Manufacturing method of annular rolled material

Abstract

Provided is a method for manufacturing a ring-shaped rolled material, which can stabilize the orientation of a ring-shaped blank without causing defects or the like in the obtained ring-shaped rolled material even if a main roller of a ring-shaped rolling device is provided with flange parts located at the upper and lower positions of the ring-shaped blank. The ring rolling device used in the manufacturing method of the ring rolled material is provided with a main roller (10) and a core roller (20), and the outer peripheral surface of the main roller is provided with a concave part (12) for accommodating the outer peripheral surfaces of the ring blank and the core roller, an upper flange part located on the upper side of the concave part, and a lower flange part located on the lower side of the concave part. The inner surface of the recess has a rolling surface in contact with the outer peripheral surface of the annular blank, an upper surface on the upper flange portion side, and a lower surface on the lower flange portion side, and the lower surface has a slope such that the opening of the recess widens. The inclination starts in a range from an intersection line of the lower surface and the rolled surface to a distance corresponding to the thickness of the annular rolled material, and the angle of the inclination is greater than 0.3 DEG and 9 DEG or less with respect to a vertical plane.

Description

[0001] This application is a divisional application of the patent application with application number 202080089438.5 and titled "Manufacturing method of ring-shaped rolled material", filed on December 16, 2020. TECHNICAL FIELD

[0002] The present application relates to a manufacturing method of a ring-shaped rolled material. BACKGROUND

[0003] As a method of manufacturing a ring-shaped rolled material by ring-rolling a ring-shaped blank, for example, as disclosed in Japanese Patent No. 5895111, there is a method in which a main roller and a core roller are brought into contact with an outer peripheral surface and an inner peripheral surface of a ring-shaped blank having a ring shape, respectively, the main roller and the core roller are rotated around a center axis while sandwiching and pressing the ring-shaped blank in a radial direction of the ring-shaped blank, and a pair of shaft rollers sandwich and press the ring-shaped blank in a direction of the center axis of the ring-shaped blank, thereby manufacturing the ring-shaped rolled material.

[0004] Further, as a manufacturing method of a ring-shaped rolled material, for example, in the specification of Chinese Patent Application Publication No. 107127279, a method of ring-rolling is described in which it is disclosed that the main roller is provided with a lower support plate located below the ring-shaped blank and an upper pressing plate located above the ring-shaped blank, the position of the upper pressing plate is adjusted by adjusting the ring-shaped member, thereby being able to easily cope with ring-shaped blanks having different heights.

[0005] PRIOR ART DOCUMENTS

[0006] PATENT DOCUMENTS

[0007] Patent Document 1: Japanese Patent No. 5895111

[0008] Patent Document 2: Specification of Chinese Patent Application Publication No. 107127279 SUMMARY

[0009] PROBLEMS TO BE SOLVED BY THE INVENTION

[0010] In the case of ring-rolling a ring-shaped blank, particularly if the ring-shaped blank has a conical shape or a shape in which the wall thickness of the ring-shaped blank is locally different, there is a problem that the posture of the ring-shaped blank during ring-rolling becomes unstable due to the difference in the circumferential speed between the main roller and the core roller as a mold and the ring-shaped blank, the difference in the amount of expansion between the thick wall portion and the thin wall portion, and the like. If the rotation of the ring-shaped blank becomes unstable, there is a problem that the ring-shaped blank excessively contacts the shaft rollers, the work table, and the like, defects are generated, or the ring-shaped rolled material after rolling becomes a deformed shape.

[0011] In order to stabilize the rotation of the ring-shaped material, a method is considered in which the posture of the ring-shaped material is stabilized by providing a flange portion at a position above and below the ring-shaped material on the main roller, but if the ring-shaped material is out of control during the ring-rolling process and comes into contact with the main roller and the core roller including the above-described flange portion, there is a problem in that the resulting ring-rolled material produces defects such as burrs, or the load acting on the ring-rolling device increases due to the impact of such contact. Thus, when a flange portion is provided on the main roller as described above, measures such as the following are required: a plurality of patterns of the shape of the main roller including the flange portion (so-called dies) are prepared, and ring-rolling is performed while adjusting the abutment with the ring-shaped material, or in order to reduce the load on the device, the process of performing ring-rolling after heating the ring-shaped material is performed more frequently (the so-called number of heating times is increased), and ring-rolling is performed little by little.

