EP1707646B1 - Method for activating surface of metal member - Google Patents
Method for activating surface of metal member Download PDFInfo
- Publication number
- EP1707646B1 EP1707646B1 EP05703844A EP05703844A EP1707646B1 EP 1707646 B1 EP1707646 B1 EP 1707646B1 EP 05703844 A EP05703844 A EP 05703844A EP 05703844 A EP05703844 A EP 05703844A EP 1707646 B1 EP1707646 B1 EP 1707646B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- gas
- furnace
- hcn
- metal
- nitriding
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Not-in-force
Links
- 229910052751 metal Inorganic materials 0.000 title claims description 59
- 239000002184 metal Substances 0.000 title claims description 59
- 238000000034 method Methods 0.000 title claims description 37
- 230000003213 activating effect Effects 0.000 title claims description 15
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims description 59
- 150000001875 compounds Chemical class 0.000 claims description 36
- 238000010438 heat treatment Methods 0.000 claims description 34
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 31
- 229910052799 carbon Inorganic materials 0.000 claims description 31
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 claims description 19
- 229910021529 ammonia Inorganic materials 0.000 claims description 18
- HSFWRNGVRCDJHI-UHFFFAOYSA-N alpha-acetylene Natural products C#C HSFWRNGVRCDJHI-UHFFFAOYSA-N 0.000 claims description 10
- 239000001294 propane Substances 0.000 claims description 8
- 125000002534 ethynyl group Chemical group [H]C#C* 0.000 claims description 7
- 230000003197 catalytic effect Effects 0.000 claims description 6
- 239000001273 butane Substances 0.000 claims description 5
- IJDNQMDRQITEOD-UHFFFAOYSA-N n-butane Chemical compound CCCC IJDNQMDRQITEOD-UHFFFAOYSA-N 0.000 claims description 5
- OFBQJSOFQDEBGM-UHFFFAOYSA-N n-pentane Natural products CCCCC OFBQJSOFQDEBGM-UHFFFAOYSA-N 0.000 claims description 5
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims description 4
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 claims description 4
- 239000005977 Ethylene Substances 0.000 claims description 4
- 229910002091 carbon monoxide Inorganic materials 0.000 claims description 4
- 229910052742 iron Inorganic materials 0.000 claims description 4
- 229910052750 molybdenum Inorganic materials 0.000 claims description 4
- 229910052759 nickel Inorganic materials 0.000 claims description 4
- 229910052804 chromium Inorganic materials 0.000 claims description 3
- 229910052802 copper Inorganic materials 0.000 claims description 3
- 229910052758 niobium Inorganic materials 0.000 claims description 3
- 229910052719 titanium Inorganic materials 0.000 claims description 3
- 229910052720 vanadium Inorganic materials 0.000 claims description 3
- 229910052726 zirconium Inorganic materials 0.000 claims description 3
- 239000007789 gas Substances 0.000 description 138
- 238000005121 nitriding Methods 0.000 description 46
- 230000004913 activation Effects 0.000 description 20
- 229910000069 nitrogen hydride Inorganic materials 0.000 description 19
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 18
- 229910000831 Steel Inorganic materials 0.000 description 18
- 239000010959 steel Substances 0.000 description 18
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 16
- 238000002347 injection Methods 0.000 description 15
- 239000007924 injection Substances 0.000 description 15
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 12
- 239000000243 solution Substances 0.000 description 12
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 10
- 229910002092 carbon dioxide Inorganic materials 0.000 description 9
- 238000006243 chemical reaction Methods 0.000 description 9
- 229910000851 Alloy steel Inorganic materials 0.000 description 8
- 229910000599 Cr alloy Inorganic materials 0.000 description 8
- 239000000788 chromium alloy Substances 0.000 description 8
- 238000009792 diffusion process Methods 0.000 description 8
- 238000005255 carburizing Methods 0.000 description 7
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 6
- 239000007864 aqueous solution Substances 0.000 description 6
- 230000015572 biosynthetic process Effects 0.000 description 6
- QDOXWKRWXJOMAK-UHFFFAOYSA-N dichromium trioxide Chemical group O=[Cr]O[Cr]=O QDOXWKRWXJOMAK-UHFFFAOYSA-N 0.000 description 6
- 229910001873 dinitrogen Inorganic materials 0.000 description 6
- 230000000694 effects Effects 0.000 description 6
- 229910052731 fluorine Inorganic materials 0.000 description 6
- 239000011737 fluorine Substances 0.000 description 6
- 230000000977 initiatory effect Effects 0.000 description 6
- 239000004579 marble Substances 0.000 description 6
