IT1205912B - Sintered alloy steel powder compacts - made from ductile iron powder mixed with high carbon ferro-alloy powder - Google Patents

Abstract

Sintered alloy steel compacts are made starting from a ferro-alloy contg. iron, carbon and alloying elements. The ferro-alloy is crushed and milled to form a pre-alloy powder which is mixed with ductile iron powder, then pressed and sintered. The ferro-alloy contains Mn and Cr, or Mn plus V, as complex carbides contg. all the carbon required in the compact. The ferro-alloy is crushed and wet milled to powder, max 10 mu m, esp. max 5 mu m size. The pre-alloy powder is then mixed with power, pressed, and sintered at 1150-1300 degrees C. The ferro-alloys may also contain Mo, V and/or Nb. By including all the alloying elements in the pre-alloy powder, a very ductile iron powder may be used in the powder mixt. so the usual compacting pressures of e.g. 500 MN/m2 can be used. Due to the carbides in alloy, it does not absorb O2 when being crushed and milled into powder. The pref. ferro-alloys are (a) 20-25% Mn, 20-25% Cr, 4-8% C, rest Fe; (b) 30-35% Mn, 35-45% Cr, 5-7% C, rest Fe; (c) 20-25% N, 20-25% Cr, 20-25% Mo, 6-8% C, rest Fe; and (d) 20-25% Mn, 20-25% V, 20-27% Mo, 7% max. C, rest Fe.