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 m 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 3.010.sup.4 m.sup.2 or more, and has a filling ratio of 80% or more in the gap in a range of 100 m 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.

The invention relates to a method for producing thermomechanically produced hot strip products in which a steel alloy is melted; the steel alloy is adjusted so that a recrystallization during the hot rolling is suppressed; the final rolling temperature is greater than 800 C.; the melted steel alloy is cast into slab ingots and after being heated to a temperature above Ac.sub.3, the slab ingots are hot rolled until they reach a desired degree of deformation and a desired strip thickness; after the rolling, the strip is cooled to room temperature and for hardening purposes, is briefly heated to a temperature >Ac3 and cooled again, characterized in that the heating takes place with a temperature increase of more than 5 K/s, more than 10 K/s, more than 50 K/s, or more than 100 K/s, and is kept at a desired target temperature for a period of 0.5 to 60 s before cooling to yield improved mechanical properties.

A backing welding process curve based on a narrow-gap U-groove and its application and product are provided. The backing welding process curve is used for welding the narrow-gap U-groove. On the basis of a CMT reference curve, at least one current pulse is introduced before and after the short-circuiting phase respectively, to increase the root weld width and avoid root concavity. Meanwhile, the peak current and cycle time are increased to enhance welding heat input, while the peak current rise rate and peak current fall rate are reduced to prolong the peak current action time.

A method for producing a steel sheet, the method containing the following successive steps: providing a cold-rolled steel sheet, the chemical composition of the steel containing in weight %: 0.15%C0.23%, 2.0%Mn2.8%, 1.0%Si2.1%, 0.02%Al1.0%, with 1.7%Si+Al2.1%, 0Nb0.035%, 0Mo0.3%, 0Cr0.4%, the remainder being Fe and unavoidable impurities, annealing the steel sheet at an annealing temperature T.sub.A so as to obtain a structure comprising at least 65% of austenite and up to 35% of intercritical ferrite, quenching the sheet at a cooling rate of at least 20 C./s from a temperature of at least 600 C. down to a quenching temperature QT comprised between Ms-170 C. and Ms-80 C., heating the sheet up to a partitioning temperature PT between 350 C. and 450 C. and maintaining the sheet at this temperature for a partitioning time Pt comprised between 80 s and 440 s, immediately cooling the sheet down to the room temperature, the steel sheet having a final microstructure consisting of, in surface fraction: between 40% and 70% of tempered martensite, between 7% and 15% of retained austenite, between 15% and 35% of ferrite, at most 5% of fresh martensite, at most 15% of bainite.

Provided are a resistance spot welding method and a method for manufacturing a resistance spot welded joint. At least one of the steel sheets used is a high strength steel sheet. The method includes a main current application step in which current is applied with a current I.sub.w and a tempering post-heat treatment step. The tempering post-heat treatment step includes a cooling process and a heating process and can include at least one of a transition process and a holding process. In the heating process, a current is applied at a current value I.sub.t, shown in formula (2), for a current application time t.sub.t.
0.8I.sub.wI.sub.t1.6I.sub.w(2)

Disclosed are an aluminum-coated blank, a manufacturing method thereof, and an apparatus for manufacturing the same. The blank includes two or more aluminum-coated steel sheets connected together by a joint, each of the steel sheets including: a base steel sheet including 0.01-0.5 wt % of carbon, 0.01-1.0 wt % of silicon, 0.5-3.0 wt % of manganese, greater than 0 but not greater than 0.05 wt % of phosphorus, greater than 0 but not greater than 0.01 wt % of sulfur, greater than 0 but not greater than 0.1 wt % of aluminum, greater than 0 but not greater than 0.001 wt % of nitrogen, and the balance of iron and other inevitable impurities; and a coating layer including aluminum and formed on at least one surface of the base steel sheet.

A method for laser soldering includes selecting a copper-containing material as a filler material, supplying the filler material at a butt joint of two components, and melting the filler material in a main process zone by means of laser radiation in an advancement direction. The filler material in the main process zone is melted by means of laser radiation of a wavelength H in the blue or green spectral range with 400 nmH600 nm.

An automated system, method and tool for portable friction welding is disclosed for joining a rotatable workpiece to a substrate. A control system is disclosed receiving a start input to cause a motor to rapidly spin the workpiece and initiate a first thrust building cycle acting through an actuator to progressively force the spinning workpiece against the substrate. The materials at this intersection heat and plasticize and the actuator translates toward the substrate until the end of the desired actuator stroke operates to cut the motor off and to initiate and then hold a second axial thrust cycle on the actuator and there through to the interface of the workpiece and substrate. A reset input at the end of a cool off phase releases the thrust in the actuator.

A tool includes a cemented carbide part and a steel part joined by brazing, where the steel part has an average hardness of between 390 and 510 HV30. The braze joint includes Ti and a TiC layer, with a thickness of between 0.03 and 5 m, adjoining to the cemented carbide part. The tool provides a strong braze joint and a steel part that have an even hardness.

An arc welding method includes welding a steel sheet while alternately switching feeding of a welding wire between forward feeding and backward feeding. The welding wire contains, in mass % with respect to a total mass to the welding wire, C: more than 0 and 0.30 or less, Si: 0.01 to 0.30, Mn: 0.5 to 2.5, S: 0.001 to 0.020, Ti: 0.05 to 0.30, and optional elements with the remainder being Fe and unavoidable impurities, and a value obtained by 2[Ti]/[Si]50[S] is more than 1.0. The welding is performed by using a shielding gas containing CO.sub.2 gas in an amount of 80 vol. % or more with respect to a total volume of the shielding gas at a frequency of 40 Hz or more and 200 Hz or less, where one cycle for determining the frequency is one forward feeding and one backward feeding.