- 230000003287 optical effect Effects 0.000 description 6
- 235000011121 sodium hydroxide Nutrition 0.000 description 6
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 5
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonia chloride Chemical compound [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 description 4
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 4
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 4
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 4
- 238000002485 combustion reaction Methods 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 4
- 238000001784 detoxification Methods 0.000 description 4
- 230000003628 erosive effect Effects 0.000 description 4
- 150000004820 halides Chemical class 0.000 description 4
- 238000001000 micrograph Methods 0.000 description 4
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 4
- 238000007254 oxidation reaction Methods 0.000 description 4
- 238000000197 pyrolysis Methods 0.000 description 4
- YMWUJEATGCHHMB-UHFFFAOYSA-N Dichloromethane Chemical compound ClCCl YMWUJEATGCHHMB-UHFFFAOYSA-N 0.000 description 3
- 150000001805 chlorine compounds Chemical class 0.000 description 3
- 239000011651 chromium Substances 0.000 description 3
- 230000001419 dependent effect Effects 0.000 description 3
- 150000002430 hydrocarbons Chemical class 0.000 description 3
- 125000002496 methyl group Chemical group [H]C([H])([H])* 0.000 description 3
- 229910052757 nitrogen Inorganic materials 0.000 description 3
- 230000035515 penetration Effects 0.000 description 3
- 229910001315 Tool steel Inorganic materials 0.000 description 2
- 230000009471 action Effects 0.000 description 2
- 235000019270 ammonium chloride Nutrition 0.000 description 2
- 239000011449 brick Substances 0.000 description 2
- 239000006227 byproduct Substances 0.000 description 2
- 239000003054 catalyst Substances 0.000 description 2
- 238000010276 construction Methods 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- -1 furnace deposits Chemical class 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 230000001590 oxidative effect Effects 0.000 description 2
- 229920006395 saturated elastomer Polymers 0.000 description 2
- 229910001220 stainless steel Inorganic materials 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- 229910021555 Chromium Chloride Inorganic materials 0.000 description 1
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 description 1
- 229910001240 Maraging steel Inorganic materials 0.000 description 1
- BZHJMEDXRYGGRV-UHFFFAOYSA-N Vinyl chloride Chemical compound ClC=C BZHJMEDXRYGGRV-UHFFFAOYSA-N 0.000 description 1
- 238000005299 abrasion Methods 0.000 description 1
- 229910000963 austenitic stainless steel Inorganic materials 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 239000007795 chemical reaction product Substances 0.000 description 1
- QSWDMMVNRMROPK-UHFFFAOYSA-K chromium(3+) trichloride Chemical compound [Cl-].[Cl-].[Cl-].[Cr+3] QSWDMMVNRMROPK-UHFFFAOYSA-K 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 150000002222 fluorine compounds Chemical class 0.000 description 1
- 125000005843 halogen group Chemical group 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 229910000734 martensite Inorganic materials 0.000 description 1
- 229910001105 martensitic stainless steel Inorganic materials 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 239000011733 molybdenum Substances 0.000 description 1
- 239000003345 natural gas Substances 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 238000010926 purge Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 238000004904 shortening Methods 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 238000005482 strain hardening Methods 0.000 description 1
- 229910000601 superalloy Inorganic materials 0.000 description 1
- 238000004381 surface treatment Methods 0.000 description 1
Images
Classifications
-
- 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
- C23C8/02—Pretreatment of the material to be coated
-
- 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
- C23C8/28—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 more than one element being applied in one step
- C23C8/30—Carbo-nitriding
-
- 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
- C23C8/28—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 more than one element being applied in one step
- C23C8/30—Carbo-nitriding
- C23C8/32—Carbo-nitriding of ferrous surfaces
Definitions
- the invention of the present application relates to a method for the pretreatment of a metal member to activate a surface of the metal member before applying diffusion treatment such as nitriding or carburizing to the metal member.
