| 摘要 |
Powders are manufactured from low carbon iron-chromium alloys by treating such an alloy, having a composition making it sensitive to sigma-phase formation, within a temperature range in which transformation to the sigmaphase occurs, preferably 600 DEG -800 DEG C., for such a period of time as to effect said sigma-phase formation, whereby the alloy is rendered brittle, and crushing and/or grinding the brittle alloy to powder. The alloys may be heated up to a temperature in said temperature range or alternatively, the alloys, already at a temperature above the range, e.g. in the molten state, may be slowly cooled through the range. They preferably have a carbon content of less than 0-20 per cent, a chromium content of 20-60 per cent, preferably contain at least 1 per cent silicon and may contain, in combination with silicon, the following metals, either alone or in combination with each other: Ni, Ti, Zr, Nb, Ta, V, Mo, W, Mn, Cu, Al and Co. The following are the compositions of alloys given by way of example, the remainder in each case consisting of iron and carbon together with the usual impurities: (i) Cr 51 per cent and cent (iii) Cr 47 per cent and Ni 12 per cent (iv) Cr 47 per cent, Ni 19 per cent and Mo 4 per cent (v) Cr 43 per cent, Ni 19 per cent, Mo 5 per cent and Cu 4 per cent (vi) Cr 43 per cent, Ni 21 per cent, Ti 2 per cent, Nb 4 per cent and Ta 1 per cent (vii) Cr 44 per cent, Ni 18 per cent, Mo 6 per cent and Cu 8 per cent (viii) Cr 45 per cent, Al 12 per cent, Si 8 per cent and Co 12 per cent (ix) Cr 35 per cent, Ti 5 per cent and Co 45 per cent (x) Cr 46 per cent, Al 10 per cent, Si 4 per cent and Zr 2 per cent (xi) Cr 40 per cent, Ni 2 per cent and Mn 40 per cent (xii) Cr 43 per cent, Ni 21 per cent, V 1 per cent, Si 3 per cent, W 4 per cent and Nb 4 per cent. The powder may be (a) incorporated in the slag-forming portion of a welding electrode (b) used in the manufacture of sintered stainless steel parts and (c) used in the manufacture of tough low carbon iron-chromium alloys when it is mixed with other alloying ingredients, in such amount that susceptibility to sigma-phase formation disappears when the mixture is melted, and the mixture is melted so that the sigma-phase disappears and a tough homogeneous alloy is formed. |
