DC arc welding is performed by alternating a short-circuit period and an arc period. The arc period includes first to fourth periods. A welding current is raised to a first current value in the first period, lowered to a second current value with a time slope in the second period, kept at the second current value in the third period, and raised to a third current value then kept at the value in the fourth period. A wire feeding speed is constant throughout the short-circuit period and the arc period. In the second period, a welding output is under constant voltage control. In the third period and the fourth period, the welding output is under constant current control of the welding output.

A welding apparatus for welding workpieces by means of a welding arc which is ignited between a non-consumable welding electrode and the workpieces and produces a molten pool, wherein the welding is performed in a welding process including a plurality of welding cycles, the parameters of which can be set via an interface of the welding apparatus. Each welding cycle of the welding process has a high-current welding phase, during which a high welding current flows, and a low-current welding phase, during which a low welding current flows. In the high-current welding phase and/or in the low-current welding phase of, with the relevant welding cycle being set accordingly, current pulses can be applied, and at the beginning of the high-current welding phase, with the relevant welding cycle being set accordingly, high-frequency ignition pulses can be applied for the contactless ignition of the welding arc.

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 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.

An arc welder includes a welding power supply, a forward/reverse welding wire feeder, and a controller for the power supply and the wire feeder. Welding is implemented by repeating unit welding steps each including a short circuit stage with the welding wire and a base material being short-circuited and an arc stage with an arc being generated between the wire and the material. A transition period continues from a starting point of the arc stage till the wire feeding rate reaches a forward maximum. An average welding current is defined as an average of the welding current during the short circuit and arc stages. Within the transition period, the controller sets a current suppression period during which welding current is smaller than the average welding current. Transition period length T0 and current suppression period length T1 are set to satisfy the inequality 0<T1/T0≤0.8.

An arc welder includes a welding power supply, a forward/reverse welding wire feeder, and a controller for the power supply and the wire feeder. Welding is implemented by repeating unit welding steps each including a short circuit stage with the welding wire and a base material being short-circuited and an arc stage with an arc being generated between the wire and the material. A transition period continues from a starting point of the arc stage till the wire feeding rate reaches a forward maximum. An average welding current is defined as an average of the welding current during the short circuit and arc stages. Within the transition period, the controller sets a current suppression period during which welding current is smaller than the average welding current. Transition period length T0 and current suppression period length T1 are set to satisfy the inequality 0<T1/T0≤0.8.

Welding is performed by alternately switching a pulse arc welding period (where welding is performed by forward feeding a welding wire by a rotation for the forward feeding of a push side feeding motor and a rotation for the forward feeding of the pull side feeding motor and feeding a peak current and a base current) and a short-circuiting transition arc welding period (welding is performed by forward/backward feeding the welding wire by the rotation for the forward feeding of the push side feeding motor and a rotation for the forward/backward feeding of the pull side feeding motor and feeding a short-circuiting current and an arc current). During the short-circuiting transition arc welding period, a forward feeding peak value Wsp and/or a backward feeding peak value Wrp of a pull feeding speed Fw are compensation-controlled based on a wire storage amount of an intermediate wire storage.

An arc welding method includes the following steps. Pulse arc welding is performed with the welding wire being fed in a forward direction during a first period. Short-circuit transfer arc welding is performed with the welding wire being fed in the forward direction and the reverse direction during a second period. The first period and the second period are alternately switched. The switching of the first period to the second period is performed in a manner such that no transfer of a molten droplet of the welding wire occurs during the final pulse cycle of the first period.

An arc welding method is described where pulse arc welding is performed with a welding wire being fed in a forward direction during a first period and short-circuit transfer arc welding is performed with the welding wire being fed in the forward direction and a reverse direction during a second period. The arc welding method alternately switches between the first period and the second period, where the switching of the first period to the second period is performed during a peak period of the pulse arc welding.

An arc welding method is described where pulse arc welding is performed with a welding wire being fed in a forward direction during a first period and short-circuit transfer arc welding is performed with the welding wire being fed in the forward direction and a reverse direction during a second period. The arc welding method alternately switches between the first period and the second period, where the switching of the first period to the second period is performed during a peak period of the pulse arc welding.