Abstract: A method for producing a machine component excellent in pitting resistance characteristics and toughness includes a carburizing step, performed on a steel material containing 0.13-0.30% C and 0.90-2.00% Cr in mass % and at least one of Si, Mn, Ni, Mo, Nb, V, Ti, B, Al, and N, balance Fe and unavoidable impurities; heating the material to 850-1030° C. to attain carbon concentration in a surface of 0.8-1.5%; cooling the material at an average rate of 5° C./sec or lower from a temperature higher than the Acm point of a surface layer to a cooling end temperature that is at least 50° C. lower than the A1 point to cause the surface layer to have a pearlite or bainite structure with dispersion; spheroidizing annealing at a temperature not higher than the Acm point at the surface layer; heating the material to not higher than the Acm point at the surface layer; and performing tempering.

Abstract: A method (100) for pressing at least one article in an arrangement as well as a pressing arrangement (500). The method comprises providing an article inside a load compartment and feeding a pressure medium into the pressure vessel and increasing (140) the pressure in the load compartment; increasing (120) the temperature and maintaining (150) the increased temperature and the increased pressure for selected periods of time (t1, t2); changing (170) the temperature from the first predetermined temperature level to a second predetermined temperature level (T2); feeding (180) a carbon-containing gas into the pressure vessel; maintaining (190) the second predetermined temperature level for a selected period of time (t3); reducing (200) the temperature in the load compartment; and discharging (210) the pressure medium from the pressure vessel and reducing (220) the pressure in the load compartment.

Abstract: Low temperature gas carburization of stainless steel using acetylene as the carburizing specie is carried out under soft vacuum conditions in the presence of hydrogen or other companion gas. Carburization is made to go faster by including HCl or other carbon-free, halogen-containing activating compound in the carburizing gas being fed to the carburization reactor.

Abstract: The present invention is to provide a storing container wherein Si does not drop onto a single crystal SiC substrate, and Si pressure distribution in an internal space can be made uniform. This storing container stores therein a single crystal SiC substrate to be etched by means of a heat treatment under Si vapor pressure. The storing container is formed of a tantalum metal, and has a tantalum carbide layer provided on an internal space side, and a tantalum silicide layer provided on the side further toward the internal space side than the tantalum carbide layer. The tantalum silicide layer supplies Si to the internal space. Furthermore, the tantalum silicide layer is different from adhered Si, and does not melt and drop.

Abstract: A ball screw has a nut formed with a helical ball rolling groove on its inner circumference. A screw shaft is formed with a helical ball rolling groove on its inner circumference. The screw shaft is inserted into the nut. A number of balls are rollably contained within a ball rolling passage formed by oppositely arranged helical ball rolling grooves of the nut and the screw shaft, respectively. The nut is made of case hardened steel. The ball rolling groove is formed by cutting and surface hardening, by vacuum carburizing hardening, without any after-processing.

Abstract: Provided is a method for carburizing a tantalum member whereby the tantalum member is less deformed by carburization and can be carburized with good flatness of the planar part thereof and in a uniform manner. The method is a method for subjecting a tantalum member 1 made of tantalum or a tantalum alloy and having a planar part 1a to a carburization process for allowing carbon to penetrate the member 1 from the surface toward the inner portion thereof and includes the steps of: setting the tantalum member 1 in a chamber 3 containing a carbon source by supporting the planar part 1a on a plurality of support rods 6 tapered at distal ends 6a thereof; and subjecting the tantalum member 1 to a carburization process by reducing in pressure and heating the interior of the chamber 3 to allow carbon derived from the carbon source to penetrate the tantalum member 1 from the surface thereof.

Abstract: A method for manufacturing a torque transmission mechanism between a starter motor and a crankshaft of an internal combustion engine, comprising a one-way clutch including an outer ring fast in rotation with the crankshaft via a front plate. This method comprises the following steps: a) forging the outer ring out of carburizing steel, b) carburizing the outer ring, c) tempering the outer ring, d) grinding an inner surface of the outer ring, e) manufacturing the front plate out of standard low equivalent carbon content steel, and f) assembling the front plate and the outer ring.

Abstract: A component of an implantable medical device comprises a body comprising at least one external surface, the body comprising at least one of titanium, titanium-based alloys, and composites thereof, and a corrosion-resistant surface region at the at least one external surface, the corrosion-resistant surface region comprising at least one of titanium nitride, dititanium nitride, and a solid solution of nitrogen dissolved in the body, wherein the corrosion-resistant surface region is formed by thermal nitridation of the body.