[0012] Therefore, the present application was completed in view of the above-described problems, and aims to provide a method for manufacturing a ring-rolled material in which, even if a flange portion is provided at a position above and below a ring-shaped material on a main roller, defects do not occur in the resulting ring-rolled material, and the posture of the ring-shaped material during rolling can be stabilized.

[0013] Solution to the problem

[0014] In order to achieve the above-described object, the present application is a method for manufacturing a ring-rolled material by performing ring-rolling on a ring-shaped material using a ring-rolling device, wherein the ring-rolling device includes a main roller and a core roller, an outer peripheral surface of the main roller has a recess portion that accommodates the ring-shaped material and an outer peripheral surface of the core roller, a first flange portion that is located on one side of the recess portion in a center axis direction of the main roller, and a second flange portion that is located on the opposite side of the first flange portion, an inner surface of the recess portion has a rolling surface that comes into contact with an outer peripheral surface of the ring-shaped material, a first inner surface on the first flange portion side, and a second inner surface on the second flange portion side, at least one of the first inner surface and the second inner surface has a slope with respect to a perpendicular surface that is perpendicular to the center axis direction of the main roller, such that the opening of the recess portion widens. The slope starts from a range from an intersection line of the at least one inner surface and the rolling surface to a distance corresponding to the thickness of the ring-rolled material. In other words, the distance between the intersection line of the at least one inner surface and the rolling surface and the end on the rolling surface side of the slope is less than the thickness of the ring-rolled material. The angle of the slope is greater than 0.3° and is 9° or less with respect to the perpendicular surface.

[0015] Preferably, the ring-shaped material is a heat-resistant alloy of a Ni-based alloy, a Co-based alloy, or an Fe-based alloy.

[0016] At least a portion of the outer peripheral surface of the ring-shaped blank can be inclined with respect to the central axis of the ring-shaped blank, and in this case, the angle between a straight line connecting the end face angle of the large-diameter outer periphery of the ring-shaped blank and the end face angle of the small-diameter outer periphery and the central axis of the ring-shaped blank can be greater than 10°. Further, in the case where the angle of inclination is greater than 10°, it is preferable that the angle of the slope of the inner surface be 0.6° or greater and 9° or less when the vertical plane is used as a reference. The lower limit of the angle of the slope is preferably 0.8° or greater, and more preferably 1° or greater. The upper limit of the angle of the slope is preferably 4° or less, and more preferably 3° or less.

[0017] At least a portion of the outer peripheral surface of the ring-shaped blank can be inclined with respect to the central axis of the ring-shaped blank, and in this case, the angle between a straight line connecting the end face angle of the large-diameter outer periphery of the ring-shaped blank and the end face angle of the small-diameter outer periphery and the central axis of the ring-shaped blank can be 10° or less. Further, in the case where the angle of inclination is 10° or less, it is preferable that the angle of the slope of the inner surface be greater than 0.3° and less than 3° when the vertical plane is used as a reference. The lower limit of the preferable angle of the slope is preferably 0.5° or greater, and more preferably 0.6° or greater. The upper limit of the angle of the slope is preferably 2.5° or less, and more preferably 2° or less.

[0018] Effects of the Invention

[0019] According to such the present application, the outer peripheral surface of the main roller has a recess that accommodates the ring-shaped blank and the outer peripheral surface of the core roller, at least one of a first inner surface on the first flange portion side of the recess and a second inner surface on the second flange portion side has a slope in the entire portion or a prescribed portion thereof, and the opening of the recess is widened. Therefore, the ring-shaped blank during rotation can be appropriately restrained, the posture of the ring-shaped blank can be stabilized, and the ring rolling can be smoothly performed. Thus, it is not necessary to prepare a plurality of types of molds or to increase the number of heating, and the cost required for the ring rolling can be reduced. In particular, even in the case where the ring-shaped blank has a tapered shape or a shape in which the wall thickness of the ring-shaped blank is locally different, the posture of the ring-shaped blank can be stabilized, and thus a near-net shape can be imparted to the obtained ring-rolled material, and the input weight of the ring-shaped blank can be reduced. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 FIG. 1 is a schematic plan view that schematically shows an example of a ring-rolling device used in a method of manufacturing a ring-rolled material according to the present application.

