WO2019131602A1 - Élément en acier nitruré, et procédé et appareil de production d'élément en acier nitruré - Google Patents

Élément en acier nitruré, et procédé et appareil de production d'élément en acier nitruré Download PDF

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WO2019131602A1
WO2019131602A1 PCT/JP2018/047505 JP2018047505W WO2019131602A1 WO 2019131602 A1 WO2019131602 A1 WO 2019131602A1 JP 2018047505 W JP2018047505 W JP 2018047505W WO 2019131602 A1 WO2019131602 A1 WO 2019131602A1
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Prior art keywords
gas
steel member
furnace
nitriding
nitrided steel
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PCT/JP2018/047505
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English (en)
Japanese (ja)
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陽一 渡邊
泰 平岡
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パーカー熱処理工業株式会社
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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/06—Surface hardening
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
    • C21D1/76—Adjusting the composition of the atmosphere
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
    • C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
    • C23C8/24—Nitriding
    • C23C8/26—Nitriding of ferrous surfaces
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B5/00—Muffle furnaces; Retort furnaces; Other furnaces in which the charge is held completely isolated
    • F27B5/04—Muffle furnaces; Retort furnaces; Other furnaces in which the charge is held completely isolated adapted for treating the charge in vacuum or special atmosphere
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B5/00—Muffle furnaces; Retort furnaces; Other furnaces in which the charge is held completely isolated
    • F27B5/06—Details, accessories, or equipment peculiar to furnaces of these types
    • F27B5/16—Arrangements of air or gas supply devices
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B5/00—Muffle furnaces; Retort furnaces; Other furnaces in which the charge is held completely isolated
    • F27B5/06—Details, accessories, or equipment peculiar to furnaces of these types
    • F27B5/18—Arrangement of controlling, monitoring, alarm or like devices

Definitions

  • the present invention relates to a nitride steel member and a method and an apparatus for manufacturing the nitride steel member. More specifically, the present invention relates to a nitride steel member having excellent fatigue resistance useful for gears, crankshafts, and the like for automobile transmissions, and a method and apparatus for manufacturing the nitride steel member.
  • a compound layer which is iron nitride is formed on the surface, and a hardened layer called a diffusion layer is formed inside.
  • the hardened layer is usually made of an alloy nitride such as Si or Cr as a base material component.
  • the atmosphere in the gas nitriding furnace is also used to control the thickness (depth) of each of these two layers and / or the type of iron nitride on the surface, etc. It is controlled appropriately. Specifically, the nitriding potential (K N ) in the gas nitriding furnace is appropriately controlled.
  • the volume fraction (type of iron nitride) of ⁇ 'phase (Fe 4 N) and ⁇ phase (Fe 2-3 N) in the compound layer formed on the surface of the steel material is controlled It is done. Specifically, it is known that the fatigue resistance is improved by forming the ⁇ ′ phase more than the ⁇ phase (“Heat treatment”, Volume 55, No. 1, pages 1 and 2 (Hiraoka, Yoichi Watanabe, Takeshi Ishida): Non-Patent Document 1). Furthermore, a nitrided steel member in which the bending fatigue strength and the surface fatigue are improved by the formation of the ⁇ ′ phase is also provided (Japanese Patent Application Laid-Open No. 2013-221203: Patent Document 1).
  • the? 'Phase is formed in the compound layer on the surface of the steel material to improve the fatigue resistance.
  • the compound layer contains not only a small amount of ⁇ phase, but in fact, it becomes a two phase state of ⁇ ' phase and ⁇ phase (Japanese Patent Application Laid-Open No. 2016-211069: Patent Document 2). That is, there is a limit in forming a compound layer mainly based on the? 'Phase in order to improve the fatigue strength.
  • a large number of voids are formed in the vicinity of the surface layer of the compound layer. These voids tend to develop into fatigue cracks.
  • Nitriding treatment in the temperature range is referred to as carbonitriding treatment in contrast to conventional nitriding treatment.
  • austenite in the structure near the surface is stabilized, and a large amount of austenite remains even if it is quenched after that. Therefore, the strain after the heat treatment is about the same as the nitriding treatment.
  • this stabilized austenite is transformed to a hard martensitic structure by being reheated to a temperature of 250 to 300.degree.
