ES2932530T3 - Method for manufacturing ring-shaped bodies - Google Patents

Abstract

The present invention is a method for making an annular shaped article having a forging step for making a disc-shaped forged article by forging an alloy material, and an annular rolling step for making an annular shaped article by annular rolling of a annular intermediate. article obtained by forming a through hole in the forged article, wherein said method is characterized in that hot forging is performed at least twice in the forging step. In hot forging, the strain rate is 0.5 s-1 or less, the absolute value εθ1 of the strain in circumferential direction in the forged item is 0.3 or more, the absolute value εh of the strain in the height direction of the forged article is 0.3 or more, and the ratio between these absolute values for deformation (εh/εθ1) is 0.4 to 2.5 inclusive. (Automatic translation with Google Translate, without legal value)

Description

DESCRIPTION

Method for manufacturing ring-shaped bodies

technical field

The present invention relates to a method for manufacturing a ring-shaped body, which is used as a raw material in the production of an annular product such as a turbine disk for aircraft engines, for example.

The present application claims the priority of Japanese Patent Application No. 2013-069205 filed on March 28, 2013.

Background art

The turbine disk is an annular element that has a through hole and is configured to rotate together with a plurality of turbine blades, which are arranged on its outer circumferential side.

The outer circumferential part of the turbine disc is exposed to the combustion gases and reaches a high temperature of 600 to 700 °C, while the inner circumferential part is kept at a relatively low temperature and therefore stress is generated. repeatedly in it as the engine is started and stopped. Accordingly, it is desired that turbine discs have superior low cycle fatigue characteristics. In addition, it is necessary for the turbine discs to have high creep resistance characteristics because centrifugal force is applied to the outer circumferential part due to the high speed of rotation around the shaft at high temperatures. Furthermore, turbine discs are required to have high tensile strength and high yield strength.

In order to ensure high enough mechanical resistance to respond to the various demands described above, the annular-shaped bodies to be used for the turbine discs are produced and manufactured by forging a material with high heat resistance consisting of a superalloy of a Ni base and cutting the obtained forged annular body, as discussed in Patent Documents 1 and 2, for example. More specifically, a ring-shaped body is given deformation and the crystal grains of the material are refined by forging, and thereby the tensile strength, fatigue resistance and the like are improved. For equipment for applying forging, it is preferable to use a hydraulically controlled forging press capable of strictly controlling the forging speed, and it has been recognized that the application of full-surface forging to simultaneously cast all the material is preferable to obtain the structure ( crystal grains) of a ring-shaped body that are circumferentially uniform.

Meanwhile, in recent years, it has been desired to increase the size of the turbine discs as more power is desired from aircraft engines. As the size of a ring-shaped body increases as the size of the turbine discs increases, a large hydraulically controlled forging press with a capacity of several tens of thousands of tons becomes necessary (for example, see Document No Patent 1).

However, the large hydraulically controlled forging presses described above are very expensive and few such presses are available worldwide; Accordingly, if such a large hydraulically controlled forging press is used, the ability to supply ring-shaped bodies may be limited and the costs of the products to be produced may remain high. The trend towards larger turbine discs in recent years has reached such a high level that closed forging can be difficult even if a large hydraulically controlled forging press is used, which can cause problems such as preferable mechanical characteristics. are difficult to achieve for some regions of the ring-shaped bodies to be forged, and it becomes difficult to ensure the uniformity of the product structure.

On the other hand, instead of casting a ring-shaped body using a forging press, a method for forming a ring-shaped body by ring rolling can be used. In this case, the cost of the equipment can be reduced and it becomes easy to sensitively produce large annular-shaped bodies. However, in general, anisotropy of mechanical characteristics (strength characteristics) occurs more easily in ring-rolled products than in pressure-forged products, and therefore ring-rolled is not suitable for the production of products that require isotropy of mechanical characteristics such as turbine discs

A method in which a ring-shaped body is cast by a combination of a forging press and ring rolling can be used; however, if this method is used, the problem may arise that final forging is required after ring rolling to obtain a desired uniform and fine structure, production processes become complex, and production costs may become tall.

To solve this problem, in Patent Document 3, a method is presented in which a forging process and a ring rolling process are used in combination, and in the forging process, hot forging is carried out. a plurality of times that the stress for a forged body in the circumferential direction £01, the deformation of the forged body in the direction of the height £h and a deformation ratio between these values £h/£01 are controlled to appropriate values, which enables the production of a ring-shaped body having a fine crystalline structure with a excellent uniformity assured at low cost.

appointment list

patent document

[Patent Document 1] JP 07-138719 A

[Patent Document 2] JP 62-211333 A

[Patent Document 3] JP 2011-255409 A

Non-patent document

[Non-Patent Document 1] “Year 2002 Research Report - Report Regarding Development of Innovative Members Using Ultra-Large Forging Press Machine”, (New Energy and Industrial Technology Development Organization, March 2003, pp. 10-11 and pp. 37- 41)

Summary of the invention

technical problem

Meanwhile, recently, the production of high-performance aircraft engines has been on the rise, and thus the demand for a large ring-shaped body has also increased. Therefore, a production method is desired which is capable of stably producing ring-shaped bodies with a uniform structure per production volume.

