Patent EP-2269758-A1 (EP)
Inventor: HUISMANN GERD DR ING
IPC: B23K9/12
Filed: 2009-07-03
Abstract: The arc welding method comprises guiding a wire (1) to a surface of a workpiece (3) by a contact tube using a wire conveying system without the reversion of the burners or wires, where the workpiece is introduced at a contact point (21) in electrical contact with the contact tube and a direct voltage is applied between the contact tube and the workpiece, so that a direct current flows between the contact tube and the workpiece during contacting a wire end (12) with the workpiece and during forming an arc (4) between the wire end and the workpiece. The arc welding method comprises guiding a wire (1) to a surface of a workpiece (3) by a contact tube using a wire conveying system without the reversion of the burners or wires, where the workpiece is introduced at a contact point (21) in electrical contact with the contact tube and a direct voltage is applied between the contact tube and the workpiece, so that a direct current flows between the contact tube and the workpiece during contacting a wire end (12) with the workpiece and during forming an arc (4) between the wire end and the workpiece, conveying the wire with a starting wire-feed speed in a starting phase and then feeding to the workpiece, where the wire end is introduced in contact with the workpiece after which the arc is ignited and the wire is freely burnt, repositioning the wire with a process wire-feed speed in a quasi-stationary working phase, where a balance weight is adjusted between the wire feed and wire melting, adjusting a transition phase, in which the wire feed speed is gradually introduced from the starting wire feed speed to the process wire-feed speed, between the starting phase and the working phase, and adjusting a welding current parameter in correlation to the wire feed speed. The contact tube is positively poled opposite to the workpiece. The welding current parameter, which is adjusted in the transition phase, comprises current level in an unpulsed operation, pulse current level in a pulsed operation, pulse current duration, pulse frequency and/or basic current level. The welding current parameter is adjusted above the melted wire end in correlation to an actual preheating of the wire. The welding current parameter is adjusted in the starting phase and/or transition phase, so that low short-circuit of material transport takes place from the wire to the workpiece. The duration of the short-circuit phase and/or the length of the arc is monitored. The welding current parameter is adjusted in the transition phase, so that melting droplets dissolve from the wire without that the wire end contacts with the workpiece, where further pulse parameter for the initial current pulse in the transition phase is adjusted than in the quasi-stationary working phase. The starting feed speed is slightly adjusted in the starting phase, so that the low contact forces are present during impacting the wire to the workpiece. During impacting the wire to the workpiece, a null point is fixed for the determination of the wire path. The welding current parameter is adjusted in correlation to the wire feed speed, so that no elongated arc length adjusts itself when a wire area is melted and receives additional heat from contact resistor at the contact point between the wire and the contact tube. The welding current parameter is adjusted in the transition phase, so that a melting of the wire is prevented above the melted wire end. The wire feed speed is increased in a time region, in which the wire area is melted. The welding wire parameter is adapted to an actual feed speed of the wire. A short current pulse is adjusted with a maximum current strength dependent of the used wire material, wire diameter and gas in the starting phase for arc ignition until a wire surface of the wire is melted at the contact point to the contact tube, where the current is immediately minimized, so that a heat input is minimized in the wire at the contact point. An independent claim is included for a welding device for carrying out an arc welding method.