The present invention discloses an annular cooling device for large-scale cylindrical shell, which comprises a plurality of inner jet devices and outer jet devices; the inner jet devices are arranged inside the cylindrical shell along the inner periphery; the outer jet devices are arranged outside the cylindrical shell along the outer periphery; each inner jet device and each outer jet device are oppositely arranged; the inner jet devices are used for spraying cooling medium to the inner wall of the cylindrical shell; the outer jet devices are used for spraying the cooling medium to the outer wall of the cylindrical shell; and the spray ranges of each inner jet device and each outer jet device in the axial direction of the cylindrical shell are both greater than the length of the cylindrical shell.

A ring molded article manufacturing method capable of reliably and efficiently producing a ring molded article in which dead metal regions are reduced, and a ring material used for producing the ring molded article, are provided. The present invention relates to the method for manufacturing a ring molded article having two convex portions which respectively protrude on both sides of the ring molded article in a direction of a center axis thereof and extend in a direction of a circumference of the ring molded article. In the manufacturing method, the ring material is placed inside two molds on which concave portions respectively corresponding to the convex portions are formed, in a condition in which the ring material is supported by a region on an outer peripheral side from an outer peripheral side corner in the concave portion of one of the two molds and a region on an inner peripheral side from an inner peripheral side corner in the concave portion of another of the two molds, the ring material is then forged so as to be pressed by the two molds in a direction of a center axis of the ring material, and the ring molded article is thus produced. In addition, the present invention relates to the ring material used for producing the ring molded article.

Construction is achieved that, together with preventing the occurrence of damage to a mandrel, is able to improve precision of the shape of a ring-shaped member after processing. A mandrel includes a pair of support shaft sections that are provided so as to be separated in the axial direction and so as to be concentric with each other, and a rolling shaft section that is concentrically provided in the axial direction between the pair of support shaft sections. One of the support shaft sections is provided in a state in which displacement in the axial direction with respect to the rolling shaft section is regulated. The other support shaft section is provided in a state in which displacement in a direction going away from the rolling shaft section is possible when a pressing force is applied in that direction.

Various implementations include a ring material used for producing a ring molded article. The ring molded article has two convex portions which respectively protrude on opposite sides of the ring molded article in a direction of a center axis thereof and extend in a direction of a circumference of the ring molded article. A straight line passing through centers of gravity of first and second side regions is inclined by an angle relative to the center axis of the ring material, the first and second side regions are obtained by virtually dividing a one half section of the ring material based on a middle of a maximum height of the ring material in the direction of the center axis of the ring material, and a range of the angle is 7 degrees to 40 degrees.

Various implementations include a ring material used for producing a ring molded article. The ring molded article has two convex portions which respectively protrude on opposite sides of the ring molded article in a direction of a center axis thereof and extend in a direction of a circumference of the ring molded article. A straight line passing through centers of gravity of first and second side regions is inclined by an angle relative to the center axis of the ring material, the first and second side regions are obtained by virtually dividing a one half section of the ring material based on a middle of a maximum height of the ring material in the direction of the center axis of the ring material, and a range of the angle is 7 degrees to 40 degrees.

A method for manufacturing a ring-rolled product, which manufactures the ring-rolled product from a ring material, includes a step of rolling the ring material, which has an operation of rolling the ring material from both inner and outer circumferential sides thereof between a mandrel roll and a main roll in a state of rotating the ring material toward one side in a circumferential direction thereof, and induction-heating the ring material by induction heating elements. An induction heating element is disposed on only an outer circumferential side of the ring material or is disposed on each of both the inner and outer circumferential sides in a region immediately before the rolling, or an inclined portion is provided in an outer-peripheral edge portion of a coil in the induction heating element.

A method for manufacturing a ring-rolled product, which manufactures the ring-rolled product from a ring material, includes a step of rolling the ring material, which has an operation of rolling the ring material from both inner and outer circumferential sides thereof between a mandrel roll and a main roll in a state of rotating the ring material toward one side in a circumferential direction thereof, and induction-heating the ring material by induction heating elements. An induction heating element is disposed on only an outer circumferential side of the ring material or is disposed on each of both the inner and outer circumferential sides in a region immediately before the rolling, or an inclined portion is provided in an outer-peripheral edge portion of a coil in the induction heating element.

A method for manufacturing a ring-rolled product forms the ring-rolled product from a ring material by using a mandrel roll and a main roll. The mandrel roll and the main roll are configured so as to contact inner and outer circumferential surfaces of the ring material, respectively, and are configured so as to press the ring material in a radial direction thereof in a state in which the ring material is rotated in a circumferential direction thereof. The method includes a step of rolling the ring material that includes an operation of induction-heating the main roll by at least one induction heating element and rolling the ring material between the mandrel roll and the main roll, which is induction-heated.

Provided is a CVT ring member having a nitrided layer on a surface thereof. The CVT ring member includes a chemical composition containing, by mass, C: 0.43 to 0.70%, Si: 2.50% or less, Mn: 1.00% or less, Cr: 1.50 to 4.00%, Mo: 0.50 to 3.00% and V: 1.00% or less while satisfying a relation of Formula 1: 159C(%)+91Si(%)+68Cr(%)+198Mo (%)+6461,000, and the balance being Fe and unavoidable impurities. The ring member has a tensile strength of 1,700 MPa or more. The nitrided layer has a surface hardness of HV800 to HV950.

Provided is a CVT ring member having a nitrided layer on a surface thereof. The CVT ring member includes a chemical composition containing, by mass, C: 0.43 to 0.70%, Si: 2.50% or less, Mn: 1.00% or less, Cr: 1.50 to 4.00%, Mo: 0.50 to 3.00% and V: 1.00% or less while satisfying a relation of Formula 1: 159C(%)+91Si(%)+68Cr(%)+198Mo (%)+6461,000, and the balance being Fe and unavoidable impurities. The ring member has a tensile strength of 1,700 MPa or more. The nitrided layer has a surface hardness of HV800 to HV950.