Patents by Inventor Yasuaki Okita
Yasuaki Okita has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).
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Patent number: 9895765Abstract: Resistance spot welding is performed on a combination of overlapping steel sheets including at least one steel sheet that has, on a surface thereof, a coated layer with zinc as a main component, by (1) starting electric current passage in a state satisfying 0.9×t?L?1.1×t; and (2) dividing electric current into main current and initial current that precedes the main current and is two-step current, setting a current value I1 during current in a first step of the initial current to satisfy Im×1.1?I1?15.0 kA with respect to a current value Im during the main current, and setting a current value I2 in the subsequent second step to no current or low current satisfying 0?I2?Im×0.7.Type: GrantFiled: December 4, 2014Date of Patent: February 20, 2018Assignee: JFE STEEL CORPORATIONInventors: Koichi Taniguchi, Yasuaki Okita, Rinsei Ikeda
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Patent number: 9895764Abstract: A resistance spot welding system includes a calculation unit that calculate and store a time variation of an instantaneous amount of heat generated, a division unit that divides a current pattern into a plurality of steps and stores a time variation of the instantaneous amount of heat generated and a cumulative amount of heat generated for each step as a target value, and an adaptive control unit that starts welding upon subsequent actual welding using, as a standard, a time variation curve of the instantaneous amount of heat generated that is stored as the target value, and adjusts welding current and voltage during welding, when a time variation amount of an instantaneous amount of heat generated deviates during any step from the time variation curve by a difference, so as to compensate for the difference during a remaining welding time in the step.Type: GrantFiled: January 24, 2014Date of Patent: February 20, 2018Assignee: JFE STEEL CORPORATIONInventors: Yasuaki Okita, Chikaumi Sawanishi, Rinsei Ikeda
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Publication number: 20180043461Abstract: A resistance spot welding device for welding at least two overlapping steel sheets held between a pair of welding electrodes is provided. The resistance spot welding device includes the pair of electrodes, an electrode force gauge that measures an electrode force, and a controller that controls an electric current supply to the electrodes according to the electrode force measured by the electrode force gauge. The controller controls the electric current such that the electrode force F measured by the electrode force gauge after the start of the electric current supply is adjusted to a prescribed value.Type: ApplicationFiled: March 3, 2016Publication date: February 15, 2018Applicant: JFE STEEL CORPORATIONInventors: Koichi Taniguchi, Yasuaki Okita, Rinsei Ikeda
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Publication number: 20180038402Abstract: Provided is a method for resistance spot-welding at least two overlapping steel sheets. When an electrode force F after an electric current supply is started changes from an initial electrode force Fi to an electrode force Fh(1) while a lapse from the start of the electric current supply is between 20 ms and 80 ms inclusive, a suspension of the electric current supply of from 20 ms to 60 ms inclusive is started. Then the electric current supply is resumed when the electrode force F reaches an electrode force Fc(1).Type: ApplicationFiled: March 3, 2016Publication date: February 8, 2018Applicant: JFE STEEL CORPORATIONInventors: Koichi Taniguchi, Yasuaki Okita, Rinsei Ikeda
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Publication number: 20180030568Abstract: A hot-pressed member is formed using a tailored blank material obtained by butt joining respective ends of two or more coated steel sheets. The hot-pressed member has two or more sites formed by the respective coated steel sheets and at least one joining portion between the sites. Depending on a type of a coated layer of each of the coated steel sheets, tw/t0 is appropriately controlled where tw is a thickness of a thinnest portion in the joining portion and t0 is a thickness of a thinnest site of the sites. A tensile strength of each of the sites is 1180 MPa or more.Type: ApplicationFiled: March 3, 2016Publication date: February 1, 2018Applicant: JFE STEEL CORPORATIONInventors: Yasuaki OKITA, Rinsei IKEDA, Seiji NAKAJIMA, Koichi NAKAGAWA
