JP2014188580A - Manufacturing method of annular molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of an annular molding capable of stably and inexpensively manufacturing the annular molding being sufficiently high in mechanical strength by securing uniformity of a structure.SOLUTION: The manufacturing method of the annular molding comprises a forging step S2 of manufacturing a discoid forging body by forging an alloy element assembly and a ring rolling step S4 of manufacturing the annular molding by ring-rolling an annular intermediate body of forming a through-hole in the forging body. In the forging step S2, hot forging is executed by at least two times or more so as to fall within a range in which a stain rate is 0.5 sor less, an absolute value εθ1 of strain in the circumferential direction of the forging body is 0.3 or more, an absolute value εh of the strain in the height direction of the forging body is 0.3 or more, and the ratio εh/εθ1 of the mutual absolute values of these strains is 0.4 or more and 2.5 or less.

Description

  The present invention relates to a method for producing an annular molded body used as a processing material when producing an annular product such as a turbine disk of an aircraft engine.

The above-described turbine disk is an annular member having a through hole, and a plurality of turbine blades are disposed on the outer peripheral side, and are configured to rotate together with the turbine blades.
In the above-described turbine disk, the outer periphery thereof is exposed to combustion gas and becomes a high temperature of about 600 to 700 ° C., while the temperature of the inner periphery is kept relatively low, and the engine is started and stopped. Thus, thermal stress is repeatedly generated inside. For this reason, excellent low cycle fatigue characteristics are required, and the outer peripheral portion is subjected to centrifugal force due to high-speed rotation around the axis at high temperature, and therefore must have high creep strength characteristics. Also, high tensile / yield strength is required.

  In order to ensure the mechanical strength that can meet such various demands, the annular molded body used for the turbine disk is, for example, as described in Patent Documents 1 and 2, a Ni-based superb material having excellent heat resistance. It is produced by forging a material made of an alloy and cutting the resulting annular forged body. That is, the forging is strained and the crystal grains are refined to improve the tensile strength and fatigue strength. As the forging equipment, a hydraulically controlled forging press capable of strict control of the forging speed is desirable. In order to obtain the uniformity in the circumferential direction of the structure (crystal grains) in the annular formed body, the entire material is simultaneously formed. It has been recognized that application of full forging is preferred.

Incidentally, in recent years, with the demand for higher output of aircraft engines, there is a demand for larger turbine disks. In order to increase the size of the annular molded body as the size of the turbine disk increases, a large hydraulic control forging press of tens of thousands of tons is required (for example, see Non-Patent Document 1).
However, the large hydraulic control forging press described above is not only very expensive but also few in the world. When such a large hydraulic control forging press is used, the supply capacity of the annular molded body is low. In addition to being limited, product costs will remain high. In addition, the trend toward larger turbine disks in recent years has reached the point where hermetic forging is difficult even when large hydraulically controlled forging presses are used. There is a problem that it is difficult to obtain and it is difficult to ensure the uniformity of the structure.

On the other hand, instead of forming the annular formed body by forging press, a method of forming by ring rolling can be considered. In this case, the equipment cost can be reduced and it is easy to cope with an increase in the size of the annular molded body. However, in general, ring-rolled products are more susceptible to anisotropy in mechanical properties (strength properties) than press-forged products, and are not suitable for products that require isotropic mechanical properties such as turbine disks. .
In addition, a method of forming an annular formed body by combining forging press and ring rolling is also conceivable, but in order to obtain a desired uniform microstructure, it is necessary to perform final forging after the ring rolling, and the manufacturing process However, there is a problem in that the manufacturing cost increases.

  Therefore, in Patent Document 3, the forging process and the ring rolling process are combined, and in the forging process, the circumferential strain εθ1 and the strain εθ1 in the height direction and the strain ratio εθ1 / εθ1 are set to appropriate values. There has been proposed a method of manufacturing an annular molded body having a fine crystal structure with sufficiently uniform uniformity at low cost by performing controlled hot forging a plurality of times.

