Abstract: A direct resistance heating simulation method is provided. In this method, a welding region and its peripheral region of steel sheets to be welded by a pair of electrodes are divided into a plurality of elements. A coupled analysis is performed such that a temperature, a metal structure, stress and strain at each element are determine in a mutually associated manner based on Joule loss obtained through a current analysis and a magnetic field analysis for each element. The coupled analysis is repeated to predict an effect of one or more parameters, including at least one of a frequency, a magnitude and an application time of electric current to be applied to the electrodes, a cooling time, a pressure applied from the electrodes to the steel sheets and a shape of the electrodes, on welding quality after a post-heating by direct resistance heating and to improve weld strength.

Abstract: A method and an apparatus for manufacturing a stepped member are provided. An intermediate portion of a shaft workpiece is radially enlarged while being compressed in an axial direction by applying alternating load to the intermediate portion in a direction intersecting the axial direction in a state in which pressure that compresses the shaft workpiece in the axial direction is applied to both ends of the shaft workpiece. The enlarged intermediate portion of the shaft workpiece is cat in a direction perpendicular to the axial direction so that the shaft workpiece is divided into two stepped members. Each of the stepped members has a shaft portion and a head portion provided at an axial end of the shaft portion, and the head portion has a larger diameter than the shaft portion.

Abstract: A heating method, a heating apparatus, and a method for manufacturing a press-molded article using the heating method are provided. Electrodes are placed on a workplace to extend across a heating target region in a first direction. At least one of the electrodes is moved in a second direction perpendicular to the first direction over the heating target region while applying electric current to the electrodes. A distribution of contact pressure between at least one of the electrodes and the workpiece along the first direction is adjusted, with a plurality of segment regions being defined by dividing the heating target region such that the segment regions are arranged side by side in the first direction, and in accordance with a length of each of the segment regions between the electrodes, to adjust a healing temperature of each of the segment regions of the heating target region.

Abstract: A heating method, a heating apparatus and a method for fabricating a press-molded article using the heating method is provided. A plate workpiece has a main heating target region having a cross sectional area monotonically varying in a first direction and a sub heating target region provided adjacent to and integrally with the main heating target region. After heating the sub heating target region, the main heating target region is heated by a direct resistance heating to heat the main heating target region and the sub heating target region to be in a target temperature range. To heat the main heating target region, at least one of a pair of electrodes arranged to extend across the main heating target region in a second direction intersecting the first direction is moved in the first direction and at a constant speed, with electric current between the pair of electrodes being adjusted.

Abstract: A heating method, a heating apparatus, and a method of manufacturing a press-molded article using the heating method are provided. A pair of electrodes is arranged on a workpiece along a first direction. Each electrode has a length extending across a first heating area of a workpiece in the first direction. At least one of the electrodes is moved in the first heating area and along a second direction intersecting the first direction at a constant speed while applying electric current between the pair of electrodes to heat the first heating area by direct resistance heating. The electric current applied between the pair of electrodes is adjusted such that a heating temperature is adjusted for each segment into which the first heating area is divided so as to be side by side in the second direction.

Abstract: In a direct resistance heating method, a current is applied to a plate workpiece having a varying cross-sectional area to heat the workpiece such that a high-temperature heating region and a non-high-temperature heating region are provided side by side. The method includes a preparation step of arranging a pair of electrodes on the workpiece, and a heating step of moving a first electrode from one end of the high-temperature heating region while applying a current to the pair of electrodes, stopping the movement of the first electrode when the first electrode reaches the other end of the high-temperature heating region, and stopping the current from being applied to the pair of electrodes when a predetermined time elapses after stopping the first electrode. A press-molded product manufacturing method includes pressing the workpiece that has been heated by direct resistance heating method using a press die to perform hot press molding.

Abstract: Provided are: a welded structural member whose spot-welded part has both strength and ductility, and whose rupture strength proven by a rupture test such as a cross tensile test is high; and a method for welding such a structural member. The welded part 3 of the welded structural member 1 made of the above steel plates bonded by overlapping their faces and forming the welded part 3 by spot welding includes: a molten and solidified part 4; and a heat-affected zone 5 surrounding the molten and solidified part 4. The hardness on the welded surface increases to harder than the hardness of the steel plates 2 (base material) along a direction from a region outside the heat-affected zone 5 toward the heat-affected zone 5.