Abstract: The present invention relates to a mechanical part, which is obtained by: processing a steel into a shape of a part, the steel having an alloy composition containing, by weight percent, C: 0.10 to 0.30%, Si: 0.50 to 3.00%, Mn: 0.30 to 3.00%, P: 0.030% or less, S: 0.030% or less, Cu: 0.01 to 1.00%, Ni: 0.01 to 3.00%, Cr: 0.20 to 1.00%, Al: 0.20% or less, N: 0.05% or less, and the remainder of Fe and inevitable impurities, and the alloy composition satisfying the following condition: [Si %]+[Ni %]+[Cu %]?[Cr %]>0.50, in which [Si %], [Ni %], [Cu %] and [Cr %] represent the concentration of Si, the concentration of Ni, the concentration of Cu and the concentration of Cr in the alloy composition, respectively; subjecting the steel to a carburizing treatment in a vacuum, followed by gradually cooling the steel; and subsequently subjecting the steel to a high-frequency hardening to thereby harden a surface of the steel.

Abstract: The present invention comprises a process for nitriding martensitic stainless steel and the alloy produced thereby comprising heating a stainless steel alloy to a temperature of from about 900° F. (480° C.) to about 2500° F. (1370° C.) in a vacuum furnace in the presence of hydrogen or argon gas in order to clean the surface. After the hydrogen or argon gas is removed from the chamber, nitrogen gas, or a different nitrogen gas derivative is injected into said furnace as a pulsed injection at a partial pressure of from about 500 torr to about 1000 torr. The steel is nitrogen alloyed at a temperature of from about 1400° F. (760° C.) to about 2200° F. (1205° C.) and then quickly quenched at ambient temperature. Preferably, after a sufficient period of time, the temperature is raised a second time from about 900° F. (480° C.) to about 2500° F. (1370° C.) prior to cooling the final product.

Abstract: A method selectively recovers a useful substance from waste including a chlorine-containing synthetic resin and metal copper in a mixed state. Metal copper is recovered from coated copper-wire waste. The method includes the steps of heat-treating the waste in form of coated copper wires, each having a coating material made of a chlorine-containing synthetic resin, in oil or under a non-oxygen condition. Here, the coating material is carbonized and a chlorine content of the coating material is reduced. Then the coating material and the copper wire are separated from each other the copper wire is recovered. The chlorine-containing synthetic resin can be treated without generating dioxin.

Abstract: A method between a diffusion and a quenching process including normalizing by step cooling including alternating temperature lowering and temperature keeping treatment for a temperature history that satisfies a predetermined condition; after normalizing, maintaining the temperature of the whole workpiece so that the whole workpiece becomes the predetermined temperature, thereby producing fine crystal grains in the workpiece; then reheating the workpiece to raise its temperature to the second temperature. There is uniformity in temperature between the surface and the inside of a workpiece, and crystal grains are prevented from being coarse.

Abstract: A chain includes a plurality of sliding members that moves relative to each other. At least one of sliding members is formed of a martensitic stainless steel, and contains, in a superficial layer thereof, elemental substances of carbon and nitrogen at a range from 0.17 to 0.50 mass % in total, while a precipitation amount of carbide and nitride is 0.05 mass % or less in total.

Abstract: A method and apparatus for manufacturing a part. The part may be positioned in a chamber. The part may be comprised of a metal and may be a positioned part. A gas containing nitrogen may be sent into the chamber. An electromagnetic field may be generated in the chamber with the gas. The electromagnetic field may heat a portion of the metal in the positioned part to a temperature from about 60 percent to about 99 percent of the melting point of the metal such that the portion of the metal has a desired hardness. The portion of the metal may extend from a surface of the positioned part to a selected depth from the surface.

Abstract: Low temperature gas carburization of stainless steel using acetylene as the carburizing specie is carried out under soft vacuum conditions in the presence of hydrogen or other companion gas. Carburization is made to go faster by including HCl or other carbon-free, halogen-containing activating compound in the carburizing gas being fed to the carburization reactor.