The inventor of the present invention has studied the method for manufacturing annular bodies discussed in Patent Document 3 and, as a result, has come to the conclusion that an annular-shaped body with fine crystal grains can indeed be obtained with a uniform grain size by hot forging in which a forged body is deformed in the circumferential direction £01, the strain for the forged body in the height direction £h, and a strain ratio between these values £h /£01 are controlled to appropriate values; however, when producing large and thick ring-shaped bodies, for example, the grain sizes of the ring-shaped bodies are not uniform in some cases due to uneven operating conditions and the like.

The present invention has been made with these circumstances in mind, and an object of the present invention is to provide a method as defined in the appended claims for manufacturing a ring-shaped body capable of producing ring-shaped bodies having excellently high mechanical strengths. while ensuring the uniformity of its structure in a stable and low cost manner.

Solution to the problem

In order to solve these problems and achieve the above-mentioned object, according to the present invention, a method as defined in claim 1 for manufacturing a ring-shaped body comprises a step of melting and casting to produce an alloy part. by melting and casting and includes a forging step of forging the alloy part to provide a forged body having a disc shape, and a ring rolling step of ring rolling an annular intermediate body prepared by forming a through hole in the forged body to provide a ring-shaped body and characterized in that the forging step consists of at least two hot forging steps, each of the hot forging steps being carried out under conditions where the speed of deformation is at most 0.5 s-1, an absolute value £01 of deformation of the forged body in its circumferential direction is at least 0.3, an absolute value £h of deformationc stress of the forged body in its vertical direction is at least 0.3, and a ratio £h/£01 between the absolute values of stress is within a range of 0.4 to 2.5. Where the alloy part is made of a Ni-based alloy, a Co-based alloy, or a Fe-based alloy.

In the method for manufacturing a ring-shaped body according to the present invention, the strain rate in the forging step is at most 0.5 s-1. When the strain rate exceeds 0.5 s-1, the temperature inside the forged body rises excessively due to processing heat (ie, a phenomenon known as “heat buildup”) that coarsens the crystal grains inside the forged body. In ring rolling after forging, the crystal grains within the forged body cannot be refined, because sufficient stress cannot be imparted to the interior of the forged body. According to the present invention, the strain rate is controlled to be within a range of 0.5 s_1 or less, and thus, the difference between the temperature on the surface of the forged body and the temperature inside the forged body during forged can be less, allowing the structure to be more uniform. In order to more safely obtain the effects mentioned above, the strain rate in the forging stage is preferably at most 0.15 s-1.

The strain rate is defined by the following expression:

[Expression 1]

In the forging stage, the absolute value £01 of the deformation in the circumferential direction is set to a large value of at least 0.3, and therefore the amount of deformation in the circumferential direction to be imparted to the annular intermediate body in the ring rolling step can be relatively reduced. In addition, because the absolute value £h of the strain to be imparted in the height direction is set to a large value of 0.3 or more, the strain to be imparted in the height direction, which is difficult to impart by rolling the ring, it can be safely delivered by a sufficient amount. Therefore, the duty ratio in the ring rolling step can be reduced, the anisotropy of the strength properties of the ring-shaped body is suppressed while the isotropy is increased, and as a result, a crystal structure can be obtained. fine in which sufficient uniformity is ensured.

The relationship £h/£01 indicates the balance between the directions of the deformation to be imparted and is an index to control the variation of the relative positions in the material before and after the process. In the next stage of ring rolling, the corresponding numerical value necessarily becomes "0" or close to "0" due to the production method, and therefore it is essential to properly set the strain ratio to be imparted in the direction of the height at the forging stage to suppress anisotropy; however, if the £h/£01 ratio is less than 0.4, its effect may be insufficient. On the other hand, if the ratio £h/£01 exceeds 2.5, the strain distribution to be imparted in the height direction may become excessive, creep may become unstable and, as a result, axial symmetry, which is essential in imparting uniformity, it can degrade.

According to the present invention, the ratio £h/£01 between the absolute values of strain is controlled to be within a range of 0.4 to 2.5, thus stabilizing creep and ensuring axial symmetry to make the structure stable. uniform.

In the method for manufacturing a ring-shaped body according to the present invention, at the step of rolling the ring, hot rolling can be performed so that an absolute value £02 of deformation of the ring-shaped body can be obtained. in its circumferential direction of at least 0.5 imparted to the ring-shaped body, and therefore, the grain size in a product region of the ring-shaped body may be an ASTM grain size number of at least 8.

In this case, in the ring rolling step, when performing hot rolling in which deformation is imparted to the ring-shaped body in the circumferential direction by the absolute value £02 of 0.5 or more, the crystal grains in the product region of the ring-shaped body The body to be processed and machined into a product is safely refined to an ASTM grain size number of at least 8. Based on the above, the mechanical strengths of the product obtained from the ring-shaped body can be increased safely.

The ASTM grain size number is understood to be determined in accordance with the standards defined by ASTM E122 by the American Society for Testing and Materials (ASTM).