JP 07-138719 A JP-A-62-211333 JP 2011-255409 A

“Survey report on research on development of innovative materials using press machines for ultra-large forging”, New Energy and Industrial Technology Development Organization, March 2003, p. 10, 11, 37-41

By the way, recently, production of high-power aircraft engines has become active, and demand for large-sized annular molded bodies has increased. Therefore, manufacturing that can stably mass-produce annular molded bodies having a uniform structure is possible. There is a need for a method.
Here, as a result of the study of the method of manufacturing the annular molded body described in Patent Document 3, the inventors of the present invention have found that the strain εθ1 in the circumferential direction and the strain εθ1 in the height direction of the forged body and the strain ratio εθ1 / εθ1 are obtained. Although it has been confirmed that by carrying out hot forging controlled to an appropriate value a plurality of times, an annular molded body with a fine crystal grain size and a uniform shape can be obtained, for example, a large-scale annular molded body with a large thickness is obtained. In rare cases, the crystal grain size of the annular molded body sometimes becomes non-uniform due to variations in operating conditions.

  The present invention has been made in view of such circumstances, and it is possible to stably and inexpensively manufacture an annular molded body having a sufficiently high mechanical strength while ensuring the uniformity of the structure. It aims at providing the manufacturing method of the cyclic | annular molded object which can be performed.

In order to solve such problems and achieve the above object, the method for producing an annular molded body of the present invention includes a forging step of forging an alloy body to produce a disk-shaped forged body, and the forging process. A ring rolling step of ring-rolling an annular intermediate body formed by forming a through hole in the body to produce an annular molded body, wherein the forging step has a strain rate of 0. 5s ⁻¹ or less, the absolute value εθ1 in the circumferential direction of the forged body is 0.3 or more, the absolute value εh in the height direction strain of the forged body is 0.3 or more, and the ratio between the absolute values of these strains The hot forging in which εh / εθ1 is in the range of 0.4 to 2.5 is performed at least twice.

In the manufacturing method of the annular molded body of the present invention, the strain rate in the forging process is 0.5 s ⁻¹ or less. Here, when the strain rate exceeds 0.5 s ⁻¹ , the crystal grain size inside the forged body is coarse due to excessive increase in the temperature inside the forged body due to processing heat (so-called heat buildup). become. In addition, in ring rolling after forging, since the inside cannot be sufficiently distorted, the crystal grains inside the forged body cannot be refined. Therefore, in the present invention, by setting the strain rate within the range of 0.5 s ⁻¹ or less, it is possible to reduce the temperature difference between the surface and the inside of the forged body during forging and to make the structure uniform. It becomes. In addition, in order to make the above-mentioned operation effect effective, it is preferable that the strain rate in the forging process is 0.15 s ⁻¹ or less.
The strain rate is defined by the following equation.

  In the forging process, since the absolute value εθ1 of the circumferential strain is set to a large value of 0.3 or more, the proportion of the circumferential strain applied to the annular intermediate in the ring rolling process can be reduced. . Furthermore, since the absolute value εh of the strain in the height direction is set to a large value of 0.3 or more, it is possible to secure a sufficient amount of strain in the height direction that is difficult to impart by ring rolling. As a result, the processing rate in the ring rolling can be reduced, the anisotropy of the strength characteristics of the annular molded body is suppressed, the isotropic property is enhanced, and a fine crystal structure with sufficiently ensured uniformity is obtained. It is done.

The ratio εh / εθ1 indicates the directional balance of applied strain, and is an index for controlling the relative position change in the material before and after processing. In the subsequent ring rolling process, the corresponding numerical value must be zero or close to zero due to the manufacturing method, so it is essential to suppress the anisotropy by appropriately taking the strain application ratio in the height direction in the forging process. However, if εh / εθ1 is less than 0.4, the effect is insufficient. On the other hand, if εh / εθ1 exceeds 2.5, the distribution in the height direction becomes excessive, the plastic flow becomes unstable, and the axial symmetry of the plastic flow that is indispensable for imparting uniformity is reduced.
Therefore, in the present invention, by defining the ratio εh / εθ1 between the absolute values of strain within the range of 0.4 to 2.5, the plastic flow is stabilized and the axial symmetry is secured, and the structure is uniform. Can be achieved.

Here, in the method for manufacturing an annular molded body according to the present invention, in the ring rolling step, hot rolling is performed to give an absolute value εθ2 of a circumferential strain in the annular molded body of 0.5 or more, and the annular molding is performed. The grain size of the product region in the body may be 8 or more in terms of ASTM grain size number.
In this case, in the ring rolling process, by performing hot rolling that gives an absolute value εθ2 of the circumferential distortion of the annular molded body of 0.5 or more, crystals in the product region that is made into a product by machining in the annular molded body The grain size is reliably refined to 8 or more by ASTM grain size number. Accordingly, it is possible to reliably increase the mechanical strength of the product obtained from the annular molded body.
The ASTM grain size number is determined according to the standard specified in ASTM standard E122 of American Society of Testing and Materials (American Society for Testing Materials).

