Abstract: The present invention provides a method for producing a ring-rolled material of an Fe—Ni based superalloy which inhibits AGG, has a fine-grained structure having an ASTM grain size number of at least 8, and has high circularity. A method for producing a ring-rolled material of an Fe—Ni based superalloy having a composition of an Alloy 718 comprises: heating a ring-shaped material for ring rolling having the composition, in a temperature range of 900° C. to 980° C., and performing finishing ring rolling, as a finishing ring rolling step; heating the ring-rolled material that has been subjected to the finishing ring rolling, in a temperature range of 980 to 1010° C.; and correcting ellipticalness while expanding a diameter of the ring-rolled material by using a ring expander.

Abstract: The present invention provides a method for producing a ring-rolled material of an Fe—Ni based superalloy which inhibits AGG, has a fine-grained structure having an ASTM grain size number of at least 8, and has high circularity. A method for producing a ring-rolled material of an Fe—Ni based superalloy having a composition of an Alloy 718 comprises: heating a ring-shaped material for ring rolling having the composition, in a temperature range of 900° C. to 980° C., and performing finishing ring rolling, as a finishing ring rolling step; heating the ring-rolled material that has been subjected to the finishing ring rolling, in a temperature range of 980 to 1010° C.; and correcting ellipticalness while expanding a diameter of the ring-rolled material by using a ring expander.

Abstract: A method for producing a ring-rolled material of an Fe—Ni based superalloy, which has a high circularity, can inhibit AGG, and can inhibit grain growth. A method for producing a ring-rolled material of an Fe—Ni based superalloy having a composition of an Alloy 718 comprises: a finishing ring rolling step of heating a ring-shaped material for ring rolling having the composition, in a temperature range of 900° C. to 980° C., and performing finishing ring rolling; and a circularity correcting step of correcting an ellipticalness of the ring-rolled material that has been rolled in the finishing ring rolling step, while expanding a diameter of the ring-rolled material by using a ring expander including a pipe-expanding cone and a pipe-expanding die, wherein the ring-rolled material that has been rolled in the finishing ring rolling step is subjected to circularity correction without being reheated or after having been heated to up to 960° C.

Abstract: A ring rolling mill includes: a rotary drive main roll and a mandrel roll, which are for reducing the thickness of and rolling a ring-shaped material from the radial direction; a pair of rotary drive axial rolls for reducing the thickness of and rolling the ring-shaped material from the axial direction; a measuring roll for measuring the diameter of the ring-shaped material during rolling; and a speed control unit for controlling the speed of the axial rolls. The speed control unit is configured to repeat measuring the diameter at predetermined time intervals ?t and comparing a measurement value Lt of the diameter at time t and a measurement value Lt+?t of the diameter at time t+?t, and the speed control unit is further configured to maintain the speed of the axial rolls unchanged upon the result of the comparison being Lt+?t<Lt.

Abstract: The present invention provides a high quality material for ring rolling. The material includes radially outer and inner peripheral surfaces. In the material, a center of gravity on a half section is located so as to be closer to the outer peripheral surface in contact with a main roll than a center of the half section in a thickness direction, a shape of the half section includes a height reducing portion having a height from a center line dividing the half section into halves in a height direction, this height is gradually reduced toward the inner peripheral surface in contact with a mandrel roll, and the shape is formed in a substantially linear symmetry such that the center line is a symmetric axis. A height of the inner peripheral surface is from 20% to 50% of a maximum height of the material.

Abstract: A manufacturing method provides a high-quality material for ring rolling. The manufacturing method of the material for ring rolling includes a step of heating a disk-shaped material for hot forging to a hot working temperature, a step of arranging the material for hot forging onto a lower die having a convex portion with a truncated conical shape, a step of forming a thin portion by pressing a center portion of the material for hot forging by using an upper die having a convex portion with a truncated conical shape, and a step of manufacturing a material for ring rolling by removing the thin portion wherein a center of gravity on a half section of the material for ring rolling is located so as to be closer to an outer peripheral surface of the half section than a center of the half section in a thickness direction of the half section.

Abstract: A ring rolling mill includes: a rotary drive main roll and a mandrel roll, which are for reducing the thickness of and rolling a ring-shaped material from the radial direction; a pair of rotary drive axial rolls for reducing the thickness of and rolling the ring-shaped material from the axial direction; a measuring roll for measuring the diameter of the ring-shaped material during rolling; and a speed control unit for controlling the speed of the axial rolls. The speed control unit is configured to repeat measuring the diameter at predetermined time intervals ?t and comparing a measurement value Lt of the diameter at time t and a measurement value Lt+?t of the diameter at time t+?t, and the speed control unit is further configured to maintain the speed of the axial rolls unchanged upon the result of the comparison being Lt+?t<Lt.

Abstract: The present invention provides a high quality material for ring rolling. The material includes radially outer and inner peripheral surfaces. In the material, a center of gravity on a half section is located so as to be closer to the outer peripheral surface in contact with a main roll than a center of the half section in a thickness direction, a shape of the half section includes a height reducing portion having a height from a center line dividing the half section into halves in a height direction, this height is gradually reduced toward the inner peripheral surface in contact with a mandrel roll, and the shape is formed in a substantially linear symmetry such that the center line is a symmetric axis. A height of the inner peripheral surface is from 20% to 50% of a maximum height of the material.

Abstract: A manufacturing method provides a high-quality material for ring rolling. The manufacturing method of the material for ring rolling includes a step of heating a disk-shaped material for hot forging to a hot working temperature, a step of arranging the material for hot forging onto a lower die having a convex portion with a truncated conical shape, a step of forming a thin portion by pressing a center portion of the material for hot forging by using an upper die having a convex portion with a truncated conical shape, and a step of manufacturing a material for ring rolling by removing the thin portion wherein a center of gravity on a half section of the material for ring rolling is located so as to be closer to an outer peripheral surface of the half section than a center of the half section in a thickness direction of the half section.