A submerged arc welding method comprises setting a first welding condition under which first average welding current is supplied to a welding wire; and setting a second welding condition under which second average welding current is supplied to a welding wire, and the first welding condition and the second welding condition are periodically switched.

Disclosed in the present disclosure is a stainless steel composite plate for a weathering steel bridge having a low yield ratio, comprising a base material and a covering material which satisfy that an atmospheric corrosion resistance index I is greater than or equal to 6.0, the total thickness being 5-60 mm, and the thickness of the covering material being 0.5-5.0 mm.

Disclosed in the present disclosure is a stainless steel composite plate for a weathering steel bridge having a low yield ratio, comprising a base material and a covering material which satisfy that an atmospheric corrosion resistance index I is greater than or equal to 6.0, the total thickness being 5-60 mm, and the thickness of the covering material being 0.5-5.0 mm.

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.

A method for producing a multilayer large pipe having an outer support layer and at least one inner liner layer. Advantages with regard to productivity and the properties of the multilayer large pipe are achieved by the sequence of method steps wherein production of a support sheet is pre-bent to a predetermined initial bending radius for the support layer and at least one liner sheet is pre-bent to a predetermined initial bending radius for the liner layer, placement of the at least one pre-bent liner sheet against the inside of the pre-bent support sheet, with a positioning and parallel alignment of its longitudinal edges extending in the direction of the bending axis in order to form the support layer and the at least one liner layer, there is integral joining of at least one of two longitudinal edges of the at least one liner sheet to the support sheet, shaping of the composite of the integrally joined support layer and at least one liner layer to form a slit multilayer large pipe by a bending machine, with nonpositive, frictional engagement in liner regions that are not integrally joined, and there is closing of the remaining gap of the slit multilayer large pipe with a longitudinal seam by welding.

A method for producing a multilayer large pipe having an outer support layer and at least one inner liner layer. Advantages with regard to productivity and the properties of the multilayer large pipe are achieved by the sequence of method steps wherein production of a support sheet is pre-bent to a predetermined initial bending radius for the support layer and at least one liner sheet is pre-bent to a predetermined initial bending radius for the liner layer, placement of the at least one pre-bent liner sheet against the inside of the pre-bent support sheet, with a positioning and parallel alignment of its longitudinal edges extending in the direction of the bending axis in order to form the support layer and the at least one liner layer, there is integral joining of at least one of two longitudinal edges of the at least one liner sheet to the support sheet, shaping of the composite of the integrally joined support layer and at least one liner layer to form a slit multilayer large pipe by a bending machine, with nonpositive, frictional engagement in liner regions that are not integrally joined, and there is closing of the remaining gap of the slit multilayer large pipe with a longitudinal seam by welding.

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.

Regulating the feed speed of multiple strips during electroslag strip cladding includes guiding a first strip and a second strip towards a work piece. A current is transferred to at least one of the first strip and the second strip to create a molten slag pool on the work piece sufficient for initiation of a cladding phase. A welding parameter associated with the cladding phase is measured and the first strip is fed towards the molten slag pool at a first variable feed speed based on the measuring of the welding parameter. The second strip is fed towards the molten slag pool at a second variable feed speed that is different from the first variable speed, but dynamically determined based on the first variable feed speed.

The invention relates to a method for submerged arc welding comprising the steps of guiding a first hot wire (4; 4a, 4b) towards a work piece and guiding a cold wire (22; 22a, 22b) at a variable feed speed. The method further comprises the steps of continuously measuring, during a welding phase, at least a first active welding parameter related to at least said first hot wire (4; 4a, 4b) adjusting the cold wire (22; 22a, 22b) feed speed in dependence on at least first active welding parameter variations, to maintain high welding stability and high weld quality. The invention also relates to a system (9) for carrying out the method. The system (9) comprises hot wire feeding means (150) for feeding a first hot wire (4; 4a, 4b) towards a work piece and cold wire feeding means (35) for feeding a cold wire (22; 22a, 22b) at a variable cold wire (22; 22a, 22b) feed speed and a control unit (31) for controlling the second wire feeding means (35). The system (9) also comprises measuring means (27) adapted to continuously measure at least a first active welding parameter related to said first hot wire (4; 4a, 4b). The control unit (31) determines target values for the cold wire (22; 22a, 22b) feed speed, each target value corresponding to a first active welding parameter value and controls said second wire feeding means (35) to adjust said cold wire (22; 22a, 22b) feed speed to said target values.

The invention relates to an electric arc-welding welding head comprising a contact device and one or more wire feeder units, the contact device encompassing an electrode assembly, the electrode assembly comprising at least two fusible continuously-fed wire electrodes arranged in a contact device. An electrically insulated duct is provided for electric insulation of at least one of the electrodes so that the electrode is electrically insulated from other electrodes in the electrode assembly. The invention also relates to an electric arc-welding contact device and an electric arc-welding welding head assembly.