Furthermore, in the method for manufacturing a ring-shaped body according to the present invention, a difference between the grain sizes in a region caused by a cross section of the ring-shaped body along a direction including an axis of the ring-shaped body is within a range of ±2 per ASTM grain size numbers.

In this case, because the difference in grain sizes in the product region in the cross section of the annular body is within ±2 per ASTM grain size numbers, sufficient uniformity of grain size of the body of annular shape in the radial direction and in the height direction is ensured.

Furthermore, in the method for manufacturing a ring-shaped body according to the present invention, the grain size of the forged body in the forging step can be controlled to an ASTM grain size number of at least 7.

In this case, because of the large amount of strain that is imparted in the forging stage as described above, the grain size of the forged body can be refined to an ASTM grain size number of at minus 7. With this case, the structure of the ring-shaped body can be refined while reducing the amount of deformation to be imparted in the next step of rolling the ring.

Furthermore, in the method for manufacturing an annular body according to the present invention, the intermediate annular body can be formed so that a ratio T/H between a thickness T of the intermediate annular body in its radial direction and a height H of the annular intermediate body in its axial direction is controlled to be within a range of 0.6 to 2.3, and then the annular intermediate body can be rolled into rings so that the difference between the grain sizes at the plural equivalent positions of the shaped body annular is arranged evenly along its circumferential direction is within ±1.5 per ASTM grain size numbers.

In this case, by molding the annular intermediate bodies so that a ratio T/H is controlled between the thickness T of the annular intermediate body in the radial direction and the height H of the annular intermediate body in the axial direction of 0.6 to 2.3 and then by rolling annular intermediate body, the difference between the sizes of the crystal grains at a plurality of mutually equivalent positions of the annular intermediate bodies set uniformly in the circumferential direction can be constrained to be within ±1.5 by ASTM grain size numbers . More specifically, for the annular-shaped body obtained by molding the annular intermediate body, the uniformity of the grain size in the circumferential direction can be ensured. Specifically, it has been known that in ring rolling, which is a local process, the processes are performed sequentially differently from general partial forging, and therefore the axial symmetry of the structure after casting is high and therefore, the deviation of the material characteristics of the ring-shaped body in the circumferential direction is small. In the present invention, by setting the above-described T/H ratio for the annular intermediate body before ring rolling within the above-described range as in the present embodiment, the shape (circularity) of the formed molded annular body can be further improved and the axial symmetry of the molded annular shaped body structure can be further increased.

In other words, since the above-described T/H ratio is controlled to be within the range of 0.6 to 2.3, rolling stability, which is essential for imparting uniformity, can be obtained. Specifically, in a region where the T/H ratio is less than 0.6, the contact area between both rolls used in rolling (a main roll and a mandrel roll) and the material becomes large and therefore the influence degree of heat release is relatively increased and, as a result, it becomes difficult to obtain the circumferential uniformity. Conversely, as the T/H ratio increases, buckling is more likely to occur. Specifically, in an area where the T/H ratio is greater than 2.3, the above-described tendency becomes greater, and therefore it becomes difficult to obtain circumferential uniformity.

In the method for manufacturing a ring-shaped body according to the present invention, the alloy part may be made of a Ni-based alloy. In this case, the forging step is preferably carried out at a temperature of 950°C to 1075°C, or the ring rolling step is preferably carried out at a temperature of 900°C to 1050°C.

Advantageous effects of the invention

According to the present invention, there is provided a method as defined in the appended claims for manufacturing a ring-shaped body capable of producing ring-shaped bodies having superior high mechanical strengths while ensuring uniformity of their shape structure. stable and low cost.

Brief description of the drawings

[FIG. 1] Fig. 1 is a plan view from above showing an embodiment of a ring-shaped body according to the present invention.

[FIG. 2] Fig. 2 is a cross-sectional view of the body seen in the direction of the arrow line X-X in Fig. 1.

[FIG. 3] Fig. 3 is a flowchart showing an embodiment of a method for manufacturing an annular body and a turbine disk according to the present invention.

[FIG. 4] Fig. 4 is a cross-sectional view showing an annular intermediate body used in the manufacturing method shown in Fig. 3.

[FIG. 5] Fig. 5 is a perspective view illustrating a ring rolling made in the manufacturing method shown in Fig. 3.

[FIG. 6] Fig. 6 is an explanatory view illustrating a step of rolling rings with the use of a mandrel roll and a main roll.

[FIG. 7] Fig. 7 is an explanatory view illustrating a ring rolling step with the use of a mandrel roll and a main roll.

[FIG. 8] Fig. 8 is a graph showing the correlation between the tensile strength and the reduction of examples of a ring-shaped body according to the present invention.

[FIG. 9] Fig. 9 is a graph showing the correlation between yield strength and shrinkage of examples of a ring-shaped body according to the present invention.

Description of embodiments

In the following, embodiments according to the present invention will be described with reference to the accompanying drawings. An annular-shaped body 10 according to the present embodiment is used as a material for molding turbine disks of aircraft engines.

As shown in FIGS. 1 and 2, the annular body 10 has through holes and has an annular shape about an axis O, and is provided with a main body 11, an internal protrusion 12 protruding from the main body 11 toward a radial inward direction, and a outer protrusion 13 protruding from the main body 11 in a radial outward direction.

