A machining head emits a laser beam for cutting sheet metal of stainless steel. A moving mechanism moves the machining head relatively to a surface of the sheet metal. A beam vibrating mechanism vibrates a laser beam in a parallel direction with a cutting advancing direction of the sheet metal. In a machining condition database, a single specific vibration frequency at which cutting of the sheet metal is possible is set to a maximum moving velocity at which cutting of the sheet metal is possible, and a plurality of vibration frequencies from a maximum frequency to a minimum frequency at which cutting of the sheet metal is possible are set to a moving velocity more than or equal to a minimum moving velocity and less than the maximum moving velocity at which cutting of the sheet metal is possible.

A reflected beam detector detects a reflected beam reflected from a sheet metal when the sheet metal is irradiated with a laser beam so that the sheet metal is cut. A processing state determination unit is provided with a standard deviation value calculation unit and a quality determination unit. The standard deviation value calculation unit calculates, in a predetermined calculation cycle, a standard deviation value of a reflected beam detection value at a monitoring wavelength from among reflected beam detection values in a predetermined wavelength band output from the reflected beam detector. The quality determination unit determines whether or not a burning defect has occurred in which a cut surface of the sheet metal is excessively melted based on a comparison result of comparing, with a first threshold value, the standard deviation value calculated by the standard deviation value calculation unit.

A wire for gas-shielded arc welding includes, based on a total mass of the wire C: 0.01 mass % or more and 0.10 mass % or less, Si: 0.05 mass % or more and 0.55 mass % or less, Mn: 1.60 mass % or more and 2.40 mass % or less, Ti: 0.05 mass % or more and 0.25 mass % or less, Cu: 0.30 mass % or less, Al: 0.10 mass % or less, P: 0.025 mass % or less, and S: 0.010 mass % or less with the remainder being Fe and inevitable impurities. In addition, the following relationship is satisfied: 0.1≤[Ti]/[Si]≤3.0, where [Si] is the content of Si (mass %) based on the total mass of the wire and [Ti] is the content of Ti (mass %) based on the total mass of the wire.

This joint component is a joint component including a first steel member, a second steel member, and a spot-welded portion that joins the first steel member and the second steel member, in which the first steel member includes a steel sheet substrate having a predetermined chemical composition and a coating that is formed on a surface of the steel sheet substrate, contains Al and Fe, and has a thickness of 25 μm or more, in a cross section in a thickness direction of the first steel member and the second steel member including the spot-welded portion, a filled metal containing Al and Fe is present in a gap between the first steel member and the second steel member in a periphery of the spot-welded portion, in the cross section, the filled metal has a cross-sectional area of 3.0×10.sup.4 μm.sup.2 or more, and has a filling ratio of 80% or more in the gap in a range of 100 μm from an end portion of a corona bond formed in the periphery of the spot-welded portion, and includes a first region and a second region.

A resistance spot welding method for spot welding plural steel sheets including at least one galvanized steel sheet containing 0.08 mass % or more of C and 0.50 mass % or more of Si and having a tensile strength of 980 MPa or more, the resistance spot welding method includes, using a pair of electrodes including a pair of electrode tips configured to sandwich and pressurize the plural steel sheets and a pressurizing force absorbing mechanism provided in at least one of the pair of electrode tips and capable of absorbing a pressurizing force in an axial direction of the electrode tips, welding by sandwiching the plural steel sheets between the pair of electrode tips and energizing the pair of electrode tips with a pressurizing force applied, while absorbing a fluctuation load of the pressurizing force generated during the energization by the pressurizing force absorbing mechanism.

One embodiment of the present invention relates to a welded member obtained by overlapping portions of two sheets of base metal and performing fillet welding thereon using weld material, and provides a welded member having excellent fatigue strength of welded portion, and a method for manufacturing same, the welded member comprising base metal, a weld bead and root-reinforcing weld metal, wherein the base metal has a tensile strength of 780 MPa, the weld bead has a toe angle of 160 degrees or greater and the weld bead and the root-reinforcing weld metal have a Vicker's hardness of 280-320 Hv and a fatigue strength of 350 MPa or higher.

An exemplary embodiment of the present invention discloses an aluminum-based blank including: a first plated steel plate; a second plated steel plate connected to the first plated steel plate; and a joint connecting the first plated steel plate and the second plated steel plate at a boundary between the first plated steel plate and the second plated steel plate.

A method is disclosed for dividing a composite material in which a brittle material layer and a resin layer are laminated, including: a resin removing step of irradiating the resin layer with a laser beam oscillated from a first laser source along a scheduled dividing line of the composite material to form a processing groove along the scheduled dividing line; a brittle material removing step of irradiating the brittle material layer with a laser beam oscillated from an ultrashort pulsed laser source along the scheduled dividing line to form a processing mark along the scheduled dividing line; and a brittle material layer dividing step of generating thermal stress in the brittle material layer by irradiating the brittle material layer with a laser beam oscillated from a second laser source from the opposite side to the resin layer to thereby divide the brittle material layer.

A steel sheet with a tensile strength (TS) of 1180 MPa or more, a member, and a method for producing them. In a region of the steel sheet within 4.9 μm in the thickness direction, a region with a Si concentration not more than one-third of the Si concentration in the chemical composition of the steel sheet and with a Mn concentration not more than one-third of the Mn concentration in the chemical composition of the steel sheet has a thickness of 1.0 μm or more. The lowest Si concentration L.sub.Si and the lowest Mn concentration L.sub.Mn in the region within 4.9 μm in the thickness direction from the surface of the steel sheet and a Si concentration T.sub.Si and a Mn concentration T.sub.Mn at a quarter thickness position of the steel sheet satisfy the following formula (1):

L.sub.Si+L.sub.Mn≤(T.sub.Si+T.sub.Mn)/4  (1).

A method for welding between two metallic plates, including: (a) fitting a solid plate without openings, configured to be transparent at at least one emission wavelength of a laser beam (F) emitted by a laser (L), between the laser (L) and at least one contact zone between the metallic plates to be welded; (a1) inerting of the contact zone via a netural gas, where the neutral gas circulates in channels delimited by the contact zone between the metallic plates and by the solid plate; (a2) exerting pressure on the two metallic plates to apply them against one another in the contact zone to be welded, where the application pressure is exerted by the solid plate directly in contact with one of the two metallic plates to be welded; and (b) emission of a laser beam, through the solid plate, to perform welding of the metallic plates in the contact zone.