  • STKM13 (a kind of carbon steel) is subjected to nitridation treatment at 640 ° C. for 90 minutes, and further to nitrogen treatment at 660 ° C. for 40 minutes and then reheat treatment at 280 ° C. for 90 minutes. It is hardened until "(New concept and practice of carburization and nitridation", Agne Technical Center, p. 142-147, 2013 (Teruaki Watanabe): Non-Patent Document 2). However, there is a problem that the compound layer on the surface remains.
  • Patent Document 1 cited by this specification is JP-A-2013-221203, and Patent Document 2 cited by this specification is JP-A-2016-211069.
  • Non-Patent Document 1 cited by this specification is “Heat treatment”, Volume 55, No.
  • Non-Patent Document 3 cited in this specification is "European Conference on Heat Treatment and Surface Engineering A3 TS Congress (Nice, France, 2017), pp. 26-29 (Y. Kawata and T. Kidachi), and Non-Patent Document 4 cited in this specification is “Japanese Heat Treatment Technology”. Association 5th Heat Treatment Technology Seminar Text ", 2012, (5) pp. 1-8 (Masahiro Okumiya).
  • the fatigue failure of machine parts results from notches which are subjected to high load stress, for example the root of a gear tooth.
  • a stress distribution according to the shape and load environment occurs only in the surface layer region (from the surface to the inside of a predetermined depth). For this reason, it is desirable to harden only the surface layer region so as not to impair the toughness and the machinability of the steel material.
  • the inventor of the present invention repeated intensive studies and various experiments to limit the configuration of the processing furnace and control the temperature and the nitriding potential of the nitriding treatment with high precision to thereby make the surface region hardened as desired. It was found that the members could be manufactured.
  • An object of the present invention is to provide a nitrided steel member whose surface region is hardened as desired, and a manufacturing method and apparatus for manufacturing such a nitrided steel member.
  • the present invention is a nitrided steel member having a carbon steel or low alloy steel as a matrix, and having a hardened layer having a martensitic structure containing 0.8% or more of nitrogen by mass% on the surface, wherein the hardened layer
  • the lower portion is provided with a diffusion layer in which nitrogen is diffused in the matrix, and the hardened layer has a thickness of 2 ⁇ m to 50 ⁇ m from the surface of the nitrided steel member, and the diffusion layer is the nitrided portion.
  • the hardness of the diffusion layer at a depth of 100 ⁇ m from the surface of the nitrided steel member, which extends to a depth of more than 100 ⁇ m from the surface of the steel member, and at a depth of 2 ⁇ m from the surface of the nitrided steel member Is a nitride steel member characterized in that it is larger than 100 HV.
  • the hardened layer having a martensitic structure containing 0.8% or more of nitrogen is limited to a thickness of 2 ⁇ m to 50 ⁇ m from the surface of the nitrided steel member, the heat treatment strain / transformation strain is small. Moreover, the hardness of the diffusion layer at a depth of 100 ⁇ m from the surface of the nitride steel member is 100 HV or more than the hardness at a depth of 2 mm from the surface of the nitride steel member, so that the hardened layer is thin. Sufficient strength can be guaranteed.
  • carbon steel carbon steel whose carbon content is 0.1% or more in mass% can be used, for example.
  • low alloy steel SCr420, SCM415, etc. can be utilized, for example.
  • the present invention is a method of manufacturing a nitrided steel member having a carbon steel or a low alloy steel as a mother phase using a circulation type processing furnace provided with a guide cylinder and a stirring fan, and at the time of nitriding treatment,
  • the temperature range in the circulating process furnace is controlled to 610 ° C. to 660 ° C.
  • the nitriding potential in the circulating process furnace is controlled to the range of 0.06 to 0.3 at the time of the nitriding treatment It is a manufacturing method of the nitriding steel member characterized by the above.
  • a hardened layer having a martensitic structure containing 0.8% or more of nitrogen is provided on the surface, and a diffusion layer in which nitrogen is diffused in the matrix is provided below the hardened layer, and the hardened layer is It has a thickness of 2 ⁇ m to 50 ⁇ m from the surface of the nitrided steel member, and the diffusion layer extends to a depth of more than 100 ⁇ m from the surface of the nitrided steel member, and 2 mm from the surface of the nitrided steel member It is possible to manufacture a nitrided steel member characterized in that the hardness of the diffusion layer at a depth of 100 ⁇ m from the surface of the nitrided steel member is greater than 100 HV or more than the hardness in the depth.