The ring-shaped body 10 is made of a Ni-based superalloy having excellent heat resistance, and in the present embodiment, the ring-shaped body 10 is made of a Ni-based alloy "Alloy718".

Alloy718 Ni-based alloy has an alloy composition that includes 50.00 to 55.00 mass% Ni, 17.0 to 21.0 mass% Cr, 4.75 to 5.60 mass% Nb, 2.8 to 3.3 mass% Mo, 0.65 to 1.15% by mass of Ti, 0.20 to 0.80% by mass of Al and 0.01 to 0.08% by mass of C, and the rest of Fe with unavoidable impurities.

In the ring-shaped body 10, the grain size of the structure in a desired region (not shown) to be machined into a turbine disk (i.e., product) (hereinafter, this region will be referred to as the "region"). of product") has an ASTM grain size number of at least 8. Furthermore, the virtual planes VS1, VS2 illustrated in Fig. 2 are cross sections of the annular-shaped body 10 along a direction including an axis O of the ring-shaped body 10, that is, the virtual planes VS1, VS2 are established at mutually equivalent positions determined by evenly dividing the ring-shaped body 10 along the direction of the circumference. The annular-shaped body 10 ensures uniformity because the difference between the grain sizes in the structure of a product region in the cross section of the virtual plane VS1 (or VS2) is within ±2 times the difference in size number of ASTM grain. The difference in the sizes of the crystal grain at the mutually equivalent positions of the ring-shaped body 10 in the circumferential direction, that is, the difference between the grain size in the virtual plane VS1 and the grain size in the virtual plane VS2 , is within ±1.5 times the difference of the ASTM grain size numbers.

Next, a method for manufacturing the ring-shaped body 10 and a method for manufacturing the turbine disk will be described with reference to Figs. 3 to 7

Melting and molding stage S1

First, the molten metal of the Ni-based alloy Alloy718 is prepared by casting. In this step, a molten raw material is prepared so that its components fall within the above-described ranges of Ni-based Alloy718 alloy components, and an ingot is produced by vacuum induction melting (VIM). This ingot is then remelted by electrical slag remelting (ESR) to produce a new ingot. In addition, this ingot undergoes Vacuum Arc Remelting (VAR) and then hot forging to produce a cylindrical billet (alloy part).

The billet is formed to have a diameter of 7 to 12 inches (more specifically, 165 to 315 mm), for example. The billet structure produced is approximately ASTM No. 6 by ASTM grain size numbers. By performing the above-described melting three times (triple melting), an extremely clean billet is produced, in which the solidification segregation is small, the solidification structure is controlled, and only an extremely small number of inclusions are included.

Forging stage S2

Next, the billet is forged so that the billet is pressed in the direction of the axis of the billet to prepare a forged body having a disk shape.

In this forging step S2, hot forging is performed at least twice so that an absolute value £01 of deformation of the forged body in the circumferential direction is 0.3 or more, an absolute value £h of deformation of the forged body in the height direction is 0.3 or more, and a ratio £h/£01 between the absolute values of deformation is within a range of 0.4 to 2.5 in a state where the billet has been heated to a temperature ranging between 950 and 1075 °C, for example.

The strain rate in hot forging in the forging stage S2 is set to 0.5 s-1 or less.

In the present embodiment, the hot forging in the forging step S2 is implemented using a hydraulically controlled forging press apparatus. The hydraulically controlled forging press apparatus is capable of adjusting the strain rate by hydraulic control during forging within the above-described ranges with high precision. Note that in the present embodiment, the strain rate in hot forging in the forging stage S2 is set to 0.01 s-1 or higher.

Furthermore, in the present embodiment, the absolute value £01 of the amount of tension imparted in the circumferential direction is set to 0.3 or more. The absolute value £h of the amount of deformation imparted in the height direction along the forging axis direction is set to be greater than 0.3.

The height of the forged body is adjusted by the forging step S2 to approximately 60 mm to 500 mm, for example. By performing the forging step described above, sufficient deformation is imparted to the forged body and the grain size of the forged body is refined to ASTM No. 7 or more by ASTM grain size numbers.

Intermediate ring drilling and rolling stage S3

Subsequently, a through hole having a circular cross section is formed in the center of the forged body obtained using a water cutter. Also, rolling of the intermediate ring is done after forming the through hole where needed. By performing the step S3 of drilling and rolling the intermediate ring, an annular intermediate body 20 is produced.

In the present embodiment, the annular intermediate body 20 has a circumferentially perpendicular cross section with a substantially polygonal shape as illustrated in Fig. 4, and includes a base portion 21 having a circumferentially perpendicular cross section with a substantially polygonal shape and a upper surface and a lower surface extending in a direction substantially perpendicular to an axis O; an inner protrusion 22 radially protruding inwardly from the base portion 21; and an outer bulge 23 radially protruding outwardly from the base portion 21.

Specifically, a height H of the annular intermediate body 20 (the base portion 21) in the direction of the axis O is set within a range of H=60mm to 500mm. Furthermore, the annular intermediate body 20 is molded so that the ratio T/H between a radial thickness T perpendicular to the axis O and the height H described above is within a range of 0.6 to 2.3.

