.29 mm
Sintered product density: 96.0%
As shown in FIG. 3, in the turbine rotor shaft according to the present embodiment, the diameter of the shaft portion changes in three stages. The shaft diameter E is representative of the value measured at the thickest part (closer to the flange), but the diameter of the shaft is also measured when measured at other points. The diameter of the product was within the range approximated to the above (+ 0.21% to + 0.57%) with respect to the target value of the final product.

As shown in FIG. 2 (A), the sintered product was pressed with an upper die and a lower die having a shape obtained by bisecting the final product in parallel with the axial direction. The sintered product was pressed four times by rotating 90 degrees in the rotation direction of the shaft. Each press pressure was 50 tons, and the press time was 1.5 seconds per stroke. The dimensions after the pressing process were as follows.
Dimension A of the final product manufactured : 14.48mm to 14.51mm
B: 0.89mm ~ 0.91mmm
C: 14.47mm-14.50mm
D: 0.89mm ~ 0.91mm
E: 7.499mm-7.501mm
Tolerance of circumferential runout: 0.004mm, Tolerance of flange perpendicular to shaft: 0.003mm, Tolerance of roundness: 0.003mm

  Although the final product size could not be obtained after sintering, the product within the final product size tolerance could be obtained in the pressing process.

A sintered product according to the present invention was produced. The molding material, heat-kneading conditions, injection molding conditions, degreasing conditions, sintering conditions, etc. were as follows. 100 compacts were molded, degreased and sintered, and dimensional variations were measured.
・ Metal powder: SNCM439 Average particle size 8.7μm Tap density 4.3g / m ³
・ Organic binder composition: Polyacetal 20Vol%, Polypropylene 20Vol%, Amorphous polyolefin 10Vol%, Paraffin wax 35Vol%, Acrylic resin 10Vol%, Fatty acid ester 5Vol%
・ Metal powder: 60Vol% Organic binder 40Vol%
・ Heat kneading: 180 ℃ for 2 hours ・ Injection molding conditions: 180 ℃ Mold temperature: 40 ℃
・ Degreasing conditions: Maximum temperature 500 ° C (nitrogen) held for 2 hours Total time 24 hours ・ Sintering conditions: Maximum temperature 1350 ° C (argon, reduced pressure atmosphere) held for 2 hours ・ HIP treatment: Processing temperature 1200 ° C (argon, 100 MPa) 2 Time hold

  A product having the same shape as in Example 1 was prepared. The target value of the final product is the same as that in the first embodiment.

Dimension A of the manufactured sintered product : 14.530mm to 14.4584mm (target value + 0.21% to + 0.58%)
B: 0.894mm to 0.899mm (Target value -0.67% to -0.11%)
C: 14.532mm ~ 14.584mm (target value + 0.22% ~ + 0.58%)
D: 0.893mm to 0.898mm (Target value -0.78% to -0.22%)
E: 7.521mm-7.540mm (Target value + 0.28%-+ 0.53%)
Circumferential runout tolerance: 0.42 mm, Flange squareness tolerance to the shaft: 0.41 mm, Roundness tolerance: 0.37 mm
Sintered product density: 99.2%

As shown in FIG. 2 (A), the sintered product was pressed with an upper die and a lower die having a shape obtained by bisecting the final product in parallel with the axial direction. The sintered product was pressed three times by rotating 120 degrees in the rotation direction of the shaft. Each press pressure was 50 tons, and the press time was 1.5 seconds per stroke. The dimensions after the pressing process were as follows.
Dimension A of the final product manufactured : 14.49mm to 14.50mm
B: 0.89mm ~ 0.91mmm
C: 14.48mm-14.51mm
D: 0.90mm ~ 0.91mm
E: 7.499mm-7.501mm
Circumferential runout tolerance: 0.003 mm, Flange squareness tolerance to the shaft: 0.004 mm, Roundness tolerance: 0.003 mm

  Although the final product size could not be obtained after sintering, the product within the final product size tolerance could be obtained in the pressing process.

[Comparative Example 1]
The following sintered bodies were produced under the same conditions as in Example 1.
Dimension A of the manufactured sintered product : 14.510mm to 14.535mm (target value + 0.07% to + 0.24%)
B: 0.892mm to 0.895mm (Target value -0.89% to -0.56%)
C: 14.508mm to 14.532mm (Target value + 0.06% to + 0.22%)
D: 0.892mm to 0.895mm (Target value -0.89% to -0.56%)
E: 7.499mm to 7.515mm (Target value -0.01% to + 0.20%)
Circumferential runout tolerance: 0.52mm, Flange squareness tolerance to shaft: 0.71mm, Roundness tolerance: 0.59mm

Using the sintered body, the sintered product was rotated 90 degrees in the rotation direction of the shaft under the same conditions as in Example 1 and pressed four times. The dimensions after the pressing process were as follows.
Dimension A of the final product manufactured : 14.49mm to 14.52mm
B: 0.89mm ~ 0.91mmm
C: 14.48mm-14.51mm
D: 0.89mm ~ 0.90mm
E: 7.499mm-7.501mm
Circumferential runout tolerance: 0.011 mm, Flange squareness tolerance to the shaft: 0.013 mm, Roundness tolerance: 0.018 mm

  A product that was close to the final product size in the sintered product size was created, but for A to E, products within the dimensional tolerance were obtained, but the circumferential runout, squareness, and roundness should be within the tolerance. I could not do it.

