MANUFACTURE OF PIPE FOR INDUCTION HEATING

PROBLEM TO BE SOLVED: To simplify the manufacture of a device, by inserting an inner pipe made of magnetic metal into an outer pipe made of non-magnetic metal with an inner diameter substantially equal to the outer diameter of the inner pipe, and compression-forming the two pipes to form a two-layer pipe for induction heating comprising the inner pipe and outer pipe. SOLUTION: A heat sensitive magnetic metal pipe 101 is mounted on a non- magnetic metal pipe 102. After the mounting, the two are compression-formed. Preferably, the compression-forming is executed at temperatures near the environ ment temperature when induction heating is carried out specifically at 100 deg.C to 300 deg.C, and more effectively at around 200 deg.C. This causes the non-magnetic metal pipe 102 to contract and brings about a gapless joint, thereby improving heating characteristics. By using copper near the heat sensitive magnetic metal pipe 101 in melting point as a material for the non-magnetic metal pipe 102, it is possible to decrease the difference in thermal expansion coefficients between the heat sensitive magnetic metal pipe 101 with its Curie temperature adjusted to an appropriate temperature and the non-magnetic metal pipe 102, and therefore decrease stresses.