| 摘要 |
PURPOSE:To improve the wear resistance and durability of the tip of the stem of a valve by using a composite tip consisting of a surface layer of an Fe-base sintered material contg. C, Cr, P and B as essential components and a joining layer of an Fe-base sintered material having a specified C content. CONSTITUTION:A composite tip joined to the tip of the stem of a valve for an internal-combustion engine is composed of a surface layer of a wear resistant Fe-base sintered material and a joining layer of an Fe-base sintered material contg. 0.1-0.8wt% C and having superior weldability. The wear resistant Fe- base sintered material consists of, by weight, 1-5% C, 5-30% Cr, 0.1-3% P and/or B, 0.5-10% one or more among Mo, W, Nb, Zr, Hf and Ta, and the balance Fe with inevitable impurities and has a structure contg. uniformly dispersed hard carbides. To the material of the surface layer may be added 0.1- 6% one or more among Mn, Cu and Ni, and to the material of the joining layer may be added 0.5-5% Cu and/or Ni and 0.1-3% one or more among P, B and Si.
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