Further, in the method for producing an annular molded body according to the present invention, the crystal grain size difference in the product region of the annular molded body in a cross section including the axis of the annular molded body is within a range of ± 2 in terms of ASTM grain size number difference. It may be there.
In this case, since the crystal grain size difference in the product region in the cross section of the annular shaped product is within the range of ± 2 in terms of ASTM grain size number difference, this annular shaped product has a crystal grain size in the radial direction and the height direction. Uniformity is ensured.

Moreover, in the manufacturing method of the annular molded body according to the present invention, in the forging step, the crystal grain size of the forged body may be 7 or more in terms of ASTM grain size number.
In this case, in the forging process, by applying a high strain amount as described above, the crystal grain size of the forged body can be refined to 7 or more by the ASTM crystal grain size number. Therefore, the structure of the annular molded body can be refined while reducing the amount of strain applied in the next ring rolling step.

Furthermore, in the manufacturing method of the annular molded body according to the present invention, the ratio T / H between the radial thickness T of the annular intermediate body and the height H along the axial direction of the annular intermediate body is 0.6 or more and 2 .3 after forming the annular intermediate so as to be in the range of 3 or less, ring rolling, the crystal grain size difference between a plurality of equivalent positions set uniformly in the circumferential direction on the annular molded body, ASTM grain size number The difference may be within a range of ± 1.5.
In this case, the annular intermediate is formed so that the ratio T / H between the radial thickness T and the height H of the annular intermediate is in the range of 0.6 to 2.3, and then ring-rolled. Thereby, the crystal grain size difference between the circumferential equivalent positions in the annular molded body can be suppressed within a range of ± 1.5 by the ASTM crystal grain size number difference. That is, the annular molded body obtained by molding this annular intermediate body ensures the uniformity of the crystal grain size in the circumferential direction. Specifically, ring rolling is local processing, but unlike general partial forging, it has high continuity of processing, so the structure has a high axial symmetry, and deviation in material properties in the circumferential direction in an annular molded body. Is known to be small. In the present invention, by setting the ratio T / H within the aforementioned range in the annular intermediate body before ring rolling, the shape (roundness) of the molded annular molded body and the axial symmetry of the structure are further increased. it can.

  That is, when the ratio T / H is in the range of 0.6 or more and 2.3 or less, rolling stability essential for imparting uniformity is brought about. Specifically, in the region where T / H is less than 0.6, the contact area between the two rolls to be rolled (main roll and mandrel roll) and the material is increased, and the influence of heat removal is relatively increased. Uniformity in direction becomes difficult to obtain. On the other hand, buckling is more likely to occur as T / H increases. Specifically, in the region where T / H exceeds 2.3, the same tendency becomes stronger, so that it is difficult to obtain circumferential uniformity.

  According to the present invention, there is provided a method for producing an annular molded body capable of stably and inexpensively producing an annular molded body having a sufficiently high mechanical strength while ensuring the uniformity of the structure. Can do.

It is a top view of the cyclic molded object which is one Embodiment of this invention. FIG. 2 is a cross-sectional view taken along the line XX in FIG. 1. It is a flowchart which shows the manufacturing method of the annular molded object and turbine disk which are one Embodiment of this invention. It is sectional drawing of the cyclic | annular intermediate body used in the manufacturing method shown in FIG. It is explanatory drawing of the ring rolling used in the manufacturing method shown in FIG. It is explanatory drawing of the ring rolling process using a mandrel roll and a main roll. It is explanatory drawing of the ring rolling process using a mandrel roll and a main roll. It is a tensile strength-drawing correlation figure of the cyclic molded object which concerns on the Example of this invention. It is a yield strength-drawing correlation diagram of an annular molded body according to an example of the present invention.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.
The annular molded body 10 according to the present embodiment is used as a processing material for molding a turbine disk of an aircraft engine.

As shown in FIGS. 1 and 2, the annular molded body 10 has a through hole and an annular shape centering on the axis O, and is directed radially inward from the main body 11 and the main body 11. And an outer ridge 13 projecting radially outward from the main body 11.
Further, the annular molded body 10 is made of a Ni-base superalloy excellent in heat resistance, and in this embodiment, is made of a Ni-base alloy Alloy718.