[0021] Figure 2 FIG. 2 is a schematic plan view that schematically shows an example of a ring-rolling device used in a method of manufacturing a ring-rolled material according to the present application. Figure 1 FIG. 3 is a schematic enlarged cross-sectional view of a main roller and a core roller in the ring-rolling device of FIG. 2.

[0022] Figure 3It is an enlarged representation Figure 2 A partial cross-sectional view of the upper flange of the main roller.

[0023] Figure 4 It is an enlarged representation Figure 2 A partial cross-sectional view of the lower flange of the main roller.

[0024] Figure 5 This is a cross-sectional view schematically illustrating an example of an annular billet used in the manufacturing method of the annular rolled material of the present invention. Detailed Implementation

[0025] Hereinafter, an embodiment of the method for manufacturing the annular rolled stock of the present invention will be described with reference to the accompanying drawings. Furthermore, the drawings are intended to clearly illustrate the embodiment of the present invention and are not necessarily drawn to scale.

[0026] In the method for manufacturing the annular rolled stock of this embodiment, for example, using Figures 1 to 4 The annular rolling apparatus shown includes a main roll 10 and a core roll 20 located on the outer and inner circumferential sides of an annular blank 1, which is the object to be rolled. The outer circumferential surfaces of the main roll 10 and the core roll 20 are opposite each other in a manner that clamps the annular blank 1. The main roll 10 is configured to rotate around its central axis 10X, and the core roll 20 is also configured to rotate around its central axis 20X. The central axes 10X of the main roll 10 and 20X of the core roll 20 are substantially parallel. The main roll 10 and the core roll 20 are used to extrude the annular blank 1 radially (hereinafter referred to as "annular radial") between the main roll 10 and the core roll 20, and the core roll 20 is configured to move relative to the main roll 10 along the annular radial. In addition, the direction of the central axis of the main roll is aligned with the direction of the central axis of the annular blank.

[0027] Furthermore, the annular rolling apparatus includes a pair of rollers 30 positioned to clamp the annular billet 1 along the central axis direction of the annular shape (hereinafter referred to as the "annular axis direction"). Additionally, for ease of explanation in this specification, along the central axis 10X or central axis 20X, Figure 2 The upper side is referred to as "upper," and the lower side as "lower." That is, a pair of rollers 30 are located on the upper and lower sides of the annular blank 1. The pair of rollers 30 press the annular blank 1 along the annular axis, and the outer circumferential surfaces of the pair of rollers 30 are opposite each other in a manner that clamps the annular blank 1. The pair of rollers 30 are configured to be able to rotate about their respective central axes.

[0028] The outer peripheral surface of the main roll 10 has: a generally U-shaped recess 12 that accommodates the annular billet 1 and the outer peripheral surface of the core roll 20, which are the objects to be rolled; a first flange portion (hereinafter referred to as the "upper flange portion") 11 located on one side in the direction of the central axis of the main roll; and a second flange portion (hereinafter referred to as the "lower flange portion") 13 located on the opposite side of the first flange portion. Furthermore, the inner surface of the recess 12 of the main roll 10 has: a rolling surface 12S that contacts the outer peripheral surface of the annular billet 1; a first inner surface (hereinafter referred to as the "upper surface") 11S on the side of the upper flange portion 11; and a second inner surface (hereinafter referred to as the "lower surface") 13S on the side of the lower flange portion 13.

