Abstract: This invention presents a method for manufacturing sintered and carburized porous stainless steel parts, comprising steps of: sintering stainless steel powders to obtain a porous sintered stainless steel, wherein the porous sintered stainless steel comprises a three dimensional network skeleton structure with a large number of interconnected pore channels; and carburizing the porous sintered stainless steel by a non-halogenated carbon-bearing gas, wherein the porous sintered stainless steel being maintained at a carburizing temperature below 600° C. such that carbon atoms can be implanted into the porous sintered stainless steel and converts a surface portion of the skeleton structure, that is in contact with the carbon-bearing gas in the interconnected pore channels, into a carburized layer. A carburized layer is formed and spread over a skeleton structure of the sintered porous body. Thereby, the strength, surface hardness, and core hardness of the sintered body are significantly increased.

Abstract: A powder metallurgical method for fabricating a high-density soft magnetic metallic material comprises steps of providing an initial powder; using a spray drying process to fabricate the initial powder into a spray-dried powder; placing the spray-dried powder in a mold and compacting the spray-dried powder under a compacting pressure and a compacting temperature to form a green compact; and sintering the green compact at a sintering temperature to form a soft magnetic metallic material. The spray-dried powder, which is fabricated by the spray drying process, has superior flowability, compactability and compressibility and is suitable for the press-and-sinter process. The soft magnetic metallic material fabricated by the present invention is outstanding in sintered density and magnetic performance. The present invention adopts the inexpensive press-and-sinter process and has a low fabrication cost.

Abstract: This invention presents a sintered and carburized porous stainless steel part with improved strength and hardness and method thereof. The sintered and carburized porous stainless steel part has a porous body with a relative density between 30% and 89%, which is sintered from a stainless steel powder, wherein exposed pore surfaces inside the porous body are carburized without forming carbides and without using an activation process in advance. A carburized layer is formed and spread into the core of the sintered porous body. Thereby, the strength, surface hardness, and core hardness of the sintered body are significantly increased.

Abstract: A method for fabricating fine reduced iron powders comprises the following steps: heating fine iron oxide powders having a mean particle size of smaller than 20 ?m to a reduction temperature of over 700° C. to reduce the fine iron oxide powder into iron powders that are partially sintered into iron powder agglomerates; and performing a crushing-spheroidizing process on the iron powder agglomerates to obtain individual iron powders having a mean particle size of smaller than 20 ?m. The method can reduce iron oxide powers into iron powders having a rounded shape and a high packing density and a high tap density, which are suitable for the metal injection molding process and the inductor fabrication process. The reduced iron powder may further be processed using an annealing process and a second crushing-spheroidizing process in sequence to further increase the sphericity, packing density, and tap density of the reduced iron powder.

Abstract: A method for improving surface mechanical properties of non-austenitic stainless steels comprises steps of: providing a non-austenitic stainless steel material; placing the non-austenitic stainless steel material in an environment containing at least one austenite-stabilizing element, and implanting the austenite-stabilizing elements into a surface of the non-austenitic stainless steel material to form a modified layer enriched with the austenite-stabilizing elements; and placing the non-austenitic stainless steel material in a carbon-bearing atmosphere to make the modified layer in contact with the carbon-bearing atmosphere, and maintaining the non-austenitic stainless steel material at a carburizing temperature below 600° C. to implant carbon into the modified layer to form a carburized layer.

Abstract: A method for fabricating fine reduced iron powders comprises the following steps: heating fine iron oxide powders having a mean particle size of smaller than 20 ?m to a reduction temperature of over 700° C. to reduce the fine iron oxide powder into iron powders that are partially sintered into iron powder agglomerates; and performing a crushing-spheroidizing process on the iron powder agglomerates to obtain individual iron powders having a mean particle size of smaller than 20 ?m. The method can reduce iron oxide powers into iron powders having a rounded shape and a high packing density and a high tap density, which are suitable for the metal injection molding process and the inductor fabrication process. The reduced iron powder may further be processed using an annealing process and a second crushing-spheroidizing process in sequence to further increase the sphericity, packing density, and tap density of the reduced iron powder.