  The alloy composition of the Ni-based alloy Alloy 718 is as follows: Ni: 50.00 to 55.00 mass%, Cr: 17.0 to 21.0 mass%, Nb: 4.75 to 5.60 mass%, Mo; 2 .8 to 3.3 mass%, Ti; 0.65 to 1.15 mass%, Al; 0.20 to 0.80 mass%, C; 0.01 to 0.08 mass%, the balance being Fe and inevitable It is considered as an impurity.

  The annular molded body 10 has a grain size of ASTM in the desired region (hereinafter referred to as “product region”) (not shown) that is machined into a turbine disk (product). 8 or more. 2 are cross sections including the axis O of the annular molded body 10, and these virtual planes VS1 and VS2 are at equivalent positions obtained by equally dividing the annular molded body 10 into two in the circumferential direction. Is set. In the annular molded body 10, the crystal grain size difference in the structure of the product region in the cross section of the virtual plane VS1 (or VS2) is within the range of ± 2 in terms of ASTM crystal grain size number difference, and uniformity is ensured. . Further, the difference in crystal grain size between the equivalent positions in the circumferential direction of the annular molded body 10, that is, the difference between the crystal grain size in the virtual plane VS1 and the crystal grain size in the virtual plane VS2 is within the range of ± 1.5 in terms of the ASTM crystal grain size number difference. It is said that.

  Next, a method for manufacturing the annular molded body 10 and a method for manufacturing the turbine disk will be described with reference to FIGS.

(Melting casting process S1)
First, a melt of Ni-based alloy Alloy 718 is melted. Here, a melting raw material is prepared so as to be in the component range of the above-described Ni-based alloy Alloy 718, and vacuum induction heating melting (VIM: Vacuum Induction Melting) is performed to produce an ingot. Next, this ingot is electroslag remelted (ESR: Electro Slag Remelting) to produce the ingot again. Further, this ingot is subjected to vacuum arc remelting (VAR) and then hot forging is performed to produce a cylindrical billet (alloy body).

  For example, the billet is formed to have a diameter of about 7 inches to 12 inches. The produced billet structure is ASTM No. It is about 6. As described above, by performing the dissolution three times (triple dissolution), a billet with a high cleanliness is produced, in which the solidification segregation of the alloy components is small and the solidification structure is controlled, and there are very few inclusions.

(Forging process S2)
Next, the billet is forged so as to press in the axial direction of the billet, and a disk-shaped forged body is produced.
In this forging process S2, the absolute value εθ1 of the circumferential strain of the forged body is 0.3 or more and the absolute strain of the forged body in the height direction with the billet temperature heated to 950 to 1075 ° C., for example. Hot forging is carried out at least twice so that the value εh is 0.3 or more and the ratio εh / εθ1 between the absolute values of these strains is in the range of 0.4 to 2.5.

And the strain rate in the hot forging in the forging step S2 is set to 0.5 s ⁻¹ or less.
In the present embodiment, the hot forging in the forging step S2 is performed using a hydraulically controlled forging press apparatus. This hydraulically controlled forging press apparatus can accurately adjust the strain rate during forging so as to be within the above-described range by hydraulic control. In the present embodiment, the strain rate in the hot forging in the forging step S2 is set to 0.01 s ⁻¹ or more.

Furthermore, in the present embodiment, the absolute value εθ1 of the strain applied in the circumferential direction is set to 0.3 or more. Moreover, the absolute value εh of the strain applied in the height direction along the axial direction of the forged body is set to 0.3 or more.
By this forging step S2, the height of the forged body is adjusted to, for example, about 60 mm to 500 mm. By such a forging process, the forged body is sufficiently strained, and the crystal grain size of the forged body is refined to 7 or more by the ASTM grain size number.

(Drilling process + Intermediate ring rolling process S3)
Next, a through hole having a circular cross section is formed by a water cutter in the center of the obtained forged body. Furthermore, intermediate ring rolling is performed as necessary after forming the through holes. The annular intermediate body 20 is produced by this drilling process + intermediate ring rolling step S3.
In the present embodiment, as shown in FIG. 4, the annular intermediate body 20 has a top surface and a bottom surface that have a substantially polygonal cross section orthogonal to the circumferential direction and extend in a direction substantially orthogonal to the axis O. A portion 21, an inner convex portion 22 projecting radially inward from the base portion 21, and an outer convex portion 23 projecting radially outward from the base portion 21 are provided.

