Heat treatment of pipes with thickened ends in an industion installation

Conclusion

In induction heating for hardening of pipes with thickened (upset) ends, preheating of these ends has to be carried out to 750–800°C immediately before the pipes are heated in the inductors of the main line. In heating prior to tempering the pipe ends also have to be preheated to 280–360°C. To eliminate nonuniformities of the temperature along the smooth part of the pipe caused by different wall thickness, it is recommended to envisage a zone of temperature equalization whose length may amount to as much as 30% of the length of the main heating line, depending on the required accuracy of heating. In the process of heating prior to hardening the pipes do not become bent. The pipes may become bent when they are not uniformly cooled in the sprayer on account of low water pressure or nonuniform feed of water over the circumference.