A method for producing a welded blank (1) includes providing two precoated sheets (2), butt welding the precoated sheets (2) using a filler wire. The precoating (5) entirely covers at least one face (4) of each sheet (2) at the time of butt welding. The filler wire (20) has a carbon content between 0.01 wt. % and 0.45 wt. %. The composition of the filler wire (20) and the proportion of filler wire (20) added to the weld pool is chosen such that the weld joint (22) has (a) a quenching factor FT.sub.WJ: FT.sub.WJ0.9FT.sub.BM0, where FT.sub.BM is a quenching factor of the least hardenable substrate (3), and FT.sub.WJ and FT.sub.BM are determined: FT=128+1553C+55Mn+267Si+49Ni+5Cr79Al2Ni.sup.21532C.sup.25Mn.sup.2127Si.sup.240CNi4NiMn, and (b) a carbon content C.sub.WJ<0.15 wt. % or, if C.sub.WJ0.15 wt. %, a softening factor FA.sub.WJ such that FA.sub.WJ>5000, where FA=10291+4384.1Mo+3676.9Si522.64Al2221.2Cr118.11Ni1565.1C246.67Mn.

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.

The present disclosure relates to the technical field of rails welding, and particularly to a method for optimizing microstructure of a rail welded joint, the method comprises the following steps: step 1): subjecting a rail web area of a to-be-cooled welded joint which is obtained by flash butt welding to an accelerated cooling by means of an accelerated cooling device and by using compressed air as a cooling medium, measuring and monitoring temperature of a central position of the rail web of the welded joint while cooling; step 2): stopping the accelerated cooling when the temperature of the central position of the rail web drops to a preset temperature, then placing the welded joint in air and naturally cooling to room temperature, wherein the rail is a pearlite rail having a carbon content of 0.6-0.9 wt %.

A welding apparatus including: a welding unit (20) that includes a pair of electrode wheels (21A, 21B) arranged to face each other with a welding object therebetween; a pressing unit (30) that includes a pair of press rolls (31A, 31B) that are arranged to face each other with the welding object therebetween and press a welded portion of the welding object welded by the electrode wheels (21A, 21B); a cooling unit (40) that supplies a cooling medium toward the welded portion pressed by the press rolls; a heating unit (50) that heats the welded portion cooled by the cooling unit (40); and a moving body (10) that supports the welding unit (20), the pressing unit (30), the cooling unit (40), and the heating unit (50), and reciprocates in a welding direction of the welding object.

A device for heating and quenching a tubular member has a central axis. The device includes a first quenching ring, a second quenching ring axially spaced from the first quenching ring, and a heating ring axially positioned between the first quenching ring and the second quenching ring. Each quenching ring and the heating ring is configured to receive the tubular member. The heating ring is fixably coupled to the first quenching ring and the second quenching ring. The heating ring includes an induction coil configured to heat an annular target zone along the tubular member. The first quenching ring is configured to deliver a first quenching fluid to the target zone and a first annular heat affected zone along the tubular member, and the second quenching ring is configured to deliver a second quenching fluid to the target zone and a second annular heat affected zone along the tubular member.

A homogenization process for coiled tubing is provided. After being preheated in a sectional manner and quenched and tempered, laser-welded low-carbon alloy steel coiled tubing is spray cooled, and then is tempered to obtain homogeneous silvery coiled tubing. Microstructural uniformity of the slivery coiled tubing after the treatment is greatly improved in a welding seam region, a heat sensing region, and a tube wall, situations in which an outer surface of the coiled tubing is burnt and oxidized in the homogenization process are reduced, and a service life of the coiled tubing is prolonged. Moreover, homogeneous coiled tubing with different yield strengths and tensile strengths can be obtained by changing a temperature of the tempering, so that production costs are reduced.

A process for the industrial production of wear-resistant steel pipes having an optimized life. The process includes providing a wear-resistant, hardenable steel sheet in an unhardened or tempered state, shaping the steel sheet into a tubular preform in which two longitudinal edges of the steel sheet are positioned opposite one another with a welding gap extending between the two edges, welding the longitudinal edges by forming a welded seam which closes the welding gap, thereby forming a steel pipe, and heat treating the steel pipe. The heat treatment of the steel pipe includes heating the steel pipe at an average heating rate of 5-400 K/s to a hold temperature which is the Ac3 temperature of the steel and 1100 C., holding the steel pipe at the hold temperature for 1-120 s, and cooling the steel pipe at an average cooling rate of 10-600 K/s to room temperature.

Provided are an austenitic steel having excellent machinability and ultra-low temperature toughness in a weld heat-affected zone including 15 wt % to 35 wt % of manganese (Mn), carbon (C) satisfying 23.6C+Mn28 and 33.5CMn23, 5 wt % or less (excluding 0 wt %) of copper (Cu), chromium (Cr) satisfying 28.5C+4.4Cr57 (excluding 0 wt %), and iron (Fe) as well as other unavoidable impurities as a remainder, wherein a Charpy impact value of a weld heat-affected zone at 196 C. is 41 J or more, and a method of manufacturing the steel. According to the present invention, a low-cost ultra-low temperature steel may be obtained, a stable austenite phase may be formed at low temperature, carbide formation may be effectively suppressed, and a structural steel having excellent machinability and ultra-low temperature toughness in a weld heat-affected zone may be provided.

A heavy weight drill pipe may include a tube body formed of AISI 1340 alloy steel, and first and second tool joints at respective ends of the tube body, and which are formed of an AISI 41XX series alloy steel. The first and second tool joints may be welded to the tube body at a weld line within a weld region. A Charpy impact toughness at the weld line or surrounding weld region may be least 12 ft-lbs. (16.5 N-m). Yield and tensile strengths at the weld line or weld region may be at least 65 ksi (448.0 MPa) and at least 106 ksi (731.0 MPa), respectively. Material properties at the weld line or weld region may be achieved by heat treating after welding. Heat treating may include austenitizing, quenching, and tempering the weld line and/or the surrounding weld region.

Electric resistance welded steel pipe securing the high strength and high toughness demanded from oil well pipe in recent years. The metal structure in a region having a width of 0.5 mm in both the thickness directions from a reference point, when using a point defined as a point of the thickness in the thickness direction from the surface in the base material part of the steel as the reference point, consists of polygonal ferrite: 10 area % or less and a balance: bainitic ferrite. The thickness is 15 mm or more.