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

(Ring rolling process S4)
Next, the annular intermediate 20 is subjected to ring rolling. In addition, this ring rolling is performed by hot rolling, and the temperature is in the range of 900 ° C. to 1050 ° C., for example.
Here, as shown in FIG. 5, the ring rolling device 30 includes a main roll 40 disposed on the outer peripheral side of the annular intermediate body 20, and a mandrel roll 50 disposed on the inner peripheral side of the annular intermediate body 20. And a pair of axial rolls 31 and 32 that are in contact with the end face in the axis O direction of the annular intermediate body 20 (in this embodiment, the upper surface and the lower surface of the base portion 21).

  The main roll 40 and the mandrel roll 50 are arranged so that the rotation axes thereof are parallel to each other, sandwich and press the annular intermediate body 20 from the inner peripheral side and the outer peripheral side, and rotate the annular intermediate body 20 in the circumferential direction. It is set as the structure rolled while making it. The pair of axial rolls 31 and 32 are configured to sandwich and press the annular intermediate body 20 in the axis O direction, and control the height dimension of the annular intermediate body 20.

  Here, as shown in FIG. 6, an accommodation recess 41 that can accommodate a part of the annular intermediate body 20 is provided on the outer peripheral portion of the main roll 40. In this embodiment, the outer side of the annular intermediate body 20 is provided. The depth is such that the outer peripheral portions of the convex portion 23, the base portion 21, and the inner convex portion 22 can be accommodated. In addition, a first molding groove 42 for molding the outer protruding portion 13 of the annular molded body 10 is formed in the bottom portion 41A of the housing recess 41 on the radially inner side (right side in FIG. 6) of the main roll 40. It is formed so as to be recessed. In addition, this 1st shaping | molding groove | channel 42 is made into the same depth as the protrusion height of the outer side protruding item | line part 13 shape | molded.

  On the other hand, on the outer peripheral portion of the mandrel roll 50, an insertion portion 51 configured to be inserted into the housing recess 41 of the main roll 40 is provided, and the annular molded body 10 is provided on the outer peripheral surface of the insertion portion 51. A second forming groove 52 for forming the inner ridge portion 12 is formed so as to be recessed toward the radially inner side (left side in FIG. 6) of the mandrel roll 50. In addition, this 2nd shaping | molding groove | channel 52 is made into the same depth as the protrusion height of the inner side protruding item | line part 12 shape | molded.

  When the main roll 40 and the mandrel roll 50 configured as described above operate so as to approach each other, the annular intermediate body 20 is sandwiched and pressed between the main roll 40 and the mandrel roll 50. Specifically, by rotating the main roll 40 around the rotation axis of the main roll 40, the main roll 40 and the mandrel roll 50 are brought close to each other, so that an intermediate ring is formed by the frictional resistance between the main roll 40 and the main roll 40. The body 20 is rotated around the axis O.

  On the other hand, the mandrel roll 50 is rotatable about the rotation axis of the mandrel roll 50 and is driven to rotate by frictional resistance with the annular intermediate body 20. The annular intermediate body 20 is plastically deformed so as to be filled in the housing recess 41 and the first molding groove 42 of the main roll 40 and the second molding groove 52 of the mandrel roll 50, and the annular molded body 10 is molded. Become. At this time, the inner ridge 12 in the annular molded body 10 is plastically deformed corresponding to the shape of the second molding groove 52. In addition, the outer ridge 13 is plastically deformed corresponding to the shape of the first forming groove 42.

By carrying out the ring rolling in this way, the annular intermediate body 20 is plastically deformed so as to extend in the circumferential direction, and the inner diameter and the outer diameter thereof are enlarged to produce the annular molded body 10 shown in FIG. It is.
And in this ring rolling process S4, it is supposed that 0.5 or more of absolute value (epsilon) (theta) 2 of the distortion | strain of the circumferential direction in the annular molded object 10 is provided. Specifically, at least one hot rolling is performed, and the absolute value εθ2 of the strain is set within a range of 0.5 to 1.3 in total.

(Heat treatment step S5 / Cutting step S6)
The annular molded body 10 produced as described above is adjusted in characteristics by heat treatment, and is formed into a final shape by cutting to be a turbine disk of an aircraft engine.

