| 摘要 |
PURPOSE:To prevent shifts of position of a track caused in heat treatment, by providing a laser welding part through the irradiation of a laser light to a part of a pair of core block halves. CONSTITUTION:A small rigid part 6 consisting of projections 6a, 6b is formed at one end of core block halves 1a' and 1b'. The halves 1a' and 1b' are brought into abutment on each other via a gap restricting spacer 4 at the upper part of both ends of the halves and via low-melting point oxide glass 5 as a bonding member at the lower part. A welding part 7 is formed by radiating a laser light to the center near the tip of the part 6 and the projections 6a, 6b are welded. Next, heat treatment is performed by applying a pressure to the arrows F, F' vertical to both sides of the core blocks. Thus, the glass 5 is welded and track width restricting grooves 3a, 3b are bent to the arrows B, B'. No track position shift is caused in the direction of the arrows A, A', because the rigidity of the part 6 is large. |