Abstract: A vacuum carburization processing method includes a preparatory heating step of increasing the temperature of a workpiece in a heating chamber to a first temperature, a carburizing step of carburizing the workpiece by supplying carburizing gas into the heating chamber from a state where the pressure inside the heating chamber is reduced to an extremely low pressure, a diffusing step of terminating the supply of the carburizing gas and making carbon diffuse from a surface of the workpiece into its internal part, and a quenching step of abruptly cooling the temperature of the workpiece from a state where the temperature of the workpiece is at a second temperature; and also includes, between the diffusing step and the quenching step, a normalizing step of reducing the temperature of the workpiece so that the temperature history of the workpiece from the first temperature to a predetermined temperature satisfies predetermined conditions, a post-normalization maintaining step, performed after the normalizing step,

Abstract: The present invention comprises a process for nitriding martensitic stainless steel and the alloy produced thereby comprising heating a stainless steel alloy to a temperature of from about 900° F. (480° C.) to about 2500° F. (1370° C.) in a vacuum furnace in the presence of hydrogen or argon gas in order to clean the surface. After the hydrogen or argon gas is removed from the chamber, nitrogen gas, or a different nitrogen gas derivative is injected into said furnace as a pulsed injection at a partial pressure of from about 500 torr to about 1000 torr. The steel is nitrogen alloyed at a temperature of from about 1400° F. (760° C.) to about 2200° F. (1205° C.) and then quickly quenched at ambient temperature. Preferably, after a sufficient period of time, the temperature is raised a second time from about 900° F. (480° C.) to about 2500° F. (1370° C.) prior to cooling the final product.

Abstract: The present invention is directed to a process for tempering steel comprising carburizing said steel in a vacuum furnace in the presence of a hydrocarbon carburizing gas in combination with hydrogen wherein said carburizing gas/hydrogen combination is administered to the vacuum furnace by cyclically reducing the pressure in the furnace followed by the pulsed addition of the hydrocarbon carburizing gas consisting of an acetylene/hydrogen mixture is in a ratio of from about 1:1 to about 1:10 to replenish the air removed in the pressure reduction step.

Abstract: A component of an implantable medical device comprises a body comprising at least one external surface, the body comprising at least one of titanium, titanium-based alloys, and composites thereof, and a corrosion-resistant surface region at the at least one external surface, the corrosion-resistant surface region comprising at least one of titanium nitride, dititanium nitride, and a solid solution of nitrogen dissolved in the body, wherein the corrosion-resistant surface region is formed by thermal nitridation of the body.

Abstract: The disclosure provides a device and method used to produce a tubular structure made of a refractory metal compound. In particular, the disclosure provides a device and method used to produce a tubular structure made of a refractory metal compound by reacting a green tubular structure made of a refractory metal with at least one reactive gas.

Abstract: A carburizing process for increasing the hardness of a case region of a steel component. In one form the application includes plating the outer surface of a stainless steel component with nickel prior to carburizing. One component includes a stainless steel object having a hardened case substantially free of continuous phase grain boundary carbides.

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: Surface processing of titanium alloy members for aerospace equipment imparts high wear resistance, lubricity and high fatigue strength. The method includes an oxygen diffusion step for causing oxygen to diffuse and penetrate in solid solution form into a surface of a titanium alloy member under an oxygen-containing gas atmosphere and a particle bombardment step for bombarding the surface of the titanium alloy member with an airflow containing particles. The aerospace equipment can include a flap rail member and slat rail member for aircraft.

Abstract: The invention relates to a method and device for thermally treating workpieces, the device including a cooling chamber and two or more cementing chambers in which the workpieces are heated to a temperature of 950 to 1200° C. by means of direct heat radiation from a heating device.

Abstract: There are provided a method, between a diffusion process and a quenching process, a normalizing process of performing step cooling in which a temperature lowering treatment and a temperature keeping treatment are alternately repeated plural times so that a temperature history from the first temperature to a predetermined temperature satisfies a predetermined condition; an after-normalizing maintaining process of maintaining the temperature of the whole workpiece for a predetermined time after the normalizing process so that the whole workpiece becomes the predetermined temperature, thereby producing fine crystal grains in the workpiece; and a reheating process of raising the temperature of the workpiece to the second temperature, after the after-normalizing keeping process.

Abstract: The present invention comprises the nitridization of stainless steel with a gaseous nitrogen compound such as nitrogen gas (N2), or ammonia (NH3) at high temperature wherein the reaction pressure is lowered. A base powder with properties similar to those of a martensitic stainless steel is prepared from a molten metal with the subsequent incorporation of selective additives such as cobalt, chromium, boron, copper, vanadium, niobium and mixtures thereof to improve high temperature resistance to scuffing and adhesive wear. The molten mixture is then atomized by water- or air-atomization to yield a base powder which is mixed with nitrogen or ammonia gas at various pressures in a static or fluidized bed to provide a nitrogen alloyed particulate, i.e., a nitrided particulate alloy. The powder is heated in a hot isostatic press under vacuum with argon gas at reduced pressure and later cooled to ambient (room) temperature.