- gas nitriding or gas carburizing that forms a nitrided layer or carburized layer in a surface of a metal member is widely applied primarily to members made of iron-based material.
- Such a chloride is placed together with a metal member in a treatment furnace and is heated there. By this heating, the chloride is decomposed to form HCl, and the thus-formed HCl decomposes a passivated film on a surface of the metal member to activate the surface so that diffusion treatment such as nitriding or carburizing as a next step is assured.
- a metal member by such a chloride results in the erosion of a furnace wall made of bricks or a metal by HCl formed through decomposition, and in gas nitriding or gas softnitriding, HCl so formed reacts with ammonia as atmosphere gas to form ammonium chloride, which not only deposits in the furnace or an exhaust system to cause troubles but also remains on the surface of the metal member (work) to induce reductions in the corrosion resistance and fatigue strength of the member.
- an activation method of the surface of a metal member with a compound of fluorine which belongs to the same halogen group, NF 3 has been put into practical use in recent years (for example, Patent Document 1).
- NF 3 is decomposed to form fluorine, and the thus-formed fluorine converts a passivated film on the surface of the metal member into a fluoride film to activate the surface of the metal member.
- the activation method of the surface of the metal member with the fluorine compound (NF 3 ) requires sophisticated treatment for the detoxification of NF 3 and HF contained in effluent gas, which prevents the wide-spread adoption of the method.
- the ammonia gas nitriding method disclosed in Patent Document 2 reductively activates a passivated film on a surface of a high-chromium alloy steel member by forming reducing radicals and CO at the surface of the alloy steel member through the pyrolysis of acetone.
- acetone is pyrolyzed on the heated surface of the high-chromium alloy steel member in accordance with the below-described formula (1) so that reducing radicals and CO are formed at the surface of the high-chromium alloy steel member.
- Patent Document 2 is good in that it has theoretically solved the problems of the chloride-dependent activation method for a surface of a metal member as disclosed in Patent Document 1. Nonetheless, the method disclosed in Patent Document 2 is accompanied by a drawback that the use of acetone, which is liquid at normal temperature and pressure, requires facilities for the introduction of acetone vapor and the difficult flow rate control of acetone makes it hard to obtain a metal member having an evenly-activated surface.
- the present inventors have struggled to develop a method that makes use of a compound, which is gaseous at normal temperature and pressure, in place of acetone involving the problems in handling, leading to the completion of the present invention. Described specifically, the present invention provides: 1.
- a method for activating a surface of a metal member which comprises heating a mixed gas of a carbon donor compound, which is gaseous at normal temperature and pressure, and ammonia as essential components to at least 300°C in a metal-made heating furnace to formHCN under catalytic action of the metal member, a metal-made inner wall of the furnace or a metal-made jig in the thus-heated mixed gas, and causing the thus-formed HCN to act on the surface of the metal member.
- carbon donor compound is at least one compound selected from acetylene, ethylene, propane, butane and carbon monoxide.
- metal-made inner wall of the heating furnace or the metal-made jig contains at least one metal selected from Fe, Ni, Co, Cu, Cr, Mo, Nb, V, Ti and Zr.
