Provided are discs and bores of a gas turbine engine having one or more graphene layers and methods of preparing the same. The one or more graphene layers are disposed adjacent to the disc rim and/or bore to improve heat transfer and reduce oxidation of the discs. Methods of preparing the graphene layers and systems for using the same are provided.

A flywheel energy storage system incorporates various embodiments in design and processing to achieve a very high ratio of energy stored per unit cost. The system uses a high-strength steel rotor rotating in a vacuum envelope. The rotor has a geometry that ensures high yield strength throughout its cross-section using various low-cost quenched and tempered alloy steels. Low-cost is also achieved by forging the rotor in a single piece with integral shafts. A high energy density is achieved with adequate safety margins through a pre-conditioning treatment. The bearing and suspension system utilizes an electromagnet that off-loads the rotor allowing for the use of low-cost, conventional rolling contact bearings over an operating lifetime of several years.

A flywheel energy storage system incorporates various embodiments in design and processing to achieve a very high ratio of energy stored per unit cost. The system uses a high-strength steel rotor rotating in a vacuum envelope. The rotor has a geometry that ensures high yield strength throughout its cross-section using various low-cost quenched and tempered alloy steels. Low-cost is also achieved by forging the rotor in a single piece with integral shafts. A high energy density is achieved with adequate safety margins through a pre-conditioning treatment. The bearing and suspension system utilizes an electromagnet that off-loads the rotor allowing for the use of low-cost, conventional rolling contact bearings over an operating lifetime of several years.

A flywheel energy storage system incorporates various embodiments in design and processing to achieve a very high ratio of energy stored per unit cost. The system uses a high-strength steel rotor rotating in a vacuum envelope. The rotor has a geometry that ensures high yield strength throughout its cross-section using various low-cost quenched and tempered alloy steels. Low-cost is also achieved by forging the rotor in a single piece with integral shafts. A high energy density is achieved with adequate safety margins through a pre-conditioning treatment. The bearing and suspension system utilizes an electromagnet that off-loads the rotor allowing for the use of low-cost, conventional rolling contact bearings over an operating lifetime of several years.

A method for manufacturing a one-piece wheel by forging includes: producing an integral forging comprising: a disc portion, a rim portion, and an annular protrusion protruding from one side of the disc portion in a forging method; producing an outer bend by bending the annular protrusion through a flow-forming process; and forming a hollow portion by welding one end of the outer bend to one side of the rim portion.

A method for manufacturing a one-piece wheel by forging includes: producing an integral forging comprising: a disc portion, a rim portion, and an annular protrusion protruding from one side of the disc portion in a forging method; producing an outer bend by bending the annular protrusion through a flow-forming process; and forming a hollow portion by welding one end of the outer bend to one side of the rim portion.

A ring molded article manufacturing method capable of reliably and efficiently producing a ring molded article in which dead metal regions are reduced, is provided. In the present invention, a material is processed by first forging so as to be shaped in a shape including a bottom which is formed in a substantially disk shape, and a peripheral wall which is inclined to a direction from a center of the bottom toward an outer periphery thereof, in a direction from the outer periphery of the bottom toward one side in a direction of a center axis of the bottom, the bottom of a first forged article obtained by the first forging is drilled, a drilled article obtained by the drilling is ring-rolled, a ring material obtained by the ring rolling is placed inside two molds, the ring material is then processed by second forging 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.

A ring molded article manufacturing method capable of reliably and efficiently producing a ring molded article in which dead metal regions are reduced, is provided. In the present invention, a material is processed by first forging so as to be shaped in a shape including a bottom which is formed in a substantially disk shape, and a peripheral wall which is inclined to a direction from a center of the bottom toward an outer periphery thereof, in a direction from the outer periphery of the bottom toward one side in a direction of a center axis of the bottom, the bottom of a first forged article obtained by the first forging is drilled, a drilled article obtained by the drilling is ring-rolled, a ring material obtained by the ring rolling is placed inside two molds, the ring material is then processed by second forging 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.

A cycle is repeated a plurality of times, which includes a forging process for placing a material to be forged in a lower die and pressing the material to be forged in this state and then separating an upper die from the material to be forged; an elevation process for lifting the material to be forged by using an elevation device to separate the material to be forged from the lower die; a rotation process for rotating the material to be forged around its center by using a rotation device; and a lowering process for placing the material to be forged rotated by the elevation device in the lower die.

Provided are: a closed-die forging method capable of preventing a temperature decrease in a to-be-forged member during forging, easy temperature monitoring during forging, and filling the cavity end portions of a die with the to-be-forged member; and a method of manufacturing a forged article using the closed-die forging method. The closed-die forging method includes covering a surface of the to-be-forged member (preferably a super-alloy) that contacts the lower die with a metal heat-insulation member (preferably stainless steel) prior to forging, except for at least a part of the surface that contacts an upper die during forging, placing the heated to-be-forged member on a lower die, and hammer-forging the to-be-forged member integrally with the metal heat-insulation member. A forged article is prepared by heat-treating the forged article obtained by the closed-die forging method (preferably in a disk shape) at temperatures not lower than the recrystallization temperature of the forged article.