Material for ring rolling

A material for ring rolling including a radially outer peripheral surface and a radially inner peripheral surface, the material for ring rolling to be formed by hot rolling in which a ring rolling mill having a main roll and a mandrel roll is used and the hot rolling is performed in a manner of reducing an interval in a radial direction of the material for ring rolling between the main roll and the mandrel roll, the main roll and the mandrel roll respectively arranged on and in contact with the outer peripheral surface and the inner peripheral surface so as to face each other, wherein:

• a center of gravity on a half section of the material for ring rolling is located so as to be closer to the outer peripheral surface than a center of the half section in a thickness direction of the half section;
• the material for ring rolling is formed such that a shape of the half section includes 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, the height of the height reducing portion 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;
• the shape of the half section further includes a linear portion arranged between the outer peripheral portion in which the outer peripheral surface is provided, and the height reducing portion, the linear portion includes both end surfaces in the height direction and is extended so as to be substantially linear, and a length of the linear portion in the thickness direction is more than 0 times and is ⅔ times or less of the maximum height of the material for ring rolling;
• and
• a height of the inner peripheral surface is from 20% to 50% of a maximum height of the material for ring rolling.