| 摘要 |
<p>There are provided an electric resistance welded steel tube for heat treatment that can be used as a highly durable material even after quenching treatment by rapid heating for hollow stabilizers or the like and a method for manufacturing such an electric resistance welded steel tube. A steel tube material, which is a steel tube having a composition constituted by, in mass percent, C: 0.15 to 0.40%, Si: 0.05 to 0.50%, Mn: 0.30 to 2.00%, Al: 0.01 to 0.10%, Ti: 0.001 to 0.04%, B: 0.0005 to 0.0050%, and N: 0.0010 to 0.0100% with Ti and N satisfying (N / 14) < (Ti / 47.9), is formed into an almost cylindrical open pipe, the ends of the open pipe are bonded to each other by electric resistance welding based on induction resistance welding in such a manner that the resultant electric resistance welded steel tube will have a bond width falling within the range of 30 to 65 µm, the electric resistance welded steel tube is heated as a whole to a temperature equal to or higher than the Ac 3 transformation temperature, and then the electric resistance welded steel tube is subjected to diameter-reducing rolling with the rolling reduction expressed by an outer diameter ratio being greater than (1 - 25 / the bond width before diameter-reducing rolling (µm)) × 100%. These steps allow the width of a low carbon layer formed on an electric resistance portion to be reduced below a predetermined value; as a result, the resultant electric resistance welded portion has a sustained hardness after quenching even after quenching treatment by rapid heating, and the electric resistance welded steel tube can be used as a highly durable material.</p> |