According to the method for manufacturing an annular molded body according to the present embodiment configured as described above, the strain rate is set to 0.5 s ⁻¹ or less in the forging step S2 in which a billet is forged to produce a forged body. And it can suppress that the temperature inside a forging body rises excessively by processing heat (so-called heat buildup). Therefore, the temperature difference between the surface and the inside of the forged body during forging can be reduced, and the structure of the forged body can be made uniform. In addition, in order to ensure that this effect is achieved, it is preferable to set the strain rate in the forging step S2 to 0.15 s ⁻¹ or less.

  Further, in the forging step S2, the absolute value εθ1 of the strain in the circumferential direction is set to a large value of 0.3 or more, so the ratio of the strain amount in the circumferential direction applied to the annular intermediate body 20 in the ring rolling step S4 is reduced. be able to. Furthermore, since the absolute value εh of the strain in the height direction is set to a large value of 0.3 or more, a sufficient amount of strain in the height direction that is difficult to impart in the ring rolling step S4 can be secured. Thereby, the processing rate in the ring rolling step S4 can be lowered, the anisotropy of the strength property of the annular molded body 10 is suppressed, the isotropic property is enhanced, and the fine crystal in which the uniformity is sufficiently secured. Organization is obtained.

  In addition, since the ratio εh / εθ1 between the absolute value εθ1 of the strain in the circumferential direction and the absolute value εh of the strain in the height direction is 0.4 or more, a sufficient strain application ratio in the height direction is ensured. Thus, even if the subsequent ring rolling step S4 cannot sufficiently impart strain in the height direction, the uniformity of the structure can be ensured. Moreover, since the ratio εh / εθ1 is 2.5 or less, the distribution in the height direction is not excessive, the plastic flow is stable, and the axial symmetry of the plastic flow that is indispensable for imparting uniformity is ensured. Can do.

  Furthermore, in this embodiment, in the forging step S2, the absolute value εθ1 of the strain applied in the circumferential direction is set to 0.3 or more, and is applied in the height direction along the axial direction of the forged body. Since the absolute value εh of the strain amount is set to 0.3 or more, it can be suppressed that the temperature inside the forged body rises due to processing heat and the crystal becomes coarse.

  Further, in the ring rolling step, since the hot rolling is performed to give an absolute value εθ2 of the circumferential strain of the annular molded body 10 of 0.5 or more, the grain size of the product region in the annular molded body 10 is It is surely refined to 8 or more by ASTM grain size number. Therefore, the mechanical strength of the product obtained from the annular molded body 10 is reliably increased.

  Further, since the crystal grain size difference in the product region in the cross section including the axis O of the annular molded body 10 is within the range of ± 2 in terms of the ASTM crystal grain size number difference, the annular molded body 10 has a radial direction and a high height. The uniformity of crystal grain size in the vertical direction is sufficiently secured.

  Further, in the forging process, by applying a high strain amount as described above, the crystal grain size of the forged body can be refined to 7 or more by ASTM grain size number. Therefore, the structure of the annular molded body 10 can be refined while reducing the amount of strain applied in the next ring rolling step.

  In addition, after the annular intermediate body 20 is molded so that the ratio T / H between the radial thickness T and the height H of the annular intermediate body 20 is in the range of 0.6 or more and 2.3 or less, Since it is set as the structure rolled, the crystal grain size difference of the circumferential equivalent position in the cyclic | annular molded object 10 can be suppressed in the range of +/- 1.5 by ASTM crystal grain size number difference. That is, in the annular molded body 10 obtained by molding the annular intermediate body 20, the uniformity of the crystal grain size in the circumferential direction is sufficiently ensured.

  In detail, the ring rolling is local processing, but unlike general partial forging, it has high continuity of processing and thus has high axial symmetry of the structure after forming, and the material properties in the circumferential direction of the annular formed body 10 are high. It is known that the deviation becomes smaller. Therefore, as in this embodiment, by setting the ratio T / H within the above-described range in the annular intermediate body 20 before ring rolling, the shape (roundness) and structure of the molded annular molded body 10 are determined. The axial symmetry of can be further increased.

  That is, when the ratio T / H is in the range of 0.6 or more and 2.3 or less, rolling stability essential for imparting uniformity is brought about. Specifically, in the region where T / H is less than 0.6, the contact area between the two rolls to be rolled (main roll 40 and mandrel roll 50) and the material is increased, and the influence of heat removal is relatively increased. It becomes difficult to obtain uniformity in the circumferential direction. On the other hand, buckling is more likely to occur as T / H increases. Specifically, in the region where T / H exceeds 2.3, the same tendency becomes stronger, so that it is difficult to obtain circumferential uniformity.

