| 摘要 |
PURPOSE: A process for preparing a bit for a punch is provided to give the simplification of handling a procedure, the easy of mass-production and the enhancement of its production. CONSTITUTION: The process is comprised of the following steps. A mold consistent with the desired shape of bits(10) to be prepared is manufactured. The steel composed of the given components and constitutive ratios is melted at 1500 to 1800°C. The melted steel is injected into the mold to heat-treat for 1 to 2 hours, with preventing from its oxidation at 850 to 950°C. The heat-treated bit is precipitated into cold oil to cool it for 0.5 to 1 hour. The removement is then performed for the remaining defects attached to the surface of the cold bit. The bit is subsequently attached by the super alloyed tip(20). The steel is also characterized by comprising 0.25 to 0.35wt% of C, 0.25 to 0.35wt% of Si, 0.35 to 0.60wt% of Mn, 0.03wt% or less of P, 0.03wt% or less of S, 2.50 to 3.50wt% of Ni, 2.50 to 3.50wt% of Cr, 0.50 to 0.70wt% of Mo and the remainder being Fe.
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