A welded member includes: a first steel sheet including a base steel sheet and a zinc-based plating layer formed on a surface of the base steel sheet; and a second steel sheet spot-welded on the first steel sheet and facing the zinc-based plating layer of the first steel sheet, a spot-welded zone being formed between the first steel sheet and the second steel sheet. A surface layer of the base steel sheet has a decarburization ratio of 30% or more. The decarburization ratio is represented by equation: Decarburization ratio (%) of surface layer=(1?average carbon concentration in surface layer/bulk carbon concentration)*100 where the surface layer refers to a region of the base steel sheet from the surface thereof to a depth of 35 ?m. A shoulder portion of the spot-welded zone includes a B-type crack having a length of 100 ?m or less, and no C-type crack.

A process and assembly for heat treating portions of a steel article, such as an advanced high strength (AHSS) steel or Gen3 steel, in order to create each of hard and transition zones in a nominally hard steel stamping, such as in a vehicle's structural stampings including a pillar, in order to design deformation zones during a collision event. In an initial operation, the invention provides for positioning of heating elements at locations along such as a blank shaped steel article. Following an initial heating, a suitable forming or stamping operation is employed to bend or reform the article with the heated zones defining the bend axles or points within the article. Following the initial heating and bending/stamping operations, additional heating elements can be positioned, such as against outer flange locations of the previously stamped article, following which a subsequent trimming or final fabricating step is employed to complete the article.

A double row tapered roller bearing includes: an outer ring having an annular shape; an inner ring disposed on an inner circumferential side of the outer ring and having an annular shape; and rollers. The inner ring has an outer circumferential surface facing the outer ring and having two rows of grooves having a bottom surface serving as a raceway surface. The rollers are tapered rollers disposed in the grooves in contact with the raceway surface of the inner ring and are also in contact with the outer ring. At outer circumferential surface of the inner ring, a region adjacent to the groove includes a hardened region extending from the inner peripheral surface of the groove to the region adjacent to the groove, and an unhardened region located at a position farther from the groove than the hardened region and being smaller in hardness than the hardened region.

A rail cooling device configured to forcibly cool a rail by jetting a coolant includes a porous plate nozzle including a plurality of nozzle holes configured to jet the coolant to an underside of the base of the rail to cool the underside of the base of the rail. Ends in a width direction of the porous plate nozzle correspond to ends of the underside of the base of the rail. Nozzle holes of the porous plate nozzle at the ends of the width direction are smaller than nozzle holes of the porous plate nozzle at a central part in the width direction, and a maximum value of a distance between centers of the nozzle holes at both ends in the width direction is 30% or more of a width of the underside of the base.

In order to prevent a spalling failure of a tooth flank (10Y) at a middle point of a tooth height and a dedendum (10Z) caused by Trochoidal interference due to meshing during operation of a gear transmission, in a gear manufacturing process, a manufacturing method is adopted in which a tooth tip edge part is softened more than the tooth flank at the middle point of the tooth height and the dedendum by performing a tempering or annealing treatment on the tooth tip edge part (10X), more preferably by a local tempering or annealing treatment. As a result, it is possible to dramatically improve ease of manufacturing control, quality control, and safety control of a gear while preventing breakage of the gear.

A rail cooling device configured to forcibly cool a rail by jetting a coolant includes a porous plate nozzle including a plurality of nozzle holes configured to jet the coolant to an underside of the base of the rail to cool the underside of the base of the rail. Ends in a width direction of the porous plate nozzle correspond to ends of the underside of the base of the rail. Nozzle holes of the porous plate nozzle at the ends of the width direction are smaller than nozzle holes of the porous plate nozzle at a central part in the width direction, and a maximum value of a distance between centers of the nozzle holes at both ends in the width direction is 30% or more of a width of the underside of the base.

An electrical steel sheet includes a main surface and an end surface. The electrical steel sheet includes a base material part and an end surface nitrided layer that is provided on the end surface in a manner adjacent to the base material part and that contains nitrogen. The end surface nitrided layer has a surface hardness of 430 HV or more and 1250 HV or less. The end surface contains nitrogen in an amount higher than a nitrogen concentration at the main surface.

A rail cooling method for forcibly cooling a rail by jetting a coolant includes jetting the coolant to a foot back part of the rail from a porous plate nozzle in which a nozzle hole at an end in a width direction is smaller than a nozzle hole at a central part in the width direction and causes a cooling capacity for the end in the width direction of the underside of the base of the rail to be lower than a cooling capacity for the central part in the width direction of the underside of the base of the rail.

There is disclosed a method of treating a metal article which tapers towards an edge. A compressive force is applied to a treatment region of the article to generate an edge region of compressive residual stress adjacent the edge, and the treatment region is spaced apart from the edge region by an intermediate region.

Provided is a method for strengthening a steel plate member employing a heating and quenching treatment. The method includes a first heating step, a partial cooling step, a second heating step and an entire cooling step, each step conducted in the written order.