... curl into a steel tube, and then use high-frequency proximity effect and skin effect heating the tube side ... ~10020~10020~10020~7020~60Main motor power(kw)5575132160200High-frequency equipment(kw)100 OR 200200200 OR 300300300OR400Of facilitiesOpen-book ... , steel butt cut, hopper, steel straightening, steel forming, high-frequency welding, to outer burr, cooling, pipe sizing, pipe straightening, ...