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Publication number: 20170348790Abstract: A steel sheet assembly includes a plurality of lapped steel sheets which have a tensile strength of 1,470 MPa or less and a thickness of 0.3 mm to 5.0 mm, the steel sheet assembly being formed by applying, in advance, an adhesive and a carbon-supplying agent to a surface of either or both of the steel sheets to be lapped and then welding the steel sheets. A weld of the assembly has a nugget diameter of 2.8?t (mm) or more, where t (mm) denotes the thickness of a thinner one of the steel sheets on both sides of a weld interface, and the amount of C is increased by 0.02 % by mass or more as compared to the steel sheets before being applied with the adhesive and the carbon-supplying agent.Type: ApplicationFiled: January 22, 2016Publication date: December 7, 2017Inventors: Hiroshi Matsuda, Yasuaki Okita, Muneo Matsushita, Rinsei Ikeda, Kenji Oi
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Patent number: 9821404Abstract: In a resistance spot welding method, test welding and actual welding in which a current pattern is divided into two or more steps are performed. In the test welding, a constant current of a different value is passed in each step, and a time variation of an instantaneous amount of heat generated per unit volume and a cumulative amount of heat generated per unit volume are stored as a target value. In the subsequent actual welding, when a time variation amount of an instantaneous amount of heat generated per unit volume deviates during any step from the results of the test welding, a current passage amount is controlled to compensate for the difference during a remaining welding time in the step. In the test welding, 0.3×Ix?Ia<Ix, where Ia is the current in the first step, and Ix is the current in second and subsequent steps.Type: GrantFiled: December 22, 2014Date of Patent: November 21, 2017Assignee: JFE STEEL CORPORATIONInventors: Chikaumi Sawanishi, Yasuaki Okita, Rinsei Ikeda
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Publication number: 20170312846Abstract: The resistance spot welding method includes performing actual welding to squeeze, by a pair of electrodes (14), a sheet combination with a sheet thickness ratio of more than 3 in which a thin sheet (11) is overlapped on at least one face of two or more overlapping thick sheets (12, 13), and passing a current while applying an electrode force to join the sheet combination, wherein in the actual welding, a pattern of the current and the electrode force is divided into two or more steps including a first step and a second step to perform welding, and an electrode force F1 in the first step and an electrode force F2 in the second step satisfy a relationship F1>F2.Type: ApplicationFiled: November 18, 2015Publication date: November 2, 2017Applicant: JFE STEEL CORPORATIONInventors: Chikaumi SAWANISHI, Yasuaki OKITA, Hiroshi MATSUDA, Rinsei IKEDA
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Patent number: 9737955Abstract: In a welded joint manufactured by a method of resistance spot welding thin steel sheets, when the diameter of a nugget formed from the thin steel sheets is denoted by d, on a horizontal plane passing through a nugget surrounded by a corona bond, distribution of an amount of P in a region in the nugget surrounded by a closed curve at a distance d/100 from an end portion of a weld zone toward the inside of the nugget and a closed curve at a distance d/5 from the end portion of the weld zone toward the inside of the nugget is analyzed by area analysis, and the proportion of the region in terms of area in which the concentration m (mass %) of P is more than twice the concentration M (mass %) of P of a base metal composition is 5% or less.Type: GrantFiled: November 6, 2012Date of Patent: August 22, 2017Assignee: JFE STEEL CORPORATIONInventors: Koichi Taniguchi, Yasuaki Okita, Rinsei Ikeda
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Publication number: 20170113295Abstract: A resistance spot welding device that joins predetermined parts to be welded includes: a storage configured to store a time variation of an instantaneous amount of heat generated per unit volume and a cumulative amount of heat generated per unit volume in test welding that precedes actual welding; and an adaptive controller and an electrode force controller configured to, in the case where the time variation of the instantaneous amount of heat generated per unit volume in the actual welding differs from a time variation curve stored as the target value, respectively control the current or a voltage during current passage and the electrode force to the parts to be welded to compensate for the difference within a remaining welding time so that the cumulative amount of heat generated per unit volume in the actual welding matches the cumulative amount of heat generated per unit volume stored in the storage.Type: ApplicationFiled: June 5, 2015Publication date: April 27, 2017Applicant: JFE STEEL CORPORATIONInventors: Chikaumi Sawanishi, Yasuaki Okita, Hiroshi Matsuda, Rinsei Ikeda