  • the present invention is provided with a circulation type processing furnace having a guide cylinder and a stirring fan, and during nitriding processing, the temperature range in the circulation type processing furnace is controlled to 610 ° C. to 660 ° C.
  • the nitriding potential in the circulation type processing furnace is controlled in the range of 0.06 to 0.3.
  • a hardened layer having a martensitic structure containing 0.8% or more of nitrogen is provided on the surface, and a diffusion layer in which nitrogen is diffused in the matrix is provided below the hardened layer, and the hardened layer is It has a thickness of 2 ⁇ m to 50 ⁇ m from the surface of the nitrided steel member, and the diffusion layer extends to a depth of more than 100 ⁇ m from the surface of the nitrided steel member, and 2 ⁇ m from the surface of the nitrided steel member It is possible to manufacture a nitrided steel member characterized in that the hardness of the diffusion layer at a depth of 100 ⁇ m from the surface of the nitrided steel member is greater than 100 HV or more than the hardness in the depth.
  • ammonia gas and ammonia decomposition gas are introduced into the circulation type processing furnace.
  • the manufacturing apparatus changes a ratio of introduction of the ammonia gas and the amount of introduction of the ammonia decomposition gas while keeping the total flow rate constant; It is preferable that the second control for changing the introduction amount of the ammonia gas can be selectively performed in a state in which the introduction of the ammonia decomposition gas is stopped.
  • the hardened layer having a martensitic structure containing 0.8% or more of nitrogen is limited to a thickness of 2 ⁇ m to 50 ⁇ m from the surface of the nitrided steel member, the heat treatment strain / transformation strain is small. Moreover, the hardness of the diffusion layer at a depth of 100 ⁇ m from the surface of the nitride steel member is 100 HV or more than the hardness at a depth of 2 mm from the surface of the nitride steel member, so that the hardened layer is thin. Sufficient strength can be guaranteed.
  • FIG. 3 is a cross-sectional photomicrograph of a nitrided steel member according to an embodiment of the present invention. It is a cross-sectional microscope picture of the nitrided steel member of FIG. 1 before reheat treatment. It is a cross-sectional microscope picture of a comparative example. It is a graph which shows the example of an experiment about hardness distribution. It is the schematic of the manufacturing apparatus of the nitride steel member by one Embodiment of this invention. It is a schematic sectional drawing of a circulation type processing furnace (horizontal gas nitriding furnace). It is a graph which shows the example of 1st control. It is a graph which shows the example of 1st control. It is a graph which shows the example of 2nd control. It is a graph which shows the example of 2nd control. It is the schematic which shows the example of the jig inserted in a furnace. It is a figure which shows the form of the Ono type rotation bending fatigue test piece.
  • FIG. 1 is a sectional photomicrograph of a nitrided steel member 100 according to an embodiment of the present invention.
  • the nitrided steel member 100 of the present embodiment is provided with a hardened layer 101 having a martensitic structure containing 0.8% or more of nitrogen on the surface, and in the lower part of the hardened layer 101, a matrix phase is provided. And a diffusion layer 102 in which nitrogen is diffused.
  • the matrix (base material) of the present embodiment is a carbon steel having a carbon content of 0.45% by mass.
  • Hardened layer 101 has a thickness of about 15 ⁇ m from the surface of nitrided steel member 100, which is in the range of 2 ⁇ m to 50 ⁇ m.
  • Diffusion layer 102 extends from the surface of nitrided steel member 100 to a depth exceeding 100 ⁇ m. Then, the hardness (for example, about 310 HV) of diffusion layer 102 at a depth of 100 ⁇ m from the surface of nitrided steel member 100 from the hardness (for example, about 180 HV) at a depth of 2 mm from the surface of nitrided steel member 100 It is larger than 100 HV. (Manufacturing conditions of one embodiment of a nitrided steel member)
  • the nitrided steel member 100 of the present embodiment is subjected to the nitronitriding treatment under the treatment conditions of the treatment temperature: 640 ° C., the nitriding potential: 0.16, and the treatment time: 2 hours using a circulation type treatment furnace described later It is quenched and further reheated at 250 ° C. for 2 hours.
  • the hardened layer 101 is strongly corroded (blackened) by the corrosive liquid for texture observation.