Abstract: A low-temperature stainless steel carburization method comprises steps: providing a stainless steel material; placing the stainless steel material in a halogen-free reducing environment and maintaining the stainless steel at a first temperature ranging 1,050 to 1,400° C.; and placing the stainless steel material in a carbon-bearing atmosphere and maintaining the stainless steel material at a second temperature lower than 600° C. to implant carbon atoms into the stainless steel material to form a carburized layer on the surface of the stainless steel material. A halide-bearing gas or solution is not to be applied to activate the passivation layer, so the fabrication cost would be reduced and the safety of carburization process would be enhanced. Besides, the environment can be prevented from halide pollution.

Abstract: A method for improving surface mechanical properties of non-austenitic stainless steels comprises steps of: providing a non-austenitic stainless steel material; placing the non-austenitic stainless steel material in an environment containing at least one austenite-stabilizing element, and implanting the austenite-stabilizing elements into a surface of the non-austenitic stainless steel material to form a modified layer enriched with the austenite-stabilizing elements; and placing the non-austenitic stainless steel material in a carbon-bearing atmosphere to make the modified layer in contact with the carbon-bearing atmosphere, and maintaining the non-austenitic stainless steel material at a carburizing temperature below 600° C. to implant carbon into the modified layer to form a carburized layer.

Abstract: A method for enhancing strength and hardness of powder metallurgy stainless steels comprises steps of fabricating a stainless steel powder into a green compact; placing the green compact in a reducing environment and maintaining the green compact at a sintering temperature to form a sintered body; and placing the sintered body in a carbon-bearing atmosphere and maintaining the sintered body at a carburizing temperature below 600° C. to implant carbon atoms into the sintered body and form carburized regions in the sintered body. Thereby, the strength and hardness of powder metallurgy stainless steels can be improved. As the carburizing temperature is lower than 600° C., chromium would not react with carbon. Therefore, the strength and hardness of powder metallurgy stainless steels can be enhanced and the superior corrosion resistance is still preserved.

Abstract: A low-temperature stainless steel carburization method comprises steps: providing a stainless steel material; placing the stainless steel material in a halogen-free reducing environment and maintaining the stainless steel at a first temperature ranging 1,050 to 1,400° C.; and placing the stainless steel material in a carbon-bearing atmosphere and maintaining the stainless steel material at a second temperature lower than 600° C. to implant carbon atoms into the stainless steel material to form a carburized layer on the surface of the stainless steel material. A halide-bearing gas or solution is not to be applied to activate the passivation layer, so the fabrication cost would be reduced and the safety of carburization process would be enhanced. Besides, the environment can be prevented from halide pollution.

Abstract: A sinter-hardening raw powder can yield a press-and-sinter compact with high hardness. The raw powder for sintering includes Fe as its primary component and also includes 0.3-0.8 wt % C, 5.0-12.0 wt % Ni, 1.0-5.0 wt % Cr, and 0.1-2.0 wt % Mo, wherein the mean particle size of the raw powder for sintering is between 50 and 100 ?m. The sintered and tempered compact, without any quenching treatment, has high hardness.

Abstract: A sinter-hardening powder can yield a sintered compact with high strength, high hardness, and high density. A raw powder for sintering includes Fe as its primary component and also comprising 0.1-0.8 wt % C, 5.0-12.0 wt % Ni, 0.1-2.0 wt % Cr, and 0.1-2.0 wt % Mo, wherein the mean particle size of the raw powder for sintering is 20 ?m or less. The sintered and tempered compact, without any quenching treatment, has high hardness, high strength, high density, and good ductility.

Abstract: The present invention relates to a sinter hardening powder that can yield a sintered compact with high strength. The present invention provides a raw powder for sintering, comprising Fe as its primary component and also comprising 0.1-0.8 wt % C, 3.5-12.0 wt % Ni, 0.1-7.0 wt % Cr, and 2.0 wt % or less of Mo, wherein the mean particle size of the raw powder for sintering is 150 ?m or less. The sintered compact having high tensile strength, high hardness, and good ductility can be formed without performing the quenching process.

Abstract: The present invention relates to a metal powder sintered body by using fine powders as the raw material and the fabrication method thereof. The sintered body has a characteristic composition including iron (Fe), carbon (C), nickel (Ni) and at least one strengthening element, in the ratios as follows: Ni: 3.0-12.0%, carbon: 0.1-0.8%, the strengthening element: 0.5-7.0%, and the remaining portion being Fe. The sintered body has high tensile strength, high hardness, and good ductility, without treatment with the quenching process.