  In order to investigate the effect of the difference between the values of A to E of the sintered product and the target value of the final product, the circumferential runout tolerance of the sintered product, and the squareness tolerance of the flange with respect to the shaft on the tolerance of the final product. Various sintered products were prepared under the same conditions as in No. 1, and the relationship between the final product after pressing 120 ° × 3 times and the sintered product before pressing was examined. The results are summarized in Table 1.

  From the results of Example 3, the flange outer diameter was + 0.0% to + 0.6%, the flange thickness was -0.8% to -0.0%, and the shaft portion The diameter is + 0.0% to + 0.6%, the circumferential runout tolerance is within 0.5 mm, the squareness tolerance of the flange with respect to the shaft is within 0.5 mm, and the sintered density is 95% or more relative density. It was found that the final product can be obtained with the desired dimensional accuracy when using the knot.

[Comparative Example 2]
Using the sintered product obtained in Example 1, the dimensional accuracy was measured when pressing was performed only once under the same conditions as in Example 1.
Dimension A of the final product manufactured : 14.50mm to 14.52mm
B: 0.89mm ~ 0.90mmm
C: 14.51mm-14.53mm
D: 0.89mm ~ 0.91mm
E: 7.503mm-7.506mm
Tolerance of circumferential runout: 0.009mm, Squareness tolerance of flange to shaft part: 0.008mm, Roundness tolerance: 0.010mm

  In the case of only one press, the dimensions A to D have the desired dimensional accuracy. However, the target value of the final product in the shaft diameter E and the runout tolerance, squareness tolerance, and roundness tolerance. Could not get a product that meets the requirements.

[Comparative Example 3]
Using the sintered product obtained in Example 1, the sintered product was rotated 180 degrees in the rotational direction of the shaft under the same conditions as in Example 1 and pressed twice.
Dimension A of the final product manufactured : 14.52mm to 14.56mm
B: 0.89mm ~ 0.91mmm
C: 14.53mm-14.56mm
D: 0.89mm ~ 0.91mm
E: 7.509mm-7.519mm
Circumferential runout tolerance: 0.014 mm, Flange squareness tolerance to the shaft: 0.018 mm, Roundness tolerance: 0.012 mm

  For products that are rotated 180 degrees and pressed twice (ie, products that are pressed from the same direction by changing the top and bottom), B and D fall within tolerances, but the flange outer diameters A and C, shaft A product satisfying the target value of the final product could not be obtained in the diameter E, the circumferential runout tolerance, the squareness tolerance, and the roundness tolerance.

  As a result of examining the rotation angle and the number of presses between the presses, the desired product can be obtained by pressing the rotation angle between the presses within 120 degrees and rotating the sintered product for 360 degrees or more. I understood.

(A) is a front view which shows the shaft for turbine rotors of the state which joined the turbine wheel, (B) is a figure which shows the joining state typically. (A) is a figure which shows typically the state which presses the sintered product of the shaft for turbine rotors with a metal mold | die (upper mold | type and lower mold | type), (B) is a 90 degree rotation angle, (C) is 120. It is a figure explaining the rotation angle of °. (A) is a front view of the shaft for turbine rotors, (B) is the partially expanded view, and is a figure which shows a measurement location. It is a flowchart which shows an example of the manufacturing process of the shaft for turbine rotors concerning this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Turbine rotor shaft 2 Shaft part 3a First flange 3b Second flange 4 Joint part 5 Turbine wheel A Outer diameter B of the first flange B Thickness of the first flange C Outer diameter of the second flange D Thickness E of the second flange Part diameter

Claims (4)

A method of manufacturing a shaft for a turbine rotor having a cylindrical shaft portion and a flange,
Including a step of pressing a sintered product having a shape close to a desired final product with the same mold a plurality of times,
The sintered product is an integrally formed product of a flange and a shaft. The outer diameter of the flange is + 0.0% to + 0.6% and the thickness of the flange is -0.8% with respect to the target value of the final product. ~ -0.0%, shaft diameter is + 0.0% to + 0.6%, circumferential runout tolerance is within 0.5mm, squareness tolerance of flange to shaft is within 0.5mm, and firing The consolidation density is 95% or higher relative density,
The mold is composed of an upper mold and a lower mold having a mold having a shape obtained by dividing the final product into two equal parts in parallel to the axial direction;
In the pressing step, after the sintered product is pressed by the mold, the sintered body is rotated 360 ° by repeating the next press by rotating the sintered body at an angle of 120 ° or less. A method for manufacturing a shaft for a turbine rotor, wherein pressing is performed until the above rotation. The method for manufacturing a shaft for a turbine rotor according to claim 1, wherein the angle is 120 ° or 90 °. The method for manufacturing a turbine rotor shaft according to claim 1, wherein the sintered product is a sintered product having a relative density of 98% or more. In the manufacturing process of the sintered product, after producing a primary sintered product having a relative density of 94% or more, a sintered product having a relative density of 98% or more is obtained by a hot isostatic pressing method. The manufacturing method of the shaft for turbine rotors of any one of Claims 1-3.

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