[0029] The rolling surface 12S of the recess 12 of the main roll 10 is inclined correspondingly to the outer circumferential surface of the rolled annular material. Similarly, the outer circumferential surface 20S of the core roll 20 is also inclined correspondingly to the inner circumferential surface of the rolled annular material. Figure 2 As shown, the gap between the rolling surface 12S of the recess 12 of the main roll 10 and the outer peripheral surface 20S of the core roll 20 forms the shape of the rolled annular material. Thus, the rolling surface 12S of the recess 12 of the main roll 10 and the outer peripheral surface 20S of the core roll 20 correspond to the desired shapes of the outer and inner peripheral surfaces of the annular material, respectively, and can be inclined in a straight line, a curved line, or a combination of straight and curved lines. The wall thickness of the annular material may also be different; therefore, the inclination angles of the outer and inner peripheral surfaces of the annular material may not be the same.

[0030] like Figure 2 As shown, the lower surface 13S of the recess 12 of the main roller 10 is given a slope such that the opening of the recess 12 widens towards the outer periphery of the main roller 10. Furthermore, in Figure 2 In this design, since the lower surface 13S has a larger area than the upper surface 11S, a slope is applied to the lower surface 13S. However, depending on the desired shape of the annular rolled material, if the upper surface 11S has a larger area than the lower surface 13S, a slope is applied to the upper surface 11S in such a way that the opening of the recess 12 widens towards the outer periphery. Alternatively, it is not possible to apply a slope to only one of the upper surface 11S or the lower surface 13S, but to apply a slope to both the upper surface 11S and the lower surface 13S.

[0031] like Figure 3As shown, the angle θa of the upper surface 11S is represented by the angle between the vertical plane H (typically a horizontal plane representing the annular radial direction) that intersects the central axis of the main roller and the upper surface 11S. The lower limit of the angle θa of the upper surface 11S varies depending on the inclination angle of the annular blank, as described later, and is preferably greater than 0.3°, more preferably greater than 0.5°, further preferably greater than 0.6°, and even more preferably greater than 1°. Furthermore, the upper limit of the angle θa of the upper surface 11S is preferably less than 9°, more preferably less than 5°, further preferably less than 3°, and even more preferably less than 2°.

[0032] In addition, such as Figure 3 As shown, the slope of the upper surface 11S is given to the range from the intersection line V of the upper surface 11S and the rolling surface 12S of the recess 12 of the main roll 10 to the end of the outer peripheral side (i.e., the entire upper surface 11S). However, in order to obtain the effect of the present invention, the slope may not start from the intersection line V with the rolling surface 12S, but rather be given to the range from the position Sa of the desired inner peripheral surface of the rolled annular material to the end of the outer peripheral side (i.e., the distance between the aforementioned intersection line V and the aforementioned position Sa is the thickness Ra of the desired upper end of the annular material). In other words, the distance between the intersection line V of the upper surface 11S and the rolling surface 12S and the end of the slope of the upper surface 11S on the rolling surface 12S side is less than the thickness Ra of the annular material.

[0033] like Figure 4 As shown, the angle θb of the lower surface 13S is represented by the angle between the vertical plane H (typically a horizontal plane representing the annular radial direction) that intersects the central axis of the main roller 10 and the lower surface 13S. The lower limit of the angle θb of the lower surface 13S varies depending on the inclination angle of the annular blank described later, and is preferably 0.3° or more, more preferably 0.5° or more, further preferably 0.6° or more, and even more preferably 1° or more. Furthermore, the upper limit of the angle θb of the lower surface 13S varies depending on the inclination angle of the annular blank described later, and is preferably less than 9°, more preferably less than 5°, further preferably less than 3°, and even more preferably less than 2°.

[0034] In addition, such as Figure 4As shown, the slope of the lower surface 13S is given to the range from the intersection line V of the lower surface 13S and the rolling surface 12S of the recess 12 of the main roll 10 to the end of the outer peripheral side (i.e., the entire lower surface 13S). However, in order to obtain the effect of the present invention, it is also possible not to start from the intersection line V with the rolling surface 12S, but to give the slope to the range from the position Sb of the desired inner peripheral surface of the rolled annular material to the end of the outer peripheral side (i.e., the distance between the aforementioned intersection line V and the aforementioned position Sb is the thickness Rb of the desired lower end of the annular material). In other words, the distance between the intersection line V of the lower surface 13S and the rolling surface 12S and the end of the slope of the lower surface 13S on the rolling surface 12S side is less than the thickness Rb of the annular material.

