On the High-Frequency Induction Heating Method of Welding Pipes

Abstract

A recent tendency toward production of boilers with greater dimensions has necessitated the corresponding growth in length of the piping in them.
In an effort to improve on the conventional type of pipe welding, the writers tried the high frequency induction heating. The present report is an examination of the following conditions encountered in such type of welding:
1) electrical 2) edge figure and inner state of welds 3) gap between heated coils and pipes 4) necessity of reducing materials. The Torikai type impulse high frequency heating apparatus was used with steel pipes, 76 mm o. d., 5 mm thick as specimens. The test results show that 1) so far as the specimens are concerned, operation at 35-40 KW for 50-70 Sec. will be best ; 2) the gap between heating coils and pipes should be 8-10 mm; 3) hydrogen gas is effective as reducing material; and 4) suitability of this method is well confirmed in spite of a considerable variance in mechanical strengths of welds obtained. In conclusion it may be said that this type of pipe welding stands a good chance of being adopted as standard.