Method of producing high density sintered articles from iron-silicon

Abstract

A method of producing Iron-Silicon high density sintered articles of intricate design comprising: (a) the blending of compressible iron or low-carbon steel powder, silicon alloyed iron or silicon powder, or combination of silicon alloyed iron and silicon powder, and lubricant, (b) cold pressing said blended mixture with pressures of less than 50 tsi to form the structure of said article with the density up to 88% of the theoretical value and with uniformly distributed hard powder consisting of silicon and/or silicon alloyed particles among ductile iron powder, (c) low temperature stress relieving heat treatment of said formed article at the temperature range of 360-800.degree. C. followed by a cooling rate of less than 120.degree. C./min that relieves compression stress in said iron or low carbon steel particles and provides partial bonding of these iron/steel particles inside said formed article but does not allow the substantial diffusion of silicon from hard powder consisting of silicon and/or silicon alloyed particles into ductile iron or steel particles, (d) impregnation or lubrication of said formed articles which provide hydrostatic pressure and radial plastic flow of the porous metal in a subsequent pressing operation, (e) densification of said formed article, stress relieved, and impregnated article by cold pressing to the density not less than 91% of the theoretical density using the same pressure as in the previous pressing stage, and finally (f) sintering the said formed article to obtain a density greater than 96% of the theoretical value at the elevated temperature up to 1420.degree. C. from 1250.degree. C.