- a passivated film on a surface of a high-alloy steel member makes it difficult to apply diffusion treatment, such as gas nitriding or gas carburizing, that forms a nitrided layer, carburized layer or carbonitrided layer on the surface of the steel member.
- diffusion treatment such as gas nitriding or gas carburizing
- an activating treatment method is provided for the surface of the metal member. This method is not accompanied by problems of conventional activation treatment with a halide, such as furnace deposits, furnace wall erosion and effluent gas detoxification treatment, and is useful as pretreatment for diffusion treatment.
- the passivated surface of the high-alloy steel member can be activated by using a gas commonly employed in gas heat treatment, and forming HCN gas in a heating furnace while making use of catalytic action of the steel member or a surface of the furnace.
- HCN-forming reactions between ammonia and the above-mentioned carbon-containing compounds can be expressed by the following formulas, respectively: NH 3 + CO ⁇ HCN + H 2 O (7) 2NH 3 + 2CO 2 ⁇ 2HCN + H 2 O + O 2 (8) 2NH 3 + C 2 H 2 ⁇ 2HCN + 3H 2 (9) 2NH 3 + C 2 H 4 ⁇ 2HCN + 4H 2 (10) 3NH 3 + C 3 H 8 ⁇ 3HCN + 7H 2 (11) 4NH 3 + C 4 H 10 ⁇ 4HCN + 9H 2 (12)
- RX gas means a gas, which is formed by mixing substantially equal chemical equivalents of a hydrocarbon gas (for example, propane gas, butane gas, or natural gas) and air and causing them to decompose in a catalyst layer maintained at 1, 000°C, contains CO and H 2 (N 2 ) as a primary component and small amounts of CO 2 and H 2 O, and is widely used as a nitriding gas.
- a hydrocarbon gas for example, propane gas, butane gas, or natural gas
- the CO contained in NH 3 :RX gas 1:1 by molar ratio, a typical composition for gas softnitriding, amounts to about 10% in terms of volume percentage.
- HCN which is required for the activation of a surface of a metal member, is therefore presumed to exist sufficiently in a gas soft nitriding furnace.
- RX gas the dew point of which is not controlled, however, there are a significant amount of H 2 O (around 2 vol.%) and about 0.5 vol.% of CO 2 . It is, therefore, judged that by their oxidizing action, the activated surface of the SUS304 plate is re-oxidized to prevent the penetration of nitrogen into the surface of the plate.
- CO gas When CO gas is selected as a carbon donor compound for the activation of a surface of a metal member, it is thus desired to use CO gas singly instead of RX gas. Because the amount of CO gas required to be injected in the present invention is as little as 1/10 (by volume) or so of a gas softnitriding atmosphere, the effects of H 2 O and CO 2 in RX gas are reduced so that RX gas may be used as a CO source in some instances.
- the activating effect for the surface of the alloy steel member in the present invention is attributed to HCN.
- the above-described activating effect is dependent on the concentration of HCN in the furnace atmosphere.
- the concentration of HCN can appropriately be in a range of from 100 to 30, 000 mg/m 3 .
- the above-described activating effect cannot be expected.
- the above-described activating effect is saturated, resulting not only in an economical disadvantage but also in the occurrence of sooting (the formation of carbon in the furnace) by pyrolysis of the carbon donor compound. Therefore, HCN concentrations outside the above-described range are not preferred.
- the dew point of the furnace atmosphere gas may preferably be 5°C or lower. If the dew point is higher than 5°C, the metal surface activated by HCN gas is re-oxidized with H 2 O in the atmosphere and accordingly, is passivated back again.
- the method according to the present invention is also advantageous from the environmental standpoint in that as explained in the reaction formula (5), the HCN attributed to the activation of the surface of the metal member is absorbed into the member and attributes to the nitriding and carburizing of the member to leave no residue on the surface of the member and the HCN discharged as effluent gas without any contribution to the reaction can be readily burned and detoxified in an ammonia combustion facility arranged as an attachment for the nitriding facility to obviate any new additional facility.
