A method for producing a steel plate member (SPM), including: a quenching step for heating the SPM to a temperature higher than an austenite transformation finish temperature A3 and subsequently cooling the SPM at a cooling rate (CR) faster than an upper critical CR; and a tempering step for reheating a second region of the SPM to a temperature higher than an austenite transformation start temperature A1 without reheating a first region of the SPM after quenching and subsequently cooling the SPM at a CR slower than a lower critical CR. In the cooling process of the tempering step, the shape of the second region is corrected in a temperature range from a temperature equal to or lower than A1 to a temperature equal to or higher than a temperature at which transformation into ferrite and pearlite is finished while maintaining the CR slower than the lower critical CR.

A hot-dip galvanized steel sheet according to one aspect of the present invention comprises a base steel sheet and a hot-dip galvanized layer formed on the surface of the base steel sheet, wherein the difference between the average of the Mn/Si values of surface oxides present on a surface portion, which is the region from the interface between the hot-dip galvanized layer and the base steel sheet to a depth of 15 nm, and the average of the Mn/Si values of internal oxides, which are present in the region from the interface to a depth of 50-100 nm, can be 0.5 or more. Mn and Si of each oxide mean the amounts (wt %) of Mn and Si components in the oxide, which are measured by EDS, and the average of Mn/Si values means the averaged value of the Mn/Si values measured for each oxide.

A welded steel part with a very high mechanical strength is provided. The welded steel part is obtained by heating followed by hot forming, then cooling of at least one welded blank obtained by butt welding of at least one first and one second sheet. The at least one first and second sheets including, at least in part, a steel substrate and a pre-coating which includes an intermetallic alloy layer in contact with the steel substrate, topped by a metal alloy layer of aluminum or aluminum-based alloy. A method for the fabrication of a welded steel part and the fabrication of structural or safety parts for automotive vehicles are also provided.

A method of manufacturing a stator is provided. The method may include stamping steel into laminations each having an inner edge area defining a residual stress associated with a magnetic permeability. The method may also include exposing the laminations to a changing magnetic field such that, for each of the laminations, a density of resulting eddy currents is greatest near the inner edge area to heat the same relative to central areas of the lamination to decrease the residual stress and core loss.

A device for hot stamping includes a lower mold having a shape corresponding to a bottom of a product material. An upper mold has a shape corresponding to a top of the product material and presses the product material with the lower mold. A blank holder is disposed inside the upper mold and fixes a blank between the upper mold and the lower mold. A cam has a shape corresponding to a flange of the product material and forms the flange of the product material by moving up or down along an inner side of the blank holder.

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 method of manufacturing a welded structure of a ferritic heat-resistant steel is provided that prevents Type IV damage and that has good on-site operability without adding a high B concentration. The method includes: the step of preparing a base material including 1.0 to 7.0% Cr, less than 0.005% B and other elements; the step of forming an edge on the base material; a pre-weld heat treatment step in which a region located between a surface of the edge and a position distant from the surface of the edge by a pre-weld heat treatment depth of 10 to 50 mm is heated to a temperature of 950 to 1050 C. and is held at this temperature for 10 to 30 minutes; a welding step in which the edge is welded to form the weld metal; and a post-weld heat treatment step in which a region located between the surface of the edge and a position distant therefrom by a distance not smaller than the pre-weld heat treatment depth and not greater than 100 mm is heated to a temperature of 680 to 750 C. and is held at this temperature for a time period not shorter than 30 minutes and satisfying the following formula, (1):

(Log(t)+10).Math.(T+273)<10539(1).

A method of manufacturing a stator is provided. The method may include stamping a fully-processed steel into a set of laminations having hardened outer edge areas. The method may further include flash annealing the laminations to concentrate thermal energy in the inner and outer edge areas relative to central areas of the laminations to drive a hardness of the inner and outer edge areas toward a hardness of the central areas to relieve residual stress and decrease iron loss of the laminations.

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 for thermally treating a flat steel product, a thermally treated flat steel product and use thereof. The method includes providing a flat steel product with a structure with a first hardness. The flat product is heated at least in sections to an austenitizing temperature. The heated flat product is cooled at least in sections so that a structure with a second hardness is formed within the flat product at least in sections, the second hardness having a higher level of hardness in comparison to the structure with the first hardness. The heating and the cooling down of the flat product are coordinated with each other such that the structure with the second hardness is formed across the thickness of the flat product and at least in one of said sections, the structure with the first hardness remains constant across the thickness of the flat product.