S4 stage ring rolling

The annular intermediate body 20 is then rolled into rings. Ring rolling is performed by hot rolling performed at a temperature in the range of 900°C to 1050°C, for example.

As shown in Fig. 5, in the present embodiment, a ring rolling apparatus 30 includes a main roller 40 arranged on an outer circumferential side of the annular intermediate body 20; a mandrel roller 50 arranged on an inner circumferential side of the annular intermediate body 20; and a pair of axial rollers 31, 32 contacting the end surfaces (in the present embodiment, the upper surface and the lower surface of the base portion 21) of the annular intermediate body 20 in the direction of axis 0.

The main roller 40 and the mandrel roller 50 are arranged so that their axes of rotation are parallel to each other and configured to squeeze and press the annular intermediate body 20 from the inner circumferential side and the outer circumferential side thereof and roll the intermediate annular body 20 while circumferentially rotating the intermediate annular body 20.

The pair of axial rollers 31, 32 are configured to squeeze and press the annular intermediate body 20 in the direction of the axis O and control the dimension of the annular intermediate body 20 in the height direction.

As shown in Fig. 6, a housing recess 41 in which a part of the annular intermediate body 20 can be accommodated is provided in an outer circumferential portion of the main roller 40, and in the present embodiment, the housing recess 41 it has a sufficient depth to accommodate the outer bulge 23, the base portion 21 and an outer circumferential part of the inner bulge 22 of the annular intermediate body 20. Further, in a lower portion 41A of this housing, the recessed portion 41, a first molding groove 42 for molding the outer protrusion 13 of the annular-shaped body 10, is formed to groove in a radially inward direction relative to the roller. 40 (to the right in Fig. 6). The first slot 42 of molding has a depth equivalent to the protrusion height of the outer protrusion 13 to be molded.

On the other hand, an engaging portion 51, which can engage with the main roller 40 inside the housing recess 41, is arranged on the outer circumferential portion of the mandrel 50, while on an outer peripheral surface of the housing portion 51 latching, a second molding groove 52 is formed to mold the inner protrusion 12 of the annular-shaped body 10 to be grooved in a radially inward direction relative to the mandrel roll 50 (to the left in Fig. 6). The second molding groove 52 has a depth equal to the protrusion height of the inner protrusion 12 to be molded.

The main roller 40 and the mandrel roller 50 configured as described above work to approach each other, and therefore the annular intermediate body 20 is pinched and pressed between the main roller 40 and the mandrel roller 50. Specifically, the main roller 40 and the mandrel roller 50 approach each other while the main roller 40 rotates about the axis of rotation of the main roller 40, and thus the annular intermediate body 20 rotates about the axis O due to the resistance to friction generated between the annular intermediate body 20 and the main roller 40.

On the other hand, the mandrel roll 50 is configured to rotate about the axis of rotation of the mandrel roll 50, and rotates driven due to the frictional resistance generated between the annular intermediate body 20 and the mandrel roll 50. The annular intermediate body 20 plastically deforms as it fills into the interior of the housing recess 41 and the first mold groove 42 of the main roll 40 and the interior of the second mold groove 52 of the mandrel roll 50, and by therefore the body 10 is molded in an annular shape. In this deformation, the inner protrusion 12 of the ring-shaped body 10 is plastically deformed along the shape of the second mold groove 52. Furthermore, the outer protrusion 13 is plastically deformed along the shape of the first mold groove 42.

By rolling the ring in the above-described manner, the annular intermediate body 20 is plastically deformed to extend in the circumferential direction and the inner diameter and outer diameter thereof are enlarged, and thus the annular body 10 is produced. formed illustrated in Fig. 7.

In this ring rolling step S4, an absolute value £02 of the deformation is imparted to the ring-shaped body 10 in the circumferential direction of 0.5 or more. Specifically, hot rolling is performed at least one or more times to set the total value of strain absolute values £02 to be within a range of 0.5 to 1.3.

Heat treatment stage S5/machining stage S6

The ring-shaped body 10 produced in the manner described above is subjected to property adjustment by heat treatment, molded into a final shape by cutting, to form a turbine disk for aircraft engines.

According to the present embodiment of a method for manufacturing a ring-shaped body described above, in the forging step S2 to produce the forged body by forging the billet, the strain rate is 0.5 s-1 or less, and therefore Thus, an excessive rise in temperature within the forged body (phenomenon known as “heat buildup”), which can occur due to processing heat, can be avoided. Accordingly, the difference between the temperature on the surface of the forged body and that inside the forged body during forging can be controlled to be small, and thus the structure of the forged body can be unified. In order to obtain these effects reliably, it is preferable that the strain rate in the forging stage S2 be set to 0.15 s-1 or less.

