Method and device for adaptive control of the weld parameters in automatic arc welding processes

An improved method in automatic arc welding of regulating the weld parameters of a weld joint formed between two workpieces to maintain the desired melt height, said method comprising

• oscillating said arc in the transverse direction of the groove between said workpieces about a longitudinally extending centerline,
• deriving a characteristic value from electrical quantities of said arc at at least two separate transverse locations spaced different distances from said centerline,
• thereafter combining mathematically said values obtained at these transverse locations and comparing the result thus obtained with a rated value indicative of the desired melt height, the departure of said result from said rated value being used to affect means arranged to set the weld parameters so as to ensure that said departure is maintained at a minimum value and the melt height is maintained at the desired value, the improvement comprising
• measuring the welding voltage at two separate transverse locations during the deposition of a root run of the weld,
• combining mathematically the value thus measured at the first one of these transverse locations,
• comparing the result thus obtained with a calculated rated value, said value corresponding to the height of the root bead of the weld, and
• using a signal corresponding to the departure of the said calculated result from said calculated rated value to control means arranged to set said weld parameters to maintain the desired melt height.

An improved device designed to carry out a method in automatic arc welding to regulate the weld parameters of a joint between two workpieces to maintain the desired melt height by deriving a characteristic value from electrical quantities of said arc oscillating in the transverse direction of the groove between said workpieces about a longitudinally extending centerline, said device comprising a welding head supporting a welding electrode, a travelling mechanism designed to displace said welding head along said groove and said centerline, an oscillating device to oscillate said arc in the transverse direction of said groove, a source of welding current connected to said electrode and the respective workpiece, a transducer to sense the position of oscillation of said arc, and measuring means to measure the welding current and/or the welding voltage, the improvement comprising means for setting said weld parameters to control the melt height in response to an output signal from a registering mechanism for the purpose of ensuring a predetermined value of the height of the root run of the weld, input means connecting said registering mechanism to said measuring means and to said transducer,

• first means included in said registering means to combine mathematically two values measured at two separate transverse locations spaced different distances from the centerline by said measuring means, and second means to compare the calculated result with an adjustable calculated rated value, said latter value corresponding to the height of the melt of the desired root run, said output signal corresponding to the difference between said calculated result and said calculated rated value.