A method for producing a steel material for line pipes including heating a steel having a specific composition to a temperature of 1000 C. to 1200 C.; performing hot rolling such that a cumulative rolling reduction ratio in a non-recrystallization temperature range is 60% or more, a cumulative rolling reduction ratio in a temperature range of (a rolling finish temperature +20 C.) or less is 50% or more, and a rolling finish temperature is the Ar.sub.3 transformation point or more and 790 C. or less; subsequently performing accelerated cooling from a temperature of the Ar.sub.3 transformation point or more, at a cooling rate of 10 C./s or more, to a cooling stop temperature of 200 C. to 450 C.; and then performing reheating such that the temperature of a surface of the steel plate is 350 C. to 550 C. and the temperature of the center of the steel plate is less than 550 C.

A system and method of welding or additive manufacturing is provided where at least two welding electrodes are provided to and passed through a two separate orifices on a single contact tip and a welding waveform is provided to the electrodes through the contact tip to weld simultaneously with both electrodes, where a bridge droplet is formed between the electrodes and then transferred to the puddle.

A contact device for a welding apparatus is disclosed. The contact device for feeding current to at least a first welding wire and a second welding wire. The contact device including first and second contact jaws. The first and second contact jaws including a slot formed therein to provide the first and second contact jaws with improved flexibility to individually and independently flex about the first and second welding wires to ensure proper contact is maintained between the contact jaws and the welding wire.

A contact device for feeding current to one or more welding wires in a welding apparatus includes a split tip nozzle having first and second diametrically opposed slots formed therein and a biasing means for supplying an adjustable biasing force to first and second split tips to bias the first and second split tips together to ensure that a desired contact between the split tip nozzle and the one or more welding wires is maintained throughout the lifecycle of the nozzle. The biasing force may be applied by any means including, for example, a compression ring, interaction of tapered surfaces between the tube and the split tip nozzle, a compression or cylinder spring pre-mounted on the first and second split tips, a tensioning screw, etc.

A one-side submerged arc welding method, includes joining two steel plates butted against each other by submerged arc welding from one side using a plurality of electrode. During the submerged arc welding, at least one of electrode distances between adjacent electrodes in an end part region of the steel plates is reduced to be smaller than the at least one of electrode distances in a region in front of the end part region. In reducing the at least one of electrode distances, an increasing section of change rate from when a change of the at least one of electrode distances starts to when the change rate of the at least one of electrode distances reaches its maximum has a time of 2 seconds or more.

A system and method of welding or additive manufacturing is provided where at least two welding electrodes are provided to and passed through a two separate orifices on a single contact tip and a welding waveform is provided to the electrodes through the contact tip to weld simultaneously with both electrodes, where a bridge droplet is formed between the electrodes and then transferred to the puddle.

A system and method of welding or additive manufacturing is provided where at least two welding electrodes are provided to and passed through a two separate orifices on a single contact tip and a welding waveform is provided to the electrodes through the contact tip to weld simultaneously with both electrodes, where a bridge droplet is formed between the electrodes and then transferred to the puddle.

For producing a welded ring, a band having a length corresponding to the circumference of the ring is bent to form a ring and its two ends are welded together. The band ends to be welded together have an offset in the circumferential direction of the ring, the offset lying in the plane of the band. The welding is performed form both lateral edges of the ring from the outside up to the offset. This avoids an overlapping weld of a welding quality that is different at the centre of the ring from that at the edges.

For producing a welded ring, a band of a length corresponding to the circumference of the ring is bent into a ring and its two ends are welded together. The band ends to be welded together have an offset in the circumferential direction of the ring, the offset lying in the plane of the band. The welding is performed from both lateral edges of the ring, from the outside to the inside up to the offset. Welding having an overall improved welding quality and a higher tensile strength is thus obtained.

A twin wire welding apparatus including a first contact tube for guiding a first consumable electrode toward a weld puddle and transferring welding current to the first consumable electrode, a second contact tube for guiding a second consumable electrode toward said weld puddle and transferring welding current to the second consumable electrode, and a single power source connected to said first and second contact tubes for providing the same potential to said two consumable electrodes, and a method for operating such an apparatus.