Abstract: A shaft holding sleeve is inserted in a fitting hole of a compressing machine of a shaft diameter enlarging apparatus that applies an axial compression stress to a shaft stock to hold an end portion of the shaft stock during a shaft diameter enlarging process for radially enlarging a portion of the shaft stock. The shaft holding sleeve includes a front end surface to be inserted in the fitting hole, an exposed portion to be exposed to an outside of the fitting hole, and at least one air communication passage extending from the front end surface to a surface of the exposed portion. A jig may be attached to the shaft diameter enlarging apparatus to facilitate the insertion of the shaft holding sleeve into the fitting hole.

Abstract: A welding structural part 1 is manufactured by overlapping the surfaces of steel sheets 2, and forming a weld zone by spot welding. The weld zone 3 includes: a weld nugget 4; and a heat affected zone 5 surrounding the weld nugget 4, wherein the hardness in the weld zone increases along an exterior region 6 of the heat affected zone 5 toward the heat affected zone 5, and then decreases along the heat affected zone 5 toward the central region of the weld nugget 4. In the boundary region between the weld nugget 4 and the heat affected zone 5, the weld nugget 4 may have a convex portion 4A bulging into the heat affected zone 5 along the overlapped portion. The steel sheets 2 contain carbon in 0.15 mass % or more.

Abstract: An induction heating coil (3) has a primary coil (4) to which electric power is supplied and a ring-shaped secondary coil (5) forming a closed circuit. The primary coil (4) has a base-side portion that covers an outer periphery of the secondary coil (5) and a distal-side portion extending from the base-side portion in the center axis direction of the secondary coil (5) in a state in which the base-side portion covers the secondary coil (5). The opening width of the base-side portion is greater than the opening width of the distal-side portion. The secondary coil (5) is provided such that it can be inserted into and removed from the inside of the primary coil (4) from the base-side portion of the primary coil (4).

Abstract: A heating method, a heating apparatus, and a hot press holding method for a plate workpiece are provided. The plate workpiece has a first region and a second region. A cross sectional area of the first region in a widthwise direction of the plate workpiece is substantially uniform along a longitudinal direction of the plate workpiece or is monotonically increased or decreased along the longitudinal direction. The second region is adjoining a portion of the first region in a monolithic manner. The method includes heating the second region, and heating at least the first region by direct resistance heating along the longitudinal direction. The second region is heated before heating the first region such that the first region and the second region are heated to be in a given temperature range.

Abstract: Object of the present invention is to provide a welding method prevented the fracture at the spot welding zone by recovering the strength of a spot welding zone, namely, the ductility and the toughness in the spot welding zone, and a weld structure manufactured by the method. In the welding method, a spot welding zone provided with a weld nugget 13a is formed by conducting spot welding on the heat treated steel sheets in a stack; the spot welding zone is tempering treated by the high-frequency electrical current application to make the weld nugget have a hardness of 150% or less of the hardness of the heat treated steel sheets, and the heat affected zone surrounding the weld nugget is made to have a hardness of 30% to 90% of the hardness at the weld nugget before the tempering treatment by the high-frequency electrical current application.

Abstract: A wire heating system includes an induction heating apparatus having a power supply and an induction coil arranged to heat a wire rod by an induction heating using current supplied from the power supply, and a controller configured to control the current to be supplied to the induction coil based on a feeding speed of the wire rod. The induction heating apparatus has a heating section in which the wire rod is heated by the induction heating using the induction coil, and a soaking section located downstream of the heating section to homogenize the temperature distribution of the induction-heated wire rod. The controller is configured to control the current to be supplied to the induction coil such that a temperature of the wire rod at a downstream end of the soaking section becomes a target temperature.

Abstract: A welding equipment for metallic materials capable of performing heat treatment such as tempering based on partial heating in spot welding is provided. The welding equipment sandwiches metallic materials with a pair of electrodes, and heats different regions of the metallic materials by energization, with the pair of electrodes maintained at the same position with respect to the metallic materials. The welding equipment includes a first heating means connected to the pair of electrodes for heating and welding the internal region of the circle defined by projecting the cross-sectional area of the axis of the electrodes on the metallic materials by applying power having a low first frequency, a second heating means for heating a ring-shaped region along the circle by applying power having a second frequency that is higher than the first frequency, and an energization control unit for independently controlling the first and the second heating means.