[0035] To manufacture annular rolled stock using such an annular rolling mill, an annular billet 1 is first fed into the annular rolling mill. Annular billets 1 made of heat-resistant alloys such as Ni-based alloys, Co-based alloys, and Fe-based alloys are suitable. Heat-resistant alloys experience a significant decrease in thermal ductility due to temperature reduction, thus the temperature range suitable for plastic processing is very small. That is, for heat-resistant alloys, the rolling time is shorter, and the effect obtained by the annular rolling mill of this embodiment, which can roll in a stable posture, is significant. The heating temperature of the annular billet 1 fed into the annular rolling mill varies depending on the material of the annular billet 1. For example, when the annular billet 1 is made of Alloy 718, a heating temperature in the range of 1000°C to 1050°C is preferred, but this range varies depending on the requirements of each product and is not limited to this temperature range.

[0036] Furthermore, the shape of the annular blank 1 can be, for example, a so-called conical annulus with its outer and inner circumferential surfaces inclined in a generally straight line, or it can be inclined in a curved shape or a combination of straight and curved shapes, or it can be a so-called irregular annulus with locally different wall thicknesses. For the inclination angle θr of such an annular blank 1, such as... Figure 5 As shown, even when the wall thickness of the annular blank varies locally, in the case of a conical annular shape, the aforementioned tilt angle θr is represented by the angle between the line D connecting the end face angle LD of the outer circumference of the major diameter of the annular blank 1 and the end face angle SD of the outer circumference of the minor diameter, and the central axis 1X of the annular shape of the annular blank 1. The lower limit of the tilt angle θr of the annular blank 1 is preferably 5° or more, more preferably 7° or more, further preferably greater than 10°, and even more preferably 15° or more. The upper limit of the tilt angle θr of the annular blank 1 is not particularly limited; for example, it is preferably 40° or less, more preferably 35° or less, and even more preferably 30° or less. The annular blank 1 used for input can, of course, be a so-called rectangular annular shape without tilt.

[0037] Then, the outer circumferential surfaces of the main roller 10 and the core roller 20 are brought into contact with the outer and inner circumferential surfaces of the annular blank 1, respectively. Furthermore, the outer circumferential surfaces of a pair of shaft rollers 30 are brought into contact with the upper and lower end faces of the annular blank 1, respectively. This is achieved by moving the main roller 10 and the core roller 20 towards... Figure 1 , Figure 2 Rotating in the direction of the arrow, while moving the core roller 20 toward the main roller 10, the annular blank 1 is clamped and pressed along the annular radial direction by the main roller 10 and the core roller 20. Furthermore, while moving a pair of shaft rollers 30 toward... Figure 1 As shown by the arrow, the annular blank 1 is rotated while a pair of rollers 30 clamp and press it along the annular axis. This process of annular rolling of the annular blank 1 yields an annular rolled product.

[0038] At this point, even if the annular blank 1 is a conical annular shape or an irregular annular shape, such as Figure 2 As shown, the lower surface 13S of the recess 12 of the main roll 10 is given an inclination such that the opening of the recess 12 widens towards the outer periphery of the main roll 10. Therefore, the annular blank 1 contained in the recess 12 of the main roll 10 is stabilized in posture by the lower surface 13S and the upper surface 11S of the recess 12, so the annular blank 1 can rotate stably around the central axis 1X. As a result, excessive contact between the annular blank 1 and the shaft roll 30 can be suppressed, and the generation of defects can be prevented. In particular, for annular blank 1 with an inclination angle θr greater than 10°, a difference in circumferential speed will be generated between the die and the blank, making it difficult to stabilize the posture during annular rolling. Therefore, the effect of the present invention is significant. Furthermore, when the outer periphery of the main roll 10 and the core roll 20 is given a predetermined shape in order to obtain an irregular annular shape, a difference in the diameter expansion between the thick-walled portion and the thin-walled portion will also be generated, making it difficult to stabilize the posture during annular rolling. Therefore, the effect of the present invention is significant.