- a further advantage of the present invention is that the time of nitriding treatment can be shortened owing to the smooth progress of the steps in the nitriding treatment process.
- Gas nitriding of a metal member is generally conducted in such a schedule as will be described below.
- the metal member is set in a furnace, and subsequent to vacuum purging or nitrogen gas replacement of the air in the furnace, the temperature is raised to a nitriding temperature of the metal member and is then maintained constantly at the temperature, both while introducing the nitriding atmosphere gas (NH 3 + N 2 ) at a rate as much as 1 to 10 times the internal volume of the furnace per hour.
- the internal pressure of the furnace is maintained at atmospheric pressure + 0.5 kPa or so by a pressure control valve, and the force-out effluent gas is caused to burn and decompose in an effluent gas combustion facility.
- Patent Document 1 According to the method disclosed in Patent Document 1 and making use of the fluorine-based gas, it is necessary, subsequent to the introduction of the fluorine-based gas and the activation treatment of the member, to exhaust the fluorine-based gas and then to introduce the nitriding atmosphere gas into the furnace as disclosed in the examples of the specification of Japanese Patent No. 2,501,925 .
- the carbon donor compound is introduced into the nitriding atmosphere gas during the step in which the metal member is heated to the nitriding treatment temperature.
- HCN is formed to activate the surface of the metal member, and the subsequent termination of the introduction of the carbon donor compound makes it possible to advance directly to the nitriding step.
- the treatment time of the nitriding step is substantially shortened, thereby making it possible to fundamentally eliminate the re-oxidation phenomenon of the surface of the metal member which has until now remained as a problem in the conventional treatment upon advancing from the activation step to the nitriding step.
- the inner wall can preferably be made of metal. Even if the inner wall is not made of metal, the present invention can still be practiced provided that the metal member to be treated acts as a catalyst for the formation of HCN or a jig adapted to hold the metal member within the furnace is made of metal.
- the metal that makes up the metal-made inner wall, metal member or jig may preferably contain, for example, one or more metals selected from Fe, Ni, Co, Cu, Cr, Mo, Nb, V, Ti and Zr.
- these metal members are held by suitable jigs and are subjected to surface activation treatment in a manner known per se in the art.
- the surface treatment gases to be fed into the furnace are the carbon donor compound, which is gaseous at normal temperature and pressure, and ammonia, which are fed from their own gas cylinders into the furnace.
- the nitriding atmosphere gas (ammonia alone, ammonia + nitrogen gas, or ammonia + nitrogen gas + hydrogen gas) is introduced into the furnace to establish a reducing atmosphere.
- heating is initiated, followed by the introduction of the carbon donor compound useful in the present invention.
- the ammonia gas and carbon donor compound form HCN under the catalytic action of the metal surface when they are heated to 300°C or higher in the furnace.
- the ratio of the flow rate of ammonia as a nitriding atmosphere gas to that of the introduced carbon donor compound should be controlled within a range of from 1:0.0001 to 1:0.1. If the flow rate of the carbon donor compound is so low that the flow rate ratio becomes smaller than 1:0.0001, HCN is formed too little to bring about its activating effect. If the flow rate of the carbon donor compound is so high that the flow rate ratio becomes greater than 1:0.1, on the other hand, the activating effect is saturated to result in an economical disadvantage.
- the carbon donor compound is composed of one or more gaseous compounds selected from acetylene, ethylene, propane, butane and carbon monoxide as described above, and can be fed into the treatment furnace concurrently with the ammonia-containing gas as mentioned above. It is preferred for the efficient utilization of the carbon donor compound to initiate the introduction of the carbon donor compound at the time point that the temperature of the ammonia-containing gas within the furnace has reached about 300°C. To raise the concentration of the carbon donor compound in the furnace atmosphere at such an early stage as permitting shortening the treatment time, however, it is desired to introduce the carbon donor compound at the same time as the initiation of heating and to assure the formation of HCN from the initial stage.