  • FIG. 1 A cross-sectional micrograph before the reheating treatment is shown in FIG. In this state, most of the region corresponding to the hardened layer 101 is an austenite phase and does not have sufficient hardness. By performing the reheat treatment, the martensitic structure in the austenite phase is increased, and accordingly, sufficient hardness can be obtained. (Configuration of comparative example)
  • Comparative Example 150 A cross-sectional micrograph of Comparative Example 150 is FIG.
  • the comparative example 150 was subjected to carbonitriding treatment using a circulation type treatment furnace described later under the treatment conditions of treatment temperature: 640 ° C., nitriding potential: 0.32 (> 0.3), treatment time: 2 hours. It is quenched afterward.
  • a compound layer 153 is formed on the surface, and a hardened layer 151 having a martensitic structure is provided below the compound layer 153, and further, the lower side of the hardened layer 151. , And the diffusion layer 152 in which nitrogen is diffused in the matrix phase. As described above, an unnecessary compound layer is formed under manufacturing conditions where the nitriding potential is high. (Effect of nitrided steel members)
  • the hardened layer having a martensitic structure containing 0.8% or more of nitrogen is limited to a thickness of 2 ⁇ m to 50 ⁇ m from the surface of the nitrided steel member, so heat treatment is performed. Low strain / transformation strain. Also, the hardness of the diffusion layer at a depth of 100 ⁇ m from the surface of the nitride steel member is 100 HV or more than the hardness at a depth of 2 ⁇ m from the surface of the nitride steel member, so that the hardened layer is thin. Sufficient strength can be guaranteed. (Range of nitrogen concentration of hardened layer)
  • the nitrogen concentration of the hardened layer 101 is the result of considering the stability of the austenite phase at room temperature. That is, by containing 0.8% or more of nitrogen (more preferably by 1.0% or more of nitrogen), most of the austenite phase is stabilized at room temperature when quenched, ie, during quenching Martensitic transformation does not occur. As a result, the strain is extremely small as compared to the case where martensitic transformation occurs during quenching. (Martensitic transformation is promoted in subsequent reheat treatment to increase hardness.) (Range of thickness of hardened layer)
  • the thickness of the hardened layer 101 basically, the thicker the thickness, the better the fatigue strength.
  • the thickness of the hardened layer 101 can be appropriately selected depending on the shape of the nitrided steel member 100 and the load environment.
  • manufacturing conditions processing temperature such that the condition that “the hardness of the diffusion layer at the depth of 100 ⁇ m from the surface of the nitride steel member is 100 HV or more greater than the hardness at the depth of 2 mm from the surface of nitride steel member”
  • the thickness of the hardened layer 101 is 2 to 50 ⁇ m.
  • the alloy component-based carbon steel in which the hardened layer 101 tends to be thick (specifically, S50C steel, 50 ⁇ m which is the result when carbonizing at a processing temperature of 660 ° C., nitriding potential: 0.17) Is the upper limit value.
  • the nitrided steel member 100 of this embodiment is characterized in that not only the hardened layer 101 but also the diffusion layer 102 has sufficient hardness.
  • the surface hardness after nitriding treatment is generally often obtained at a depth of 50 ⁇ m from the surface.
  • the hardness at a depth position of 100 ⁇ m from the surface is to be evaluated.
  • the hardness at a depth of 2 mm from the surface is defined as an evaluation object for an internal structure not affected by nitriding.
  • the nitriding potential K N is defined by the following equation (2).
  • K N P NH 3 / P H 2 3/2 (2)
  • P NH3 is the ammonia partial pressure in the furnace
  • P H2 is the hydrogen partial pressure in the furnace.
  • the nitriding potential K N is known as an index indicating the nitriding ability of the atmosphere in the gas nitriding furnace.
  • the reaction of the formula (3) mainly occurs, and the nitriding reaction of the formula (1) can be almost neglected quantitatively. Therefore, if the in-furnace ammonia concentration consumed in the reaction of the equation (3) or the hydrogen gas concentration generated in the reaction of the equation (3) is known, the nitriding potential can be calculated. That is, since hydrogen and nitrogen to be generated are 1.5 mol and 0.5 mol respectively from 1 mol of ammonia, if the ammonia concentration in the furnace is measured, the hydrogen concentration in the furnace can also be understood, and the nitriding potential should be calculated. Can. Alternatively, if the in-furnace hydrogen concentration is measured, the in-furnace ammonia concentration can be known, and the nitriding potential can be calculated again.