[0039] Example

[0040] The embodiments of the present invention will be described below. First, as shown in Table 1, tests were conducted on annular billets by applying a slope angle θb ranging from 0° to 12° to the entire lower surface of the concave portion of the main roll of the annular rolling apparatus. Furthermore, tests were conducted on two types of annular billets: conical annular billets with a slope angle greater than 10° and conical annular billets with a slope angle less than 10°. Moreover, the stability of the annular billets during the annular rolling process and the defects of the resulting annular rolled product were evaluated. The results are recorded in Table 1.

[0041] Furthermore, tests were conducted to roll annular billets by applying a 1.5° slope angle θb to the entire lower surface of the concave portion of the main roll of the annular rolling mill, and by applying slope angles θa ranging from 0° to 12° to the entire upper surface of the concave portion of the main roll. Similarly, tests were conducted on two types of annular billets: conical annular billets with a slope angle greater than 10° and conical annular billets with a slope angle less than 10°. Moreover, the stability of the annular billets during the annular rolling process and the defects in the resulting annular rolled products were evaluated. The results are recorded in Table 2.

[0042] [Table 1]

[0043]

[0044] [Table 2]

[0045]

[0046] For "rolling stability" in the table, motion images were taken from the top and side directions of the annular billet to observe its behavior during annular rolling. A "◎" was awarded for no abnormal movement (slipping, undulation, loss of control) during the annular rolling process, a "○" was awarded for minor abnormal movement, and a "×" was awarded for major abnormal movement (failure to roll to the desired size within the target time, or interruption of rolling). Additionally, intermediate conditions were awarded a "△".

[0047] For the "defects" in the table, the defects of the obtained annular rolled material are removed by grinding, and the weight reduction after removing the defects is measured. The case where the weight reduction is less than 0.1% of the weight of the annular billet is evaluated as "◎", the case where it is more than 0.1% but less than 0.3% is evaluated as "○", the case where it is more than 0.3% but less than 1.5% is evaluated as "△", and the case where it is more than 1.5% is evaluated as "×".

[0048] As shown in Tables 1 and 2, if the slope angles of the lower and upper surfaces of the concave portion of the main roller are both too small (e.g., 0.1°), the constraint exerted by the lower and upper surfaces on the annular billet will be too great, becoming a resistance to the rotation of the annular billet and causing instability. Conversely, if the slope angle is too large (e.g., greater than 10°), the annular billet will not be held sufficiently, its posture will be tilted, and due to friction with the main roller, the instability of rotation will increase.

[0049] Furthermore, if a ring-shaped billet with a large inclination angle is fed in, the difference in circumferential speed between the main roll and the ring-shaped billet will cause the billet to tilt during the ring rolling process. However, without constraining the inclination angle of the ring-shaped billet, the rotational stability of the ring-shaped billet can be obtained. Rolling stability and the generation of defects show a similar tendency to some extent.

[0050] In particular, the results shown in Tables 1 and 2 demonstrate that regardless of the inclination angle of the annular billet, when the angle of inclination formed on either the lower or upper surface of the main roll is within the range of 0.5° to less than 3°, rolling stability is excellent and defects are few. Specifically, when the inclination angle of the annular billet is less than 10°, rolling stability is excellent within the range of greater than 0.3° to less than 3°, and both rolling stability and defects are significantly excellent within the range of 0.5° to less than 2°. Furthermore, when the inclination angle of the annular billet is greater than 10°, rolling stability is excellent within the range of 0.6° to less than 9°, and both rolling stability and defects are significantly excellent within the range of 1° to less than 3°.

[0051] Explanation of reference numerals in the attached figures

[0052] 1. Annular billet; 10. Main roll; 11. First flange (upper flange); 11S. First inner surface (upper surface); 12. Recess; 12S. Rolling surface; 13. Second flange (lower flange); 13S. Second inner surface (lower surface); 20. Core roll; 30. Shaft roll.

