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: 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: 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.