  • the ammonia gas flowed into the gas nitriding furnace is discharged to the outside of the furnace after circulating in the furnace. That is, in the gas nitriding process, the existing gas is continuously discharged to the outside of the furnace by continuously flowing fresh (new) ammonia gas into the furnace with respect to the existing gas in the furnace (pushed by the supply pressure) .
  • the flow rate of ammonia gas introduced into the furnace is small, the gas residence time in the furnace will be long, so the amount of ammonia gas to be decomposed will increase and nitrogen gas generated by the decomposition reaction + The amount of hydrogen gas increases.
  • the flow rate of ammonia gas introduced into the furnace is high, the amount of ammonia gas discharged out of the furnace without being decomposed increases and the amount of nitrogen gas + hydrogen gas generated in the furnace decreases Do.
  • FIG. 5 is a schematic view showing a manufacturing apparatus for manufacturing a nitrided steel member according to an embodiment of the present invention.
  • the manufacturing apparatus 1 of the present embodiment includes the circulation type processing furnace 2, and only two types of ammonia and ammonia decomposition gas are used as the gas introduced into the circulation type processing furnace 2. ing.
  • the ammonia decomposition gas is a gas also called AX gas, and is a mixed gas consisting of nitrogen and hydrogen in a ratio of 1: 3.
  • ammonia and ammonia decomposition gas Only three types of nitrogen gas may be selected.
  • FIG. 6 An example of the cross-sectional structure of the circulation type processing furnace 2 is shown in FIG.
  • a cylinder 202 called retort is disposed in a furnace wall (also called a bell) 201, and a cylinder 204 called an internal retort is disposed further inside thereof.
  • the introduced gas supplied from the gas introducing pipe 205 passes around the object to be treated and then passes through the space between the two cylinders 202 and 204 by the action of the stirring fan 203 as shown by the arrows in the figure. It circulates.
  • 206 is a flared gas hood
  • 207 is a thermocouple
  • 208 is a lid for the cooling operation
  • 209 is a fan for the cooling operation.
  • the circulation type processing furnace 2 is also called a horizontal gas nitriding furnace, and the structure itself is known.
  • the workpiece S is carbon steel or low alloy steel, and is, for example, a crankshaft or a gear, which is an automobile part.
  • a furnace opening / closing lid 7 a stirring fan 8, a stirring fan drive motor 9, and an atmosphere gas concentration detection device 3 , A nitriding potential regulator 4, a programmable logic controller 30, and an in-furnace introduced gas supply unit 20.
  • the stirring fan 8 is disposed in the processing furnace 2, rotates in the processing furnace 2, and stirs the atmosphere in the processing furnace 2.
  • the stirring fan drive motor 9 is connected to the stirring fan 8 so as to rotate the stirring fan 8 at an arbitrary rotational speed.
  • the atmosphere gas concentration detection device 3 is configured by a sensor that can detect the hydrogen concentration or the ammonia concentration in the processing furnace 2 as the atmosphere gas concentration in the furnace.
  • the detection main body of the sensor is in communication with the inside of the processing furnace 2 through the atmosphere gas pipe 12.
  • the atmosphere gas pipe 12 is formed by a path that directly communicates the sensor main body of the atmosphere gas concentration detector 3 with the processing furnace 2, and the furnace gas waste pipe connected to the exhaust gas combustion decomposition device 41 halfway 40 are connected. Thereby, the atmosphere gas is distributed to the gas to be discarded and the gas supplied to the atmosphere gas concentration detection device 3.
  • the atmosphere gas concentration detection device 3 detects the atmosphere gas concentration in the furnace, the atmosphere gas concentration detection device 3 outputs an information signal including the detected concentration to the nitriding potential regulator 4.
  • the nitriding potential regulator 4 includes an in-furnace nitriding potential calculator 13 and a gas flow rate output adjuster 30.
  • the programmable logic controller 31 also has a gas introduction amount control device 14 and a parameter setting device 15.
  • the in-furnace nitriding potential calculation unit 13 calculates the nitriding potential in the processing furnace 2 based on the hydrogen concentration or the ammonia concentration detected by the in-furnace atmosphere gas concentration detection unit 3. Specifically, an arithmetic expression of the nitriding potential programmed according to the actual furnace introduced gas is incorporated, and the nitriding potential is calculated from the value of the atmosphere gas concentration in the furnace.
  • the parameter setting device 15 includes, for example, a touch panel, and can set and input a total flow rate of gas introduced into the furnace, a gas type, a processing temperature, a target nitriding potential, and the like. Each setting parameter value set and input is transmitted to the gas flow rate output adjusting means 30.
