Alloys steel powders

Claim 1

In a method of manufacturing heat treated hardened steel components comprising the steps of annealing a steel powder in an atmosphere consisting wholly or essentially of hydrogen or dissociated ammonia at a temperature between 700° and 900° C. to produce one or more compacts from the annealed powder, sintering the compacts in an atmosphere consisting wholly or essentially of hydrogen or dissociated ammonia at a temperature between 900° and 1300° C., densifying the sintered compacts and heat treating the densified components, the improvement comprising (i) forming said steel powder by water atomising a prealloyed steel melt to produce a powder consisting of, by weight, from 0.9 to 1.5% carbon, 1.2 to 2.0% chromium, less than 0.05% silicon, less than 0.1% manganese and an element selected from the group consisting of 0.2 to 1.0 molybdenum, 0.2 to 1.0% nickel, up to 0.3% phosphorous, and up to 1.0% copper, and combinations of two or more of said elements, the balance, apart from impurities, being iron, and (ii) sintering the compacts in an atmosphere consisting wholly or essentially of hydrogen or dissociated ammonia having a dewpoint of less than -10° C. at a temperature between 900° and 1300° C., such that the oxygen content of the sintered compacts is reduced to less than 250 parts per million.