A method for the manufacture of a cold-rolled steel sheet of thickness e.sub.f between 0.5 mm and 3 mm is provided. At least two hot-rolled sheets of thickness e.sub.i are supplied and butt welded, so as to create a welded joint (S1) with a direction perpendicular to the direction of hot rolling. The at least two hot-rolled sheets are pickled by continuous passage through a bath, then the assembly is cold rolled, in a step (L1), to an intermediate thickness e.sub.int, the direction of cold rolling (DL.sub.1) coinciding with the direction of hot rolling. The cold rolling is carried out with a reduction ratio

[00001]${\mathrm{.Math.}}_1=\mathrm{Ln}\left(\frac{e_i}{e_{\mathrm{int}}}\right)$

such that:

[00002]$0.3.Math.5\frac{\mathrm{Ln}.Math..Math.\left(\frac{\mathrm{ei}}{e.Math..Math.\mathrm{int}}\right)}{\mathrm{Ln}.Math..Math.\left(\frac{e.Math.i}{e.Math.f}\right)}0.6.Math.5,$

then the welded joint (S1) is removed so as to obtain at least two intermediate cold-rolled sheets. Then the two intermediate cold-rolled sheets are butt welded, so as to create a welded joint (S2), the direction of which is perpendicular to the direction of hot rolling, then the assembly of the at least two intermediate cold-rolled and welded sheets is cold-rolled, in a step (L2), to the final thickness e.sub.f, the direction (DL.sub.2) of the cold rolling step (L2) coinciding with the direction of rolling (DL.sub.1).

The method includes: the step of preparing a steel material and a work portion; the step of placing the steel material on the work portion; and the steps of obtaining the rolling bearing ring by heating the steel material on the work portion to a temperature equal to or higher than an A.sub.1 transformation point, thereafter punching a part of the steel material into a ring shape, and thereafter quenching the steel material in a ring shape on the work portion. In the step of obtaining the rolling bearing ring, heating and punching are performed in the state where oxidation of the steel material is suppressed, and in the state where tensile force is applied between the first portion and the second portion in the steel material.

A method for manufacturing a spring is disclosed that comprises: forming the spring from a material; heat treating the spring; performing a first machining step to the ends of the spring; subjecting the spring to a first stress relief heat treatment; performing a second machining step to the ends of the spring; and subjecting the spring to a second stress relief heat treatment step. A spring that is manufactured by this method is also described. This spring may then be used in a pressure relief valve, as well as in other assemblies.

In a laser processing apparatus for refining magnetic domains of a grain-oriented electromagnetic steel sheet by setting a laser beam to be focused on the grain-oriented electromagnetic steel sheet and scanned in a scanning direction, the laser beam focused on the grain-oriented electromagnetic steel sheet is linearly polarized light, and the angle between the linear polarization direction and the scanning direction is equal to or higher than 0 and lower than 45.

Formation of a deformation along a surface of a sheet metal panel of an electronic device is minimized or prevented by determining an area of the surface to which a deformation has developed or is predicted to develop, where the deformation forms or is predicted to form in response to one or more of the surface features being provided into the surface. A score line is provided along the surface that is at or proximate the area.

A metal plate for laser processing (such as a stainless steel plate or a titanium plate) and preferably an austenitic stainless steel plate suitable for use as a metal mask or the like which undergoes fine processing with a laser has an average grain diameter d (m) and a plate thickness t (m) which satisfy the equation d0.0448.Math.t1.28.

A method is for manufacturing a core plate having an annular core back and teeth extending from the core back toward the center. The core plate is obtained by performing a punching step, a winding step, a straining step and an annealing step. At the straining step, compressive strain is applied to the core back or the band-shaped core back that is to be the core back after winding. At the annealing step, the core back or the band-shaped core back is annealed to be recrystallized after the applying of strain.

A method of treating a surface of a gear for a strain wave reduction gear mechanism. The method includes: taking a gear for a strain wave reduction gear mechanism as a workpiece, the gear is formed from a machine structural steel containing at least 0.2% carbon and being subjected to heat treatment after having been machined; performing a first process in which carbide particles are ejected against a surface of the workpiece so as to remove machining marks on the surface of the workpiece and so as to cause elemental carbon in the carbide particles to diffuse and permeate into the surface of the gear; and after the first process, performing a second process in which spherical particles are ejected against a surface of the workpiece for increasing an internal compressive residual stress of the gear surface by a magnitude of at least 50 MPa.

A method for processing a steel plate capable of removing residual strain at a trim edge thereof without causing overheating in areas of the steel plate other than the trim edge is provided. A method of processing a steel plate includes punching a steel plate and disposing heating electrodes in such a way that a trim edge punched in the punching is positioned between electrode surfaces facing each other and then heating a part of the steel plate including the trim edge.

An air conditioner according to the present embodiment includes: an outdoor unit including a compressor, an outdoor heat exchanger, and a main expansion device, wherein a refrigerant is circulated by a refrigerant pipe configured to connect the compressor, the outdoor heat exchanger, and the main expansion device, an indoor unit including an indoor heat exchanger; and a connection pipe configured to connect the outdoor unit and the indoor unit, wherein the air conditioner has a cooling capability between 23 kW and 35 kW, a mixed refrigerant containing R32 of 50% or more is used as the refrigerant, and the refrigerant pipe comprises a ductile stainless steel pipe having a delta ferrite matrix structure of 1% or less on a basis of a grain area.