| 摘要 |
PURPOSE:To continuously produce timepiece parts having excellent finish appearance and stable quality by using a low-medium carbon steel as a material and subjecting said steel to heat treatment under specific conditions then to machining at the time of producing timepiece parts which are small and have intricate shapes. CONSTITUTION:The low-medium carbon steel contg. 0.1-0.6wt% C is heated to the temp. range of Ac1-Ac3 transformation points of said steel and is cooled down to the Ac1 transformation point or below to about room temp. Such heating-cooling temp. cycle is repeated >=5 times to form two-phase mixed structure in which pearlite is finely dispersed in the ferrite base. The precision worked parts having an excellent free-cutting property, good finish appearance and excellent quality are obtd. The free-cutting property is additionally improved by adding a small amt. of the free-cutting component such as S, Te or Pb into the stock low-medium carbon steel.
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