The equipment for arc welding with coated electrodes in the area of the perturbing magnetic field

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Application

Reduction in time and material costs during performance of welding works in the presence of the perturbing magnetic field.

Current stage

The design documentation has been developed; prototypes of the equipment have been manufactured.

Summary

The residual magnetization of elements in pipeline transportation makes it difficult to produce non-detachable connections using the arc welding due to the magnetic blow. It is especially relevant right after the magnetic inspection of products, as a result of which the value of the magnetic field strength in the welding area can reach up to 100 mT, which exceeds the allowable level by 50 times and, as a consequence, the process of arc welding becomes impossible. The currently used devices of forced metal demagnetization in the welding area (PKNT, LABS-7K, AURA-7001-3, etc.) propose an operative control of the magnetic field strength and an appropriate adjustment of the set parameters of their operation modes during the welding process, which is difficult to implement in practice. In addition, mounting of such equipment on welded elements and the initial set-up of the operation mode require the involvement of experienced staff and considerable time consumption. The results of operation of such equipment are characterized by low efficiency of the use of material resources. An innovative solution to the problem of arc welding of magnetized items is the use of a specialized power supply that forms rectangular current pulses in a welding circuit whose polarity changes at specific deviation of the arc from the axis of the electrode. Such an algorithm of current switching in the welding circuit eliminates arc extinction, stabilizes its spatial position, and ensures formation of a high-quality weld joint in the presence of the perturbation action of an external magnetic field with a strength of up to 100 mT.

                               

Fig. 1.

The result of an attempt to weld a magnetized pipe using a standard welding current supply (welding is impossible)

 

Fig. 2.

The result  of an attempt to weld a magnetized pipe welding using IST-201

(TPU development)