Abstract: Methods for depositing a coating on a metal surface can include heating a metal surface to a temperature not greater than its melting point; while heating the metal surface, applying a vacuum thereto; and while heating the metal surface, releasing the vacuum and backfilling with a first purge gas, where the first purge gas is reactive with the heated metal surface so as to deposit at least one layer of a coating thereon. The present methods can be used to deposit a coating in situ during the fabrication of solar receivers, in which the solar receivers contain an annulus defined by a metal tube as the inner surface and a material that is at least partially transparent to solar radiation as the outer surface.

Abstract: Provided is a method for carburizing a tantalum member whereby the tantalum member is less deformed by carburization and can be carburized with good flatness of the planar part thereof and in a uniform manner. The method is a method for subjecting a tantalum member 1 made of tantalum or a tantalum alloy and having a planar part 1a to a carburization process for allowing carbon to penetrate the member 1 from the surface toward the inner portion thereof and includes the steps of: setting the tantalum member 1 in a chamber 3 containing a carbon source by supporting the planar part 1a on a plurality of support rods 6 tapered at distal ends 6a thereof; and subjecting the tantalum member 1 to a carburization process by reducing in pressure and heating the interior of the chamber 3 to allow carbon derived from the carbon source to penetrate the tantalum member 1 from the surface thereof.

Abstract: A method for manufacturing a carburized part that includes vacuum carburizing a steel under a reduced pressure of 2 kPa or less, so that a surface carbon concentration after slow cooling performed after carburizing falls in a range of 0.9 to 1.5%, performing the slow cooling by air cooling at such a cooling rate that causes pearlite transformation, to transform a surface structure into pearlite; and thereafter, performing induction hardening under such heating and cooling conditions that produce fine carbides in a range of up to 0.1 mm from a surface by finely dividing cementite in the pearlite structure, where the fine carbides contain 90% or more of carbides of 1 ?m or less.

Abstract: The present invention is directed to a process for tempering steel comprising carburizing said steel in a vacuum furnace in the presence of a hydrocarbon carburizing gas in combination with hydrogen wherein said carburizing gas/hydrogen combination is administered to the vacuum furnace by cyclically reducing the pressure in the furnace followed by the pulsed addition of the hydrocarbon carburizing gas consisting of an acetylene/hydrogen mixture is in a ratio of from about 1:1 to about 1:10 to replenish the air removed in the pressure reduction step.

Abstract: A method of manufacturing a sheave member for a belt-type continuously variable transmission includes a forming step wherein an intermediate product having a sheave surface is formed by forging a steel material; a carburization step wherein the intermediate product is heated in a carburization gas; a gradual cooling step wherein the cooling speed is equal to or less than 20° C./sec, at least until the temperature of the intermediate product has passed through the transformation point; a high-frequency electrical heating step wherein a selected portion(s) of the intermediate product is heated; a water quenching step wherein the selected portion is quenched by contact with water; and a finishing step wherein a grinding process is applied to the intermediate product to attain the final shape. In the cooling step, preferably, the intermediate product is contacted with a cooling gas at a pressure lower than atmospheric pressure.

Abstract: A method and measurement system for the control of an active charge surface in a low pressure carburizing process can avoid formation of by-products and achieve regular carburized layers. This can be achieved through sampling of outlet gas at a specified time and comparison with experimentally set model characteristics.

Abstract: A surface carburization technique of medical titanium alloy femoral head in total hip arthroplasty comprises subjecting medical titanium alloy TC4 to surface carburization by using acetylene as carburizing agent to carry out gaseous carburization at high temperature to give medical titanium alloy femoral head in total hip arthroplasty with TiC ceramic on surface thereof. The TiC ceramic layer on femoral head can be more than 100 micron thick, which is relatively thick, overcomes the disadvantages in available medical titanium alloy material, and is particularly useful for replacement of total hip or knee arthroplasty.

Abstract: The invention relates to a process for the low-pressure carburisation of metal workpieces in an evacuable furnace, in which acetylene is added to the furnace atmosphere as the carburisation gas, wherein the partial pressure of the acetylene is varied intermittently and wherein the partial pressure of the acetylene in the furnace atmosphere is kept below 10 mbar. In order to specify a process for the low-pressure carburisation of metal workpieces that leads to an improvement, particularly with regard to the carburisation result, the invention proposes the use of a pot furnace as the furnace.