  • the gas flow rate output adjusting means 30 sets the nitriding potential calculated by the in-furnace nitriding potential calculating device 13 as an output value, sets a target nitriding potential (the set nitriding potential) as a target value, and outputs ammonia gas and ammonia decomposition gas. Control is performed with each introduction amount as an input value. More specifically, the first control for changing the introduction ratio of the ammonia gas and the ammonia decomposition gas while maintaining the total flow rate of the ammonia gas introduction amount and the ammonia decomposition gas constant, and the ammonia gas in a state where the introduction of the ammonia decomposition gas is stopped It is possible to selectively carry out a second control for changing the introduction amount of. The output value of the gas flow rate output adjustment means 30 is transmitted to the gas introduction amount control means 14.
  • the gas introduction amount control means 14 sends control signals to the first supply amount control device 22 for ammonia gas and the second supply amount control device 26 for ammonia decomposition gas in order to realize the introduction amount of each gas. It has become.
  • the in-furnace introduced gas supply unit 20 of the present embodiment includes a first in-furnace introduced gas supply unit 21 for ammonia gas, a first supply control device 22, a first supply valve 23, and a first flow meter 24. ,have. Further, the in-furnace introduced gas supply unit 20 of the present embodiment includes a second in-furnace introduced gas supply unit 25 for ammonia decomposition gas (AX gas), a second supply amount control device 26, and a second supply valve 27. , And a second flow meter 28.
  • AX gas ammonia decomposition gas
  • the ammonia gas and the ammonia decomposition gas are mixed in the in-furnace gas introduction pipe 29 before entering the processing furnace 2.
  • the first in-furnace introduction gas supply unit 21 is formed of, for example, a tank filled with a first in-furnace introduction gas (in this example, ammonia gas).
  • a first in-furnace introduction gas in this example, ammonia gas
  • the first supply amount control device 22 is formed by a mass flow controller, and is interposed between the first in-furnace introduced gas supply unit 21 and the first supply valve 23.
  • the opening degree of the first supply amount control device 22 changes in accordance with the control signal output from the gas introduction amount control means 14.
  • the first supply control unit 22 detects the amount of supply from the first in-furnace introduced gas supply unit 21 to the first supply valve 23, and sends an information signal including the detected supply to the gas introduction control means 14. It is designed to output.
  • the control signal may be used for correction of control by the gas introduction amount control means 14 or the like.
  • the first supply valve 23 is formed by a solenoid valve that switches the open / close state according to the control signal output from the gas introduction amount control means 14, and between the first supply amount control device 22 and the first flow meter 24. It is interspersed.
  • the second furnace introduction gas supply unit 25 is formed of, for example, a tank filled with a second furnace introduction gas (in this example, an ammonia decomposition gas).
  • the second supply control device 26 is formed by a mass flow controller, and is interposed between the second in-furnace introduced gas supply unit 25 and the first supply valve 27.
  • the opening degree of the first supply control unit 26 changes in accordance with the control signal output from the gas introduction control unit 14.
  • the third supply control unit 26 detects the amount of supply from the second in-furnace introduced gas supply unit 25 to the second supply valve 27, and sends an information signal including the detected supply to the gas introduction control means 14. It is designed to output.
  • the control signal may be used for correction of control by the gas introduction amount control means 14 or the like.
  • the second supply valve 27 is formed by an electromagnetic valve that switches the open / close state according to the control signal output from the gas introduction amount control means 14, and between the second supply amount control device 26 and the second flow meter 28. It is interspersed.
  • the article S is introduced into the circulation type processing furnace 2 and the circulation type processing furnace 2 is heated to a desired processing temperature. Thereafter, a mixed gas of ammonia gas and ammonia decomposition gas or only ammonia gas is introduced into the processing furnace 2 at a set initial flow rate from the in-furnace introduced gas supply unit 20.
  • the setting initial flow rate can also be set and input in the parameter setting device 15, and is controlled by the first supply amount control device 22 and the second supply amount control device 26 (both mass flow controllers).
  • the stirring fan drive motor 9 is driven to rotate the stirring fan 8 and stir the atmosphere in the processing furnace 2.
