The Forming Speed of The Welded Steel Pipe Unit

The speed of the welded steel pipe unit is limited by the high-frequency welding speed. Generally speaking, the unit speed can be opened at a speed of 100 m/s, and the speed of the unit in the world is even 400 m/s Welding, especially in the induction welding can only be 60 meters/second or less, more than 10mm of steel plate molding, the domestic unit production molding speed can only reach 8 to 12 m/s. The welding speed affects the welding quality of welded steel pipe. When the welding speed is high, it will help to shorten the heat affected zone and facilitate the extrusion of the oxide layer from the molten groove. On the other hand, when the welding speed is very low, the heat affected zone becomes wider, resulting in a larger welding burr, , Weld quality deteriorated. Of course, the welding speed of welded steel pipe unit by the output power limit, it is impossible to mention very high. Domestic unit operating experience shows that 2 ~ 3 mm steel pipe welding speed can reach 40 m/s, 4 ~ 6mm steel pipe welding speed can reach 25 m/s, 6 ~ 8 mm welded steel pipe welding speed can reach 12 m/10 ~ 16 mm welded steel pipe welding speed of 12 m/s or less. Contact welding speed can be higher, induction welding will be lower.

Two Ways of High-frequency Welding

Steel pipe has a variety of production processes. High-frequency welding technology is one of them, it usually used by pipe manufacturers to produce ERW steel pipe. Actually, high-frequency welding can be divided into two ways, resistance welding and IWinduction welding.

What is resistance welding?

The resistance welding is carried out by using a pair of copper electrodes to contact on both sides of the welded steel pipe, induction current penetration is good, the two effects of high frequency current are maximized using since the copper electrode directly contact with the steel plate. The welding efficiency of the resistance welding is high and the power consumption is low, so it is widely used in the production of high speed and low precision pipe. And in the production of special thick steel pipe, it is also necessary to use resistance welding.

But there are two shortcomings in resistance welding: first, copper electrode is in touch with steel plate, so it will wear quickly; second, due to the influence of the flatness of the surface of the steel plate and the straightness of the edge, the current stability of resistance welding is poor, the burr inside and outside the weld is higher. So pipe manufacturers generally do not used this way when welding high-precision and thin-walled tube.

What is IWinduction welding?

IWinduction welding is way that using a turn or more turns of the induction coil harness the outside of welded steel pipe. The effect of multi-turn is better than that of single turn, but the fabrication and installation of multi-turn induction coil is more difficult. When the spacing between induction coil and the steel pipe surface is small, the efficiency is higher, but it is easy to cause electro-discharge between the induction coil and the pipe. Generally, it is appropriate that keep the induction coil from the surface of the steel pipe having 5 ~ 8 mm gap. When using IWinduction welding, as the induction ring is not in contact with the steel plate, there is no wear, which ensures the stability of the welding. The quality of welding steel pipe surface is good, and the weld is flat, so in the production of high-precision pipe,such as API and others, it basically uses the form of induction welding.

Two Ways of High-frequency Welding

Steel pipe has a variety of production processes. High-frequency welding technology is one of them, it usually used by pipe manufacturers to produce ERW steel pipe. Actually, high-frequency welding can be divided into two ways, resistance welding and IWinduction welding.

What is resistance welding?

The resistance welding is carried out by using a pair of copper electrodes to contact on both sides of the welded steel pipe, induction current penetration is good, the two effects of high frequency current are maximized using since the copper electrode directly contact with the steel plate. The welding efficiency of the resistance welding is high and the power consumption is low, so it is widely used in the production of high speed and low precision pipe. And in the production of special thick steel pipe, it is also necessary to use resistance welding.

But there are two shortcomings in resistance welding: first, copper electrode is in touch with steel plate, so it will wear quickly; second, due to the influence of the flatness of the surface of the steel plate and the straightness of the edge, the current stability of resistance welding is poor, the burr inside and outside the weld is higher. So pipe manufacturers generally do not used this way when welding high-precision and thin-walled tube.

What is IWinduction welding?

IWinduction welding is way that using a turn or more turns of the induction coil harness the outside of welded steel pipe. The effect of multi-turn is better than that of single turn, but the fabrication and installation of multi-turn induction coil is more difficult. When the spacing between induction coil and the steel pipe surface is small, the efficiency is higher, but it is easy to cause electro-discharge between the induction coil and the pipe. Generally, it is appropriate that keep the induction coil from the surface of the steel pipe having 5 ~ 8 mm gap. When using IWinduction welding, as the induction ring is not in contact with the steel plate, there is no wear, which ensures the stability of the welding. The quality of welding steel pipe surface is good, and the weld is flat, so in the production of high-precision pipe,such as API and others, it basically uses the form of induction welding.

What is the High-frequency Welding?

High-frequency welding is a welding method that using resistance heat produced by high-frequency current flowing through workpiece serial interface to heat, and in the case of applying forging force, makes the workpiece metal to be interconnected. It is similar to ordinary resistance welding, but there are also many important differences. High-frequency welding for carbon steel pipe production has been 40 years of history. With a larger power supply, high-frequency welding can achieve a higher welding speed (higher than the maximum welding speed of TIG welding more than l0 times) for the different materials, caliber and wall thickness of the steel pipe. So high-frequency welding has a high productivity in the production of general-purpose steel pipe. But high frequency welding speed usually makes removing the burrs difficult. This is also one of the reason why high-frequency welded steel pipe is not accepted yet by the chemical industry and the nuclear industry currently.