イナート・ガス・アーク再溶融法による球状黒鉛鋳鉄の表面硬化

抄録

  A thin surface layer of spheroidal graphite cast iron was once melted by applying inert gas tungsten arc and solidified. Some properties of the hardened chill layer are related to the parameter f(J)=⁸√I⁴/E²V for heat input of arc, where I is arc current, E is arc voltage and V is ratc of melting. Depth p, aspect ratio b/p and hardness H_v of hardened layer are proportional to the parameter f(J) and are given by the equations.
      p=0.038f(J)-0.3
      b/p=−0.043f(J)+7.1
      Hv=−2.33f(J)+910
  A harder chill layer is formed on the iron containing Mo, W, or Cr. Complete transformation of primary austenite to martensite during cooling down to room temperature results in the highest hardness. Tempering the chill layer is also effective to hardening. Rapid chilling of spheroidal graphite cast iron by inert gas tungsten arc melting as an energy source promises to provide a new method for controlling microstructure and mechanical properties.