Claims

1. A method for manufacturing annular rolled steel, comprising manufacturing annular rolled steel by annular rolling mill on an annular billet, wherein, The manufacturing method of the annular rolled material includes the following steps: In the process of feeding the annular billet into the annular rolling mill, at least a portion of the outer circumferential surface of the annular billet is inclined relative to the central axis of the annular billet, the angle between the straight line connecting the end face angles of the major and minor diameter outer circumferences of the annular billet and the central axis of the annular billet is greater than 10°, and the annular billet is made of a heat-resistant alloy selected from Ni-based alloys, Co-based alloys, and Fe-based alloys; and A process of rolling an annular billet using the aforementioned annular rolling apparatus, wherein the annular rolling apparatus comprises a main roll and a core roll, the main roll being located on the outer circumference of the annular billet, and the core roll being located on the inner circumference of the annular billet. The outer circumferential surface of the main roll has: a recess that accommodates the annular billet and the outer circumferential surface of the core roll; a first flange located on one side of the main roll relative to the recess along the central axis direction; and a second flange located on the opposite side of the first flange. The inner surface of the recess has: a rolled surface that contacts the outer peripheral surface of the annular billet; a first inner surface on the side of the first flange; and a second inner surface on the side of the second flange. At least one of the first inner surface and the second inner surface has an inclination relative to a vertical plane that intersects perpendicularly with respect to the central axis of the main roll, such that the opening of the recess widens toward the outer periphery of the main roll. The inclination begins within a range from the line of intersection of the at least one inner surface and the rolling surface to a distance equivalent to the thickness of the annular rolled material, and the angle of the inclination is greater than 0.3° and less than 3° relative to the vertical plane.

2. A method for manufacturing annular rolled stock, comprising manufacturing annular rolled stock by annular rolling device for annular rolling of annular billet, wherein, The manufacturing method of the annular rolled material includes the following steps: In the process of feeding the annular billet into the annular rolling mill, at least a portion of the outer circumferential surface of the annular billet is inclined relative to the central axis of the annular billet; the angle between the straight line connecting the end face angles of the major and minor diameter outer circumferences of the annular billet and the central axis of the annular billet is less than 10°; and the annular billet is made of a heat-resistant alloy selected from Ni-based alloys, Co-based alloys, and Fe-based alloys. A process of rolling an annular billet using the aforementioned annular rolling apparatus, wherein the annular rolling apparatus comprises a main roll and a core roll, the main roll being located on the outer circumference of the annular billet, and the core roll being located on the inner circumference of the annular billet. The outer circumferential surface of the main roll has: a recess that accommodates the annular billet and the outer circumferential surface of the core roll; a first flange located on one side of the main roll relative to the recess along the central axis direction; and a second flange located on the opposite side of the first flange. The inner surface of the recess has: a rolled surface that contacts the outer peripheral surface of the annular billet; a first inner surface on the side of the first flange; and a second inner surface on the side of the second flange. At least one of the first inner surface and the second inner surface has a slope relative to a vertical plane that intersects perpendicularly with respect to the central axis of the main roll, such that the opening of the recess widens toward the outer periphery of the main roll. The slope begins within a range from the line of intersection of the at least one inner surface and the rolling surface to a distance equivalent to the thickness of the annular rolled material, and the angle of the slope is greater than 0.3° and less than 2.5° relative to the vertical plane.

3. The method for manufacturing annular rolled steel according to claim 1 or 2, wherein, The annular rolling stock fed into the annular rolling apparatus is a heat-resistant alloy based on Ni, and is heated to a temperature in the range of 1000°C to 1050°C.

4. The method for manufacturing annular rolled steel according to claim 1, wherein, The angle of the slope, when referenced to the vertical plane, is greater than 0.3° and less than 2.5°.

5. The method for manufacturing annular rolled steel according to claim 1 or 2, wherein, The slope begins at a position corresponding to the thickness of the annular rolled material from the rolling surface.

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