  As described above, according to the method for manufacturing an annular molded body according to the present embodiment, an annular molded body having a sufficiently high mechanical strength while ensuring the uniformity of the structure is manufactured stably and at low cost. It becomes possible.

The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.
For example, the shapes of the annular molded body 10 and the annular intermediate body 20 are not limited to this embodiment, and can be appropriately changed in design in consideration of the shape of the annular product such as a turbine disk to be produced. .
In addition, the annular molded body 10 and the annular intermediate body 20 have been described as being constituted by the Ni-based alloy Alloy 718. However, the present invention is not limited to this, and other materials (for example, Waspaloy (registered trademark) (United Technology Inc.) .), Alloy 720, Co-based alloy, Fe-based alloy, etc.).

In addition, it has been described that the melt of the Ni-based alloy Alloy 718 is melted and the billet is produced by casting. However, the present invention is not limited to this, and the billet is produced by a powder molding method. It is good also as a structure which performs a ring rolling process.
Moreover, you may produce a billet by double melt | dissolution (VIM + ESR or VIM + VAR) instead of producing by the above-mentioned triple melt | dissolution.

  Moreover, in this embodiment, although demonstrated as what has a perforation process which forms a through-hole by the water cutter in the center part of a disk-shaped forged body, it is not limited to this, By methods other than a water cutter A through hole may be formed. Alternatively, a through hole may be formed at the time of forging, and the drilling process itself may be omitted. Further, drilling with a water cutter or the like is possible in the middle of the forging process.

  Further, in FIG. 3, after the annular formed body 10 is formed by the ring rolling step S4, before the heat treatment step S5, the annular formed body 10 is subjected to processing such as partial forging for the purpose of giving a shape and adjusting the shape dimension. May be.

  In this embodiment, the difference between the crystal grain size in the virtual plane VS1 and the crystal grain size in the virtual plane VS2 is determined according to ASTM using equivalent positions (virtual planes VS1, VS2) obtained by equally dividing the annular molded body 10 in the circumferential direction. Although the crystal grain size number difference is assumed to be within a range of ± 1.5, the number of virtual planes to be compared is not limited to two. That is, since the annular molded body 10 is ensured equivalence in the entire circumference in the circumferential direction, not only in the above-described two divisions, but also in the crystal grain size difference between equivalent positions divided into three or more equally in the circumferential direction, The difference in ASTM grain size number is within a range of ± 1.5. Further, in the annular molded body 10, the circumferential position for setting the equivalent position is not limited.

  Hereinafter, the present invention will be specifically described by way of examples. However, the present invention is not limited to this embodiment.

(Sample preparation)
First, a melt of Ni-based alloy Alloy 718 was melted. Specifically, the melting raw material was prepared so as to be in the component range of the Ni-based alloy Alloy 718 described in the above embodiment. And triple dissolution was given to this molten metal. Specifically, vacuum induction heating melting (VIM), electroslag remelting (ESR), and vacuum arc remelting (VAR) were performed to produce a cylindrical billet with a diameter of 254 mm.

Next, a forging process was performed on the billet to produce a disk-shaped forged body. Forging was performed twice by hot forging in which the temperature of the billet was heated to 1000 ° C.
The forging process is performed under the conditions shown in Table 1 with respect to the absolute value εθ1 of the strain in the circumferential direction of the forged body, the absolute value εh of the strain in the height direction of the forged body, the ratio εh / εθ1 between the absolute values of these strains, and the strain rate. It carried out in.

  Next, a through hole was formed in the center of the forged body with a water cutter, and an annular intermediate 20 was produced. The annular intermediate 20 was molded such that the ratio T / H between the thickness T and the height H was a value shown in Table 1.

Next, the annular intermediate 20 was subjected to ring rolling. The ring rolling was performed twice by hot rolling in which the temperature of the annular intermediate 20 was heated to 1000 ° C. In addition, the ring rolling was performed so that the total of the absolute value εθ2 of the circumferential strain of the annular molded body 10 was in the condition shown in Table 1 by these two hot rollings.
Next, the annular molded body 10 was subjected to heat treatment. As a direct aging material, water-cooled after ring rolling, 718 ° C./8 hours + 621 ° C./8 hours + A. C. An aging treatment was produced. Further, as a solution aging material, 970 ° C./1 hour + W. Q. 718 ° C./8 hours + A. After solution treatment. C. An aging treatment was produced.

