Abstract: In an alignment stocker having an opening and plural shelf members, metal rings are pushed between the plural shelf members. The meta rings are deformed into an approximately polygonal shape to pass through the opening, in an arranged State of the metal rings, by pressing and holding from insides thereof, and are extracted from the opening. Using a heat treatment jig, which has the same opening as that of the shelf member and enables the metal rings to be mounted parallel to each other in a vertical direction and to be spaced the predetermined interval from each other, the metal rings held from the insides thereof in the arranged state, are inserted from the opening of the heat treatment jig into the heat treatment jig, are mounted in the heat treatment jig by releasing the inside holding, and then are heated and extracted from the shelf members.

Abstract: Disclosed are a conveyance rack for retaining and conveying resilience-memory metal rings and a method for retaining the metal rings. The conveyance rack is provided with a base and a plurality of retaining shafts which extend parallel to each other, being erected on the base, and which are provided with, on the side walls thereof, a plurality of protrusions abutting on the lower end surfaces of the metal rings. The protrusions abut on the lower end surfaces of the metal rings by point contact.

Abstract: Provided are a conveying jig, a method of manufacturing the conveying jig, and a method of heat-treating metal rings using the conveying jig. The conveying jig is provided with a base and ten holding shafts raised from the base. Ridges and grooves are alternatively provided in the side wall of each holding shaft. The metal rings are held in position by being engaged in the grooves in the holding shafts. The space enclosed within the holding shafts is communicated with the atmosphere, and this allows, when the metal rings held by the conveying jig are subjected to heat treatment in a heat treatment furnace, an atmospheric gas to circulate in the space enclosed within the holding shafts.

Abstract: Disclosed are a conveyance rack for retaining and conveying resilience-memory metal rings and a method for retaining the metal rings. The conveyance rack is provided with a base and a plurality of retaining shafts which extend parallel to each other, being erected on the base, and which are provided with, on the side walls thereof, a plurality of protrusions abutting on the lower end surfaces of the metal rings. The protrusions abut on the lower end surfaces of the metal rings by point contact.

Abstract: Elastic metal rings are pushed between plural shelf members which have an opening, are provided parallel to each other in a vertical direction and are spaced a predetermined interval from each other, the opening having an inner periphery of which total sides are longer than a periphery of each elastic metal ring. Each of all the metal rings is deformed into an approximately polygonal shape, which allows all the metal rings to pass through the opening, from arrangement condition of the metal rings, and all the metal rings are pressed and held from insides thereof and are extracted from the opening. A heat treatment jig, which has the same opening as that of the shelf member and enables the metal rings to be mounted parallel to each other in a vertical direction and to be spaced the above predetermined interval from each other, is used.

Abstract: Provided are a conveying jig, a method of manufacturing the conveying jig, and a method of heat-treating metal rings using the conveying jig. The conveying jig is provided with a base and ten holding shafts raised from the base. Ridges and grooves are alternatively provided in the side wall of each holding shaft. The metal rings are held in position by being engaged in the grooves in the holding shafts. The space enclosed within the holding shafts is communicated with the atmosphere, and this allows, when the metal rings held by the conveying jig are subjected to heat treatment in a heat treatment furnace, an atmospheric gas to circulate in the space enclosed within the holding shafts.

Abstract: This invention provides a process for producing a high-concentration carburized steel which can realize dispersion of a large amount of fine and spherical carbides without causing lowered service life of a furnace, deformed steel products, and lowered working efficiency. The production process comprises (i) a primary carburization step for carburizing a steel product having a predetermined composition at a primary carburization temperature (T1) (° C.) until the surface carbon concentration (C) reaches a predetermined carbon concentration, (ii) a cooling step of, after the completion of the primary carburization step, cooling the steel product at a cooling rate of not less than 1° C./min to Ar1 point or less, (iii) a secondary carburization initial step of raising the temperature of the steel product to a secondary carburization start temperature (T2s), which is at least 100° C.

Abstract: A metal ring made of maraging steel is heated in the presence of a halogen compound gas, so as to eliminate an oxide film from the surface of the metal ring and to form a halogenous compound film. Thereafter, the metal ring is heated under a vacuum or reduced pressure atmosphere to eliminate the halogenous compound film, and then it is maintained under an atmosphere comprising ammonia at a processing temperature ranging between 450° C. and 500° C. for a processing time ranging between 30 and 120 minutes, so as to carry out a nitriding processing. The above nitriding processing comprises the steps of: placing the above metal ring into a heating furnace and raising the temperature inside the heating furnace to the above processing temperature; introducing a first mixed gas consisting of 50% to 90% ammonia byvolume, 0.1% to 0.