  • the in-furnace nitriding potential calculator 13 of the nitriding potential regulator 4 calculates the in-furnace nitriding potential (at the beginning, it is a very high value (because there is no hydrogen in the furnace) but there is decomposition of ammonia gas (hydrogen generation) Decreases as the process progresses), and it is determined whether or not the sum of the target nitriding potential and the reference deviation value is exceeded.
  • the reference deviation value can also be set and input in the parameter setting device 15.
  • the nitriding potential adjuster 4 causes the gas introduction amount control means 14 to introduce the introduction amount of gas introduced into the furnace. Start control of the
  • the furnace nitriding potential calculator 13 of the nitriding potential controller 4 calculates the furnace nitriding potential based on the inputted hydrogen concentration signal or ammonia concentration signal. Then, the gas flow rate output adjusting means 30 uses the nitriding potential calculated by the in-furnace nitriding potential calculator 13 as an output value, and uses the target nitriding potential (the set nitriding potential) as a target value. Implement PID control with an input value.
  • the first control for changing the introduction ratio of the ammonia gas and the introduction amount of the ammonia decomposition gas while keeping the total flow rate of the introduction amount of the ammonia gas constant and stopping the introduction of the ammonia decomposition gas A second control of changing the introduction amount of ammonia gas in the state is selectively performed.
  • each set parameter value set and input by the parameter setting device 15 is used.
  • the setting parameter value for example, different values are prepared in accordance with the value of the target nitriding potential.
  • the gas flow rate output adjusting means 30 controls the introduction amount of each in-furnace introduced gas as a result of the PID control. Specifically, the gas flow rate output adjustment means 30 determines the flow rate of each gas, and the output value is transmitted to the gas introduction amount control means 14.
  • the gas introduction amount control means 14 sends control signals to the first supply amount control device 22 for ammonia gas and the second supply amount control device 26 for ammonia decomposition gas in order to realize the introduction amount of each gas.
  • the nitriding potential in the furnace can be stably controlled in the vicinity of the target nitriding potential. As a result, it is possible to carry out the nitridation treatment of the article S with extremely high quality.
  • the cooling step after the nitridation treatment in the manufacturing apparatus 1 concerned.
  • the article S is removed from the furnace while maintaining the heating temperature after the nitriding treatment in the manufacturing apparatus 1. It is necessary to transport it to the quenching device (e.g., an oil tank) and then to quench it.
  • the quenching device e.g., an oil tank
  • the reheating step can also be performed in the manufacturing apparatus 1, it is generally performed in another tempering furnace outside the furnace.
  • FIGS. 7A and 7B An example in which the first control is adopted is shown in FIGS. 7A and 7B.
  • the total flow rate of the introduced amount of ammonia gas and the introduced amount of ammonia decomposition gas is constant at 166 (l / min), and the nitriding potential is as high as 0.16. It is controlled.
  • FIGS. 8A and 8B An example in which the second control is adopted is shown in FIGS. 8A and 8B.
  • the introduction of the ammonia decomposition gas is stopped, and only the introduction amount of the ammonia gas is feedback-controlled in small steps in the vicinity of 220 (l / min), whereby the nitriding potential is 0.16. It is controlled with high precision.
  • the first control be performed.
  • the first control has a nitriding potential. It is difficult to control with high accuracy. In such a case, it is preferable to shift to the second control to perform nitriding potential control.
  • the carbonizing treatment is performed at a treatment temperature of 640 ° C., a nitriding potential of 0.16, and a treatment time of 2 hours.
  • the nitrogen treatment it was transported to an oil tank separately installed outside the furnace while maintaining the temperature, and then cooling was performed (hereinafter, the procedure of carrying to the oil tank after the carbonizing treatment and cooling as described above; Called
  • the article S using the jig shown in FIG. 9, as a steel material at the center of the A surface (furnace lid side), the B surface (center in the furnace), and the C surface (deep side in the furnace).
  • a coin-shaped test piece of S45C steel and having a diameter of 20 x 5 mm was used.
  • the compound layer was formed on any surface, and it was recognized that the hardened layer thickness by martensite tends to be larger as the surface was set in the depth direction. It is considered that this is because the in-furnace uniformity of the nitriding potential is not good.
  • Comparative Example 3 after carbonitriding at a treatment temperature of 700 ° C., a nitriding potential of 0.1, and a treatment time of 1.5 hours, it was oil-cooled and subjected to reheat treatment at 250 ° C. for 2 hours. As a result, a hardened layer of martensitic structure was obtained with a thickness of 40 ⁇ m on the surface.
