How to raise the temperature by controlling the welding seam steel pipe piling surface quality

The strip is into the welded pipe unit, the multi-channel roll rolling, gradually rolled strip steel, formed with an opening gap round tube, adjust the amount of reduction squeeze rollers, so that the weld gap control in 1 ~ 3mm, and to weld ends flush. If the gap is too large, resulting in reduced proximity effect, eddy current lack of heat, poor weld joint between grain yield incomplete fusion or cracking. If the gap is too small, causing the proximity effect increases, excessive soldering heat, causing the weld burning; or weld by extrusion, rolling to form a pit, the impact piling pipe weld surface quality.

Soldering temperature is mainly affected by the impact of high-frequency eddy current heating power, according to the relevant formula, high-frequency eddy current frequency heating power is mainly affected by the impact of thermal power and eddy current excitation frequency is proportional to the square; while current excitation frequency but also by the excitation voltage, current and capacitance, inductance. Excitation frequency formula is:

f = 1 / [2π (CL) 1/2]

The formula: f-excitation frequency (Hz); C-excitation circuit of the capacitance (F), capacitance = power / voltage; L-excitation loop, inductance = flux / current

The above formula, the excitation frequency of the excitation circuit capacitance, inductance is inversely proportional to the square root, or the voltage and current proportional to the square, as long as the change in the circuit capacitance, inductance, or voltage and current can change the size of the excitation frequency, so as to achieve control of welding temperature. For low carbon steel, welding temperature control in the 1250 ~ 1460 ℃, can meet the pipe wall thickness 3 ~ 5mm penetration requirements. In addition, the soldering temperature can be achieved by adjusting the welding speed.

Heat input is low, the heated soldering temperatures reach the edge of the weld metal structure remains solid, forming incomplete fusion or penetration; when the input hot enough, over the edge of the weld is heated soldering temperatures, resulting in over-burn or melt drops, so that the weld formation Cave.