Manufacturing method for material for ring rolling
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.
1. A manufacturing method for a material for ring rolling, to be shaped by rolling, to manufacture a ring product to be used in high temperature environments, the manufacturing method comprising:
heating a disk-shaped material for hot forging to a hot working temperature;
forming a portion having a reduced thickness in the disk-shaped material by pressing a center portion of the disk-shaped material with an upper die having a convex portion with a truncated conical shape and a lower die having a convex portion with a truncated conical shape; and
manufacturing the material for ring rolling by removing the portion having the reduced thickness, wherein a shape of a half section of the material for ring rolling includes a shape forming: a height reducing portion having a height from a center line which divides the half section into halves in a height direction of the half section, gradually reduced toward an inner peripheral surface of the material for ring rolling, and a linear portion including end surfaces which are respectively positioned upward and downward and respectively have constant heights, and wherein the height reducing portion and the end surfaces of the linear portion are shaped during the forming of the portion having the reduced thickness by the pressing with the upper die and the lower die;
wherein a center of gravity on the half section of the material for ring rolling is located so as to be closer to an outer peripheral surface of the material for ring rolling than a center of the half section in a thickness direction of the half section,
wherein the material for ring rolling is formed such that a shape of the half section includes the height reducing portion having the height from the center line which divides the half section into halves in the height direction is gradually reduced toward the inner peripheral surface and the shape of the half section is formed in a substantially linear symmetry so as to define the center line as a symmetrical axis of the half section, and
wherein a height of the inner peripheral surface is from 20% to 50% of a maximum height of the material for ring rolling.