| 摘要 |
<p>PURPOSE:To enable the induction heating enabling to effectively eliminate uneven heat due to a thickness deviation by selecting frequency of electric source so that heat-penetrated depth becomes a specific ratio to the thickness at the thinnest part in the circumferential direction of a pipe at the time of induction-heating by inserting the pipe to be treated into an annular coil. CONSTITUTION:At the time of executing the induction heating by inserting a metal pipe into an annular coil, the electric source having a frequency so that the heat-penetrated depth delta becomes 50-100% of the thickness tmin at the thinnest part of the metal pipe, is supplied into the annular coil. By this method, in both parts of the thin part and the thick part, generated Joule heat becomes I<2>.Rdelta (Rdelta is resistance in the range of the penetrated depth delta) to uniformly transmit the Joule heat and the uneven heat is drastically reduced and the quality, etc., after executing the heat treatment is improved.</p> |