In addition, since a high value of 0.3 or more is set as the absolute value £01 of the deformation in the circumferential direction in the forging step S2, the ratio of the amount of deformation in the circumferential direction to be imparted to the intermediate annular body 20 at ring rolling step S4 can be reduced. In addition, because a high value of 0.3 or more is set as the absolute value £h of the deformation in the height direction, the amount of deformation in the height direction, which is otherwise difficult to impart, it can be sufficiently imparted in the ring rolling step S4. Therefore, the duty ratio in the ring rolling step S4 can be reduced, the anisotropy of the strength properties of the ring-shaped body 10 is suppressed while the isotropy is increased, and as a result, a fine crystalline structure in which sufficient uniformity is ensured.

In addition, because a high value of 0.4 or more is set as the ratio £h/£01 between the absolute value £01 of the deformation in the circumferential direction and the absolute value £h of the deformation in the height direction , a sufficient ratio of the deformation can be imparted in the height direction and, as a result, the uniformity of the structure can be ensured even if sufficient stress cannot be imparted in the height direction in the next rolling stage of the ring S4. Also, because the ratio £h/£01 is 2.5 or less, the distribution in the height direction would not be excessive and therefore the plastic flow becomes stable and therefore Therefore, the axial symmetry of the plastic flow essential to impart uniformity can be guaranteed. It is preferable that the ratio £h/£01 between the absolute values of the strain is from 0.6 to 2.1. Accordingly, the axial symmetry of the plastic flow can be increased, and thus the uniformity of the structure can be more reliably ensured.

Furthermore, in the present embodiment, because the absolute value £01 of the amount of deformation to be imparted in the circumferential direction is set to 0.3 or more and the absolute value £h of the amount of deformation to be imparted in the circumferential direction of the height along the axis of the forged body is set to 0.3 or more in the S2 forging stage, the coarsening of crystal grains, which may occur due to the temperature rise inside the forged body due to heat, can be avoided processing.

In addition, since, in the ring rolling step, hot rolling is performed in which deformation is imparted to the ring-shaped body 10 in the circumferential direction by the absolute value £02 of 0.5 or more, the grains of crystal in the product region of the ring-shaped body body 10 is safely refined to an ASTM grain size number of at least 8. Accordingly, the mechanical strengths of the product obtained from body 10 ring-shaped increase reliably. Note that £02 is preferable to be 1.3 or less. In addition, the grain size of the ring-shaped body 10 preferably has an ASTM grain size number of 8 to 13. Therefore, the mechanical strengths of the product obtained from the ring-shaped body 10 can be increased reliably.

Since the difference in the grain sizes in the product region in the cross section along a direction including the O axis of the ring-shaped body 10 is within ±2 per ASTM grain size numbers, uniformity enough of the grain size of the body 10 to be annular in the radial direction and in the height direction is ensured.

Also, because a large amount of stress is imparted in the forging stage as described above, the grain size of the forged body can be refined to an ASTM grain size number of at least 7. Therefore, the The structure of the ring-shaped body 10 can be refined while reducing the amount of deformation to be imparted in the next step of rolling the ring.

In addition, since the rolling of the ring is performed after the annular intermediate body 20 is molded so that the ratio T/H between the radial thickness and the height H of the annular intermediate body 20 is within a range of 0.6 to 2.3, the difference between the grain sizes at mutually equivalent positions in the ring-shaped body 10 along the circumferential direction can be reduced to within ±1.5 per ASTM grain size numbers. In other words, for the annular-shaped body 10 obtained by molding the annular intermediate body 20, a sufficiently high uniformity of the grain sizes in the circumferential direction can be ensured.

Specifically, it has been known that in ring rolling, which is a local process, the processes are performed sequentially differently from general partial forging, and thus the axial symmetry of the structure after casting is high and therefore, the deviation of the material characteristics of the ring-shaped body 10 in the circumferential direction is small. Accordingly, by adjusting the above-described T/H ratio for the intermediate annular body 20 before ring rolling within the above-described range as in the present embodiment, the shape (circularity) of the molded annular body 10 can be further improved. more and the axial symmetry of the structure of the molded ring-shaped body 10 can be further increased.

In other words, since the above-described T/H ratio is controlled to be within the range of 0.6 to 2.3, rolling stability, which is essential for imparting uniformity, can be obtained. Specifically, in an area where the T/H ratio is less than 0.6, the contact area between both rolls used in rolling (the main roll 40 and the mandrel roll 50) and the material becomes large, and therefore, the degree of influence of heat release is relatively increased and, as a result, it becomes difficult to obtain circumferential uniformity. Conversely, as the T/H ratio increases, buckling is more likely to occur. Specifically, in a region where the T/H ratio is greater than 2.3, the above-described trend becomes higher, and thus it becomes difficult to obtain circumferential uniformity.

As described above, according to the method for manufacturing an annular-shaped body that is the present embodiment, it becomes possible to produce annular-shaped bodies, in which the uniformity of the structure is ensured and the mechanical strengths are high enough, reliably and at low cost.

The present invention is defined in the appended claims, and the present embodiment may also be implemented by various modifications and alterations within the scope of the appended claims.

For example, the shape of the annular-shaped body 10 and the annular intermediate body 20 is not limited to the present embodiment, and the design can be modified as necessary considering the shape of the annular product, such as a turbine disc that is going to produce.

