A system and method for submerged arc welding. The system advances a consumable welding electrode toward a workpiece, and then stops the advancement when the consumable electrode makes contact with the workpiece. The system provides a preheating current level through the consumable welding electrode proximate the workpiece while the consumable welding electrode is in contact with the workpiece during a preheating period of time to preheat the portion of the consumable welding electrode without establishing an arc. The system then retracts the consumable welding electrode from the workpiece and increases the preheating current level to a welding current level over an arc establishment period of time to establish an arc between the consumable welding electrode and the workpiece. The system then begins to form a weld by advancing the consumable welding electrode toward the workpiece again, resulting in melting the consumable welding electrode and depositing molten metal onto the workpiece.

A submerged arc welding apparatus includes a first wire feeder feeding a first hot wire towards a work piece; a first contact tube transferring current to the first hot wire for arc generation to create a weld puddle; a second wire feeder feeding a cold wire at a variable feed speed towards the weld puddle; one or more sensors configured to continuously measure, during a welding phase, at least a first active welding parameter related to at least the first hot wire; and a control unit. The control unit is configured to determine different target values for the variable feed speed of the cold wire based on different values of the at least a first active welding parameter such that a different target value for the variable feed speed of the cold wire is determined according to a different value of the at least a first active welding parameter.

The invention relates to a method of making a steel Yankee cylinder 1 by welding a cylindrical shell 2 to two end walls 3, 4 such that the cylindrical shell 2 and the end walls 3,4 together form the Yankee cylinder 1. The welding operation is carried out exclusively from the outside of the Yankee cylinder 1 and in the welding operation is carried out as a butt welding operation in which a backing material 7 is used on the inside of the Yankee cylinder 1 such that, between each end wall 3, 4 and the cylindrical shell 1, a single weld bead 8 is formed which extends all the way between the opposing surfaces 5, 6 and completely fuses the opposing surfaces 5, 6 of each end wall 3, 4 and the cylindrical shell 2 respectively.

The invention relates to a method of making a steel Yankee cylinder 1 by welding a cylindrical shell 2 to two end walls 3, 4 such that the cylindrical shell 2 and the end walls 3,4 together form the Yankee cylinder 1. The welding operation is carried out exclusively from the outside of the Yankee cylinder 1 and in the welding operation is carried out as a butt welding operation in which a backing material 7 is used on the inside of the Yankee cylinder 1 such that, between each end wall 3, 4 and the cylindrical shell 1, a single weld bead 8 is formed which extends all the way between the opposing surfaces 5, 6 and completely fuses the opposing surfaces 5, 6 of each end wall 3, 4 and the cylindrical shell 2 respectively.

An arc electric welding head comprising a first contact device housing a first duct for feeding a first electrode and providing electrical contact between a first power source and said first electrode, a second contact device housing a second duct for feeding a second electrode and providing electrical contact between a second power source and said second electrode, said first and second contact devices being electrically insulated from each other, said first and second ducts being parallel.

Embodiments of additive manufacturing systems are disclosed. In one embodiment, an additive manufacturing system includes an array of multiple electrodes for sequentially depositing material layer-by-layer to form a three-dimensional (3D) part. The system includes a power source to provide electrical power for establishing a welding arc for each electrode. The system includes a drive roll to drive each electrode. The system also includes a controller to operate the system at a first deposition rate to form first resolution contour portions of a layer of the part. The controller also operates the system at a second deposition rate to form second resolution fill portions of the layer of the part. The system provides variable width deposition at the second deposition rate using a variable number of the electrodes. The first deposition rate is lower than the second deposition rate, and the first resolution is higher than the second resolution.

Systems for multi-wire submerged arc welding including a flux-cored wire electrode comprising an internal flux, the internal flux comprising about 5% to about 70% of a carbonate compound and less than 25% of calcium fluoride (CaF.sub.2) by weight of the flux; an external flux for submerged arc welding, are provided such that, after a submerged arc welding process, the systems provide a weld metal comprising nitrogen in an amount of less than 100 ppm. Methods of performing multi-wire submerged arc welding using a flux-cored electrode and an external flux are also described.

A method comprising an arc ignition phase (IP), an arc-stabilizing phase (AP) and a stable arc phase (SP). The arc stabilizing phase comprises an initial sub-phase (IS) comprising the step of feeding at least one hot wire (4, 12) at constant feed speed and a main sub-phase (MS) comprising the steps of feeding said hot wire at constant feed speed and feeding at least one cold wire (22) at constant feed speed. The stable arc phase comprises the steps of continuously adjusting the feed speed of the hot wire and continuously adjusting the feed speed of the cold wire. The invention also relates to a welding apparatus (1) for carrying out the method. The welding apparatus comprises a hot wire feeding means (150), a contact means (2), a cold wire feeding means (35) and a control unit (31). The control unit is adapted to control said hot wire feeding means to feed the hot wire at a constant feed speed during the initial sub-phase, feed the hot wire at a constant feed speed during the main sub-phase and to continuously during the stable arc phase adjust the feed speed of the hot wire. The control unit is adapted to control said cold wire feeding means to feed the cold wire at a constant feed speed during the main sub-phase and continuously during the stable arc phase adjust the cold wire feed speed.

A self-propelled welding carriage has a body supported by a wheeled suspension having a plurality of wheels including a carriage guide wheel having a tapered rim sized and shaped to roll in conforming contact with a carriage guiding seam of a workpiece, restricting lateral movement of the welding carriage for alignment with the carriage guiding seam. Welding equipment is mounted to the body, and has a welding torch for welding an unwelded seam of the workpiece. The welding torch is mounted to the body relative to the carriage guide wheel for disposition of a welding torch tip of the welding torch in alignment with the unwelded seam of the workpiece to weld the unwelded seam when the welding carriage moves with the carriage guide wheel rolling in the carriage guiding seam. The welding carriage has a motor coupled to drive the carriage guide wheel to propel the welding carriage.

An arc electric welding head comprising a first contact device housing a first duct for feeding a first electrode and providing electrical contact between a first power source and said first electrode, a second contact device housing a second duct for feeding a second electrode and providing electrical contact between a second power source and said second electrode, said first and second contact devices being electrically insulated from each other, said first and second ducts being parallel.