Abstract: Provided is a low thermal expansion alloy wherein martensitic transformation does not occur even at ?120° C. This low thermal expansion alloy contains, in mass %, 1.50-5.00% of Co, while containing Ni in such an amount that if [Ni] (mass %) is the content of Ni and [Co] (mass %) is the content of Co, [Co]??4×[Ni]+136 and [Co]??4×[Ni]+139 are satisfied, with the balance being made up of Fe and unavoidable impurities. This low thermal expansion alloy has an average thermal expansion coefficient of 0.5×10?6/° C. or less for the range of 0-30° C., while having a martensitic transformation temperature of ?120° C. or less.

Abstract: A low thermal expansion alloy having a high rigidity and a low thermal expansion coefficient comprising, by mass %, C: 0.040% or less, Si: 0.25% or less, Mn: 0.15 to 0.50%, Cr: 8.50 to 10.0%, Ni: 0 to 5.00%, and Co: 43.0 to 56.0%, S: 0 to 0.050%, and Se: 0 to 0.050% and having a balance of Fe and unavoidable impurities, the contents of Ni, Co, and Mn represented by [Ni], [Co], and [Mn] satisfying 55.7?2.2[Ni]+[Co]+1.7[Mn]?56.7 and the structure being an austenite single phase.

Abstract: The abrasive resistant high manganese cast steel of the present invention has a high wear resistance and a high shock resistance, and contains 1.3-1.4 weight % of C, 0.05-0.20 weight % of Si, 14.0-15.0 weight % of Mn, 0.5-1.5 weight % of Cr, 0.3-0.8 weight % of V, 0.2-0.4 weight % of Ti, and 0.5-1.0 weight % of Mo, and a balance of Fe and inevitable impurities.

Abstract: A shaping ferrous metal member used in a metal-working apparatus is heat-treated at about 1,000.degree. C. for several hours in an incompletely burning fuel gas, to provide a burned gas atmosphere composed of 0.5 to 5.0% of CO, 8 to 12% of CO.sub.2, 0 to 0.5% of O.sub.2. A tough iron oxide layer of high quality is tightly deposited with a uniform thickness by said heat-treatment on the surface of shaping metal member which is abrasively contacted by a sliding semifinished metal product. The advantageous effect of this method is that a consumable shaping metal member has a life 2 to 4 times longer than that of a metal member which is conventionally heat-treated in a completely-burning fuel gas.