Abstract: A carburizing process for increasing the hardness of a case region of a steel component. In one form the application includes plating the outer surface of a stainless steel component with nickel prior to carburizing. One component includes a stainless steel object having a hardened case substantially free of continuous phase grain boundary carbides.

Abstract: A method for producing a carburized part by carburizing a steel member under a vacuum in a decompression furnace while feeding carburizing gas comprises a step for forming an oxide film on at least a part of a surface of the steel member, a step for generating carbon by reducing the oxide film with the carburizing gas, and a step for carburizing the surface of the steel member under a vacuum by diffusing the carbon.

Abstract: A method for manufacturing a carburized part that includes vacuum carburizing a steel under a reduced pressure of 2 kPa or less, so that a surface carbon concentration after slow cooling performed after carburizing falls in a range of 0.9 to 1.5%, performing the slow cooling by air cooling at such a cooling rate that causes pearlite transformation, to transform a surface structure into pearlite; and thereafter, performing induction hardening under such heating and cooling conditions that produce fine carbides in a range of up to 0.1 mm from a surface by finely dividing cementite in the pearlite structure, where the fine carbides contain 90% or more of carbides of 1 ?m or less.

Abstract: A method of carburizing and quenching a steel member includes: a reduced pressure carburization step in which a steel member is contacted with carburization gas under reduced pressure, a slow cooling step in which the steel member is then slowly cooled in a cooling gas, and a quenching step of heating a selected portion of the cooled steel member using high-density energy and subsequently subjecting the selected portion to rapid cooling. The steel member subjected to the low-pressure carburization step includes a first portion in which a diffusion rate of carbon taken therein during carburization is high because of its shape and a second portion in which the diffusion rate of carbon is lower than that of the first portion. The reduced-pressure carburization step is controlled to give a carbon concentration at the surface of the first portion in a range of 0.65±0.1 weight % after diffusion.

Abstract: The invention provides a carburization treatment method in which the carburization treatment is conducted under a condition where an atmosphere within the furnace is maintained at a high carbon potential which is slightly blow a carbon solid solubility. Preferably, the internal pressure within the furnace is kept at 0.1 to 101 kPa, the hydrocarbon gas is one, two or more than two kinds of gases selected from the group consisting of C3H8, C3H6, C4H10, C2H2, C2H4, C2H6 and CH4, while the oxidative gas is an air, an O2 gas, or CO2 gas.

Abstract: The invention relates to a method of gas carburizing a metallic article, where at least the surface region of the article consists of an alloy with a chromium content of at least 10 wt %. The carburizing is carried out by means of a gas containing carbon, which gas is heated to a temperature below approximately 5500C. The gas is an un-saturated hydrocarbon gas.

Abstract: The subject of this invention relates to method carburizing of steel products, mainly parts of machines, vehicles and every mechanical apparatus, in vacuum furnaces under reduced pressure and elevated temperature. The method of under-pressure carburizing of steel workpieces according to present invention relates to introduction of active nitrogen carrier during heating up of the load. Introduction of the active nitrogen carrier is terminated when the load reaches temperature required to start carburizing process; from this temperature the carbon carrier is added. Pressure in the furnace chamber during continuous or pulse introduction of the active nitrogen carrier should be maintained within the ranges from 1 to 500 mbar.

Abstract: The subject of present invention relates to mixture for carburizing of steel products, mainly parts of machines, vehicles and every mechanical apparatus, used in vacuum furnaces. Present invention relates to mixture for under-pressure carburizing containing the carbon carrier comprising two unsaturated hydrocarbons, likely ethylene and acetylene, in volume ratio from 0.1 to 2.00. The carbon carrier can be further mixed with hydrogen or ammonia.

Abstract: A reduced-pressure heat treatment jig is used for supporting a workpiece of iron when the workpiece is subjected to heat treatment in a reduced-pressure atmosphere in which pressure is reduced compared to atmospheric pressure. The jig is formed of an iron material and is formed with a film on at least a contact surface with the workpiece, the film being formed of a material which persists during the heat treatment. The film preferably includes a metal oxide having an evaporating temperature higher than the heat treatment temperature in the reduced-pressure atmosphere. The film preferably contains aluminum oxide.