  • the difference ( ⁇ HV) between the hardness of the diffusion layer 102 at a depth of 100 ⁇ m from the surface and the hardness at a depth of 2 mm from the surface was 70 HV ⁇ 100 HV.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Organic Chemistry (AREA)
  • Metallurgy (AREA)
  • Physics & Mathematics (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Thermal Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)
  • Muffle Furnaces And Rotary Kilns (AREA)

Abstract

La présente invention concerne un élément en acier nitruré qui contient un acier au carbone ou un acier faiblement allié en tant que phase de matrice, et est caractérisé en ce qu'il comporte une couche durcie ayant une structure martensitique contenant 0,8 % ou plus d'azote à la surface de l'élément, comportant une couche de diffusion, dans laquelle de l'azote diffuse dans la phase de matrice, au-dessous de la couche durcie, et en ce que la couche durcie a une épaisseur de 2 à 50 µm depuis la surface de l'élément en acier nitruré, la couche de diffusion s'étend jusqu'à une profondeur supérieure à 100 µm depuis la surface de l'élément en acier nitruré, et la dureté de la couche de diffusion à une profondeur de 100 µm depuis la surface de l'élément en acier nitruré est d'au moins 100 HV supérieure à la dureté à une profondeur de 2 mm depuis la surface de l'élément en acier nitruré.
PCT/JP2018/047505 2017-12-27 2018-12-25 Élément en acier nitruré, et procédé et appareil de production d'élément en acier nitruré WO2019131602A1 (fr)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2020175453A1 (fr) * 2019-02-26 2020-09-03 パーカー熱処理工業株式会社 Élément en acier de nitruration, et procédé et dispositif de fabrication d'élément en acier de nitruration
EP4043606A4 (fr) * 2019-10-11 2023-06-14 Parker Netsushori Kogyo Co., Ltd. Appareil de durcissement de surface et procédé de durcissement de surface
EP4249625A4 (fr) * 2020-11-18 2023-12-27 Parker Netsushori Kogyo Co., Ltd. Procédé et appareil de traitement d'un élément métallique

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JP2007046088A (ja) * 2005-08-09 2007-02-22 Yuki Koshuha:Kk 浸窒焼入品及びその製造方法
JP2010007128A (ja) * 2008-06-26 2010-01-14 Toyota Motor Corp 熱処理治具および熱処理装置
JP2011219851A (ja) * 2010-04-14 2011-11-04 Nhk Spring Co Ltd ばねおよびその製造方法
JP2013221203A (ja) * 2012-04-18 2013-10-28 Dowa Thermotech Kk 窒化鋼部材およびその製造方法
JP2014047410A (ja) * 2012-09-03 2014-03-17 Yuki-Koushuha Co Ltd 鉄基合金材及びその製造方法
JP2017171951A (ja) * 2016-03-18 2017-09-28 新日鐵住金株式会社 鋼部品及びその製造方法

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Publication number Priority date Publication date Assignee Title
JP2007046088A (ja) * 2005-08-09 2007-02-22 Yuki Koshuha:Kk 浸窒焼入品及びその製造方法
JP2010007128A (ja) * 2008-06-26 2010-01-14 Toyota Motor Corp 熱処理治具および熱処理装置
JP2011219851A (ja) * 2010-04-14 2011-11-04 Nhk Spring Co Ltd ばねおよびその製造方法
JP2013221203A (ja) * 2012-04-18 2013-10-28 Dowa Thermotech Kk 窒化鋼部材およびその製造方法
JP2014047410A (ja) * 2012-09-03 2014-03-17 Yuki-Koushuha Co Ltd 鉄基合金材及びその製造方法
JP2017171951A (ja) * 2016-03-18 2017-09-28 新日鐵住金株式会社 鋼部品及びその製造方法

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2020175453A1 (fr) * 2019-02-26 2020-09-03 パーカー熱処理工業株式会社 Élément en acier de nitruration, et procédé et dispositif de fabrication d'élément en acier de nitruration
EP4043606A4 (fr) * 2019-10-11 2023-06-14 Parker Netsushori Kogyo Co., Ltd. Appareil de durcissement de surface et procédé de durcissement de surface
EP4249625A4 (fr) * 2020-11-18 2023-12-27 Parker Netsushori Kogyo Co., Ltd. Procédé et appareil de traitement d'un élément métallique

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