| 摘要 |
<p>PROBLEM TO BE SOLVED: To enable the improvement of pitch precision of fitting holes at a low cost by boring the fitting holes after partial hardening a race groove part in a martensitic stainless steel-made rail. SOLUTION: As the partial hardening treatment, e.g. the hardening after induction-heating with high-frequency current etc., or a laser beam hardening, is adopted. In the case that the shortest distance between the bottom part of the race groove part and the fitting hole exceeds 2 mm, the induction heating coils 4 are disposed so as to be faced to the race groove parts 2 on both sides of the rail 1 and only race groove parts 2 are heated to 1070-1200 deg.C on the surface temp. Thereafter, cooling water spraying nozzles 5 disposed between the coils 4, are actuated to execute the hardening and successively, subzero treatment is executed. The hardness of the race groove part 2 is secured with the partial hardening and bend-straightening treatment after the hardening treatment can easily be executed. After straightening, the fitting holes 3 are easily bored because the boring core part is not hardened, and adverse effect of the heating etc. is avoided and the pitch precision is improved.</p> |