The ring-shaped body 10 and the intermediate ring-shaped body 20 are made of Ni base alloy Alloy718 as described above; however, the material of the annular shaped body 10 and the annular intermediate body 20 is not limited to this, and the annular shaped body 10 and the annular intermediate body 20 may be made of a Ni-based alloy, a Ni-based alloy Co, or an Fe-based alloy.

In the embodiment described above, the molten metal for the Ni-based alloy Alloy718 is cast and the billet is produced by casting, but the present invention is not limited to this. Alternatively, a billet can be produced by powder casting and the billet produced is then subjected to the forging step and ring rolling step.

Also, as an alternative, the billet can be produced by double smelting (VIM ESR or VIM VAR) instead of producing the billet by triple smelting described above.

The present embodiment includes the step of drilling to form the through hole in the center of the disc-shaped forged body using the water cutter, but the present invention is not limited to this. Alternatively, the through hole may be formed by means other than a water cutter. Also, alternatively, the through hole can be formed at the time of forging and thus the drilling step can be omitted. Still more alternatively, the drilling can be done in the course of the forging step using the water cutter or the like.

In addition, after the ring-shaped body 10 is molded by the ring rolling step S4 illustrated in Fig. 3 and before the heat treatment step S5 illustrated in Fig. 3, additional processes such as partial forging may be performed to imparting a shape to the body 10 in an annular shape or to adjust its dimensions.

In the present embodiment, the mutually equivalent positions (the virtual planes VS1, VS2) in the ring-shaped body 10 determined by evenly dividing the ring-shaped body 10 into halves in the circumferential direction are used as reference positions to control the difference between the grain size in the virtual plane VS1 and the grain size in the virtual plane VS2 within ± 1.5 per ASTM grain size numbers; however, the number of virtual planes used for comparison is not limited to two. In other words, since the equivalence of the annular body 10 is fully ensured in the circumferential direction, the difference between the grain sizes at the mutually equivalent positions determined by evenly dividing the annular body 10 into three parts along the circumferential direction it can be controlled to be within ±1.5 by ASTM grain size numbers rather than by determining the difference between the grain sizes at the mutually equivalent positions determined by evenly dividing the annular shaped body 10 in two. The circumferential positions on the ring-shaped body 10 at which the mutually equivalent positions are to be established are not limited to those described above in the present embodiment.

examples

The present invention will be described in more detail below with reference to Examples. However, the present invention is not limited to the following examples.

Preparation of sample

First, the molten metal for the Ni-based alloy, Alloy718, was cast. Specifically, the smelting raw material was prepared to meet the condition of the range of components of the Ni-based alloy, Alloy718, mentioned in the above-described embodiment. A triplex melt was then carried out on this molten metal. Specifically, vacuum induction melting (VIM), electroslag remelting (ESR) and vacuum arc remelting (VAR) were carried out to produce a cylindrical billet with a diameter of 254 mm.

Subsequently, the billet was subjected to the forging step to prepare a disc-shaped forged body. For forging, hot forging was performed twice where the billet was heated to 1000 °C.

The forging step was carried out under the following conditions illustrated in Table 1 with respect to the absolute value £01 of deformation of the forged body in the circumferential direction, the absolute value £h of deformation of the forged body in the height direction , the relationship £h/£01 between the absolute values of the strain and the strain rate.

Subsequently, the through hole was formed by a water cutter in the center of the forged body to prepare an annular intermediate body. The annular intermediate body 20 was molded so that the ratio T/H between its thickness T and its height H was the value shown in Table 1.

Next, the annular intermediate body 20 was subjected to ring rolling. For ring rolling, two hot rollings were carried out in which the annular intermediate body was heated to 1000°C. The rolling of the ring was performed so that the total sum of the absolute value £02 of the hoop strain in the ring-shaped body 10 satisfied the following conditions illustrated in Table 1 by performing hot forging twice.

Then, the ring-shaped body 10 was subjected to heat treatment. As the direct aging material, a material which had undergone an aging treatment under conditions of 718°C/8 hours 621°C/8 hours air cooling (AA) was prepared. As a solution aging material, a material which had been subjected to an aging treatment under the condition of 718 °C/8 hours air cooling (AA) was prepared after the solution treatment under the condition of 970 °C/1 hour cooling. Water Quick (WQ) performed after rolling the ring.

Grain size measurement

Using the prepared ring-shaped body 10, the maximum crystal grains in the product regions within the cross sections including the virtual planes VS1, VS2 and the average grain sizes around the maximum crystal grain were measured and compared. For the average grain size around the maximum crystal grain, an average grain size over an observed portion of the maximum crystal grain (excluding the maximum crystal grain) was used. Results are shown in table 2.

Table 2

High temperature tensile characteristics determination test

Among the ring-shaped bodies prepared in the manner described above, with respect to those prepared for Example 1 of the present invention and Comparative Example 3, tensile test piece samples were taken from locations in the circumferential direction, in the height direction and the radial direction from the mutually equivalent positions including the virtual planes VS1, VS2 illustrated in Fig. 1, and high-temperature tensile tests were carried out at 650 °C, respectively. The tests were carried out using ASTM E8 small size test pieces with a parallel portion diameter of 6.35 mm and in accordance with ASTM E21, and measured for tensile strength, yield strength (0.2% yield strength) and the reduction. To examine the deviations of the circumferential, height and radial measurement values, the height and radial ratios were calculated with the circumferential measurement value set as the reference value "1" (100%). Fig. 8 illustrates the correlation between tensile strength and shrinkage, and Fig. 9 illustrates the correlation between yield strength and shrinkage.