Abstract: A surface carburization technique of medical titanium alloy femoral head in total hip arthroplasty comprises subjecting medical titanium alloy TC4 to surface carburization by using acetylene as carburizing agent to carry out gaseous carburization at high temperature to give medical titanium alloy femoral head in total hip arthroplasty with TiC ceramic on surface thereof. The TiC ceramic layer on femoral head can be more than 100 micron thick, which is relatively thick, overcomes the disadvantages in available medical titanium alloy material, and is particularly useful for replacement of total hip or knee arthroplasty.

Abstract: The present invention relates to a mechanical part, which is obtained by: processing a steel into a shape of a part, the steel having an alloy composition containing, by weight percent, C: 0.10 to 0.30%, Si: 0.50 to 3.00%, Mn: 0.30 to 3.00%, P: 0.030% or less, S: 0.030% or less, Cu: 0.01 to 1.00%, Ni: 0.01 to 3.00%, Cr: 0.20 to 1.00%, Al: 0.20% or less, N: 0.05% or less, and the remainder of Fe and inevitable impurities, and the alloy composition satisfying the following condition: [Si %]+[Ni %]+[Cu %]?[Cr %]>0.50, in which [Si %], [Ni %], [Cu %] and [Cr %] represent the concentration of Si, the concentration of Ni, the concentration of Cu and the concentration of Cr in the alloy composition, respectively; subjecting the steel to a carburizing treatment in a vacuum, followed by gradually cooling the steel; and subsequently subjecting the steel to a high-frequency hardening to thereby harden a surface of the steel.

Abstract: A method for producing a carburized part by carburizing a steel member under a vacuum in a decompression furnace while feeding carburizing gas comprises a step for forming an oxide film on at least a part of a surface of the steel member, a step for generating carbon by reducing the oxide film with the carburizing gas, and a step for carburizing the surface of the steel member under a vacuum by diffusing the carbon.

Abstract: There are provided a method, between a diffusion process and a quenching process, a normalizing process of performing step cooling in which a temperature lowering treatment and a temperature keeping treatment are alternately repeated plural times so that a temperature history from the first temperature to a predetermined temperature satisfies a predetermined condition; an after-normalizing maintaining process of maintaining the temperature of the whole workpiece for a predetermined time after the normalizing process so that the whole workpiece becomes the predetermined temperature, thereby producing fine crystal grains in the workpiece; and a reheating process of raising the temperature of the workpiece to the second temperature, after the after-normalizing keeping process.

Abstract: A super carburized, low-distortion quenched member with higher performance and minimized heat-treatment distortion is provided. A process for the production thereof includes a primary treatment and a secondary treatment. The primary treatment includes heating a steel member for a machine structure to a temperature within an austenite region by vacuum carburizing (low-pressure carburizing) to have carbon dissolved at least at a eutectoid carbon concentration of a surface layer portion of the member and then quenching the member to have at least one of ultrafine carbide and nuclei of the carbide formed in the surface layer portion of the member. The secondary treatment includes subsequently heating and soaking the member to a temperature within the austenite region and then conducting rapid quenching to have ultrafine carbide precipitated in an outermost surface layer portion.

Abstract: A method of oxygen-free heat treatment of a steel part in an atmospheric pressure furnace is disclosed. The present method employs an oxygen-free controlled gas atmosphere including hydrogen gas in concentrations between about 1.0 percent to 10.0 percent, a hydrocarbon gas, such as propylene, in concentrations of between about 0.1 percent and 10.0 percent that varies as a function of time, with the balance of the gas atmosphere being nitrogen. The presently disclosed oxygen-free heat treatment process, preferably a carburization process, uses a precisely controlled atmosphere to minimize inter-granular oxidation, eliminate the formation of soot and cementite or other metallic carbides, and avoid hydrogen embrittlement.

Abstract: The present invention provides a vacuum heat treating method, such as carburization, carbonitridation, high temperature carburization, high concentration carburization and the like, performed while supplying a mixed gas of ethylene gas and hydrogen gas under reduced pressures. The method includes: detecting a quantity of ethylene gas and that of hydrogen gas in a vacuum heat treating furnace (1); calculating an equivalent carbon concentration of atmosphere on the basis of the detected quantity of ethylene gas and that of hydrogen gas; and comparing the calculated value with a targeted value which is set on the basis of a material specification and required heat treatment performance of an object to be treated (a workpiece), to control quantities of ethylene gas and hydrogen gas supplied into the vacuum heat treating furnace (1) on the basis of a difference between the calculated value and the targeted value. A heat treatment quality required for the workpiece can be obtained with accuracy and reproducibility.