Differences Between ERW Steel Pipe and HFW Steel Pipe

The didderence of ERW, HFW welding processes. ERW welding process refers the heat generated by the resistance to current flowthat pass through the jointed metals. So a large current is needed to electrify the whole surface of the steel plate or coil to the length of welding. In the ERW welding process, the electric current that pass through the entire conductor is at 50/60 Hz. HFW welding process ...
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The didderence of ERW, HFW welding processes.

ERW welding process refers the heat generated by the resistance to current flowthat pass through the jointed metals. So a large current is

needed to electrify the whole surface of the steel plate or coil to the length of welding. In the ERW welding process, the electric current that

pass through the entire conductor is at 50/60 Hz.

HFW welding process is not the same case with the high-frequency process, since it is only a section of the steel metals is heated by the

induction of electric coil. High-frequency is generated by either AC or DC current. In these cases, the constant current welding generator and

constant voltage high-frequency welding generator are used.

Constant current welding machine generates power in 100-800 kHz. In the elder processes, the conversion of 60 Hz. AC current to HF was

done by using triode and tank circuits. New welding machine usesmetal oxide silicon, filed-effect transistors, usually associated with parallel

resonant circult. The constant voltage version generators use insulated gate bipolar transistors designed to power about 2000 kW with

frequency rages of 100-600 KHz.

HFW is required in API 5L PSL2 ERW steel pipe

According the API 5L and ISO 3183 specification, for PSL2 pipes in welded process the HFW welding is a mandatory requirements for ERW

steel pipes. As it is an improvement from the inherent problem of hardness, lack of fusion and susceptibility of stress corrosion cracking(SCC)

ERW steel pipe includes HFW steel pipe

ERW is general designation of resistance welded steel pipes. It can be sorted into two types: alternated current welding(AC) and direct current

welding(DC). According to different frequency, AC welding can be divided into low frequency welding intermediate frequency welding, ultra

frequency welding and high frequency welding. The high frequency welding (HFW) is mainly used in ordinary or thin wall steel pipe. It includes

contact welding and induction welding. Directcurrent welding is generally used for small caliber steel tubes in general, HFW is one of ERW production

methods, it adopts the high frequency welding process. So ERW includes HFW steel pipe.

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