In Comparative Examples 1 and 2, where the strain rate at the forging stage exceeds 0.5 s-1, the difference between the maximum grain size and the average grain size around the maximum grain size was large and the structure was observed to be non-uniform. This was estimated to have occurred because local coarsening of the glass grains within the forged body occurred due to excessive temperature rise within the forged body, which had been caused by processing heat (i.e., because a phenomenon known as “heat buildup” had occurred).

On the contrary, in Examples 1 to 4 of the present invention, in which the strain rates in the forging stage were 0.5 s-1 or less, the difference between the maximum grain size and the mean grain size around the maximum grain size was small, and the structures were observed to be sufficiently unified. It was estimated that sufficiently unified structures were obtained due to the small difference between the temperature on the surface and the temperature inside the forged body during forging, which was achieved by controlling the strain rate in the range of 0.5 s-1 or less. Note that in Examples 1, 2 and 4 of the present invention where the strain rates were controlled to be within the range of 0.15 s -1 or less, the structures were better unified.

As shown in FIGS. 8 and 9, as a result of high temperature tensile strength determination tests, Example 1 of the present invention was found to be better than Comparative Example 2 in terms of the overall tensile strength, the limit 0.2% elastic and shrinking.

More specifically, it was observed that in Example 1 of the present invention, the isotropy of strength characteristics was increased, and Example 1 of the present invention had a fine crystal grain structure in which sufficient structural uniformity was ensured.

industrial applicability

According to the method for manufacturing a ring-shaped body of the present invention as defined in the appended claims, ring-shaped bodies in which the uniformity of the structure is ensured and the mechanical strengths are high enough can be produced in stable form and at low cost. Accordingly, the method for manufacturing a ring-shaped body of the present invention as defined in the appended claims can suitably be used in the production of turbine discs and the like of aircraft engines.

Reference symbol list

10 Ring-shaped body

20 Annular intermediate body

H Height of the annular intermediate body in the axial direction

OR Axis

S2 Forging stage

S4 Ring Rolling Stage

T Thickness of the annular intermediate body in the radial direction

VS1 Virtual plane (equivalent position)

VS2 Virtual plane (equivalent position)

Claims (8)

1. A method of manufacturing a ring-shaped body comprising a casting and casting step to produce an alloy part by casting and casting, a forging step for forging the alloy part to provide a forged body having a disc shape , and a ring rolling step of ring rolling an annular intermediate body prepared by forming a through hole in the forged body to provide an annular shaped body, wherein the alloy part is made of a Ni-based alloy, a Co-based alloy or an Fe-based alloy, characterized in that the forging stage consists of at least two hot forging stages, each of the hot forging stages is carried out under the conditions that the strain rate is a maximum of 0.5 s-1, a value absolute value £01 of deformation of the forged body in its circumferential direction is at least 0.3, an absolute value £h of deformation of the forged body in its vertical direction is at least 0.3, and a relationship £h/£01 between the absolute values of the deformation is within a range of 0.4 to 2.5, in which the strain rate is defined by the following expression: Strain rate ( s x ) V 2 /3 (£h2 £e2 (~£h ~ Ee)^) time (s) deforged The method for manufacturing a ring-shaped body according to claim 1, characterized in that a difference between grain sizes in a region produced by a cross section of the ring-shaped body in a plane (VS1, VS2) perpendicular to an annular shaped body circumferential direction is within a range of ±2 per ASTM grain size numbers. The method for manufacturing a ring-shaped body according to claim 1 or 2, characterized in that in the forging step, the grain size of the forged body is an ASTM grain size number of at least 7. 4. The method for manufacturing an annular-shaped body according to any one of claims 1 to 3, characterized in that the annular intermediate body is formed so that the ratio T/H between the thickness T of the annular intermediate body in its direction radial and the height H of the annular intermediate body in its axial direction is controlled to be within a range of 0.6 to 2.3, and then the annular intermediate body is rolled into a ring shape so that the difference between the grain sizes in Plural equivalent positions of the ring-shaped body arranged uniformly along its circumferential direction shall be within ±1.5 per ASTM grain size numbers. The method for manufacturing a ring-shaped body according to any one of claims 1 to 4, characterized in that in the ring rolling step, hot rolling is carried out so as to impart the shape to the body. annular an absolute value £02 of tension in the ring-shaped body in its circumferential direction from 0.5 to 1.3. The method for manufacturing a ring-shaped body according to any one of claims 1 to 5, characterized in that the alloy part is made of a Ni-based alloy. 7. The method for manufacturing a ring-shaped body according to claim 6, characterized in that the forging step is carried out at a temperature of 950 °C to 1,075 °C. The method for manufacturing a ring-shaped body according to claim 6 or 7, characterized in that the ring rolling step is carried out at a temperature of 900°C to 1,050°C.