(Crystal grain size measurement)
Using the produced annular molded body 10, the maximum crystal grain size in the product region in the cross section including the virtual planes VS1 and VS2 and the average crystal grain size around the maximum crystal grain were measured and compared. The average crystal grain size around the maximum crystal grain was the average crystal grain size of the maximum crystal grain confirmation part (excluding the maximum crystal grain). The results are shown in Table 2.

(High temperature tensile property confirmation test)
Of the annular molded body 10 produced as described above, for the inventive example 1 and the comparative example 3, tensile test pieces in the circumferential direction, the height direction, and the radial direction from the equivalent positions including the virtual planes VS1 and VS2 in FIG. Each was sampled and subjected to a 650 ° C. high temperature tensile test. The test was conducted in accordance with ASTM E21 using an ASTM E8 small size test piece having a parallel part diameter of 6.35 mm, and the tensile strength, proof stress (0.2% proof stress), and drawing were measured. Moreover, in order to confirm the deviation of each measured value of the circumferential direction, the height direction, and the radial direction, the ratio of the height direction and the radial direction when the circumferential measured value was set to 1 (100%) was calculated. FIG. 8 shows a tensile strength-drawing correlation diagram, and FIG. 9 shows a proof stress-drawing correlation diagram.

In Comparative Examples 1 and 2 in which the strain rate in the forging process exceeds 0.5 s ⁻¹ , the maximum crystal grain size and the average crystal grain size in the vicinity thereof are greatly different, and it is confirmed that the structure is not uniformized. . It is presumed that the crystal grain size inside the forged body is locally coarsened due to excessive increase in the temperature inside the forged body due to processing heat (so-called heat buildup).
On the other hand, in the present invention example 1-4 in which the strain rate in the forging process is 0.5 s ⁻¹ or less, the difference between the maximum crystal grain size and the average crystal grain size in the vicinity thereof is small, and the structure is sufficiently uniformized. That is confirmed. By setting the strain rate within the range of 0.5 s ⁻¹ or less, it is presumed that the temperature difference between the surface and the inside of the forged body during forging is reduced, and the structure can be made uniform. In Examples 1, 2, and 4 of the present invention in which the strain rate is 0.15 s ⁻¹ or less, the structure is further uniformized.

  Further, as shown in FIGS. 8 and 9, as a result of the high-temperature tensile property confirmation test, Example 1 of the present invention is superior to Comparative Example 2 in all of tensile strength, 0.2% proof stress, and drawing. confirmed. That is, it was found that Example 1 of the present invention has a fine crystal structure in which the isotropy of strength characteristics is enhanced and the uniformity is sufficiently ensured.

DESCRIPTION OF SYMBOLS 10 Ring molded object 20 Ring intermediate body H Height along the axial direction of a ring intermediate body O Axis line S2 Forging process S4 Ring rolling process T Thickness of radial direction in ring intermediate body VS1 Virtual plane (equivalent position)
VS2 virtual plane (equivalent position)

Claims (4)

A forging step of forging an alloy body to produce a disc-shaped forged body, a ring rolling step of ring-rolling an annular intermediate formed by forming a through hole in the forged body, and producing an annular shaped body, A method for producing an annular molded body comprising:
In the forging step, the strain rate is 0.5 s ⁻¹ or less, the absolute strain value εθ1 in the circumferential direction of the forged body is 0.3 or more, and the absolute strain value εh in the height direction of the forged body is 0.3. As described above, a method for producing an annular molded body is characterized in that hot forging is performed at least twice or more so that the ratio εh / εθ1 between the absolute values of these strains is in the range of 0.4 to 2.5.   2. The annular molding according to claim 1, wherein a crystal grain size difference in a product region of the annular molded body in a cross section including an axis of the annular molded body is within a range of ± 2 in terms of ASTM grain size number difference. Body manufacturing method.   3. The method for producing an annular molded body according to claim 1, wherein in the forging step, a crystal grain size of the forged body is set to 7 or more in ASTM grain size number.   The annular intermediate body has a ratio T / H between a radial thickness T of the annular intermediate body and a height H along the axial direction of the annular intermediate body in the range of 0.6 to 2.3. After forming, the ring rolling is performed, and the crystal grain size difference between a plurality of equivalent positions set uniformly in the circumferential direction in the annular molded body is set within a range of ± 1.5 in terms of ASTM crystal grain size number difference. The method for producing an annular molded body according to any one of claims 1 to 3.

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