Abstract: A Mo source powder is added to and mixed with an iron-based powder containing 1.0% by mass or less of prealloyed Mn to yield a powder mixture containing 0.2 to 10.0% by mass of Mo, the resulting powder mixture is subjected to heat treatment in a reducing atmosphere to thereby yield an alloyed steel powder containing Mo as a powder partially diffused and bonded to a surface of the iron-based powder particles. The prepared alloyed steel powder for powder metallurgy has satisfactory compactability. The use of this alloyed steel powder can produce a sintered powder metal body (an intermediate material after compaction and preliminary sintering in re-compaction of sintered powder materials process) for highly strong sintered member.

Abstract: Desulfurization is carried out by blowing CaO into molten iron, and a gas mixture of an inert gas and a hydrocarbon gas is used as a carrier. The ratio of the hydrocarbon gas to the desulfurizing agent is maintained in the range of from about 2.0 to about 50 Nl/kg. This desulfurizing method improves the desulfurization efficiency of the desulfurizing agent, increases the productivity of the desulfurizing process, and reduces the amount of slag generated in the desulfurizing process. Alternatively, a desulfurizing flux is blown into the molten iron together with a carrier gas comprising a gas mixture of an inert gas and a hydrocarbon gas or an inert gas alone at the start of desulfurization. The hydrocarbon gas in the carrier gas is increased, is added, or the unit gas is replaced by the hydrocarbon gas at adequate timing, whereby the desulfurization efficiency is improved.

Abstract: An apparatus in which a metal strip is passed in contact partly around the outer circumferences of a number of spaced cooling rolls through which coolant passes. The apparatus includes temperature detectors for detecting the temperature of the strip before contact with each of the cooling rolls, and coolant temperature regulators controlled in accordance with the detected temperature of the strip to adjust the temperature of the coolant passing through each cooling roll to a range which limits the temperature drop of the strip such that unacceptable irregularities or distortions in the configuration of the strip cannot occur. The coolant used for each cooling roll is selected with a boiling point appropriate to the respective detected temperature for each roll. In the preferred arrangement, further temperature detectors are provided for each cooling roll to detect the temperature of the coolant, and output signals from both detectors are inputted to a control for regulating a flow rate valve.