A method for manufacturing iron-based metallurgical parts, the method comprising: mixing graphite powder; pressing; presintering; oxidizing the presintered metallurgical part to form an oxide layer having a thickness of 1 m to 50 m on its surface to form an oxidized presintered metallurgical part; sintering; machining; carburizing; quenching and tempering. An oxide layer is formed on the surface of a part by oxidization, oxygen in the oxide layer is chemically reacted with the carbon in the surface layer of the product during the sintering, and the resulting product enters a sintering atmosphere in the form of gas to form a decarburized layer having a certain thickness on the surface of the part, so that the decarburization is realized.

A cemented carbide composed of a first hard phase, a second hard phase and a binder phase, in which the first hard phase is composed of tungsten carbide particles, the second hard phase is composed of at least one first compound selected from the group consisting of TiNbC, TiNbN and TiNbCN, the second hard phase has an average particle diameter of 0.25 ?m or less, the second hard phase has a dispersity of more than 0.70 and 17.0 or less, the second hard phase has a content of 0.1 vol % or more and 15 vol % or less, the binder phase contains at least one first element selected from the group consisting of iron, cobalt and nickel, and the binder phase has a content of 0.1 vol % or more and 19.0 vol % or less.

A cemented carbide composed of a first hard phase, a second hard phase and a binder phase, in which the first hard phase is composed of tungsten carbide particles, the second hard phase is composed of at least one first compound selected from the group consisting of TiNbC, TiNbN and TiNbCN, the second hard phase has an average particle diameter of 0.25 ?m or less, the second hard phase has a dispersity of more than 0.70 and 17.0 or less, the second hard phase has a content of 0.1 vol % or more and 15 vol % or less, the binder phase contains at least one first element selected from the group consisting of iron, cobalt and nickel, and the binder phase has a content of 0.1 vol % or more and 19.0 vol % or less.

There is provided a method for manufacturing a rare earth sintered magnet by many times repetitively finely pulverizing a rare earth alloy on a jet mill by supplying high-pressure nitrogen gas to narrow grain size distribution to make an easy alignment in a magnetic field, and by micronizing crystal grains by using a hydrogenation-disproportionation-desorption-recombination (HDDR) process, to improve the coercivity and thermostability of the rare earth sintered magnet.

There is provided a method for manufacturing a rare earth sintered magnet by many times repetitively finely pulverizing a rare earth alloy on a jet mill by supplying high-pressure nitrogen gas to narrow grain size distribution to make an easy alignment in a magnetic field, and by micronizing crystal grains by using a hydrogenation-disproportionation-desorption-recombination (HDDR) process, to improve the coercivity and thermostability of the rare earth sintered magnet.

The purpose of the present invention is to obtain an additive manufacturing device capable of manufacturing while reducing the flow rate of Ar gas. This additive manufacturing device is characterized in that a reduced-pressure atmosphere is maintained in a manufacturing area, an inert gas is supplied to the manufacturing area, the proportion of gaseous impurities in the manufacturing area is detected, and in case where the proportion of gaseous impurities exceeds a threshold value, the supply of inert gas is reduced.

The present invention discloses a W-containing RFeBCu serial sintered magnet and quenching alloy. The sintered magnet contains an R.sub.2Fe.sub.14B-type main phase, the R being at least one rare earth element comprising Nd or Pr; the crystal grain boundary of the rare earth magnet contains a W-rich area above 0.004 at % and below 0.26 at %, and the W-rich area accounts for 2.0 vol %-11.0 vol % of the sintered magnet. The sintered magnet uses a minor amount of W pinning crystal to segregate the migration of the pinned grain boundary in the crystal grain boundary to effectively prevent abnormal grain growth and obtain significant improvement. The crystal grain boundary of the quenching alloy contains a W-rich area above 0.004 at % and below 0.26 at %, and the W-rich area accounts for at least 50 vol % of the crystal grain boundary.

The present invention discloses a W-containing RFeBCu serial sintered magnet and quenching alloy. The sintered magnet contains an R.sub.2Fe.sub.14B-type main phase, the R being at least one rare earth element comprising Nd or Pr; the crystal grain boundary of the rare earth magnet contains a W-rich area above 0.004 at % and below 0.26 at %, and the W-rich area accounts for 2.0 vol %-11.0 vol % of the sintered magnet. The sintered magnet uses a minor amount of W pinning crystal to segregate the migration of the pinned grain boundary in the crystal grain boundary to effectively prevent abnormal grain growth and obtain significant improvement. The crystal grain boundary of the quenching alloy contains a W-rich area above 0.004 at % and below 0.26 at %, and the W-rich area accounts for at least 50 vol % of the crystal grain boundary.

A method for manufacturing an austenitic stainless steel workpiece including the following successive steps: 1) providing a powder and sintering the powder to form a sintered alloy with an austenitic structure; the alloy having a nitrogen content greater than or equal to 0.1% by weight, 2) treating the sintered alloy to transform the austenitic structure into a ferritic structure or ferrite+austenite two-phase structure on a surface layer of the alloy, 3) treating the sintered alloy to transform the ferritic or ferrite+austenite two-phase structure obtained in step 2) into an austenitic structure and, after cooling, forming the workpiece which, on the layer subjected to the transformations in steps 2) and 3), has a density higher than that of the core of the workpiece. The present description also relates to the workpiece obtained by the method which has a very dense surface layer (99%).

An apparatus (150) for controlling a sintering process in a sintering furnace (100), includes a preheating zone (120) and a high heat zone (130), further comprising at least two measuring devices (151, 152, 153, 154), wherein the at least two measuring devices comprise at least one measuring device in the preheating zone (120) and at least one measuring device in the high heat zone (130) for analyzing a furnace atmosphere at the respective zone, and adjusting means (155, 156) for adjusting a composition of the furnace atmosphere based on measurement values acquired by the at least two measuring devices (151, 152, 153, 154) in the respective zones (110, 120, 130, 140).