Demagnetization of SSAW steel pipe

In the pipeline industry, we are often encountered with magnetic steel pipe, steel pipe with magnetic and without demagnetization operation is hard to weld, and the welding precision is not high, therefore, steel pipe with magnetic must carry out demagnetization.
Steel demagnetization is actually very simple, can be divided into simple demagnetization and complex  demagnetization:
1, simple demagnetization: demagnetization coil wound on the pipe outside, alternating current on the coil, slowly decrease the AC (the slower the better), until reduced to zero. At the end of demagnetization. Results: not change the physical properties of the steel pipe, but once met the outer magnetic field again, the steel will be magnetized.
2, complex demagnetization: the heat treatment process can completely realize demagnetization, however, after the demagnetization of degaussing, hardness and rigidity of steel pipe will change, once meet the external magnetic field, after the magnetic field disappeared, the steel pipe will basically no remanence.
According to the above two kinds of way of steel demagnetization - single demagnetization and complexde magnetization, there is a common point that it can not contact with the strong magnetic field after the demagnetization, otherwise it will be again magnetized.
At present, large diameter SSAW steel pipe generally uses DC demagnetization coil, the demagnetization coil is added into the magnetic particle inspection machine, but the demagnetizing effect does not satisfy the customer, the problem lies in the DC demagnetizing field only generates half cycle reverse magnetic field, only can offset reverse part of the internal remanent large diameter SSAW steel pipe, its remanence stays within the required range, so the effect is not very stable. It can be achieved in the field, after handling, beaten, and exceed the standard magnetic field again. The reason is that the domain of large diameter spiral pipe to demagnetization without "internal magnetic exercise" is not very stable.
Large diameter SSAW steel pipe demagnetization
Remanence national standard is below 30GS, HT30D steel demagnetization system can be stable to pipe remanence of about 10GS, to avoid rebound of the remanence in the process of transportation.
Size specifications: 400*500*600mm
Working voltage: 220V
Working current: 5-20A continuously adjustable
Working frequency: 0-50Hz continuously adjustable
Demagnetization coil diameter size: 100-250 (according to customer requirements).