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Patent number: 9475147Abstract: Provided is a method of resistance spot welding of welding a sheet set including a high strength steel sheet with which a high joint strength can be achieved even for a high Ceq material. A method of resistance spot welding a sheet set of two or more lapped steel sheets by weld the sheet set while clamping and pressing the sheet set between a pair of welding electrodes includes a first welding step of applying an weld current Im (kA) and forming a nugget having a nugget diameter d (mm) that satisfies the following inequality (1); a cooling step, subsequent to the foregoing first welding, of cooling the sheet set while continuing to press the sheet set; and a second welding step of performing two-step welding, 3×?tm?d?6×?tm??(1), where tm is the thickness (mm) of the thinnest one of the foregoing two or more steel sheets.Type: GrantFiled: October 17, 2012Date of Patent: October 25, 2016Assignee: JFE STEEL CORPORATIONInventors: Koichi Taniguchi, Yasuaki Okita, Rinsei Ikeda
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Publication number: 20160271719Abstract: Resistance spot welding is performed on a combination of overlapping steel sheets including at least one steel sheet that has, on a surface thereof, a coated layer with zinc as a main component, by (1) starting electric current passage in a state satisfying 0.9×t?L?1.1×t; and (2) dividing electric current into main current and initial current that precedes the main current and is two-step current, setting a current value I1 during current in a first step of the initial current to satisfy Im×1.1?I1?15.0 kA with respect to a current value In, during the main current, and setting a current value I2 in the subsequent second step to no current or low current satisfying 0?I2?Im×0.7.Type: ApplicationFiled: December 4, 2014Publication date: September 22, 2016Applicant: JFE STEEL CORPORATIONInventors: Koichi TANIGUCHI, Yasuaki OKITA, Rinsei IKEDA
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Publication number: 20160271720Abstract: In a resistance spot welding method, test welding and actual welding in which a current pattern is divided into two or more steps are performed. In the test welding, a constant current of a different value is passed in each step, and a time variation of an instantaneous amount of heat generated per unit volume and a cumulative amount of heat generated per unit volume are stored as a target value. In the subsequent actual welding, when a time variation amount of an instantaneous amount of heat generated per unit volume deviates during any step from the results of the test welding, a current passage amount is controlled to compensate for the difference during a remaining welding time in the step. In the test welding, 0.3×Ix?Ia<Ix, where Ia is the current in the first step, and Ix is the current in second and subsequent steps.Type: ApplicationFiled: December 22, 2014Publication date: September 22, 2016Applicant: JFE STEEL CORPORATIONInventors: Chikaumi SAWANISHI, Yasuaki OKITA, Rinsei IKEDA
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Publication number: 20160236294Abstract: Proposed is a resistance spot welding method to join parts to be welded which are a plurality of overlapping metal sheets, including: dividing a current pattern into two or more steps for welding; before actual welding, performing test welding; and subsequently, as actual welding, performing adaptive control welding, in which the two or more steps for welding include a step of securing a current path between the sheets directly below the electrodes and a subsequent step of forming a nugget having a predetermined diameter, and a welding interval time is provided between these steps. This method thus yields a good nugget without causing splashing even under special welding conditions.Type: ApplicationFiled: September 12, 2014Publication date: August 18, 2016Applicant: JFE STEEL CORPORATIONInventors: Chikaumi SAWANISHI, Yasuaki OKITA, Rinsei IKEDA
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Publication number: 20160008913Abstract: Proposed is a method of resistance spot welding to join a plurality of overlapping metal sheets, including: dividing a current pattern into two or more steps for welding; before actual welding, performing test welding to store, for each step as a target value, a time variation of an instantaneous amount of heat generated per unit volume and a cumulative amount of heat generated per unit volume; and subsequently, as actual welding, starting welding using, as a standard, a time variation curve of the instantaneous amount of heat generated per unit volume obtained by the test welding, and when a time variation amount of an instantaneous amount of heat generated deviates during any step from the time variation curve by a difference, performing adaptive control welding to control a current passage amount in order to compensate for the difference during a remaining welding time in the step.Type: ApplicationFiled: January 24, 2014Publication date: January 14, 2016Applicant: JFE STEEL CORPORATIONInventors: Yasuaki OKITA, Chikaumi SAWANISHI, Rinsei IKEDA, Kenji OI