Abstract: An induction heating system includes induction heating apparatuses, each including a high-frequency current transformer, a low-frequency current transformer and a heating coil, a high-frequency input switch connected to the high-frequency current transformer, a low-frequency input switch connected to the low-frequency current transformer, a first power source to output a high-frequency electric power and a low frequency electric power, a second power source, a first power source output switch connectable to the first power source, a second power source output switch connectable to the second power source, and a switch controller. Each induction heating apparatus includes a heater controller to send a signal to the switching controller to turn on one of the first power source output switch and the second power source output switch, to turn off the other, and to switch on or off each of the high-frequency input switch and the low-frequency input switch.

Abstract: A welding equipment for metallic materials capable of performing heat treatment such as tempering based on partial heating in spot welding is provided. The welding equipment 1 sandwiches metallic materials 9 with a pair of electrodes 4, 4, and heats different regions of the metallic materials 9 by energization, with the pair of electrodes 4, 4 maintained at the same position with respect to the metallic materials 9. The welding equipment includes a first heating means 6 connected to the pair of electrodes 4, 4 for heating and welding the internal region of the circle defined by projecting the cross-sectional area of the axis of the electrodes on the metallic materials by applying power having a low first frequency, a second heating means 8 for heating a ring-shaped region along the circle by applying power having a second frequency that is higher than the first frequency, and an energization control unit 10 for independently controlling the first and the second heating means 6, 8.

Abstract: The present invention includes: a hardening control unit (70) for controlling an induction hardening apparatus (10, 10A) based on setup conditions data regarding the induction hardening apparatus (10, 10A); a hardening monitoring unit (20) that measures, as measurement data, the electric quantity in an electric circuit configured to include a high-frequency inverter (11), a capacitor (12), and a heating coil (14, 14A, 14B) and that monitors an induction hardening status; and a data collecting unit (80) that collects the data from various sensors in the induction hardening apparatus (10, 10A, 10B) obtained when the induction hardening apparatus (10) subjects the work (15, 15A, 15B) to an induction hardening based on the setup conditions data outputted from the hardening control unit (70) and that collects the measurement data from the hardening monitoring unit (20) to store the collected data from the various sensors and the measurement data so that the collected data from the various sensors and the measureme

Abstract: An induction hardening monitoring apparatus (20) comprising: a current sensor (21) for detecting output current from a high-frequency inverter (11); a voltage sensor for detecting a voltage generated in a heating coil (14) connected between output terminals of the high-frequency inverters (11) together with a capacitor (12) in an equivalent circuit manner; and a controller (23) for monitoring a hardening processing based on a detection signal from the current sensor (21) and a detection signal from a voltage sensor (22), wherein the controller (23) monitors a hardening processing by calculating an effective value of output current from the high-frequency inverter (11) based on a detection signal from the current sensor (21) and calculating an effective value of voltage generated in a heating coil (14) based on a detection signal from the voltage sensor (22); or further calculating load impedance based on each effective value.

Abstract: A welding structural part 1 is manufactured by overlapping the surfaces of steel sheets 2, and forming a weld zone by spot welding. The weld zone 3 includes: a weld nugget 4; and a heat affected zone 5 surrounding the weld nugget 4, wherein the hardness in the weld zone increases along an exterior region 6 of the heat affected zone 5 toward the heat affected zone 5, and then decreases along the heat affected zone 5 toward the central region of the weld nugget 4. In the boundary region between the weld nugget 4 and the heat affected zone 5, the weld nugget 4 may have a convex portion 4A bulging into the heat affected zone 5 along the overlapped portion. The steel sheets 2 contain carbon in 0.15 mass % or more.

Abstract: The present invention includes: a hardening control unit (70) for controlling an induction hardening apparatus (10, 10A) based on setup conditions data regarding the induction hardening apparatus (10, 10A); a hardening monitoring unit (20) that measures, as measurement data, the electric quantity in an electric circuit configured to include a high-frequency inverter (11), a capacitor (12), and a heating coil (14, 14A, 14B) and that monitors an induction hardening status; and a data collecting unit (80) that collects the data from various sensors in the induction hardening apparatus (10, 10A, 10B) obtained when the induction hardening apparatus (10) subjects the work (15, 15A, 15B) to an induction hardening based on the setup conditions data outputted from the hardening control unit (70) and that collects the measurement data from the hardening monitoring unit (20) to store the collected data from the various sensors and the measurement data so that the collected data from the various sensors and the measureme