Abstract: The present invention provides a method for mixing a raw material powder for powder metallurgy that allows efficient mixing at a low cost with a simple measure and easy adjustment of the apparent density by performing first agitation mixing in which a powder mixture obtained by adding, to an iron powder, one or two or more members selected from lubricant powders, free-machining agent powders, and lubricant powders for sliding surface, an alloying powder, and a binding agent is agitated while increasing the temperature to a temperature TK equal to or higher than the melting point TM of the binding agent, the resultant is agitated while maintaining the temperature TK, and the resultant is further agitated while reducing the temperature from the temperature TK, and performing second agitation mixing in which the obtained powder mixture is agitated while cooling.

Abstract: The present invention provides a method for mixing a raw material powder for powder metallurgy that allows efficient mixing at a low cost with a simple measure and easy adjustment of the apparent density by performing first agitation mixing in which a powder mixture obtained by adding, to an iron powder, one or two or more members selected from lubricant powders, free-machining agent powders, and lubricant powders for sliding surface, an alloying powder, and a binding agent is agitated while increasing the temperature to a temperature TK equal to or higher than the melting point TM of the binding agent, the resultant is agitated while maintaining the temperature TK, and the resultant is further agitated while reducing the temperature from the temperature TK, and performing second agitation mixing in which the obtained powder mixture is agitated while cooling.

Abstract: It is provided a method for the manufacture of a corrosion-resistant sintered alloy steel, which comprises providing a stainless steel powder; adding a binder to said steel powder; molding the mixture; and carrying out the steps of (1) heating the resultant molding to remove the binder therefrom, (2) sintering the thus debound molding under reduced pressure up to 30 Torr, and (3) further sintering at a higher temperature than those of steps (1) and (2) in a non-oxidative atmosphere under substantially atmospheric pressure. It is also provided a corrosion-resistant sintered alloy steel which comprises a stainless steel, said alloy steel having a density ratio of not less than 92%, a maximum diametric of pore present in the structure of not larger than 20 .mu.m, and a content of Cr at the surface of the steel as being sintered which is not less than 80% of a content of Cr in the inside thereof.

Abstract: Provided herein are high-strength high-toughness sintered alloy steel and composite alloy steel powder useful for the production thereof. The sintered alloy steel contains, as the alloy components in the final product, Ni, Mo, and/or W, and C, if necessary, said alloy being composed of 0.50-3.50 wt % of Ni, 0.65-3.50 wt % of Mo+1/2W, (and 0.3-0.8 wt % of C, if necessary), and the remainder of Fe and inevitable impurities, and has a density higher than 7.0 g/cm.sup.3 and a tensile strength higher than 130 kgf/mm.sup.2 after quenching and tempering. The composite alloy steel powder is composed of iron powder particles and powdery alloy components attached by diffusion to part of the surface of the iron powder particles, with the content of Ni and the content of Mo+1/2W in the steel powder of particle diameter smaller than 45 .infin.m being in the range of 2.0-4.2 times the average content in the entire steel powder.

Abstract: An alloy steel powder having a basic alloy composition, which is composed of at least one of manganese, chromium, molybdenum and vanadium, and the remainder being iron, and having low carbon, nitrogen and oxygen contents is excellent in the compressibility and moldability at the press molding and further excellent in the carburizing property and hardenability in its sintered steel or powder forged steel.

Abstract: A process and an apparatus for producing low-oxygen iron-base metallic powder are disclosed. The low-oxygen iron-base metallic powder is produced by alloying and/or admixing iron-base metallic raw powder to be subjected to a final reduction, which has an apparent density in filled state corresponding to 16-57% of theoretical true density, an oxygen content of not more than 6% by weight and a particle size of not more than 1 mm, with carbon or carbonaceous granule in an amount corresponding to not more than an target alloying carbon content of a final product (% by weight) + an oxygen content of the powder just before the final reduction (% by weight) .times. 1.35 to form a starting powder, preheating the starting powder at a temperature of 780.degree.-1,130.degree. C. in a non-oxidizing atmosphere having a theoretical oxygen partial pressure of not more than 2.1.times.10.sup.-1 mmHg and a dew point of not more than +5.degree. C.

Abstract: A shaft furnace for producing low-oxygen iron-base metallic powder for metallurgy is disclosed. The shaft furnace comprises a zone of storing and feeding a metallic raw powder, a preheating zone, an induction heating zone and a zone of cutting and cooling a product cake in a vertical array from top to bottom. The preheating zone and induction heating zone have a special structure for ensuring a smooth descent of the raw powder and the cake.

Abstract: A process for producing low-oxygen iron-base metallic powder are disclosed. The low-oxygen iron-base metallic powder is produced in a shaft-type apparatus comprising a preheating zone and an induction heating zone by alloying and/or admixing iron-base metallic raw powder to be subjected to a final reduction, which has an apparent density corresponding to 16 to 57% of theoretical true density, an oxygen content of not more than 6% by weight and a particle size of not more than 1 mm, with carbon or carbonaceous granule in an amount corresponding to not more than a target alloying carbon content of a final product (% by weight)+ an oxygen content of the powder just before the final reduction (% by weight).times. 1.35 to form a starting powder, preheating the starting powder at a temperature of 780.degree. to 1,200.degree. C. in a non-oxidizing atmosphere having a thermodynamically calculated oxygen partial pressure of not more than 2.1.times.10.sup.-1 mmHg and a dew point of not more than +5.degree. C.

Abstract: A metal block having a high density can be easily obtained directly from metal powder by charging the metal powder in a metallic container, disposing carbonaceous powder through a partition plate on the metal powder so as to interrupt the metal powder from the air, uniformly heating the metal powder in the air together with the container and subjecting the metal powder in the air together with the container to a primary hot working and to a secondary hot working with or without effecting a uniform heating step.

Abstract: Iron or iron alloy powders having a low oxygen content to be used for powder metallurgy are produced by subjecting iron or iron alloy powder materials having an oxygen content of not more than 8% by weight and a total carbon amount including carbon alloyed in said powders being not more than 6% by weight corresponding to the oxygen content to an induction heating under a relative density of 5-65% based on a density of the molding steel of said powders by means of an alternating current of 50 cycles-1 megacycle to heat said powders at a temperature of 750.degree.-1,400.degree.C to effect reduction rapidly.