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Publication number: 20160008914Abstract: A resistance spot welding system includes a calculation unit that calculate and store a time variation of an instantaneous amount of heat generated, a division unit that divides a current pattern into a plurality of steps and stores a time variation of the instantaneous amount of heat generated and a cumulative amount of heat generated for each step as a target value, and an adaptive control unit that starts welding upon subsequent actual welding using, as a standard, a time variation curve of the instantaneous amount of heat generated that is stored as the target value, and adjusts welding current and voltage during welding, when a time variation amount of an instantaneous amount of heat generated deviates during any step from the time variation curve by a difference, so as to compensate for the difference during a remaining welding time in the step.Type: ApplicationFiled: January 24, 2014Publication date: January 14, 2016Applicant: JFE STEEL CORPORATIONInventors: Yasuaki OKITA, Chikaumi SAWANISHI, Rinsei IKEDA
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Publication number: 20140305912Abstract: Provided is a method of resistance spot welding of welding a sheet set including a high strength steel sheet with which a high joint strength can be achieved even for a high Ceq material. A method of resistance spot welding a sheet set of two or more lapped steel sheets by weld the sheet set while clamping and pressing the sheet set between a pair of welding electrodes includes a first welding step of applying an weld current Im (kA) and forming a nugget having a nugget diameter d (mm) that satisfies the following inequality (1); a cooling step, subsequent to the foregoing first welding, of cooling the sheet set while continuing to press the sheet set; and a second welding step of performing two-step welding, 3×?tm?d?6×?tm??(1), where tm is the thickness (mm) of the thinnest one of the foregoing two or more steel sheets.Type: ApplicationFiled: October 17, 2012Publication date: October 16, 2014Inventors: Koichi Taniguchi, Yasuaki Okita, Rinsei Ikeda
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Publication number: 20140308070Abstract: In a welded joint manufactured by a method of resistance spot welding thin steel sheets, when the diameter of a nugget formed from the thin steel sheets is denoted by d, on a horizontal plane passing through a nugget surrounded by a corona bond, distribution of an amount of P in a region in the nugget surrounded by a closed curve at a distance d/100 from an end portion of a weld zone toward the inside of the nugget and a closed curve at a distance d/5 from the end portion of the weld zone toward the inside of the nugget is analyzed by area analysis, and the proportion of the region in terms of area in which the concentration m (mass %) of P is more than twice the concentration M (mass %) of P of a base metal composition is 5% or less.Type: ApplicationFiled: November 6, 2012Publication date: October 16, 2014Inventors: Koichi Taniguchi, Yasuaki Okita, Rinsei Ikeda
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Patent number: 8389128Abstract: A high tensile-strength galvanized steel sheet includes C: at least 0.05% but less than 0.12%, Si: at least 0.01% but less than 0.35%, Mn: 2.0% to 3.5%, P: 0.001% to 0.020%, S: 0.0001% to 0.0030%, Al: 0.005% to 0.1%, N: 0.0001% to 0.0060%, Cr: more than 0.5% but not more than 2.0%, Mo: 0.01% to 0.50%, Ti: 0.010% to 0.080%, Nb: 0.010% to 0.080%, and B: 0.0001% to 0.0030%, the remainder being Fe and unavoidable impurities, wherein the high tensile-strength galvanized steel sheet has a microstructure that contains 20% to 70% by volume ferrite having an average grain size of 5 ?m or less. The high tensile-strength galvanized steel sheet has a tensile strength of at least 980 MPa, and excellent formability and weldability.Type: GrantFiled: April 7, 2008Date of Patent: March 5, 2013Assignee: JFE Steel CorporationInventors: Shusaku Takagi, Hidetaka Kawabe, Kohei Hasegawa, Toshihiko Ooi, Yasuaki Okita, Michitaka Sakurai
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Publication number: 20100132849Abstract: A high tensile-strength galvanized steel sheet includes C: at least 0.05% but less than 0.12%, Si: at least 0.01% but less than 0.35%, Mn: 2.0% to 3.5%, P: 0.001% to 0.020%, S: 0.0001% to 0.0030%, Al: 0.005% to 0.1%, N: 0.0001% to 0.0060%, Cr: more than 0.5% but not more than 2.0%, Mo: 0.01% to 0.50%, Ti: 0.010% to 0.080%, Nb: 0.010% to 0.080%, and B: 0.0001% to 0.0030%, the remainder being Fe and unavoidable impurities, wherein the high tensile-strength galvanized steel sheet has a microstructure that contains 20% to 70% by volume ferrite having an average grain size of 5 ?m or less. The high tensile-strength galvanized steel sheet has a tensile strength of at least 980 MPa, and excellent formability and weldability.Type: ApplicationFiled: April 7, 2008Publication date: June 3, 2010Applicant: JFE STEEL CORPORATIONInventors: Shusaku Takagi, Hidetaka Kawabe, Kohei Hasegawa, Toshihiko Ooi, Yasuaki Okita, Michitaka Sakurai