- FIG. 1 shows a Muffle furnace 1, an outer shell 2 of the Muffle furnace, a heater 3, an internal container (retort) 4, a gas inlet pipe 5, an exhaust pipe 6, a motor 7, a fan 8, a metal-made jig 9, a gas guide cylinder 10, an inverted funnel 11, a vacuum pump 12, an effluent gas combustion facility 13, a carbon donor compound gas cylinder 14, an ammonia gas cylinder 15, a nitrogen gas cylinder 16, a hydrogen gas cylinder 17, a flowratemeter 18, and a gas control valve 19.
- Effluent gas from the furnace was branched off to have a portion of the effluent gas absorbed in a 2 wt.% aqueous solution of caustic soda, and an analysis was performed for HCN. From the analysis results of the HCN-absorbed solution, the average HCN concentration in the furnace atmosphere during the acetylene gas injection period was 8,000 mg/m 3 . Some of the SUS304 specimens were weighed to determine a weight increase after the nitriding treatment. As a result, the weight increase was determined to be 20 g/m 2 . Some of the SUS304 specimens were cut, and their cut surfaces were polished, etched with Marble's solution, and then observed under an optical microscope.
- Nitrided layers of 50- ⁇ m uniform thickness were found to be formed (a 500x micrograph is shown in FIG. 2 ). Some of the remaining specimens were measured for surface hardness at 5 points by a Vickers hardness tester. All the values (Hv) distributed between 1,200 and 1,250.
- SUS304 plates were set in the Muffle furnace employed in Example 1, NH 3 gas and N 2 gas were fed at flow rates of 200 L/H, respectively, and the furnace atmosphere was heated from room temperature to 550°C in 75 minutes. At the time point that the atmosphere temperature had reached 100°C in the course of the heating (at the 18 th minute after the initiation of the heating), an injection of propane gas was initiated at 5 L/hr. After heated to 550°C, the atmosphere temperature was maintained for 2 hours. At that time point, the injection of propane gas was terminated and instead, NH 3 gas and N 2 gas were then fed at 550°C for 4 hours to allow nitriding to proceed. Subsequently, the heating was stopped and N 2 gas alone was continuously fed to cool down the furnace. When the atmosphere temperature had dropped to 100°C or lower, the specimens were taken out of the furnace.
- Effluent gas from the furnace was branched off to have a portion of the effluent gas absorbed in a 2 wt.% aqueous solution of caustic soda, and an analysis was performed for HCN. From the analysis results of the HCN-absorbed solution, the average HCN concentration in the furnace atmosphere during the propane gas injection period was 400 mg/m 3 .
- Some of the SUS304 specimens were weighed to determine a weight increase after the nitriding treatment. As a result, the weight increase was determined to be 18 g/m 2 .
- Some of the SUS304 specimens were cut, and their cut surfaces were polished, etched with Marble's solution, and then observed under an optical microscope. Nitrided layers of 45- ⁇ m uniform thickness were found to be formed. Some of the remaining specimens were measured for surface hardness at 5 points by a Vickers hardness tester. All the values (Hv) distributed between 1,200 and 1,250.
- SUS304 plates were set in the Muffle furnace employed in Example 1, NH 3 gas and N 2 gas were fed at flow rates of 200 L/H, respectively, and the furnace atmosphere was heated from room temperature to 550°C in 75 minutes. At the time point that the atmosphere temperature had reached 100°C in the course of the heating (at the 18 th minute after the initiation of the heating), an injection of CO gas was initiated at 5 L/hr. After heated to 550°C, the atmosphere temperature was maintained for 2 hours. At that time point, the injection of CO gas was terminated and instead, NH 3 gas and N 2 gas were then fed for 4 hours to allow nitriding to proceed. Subsequently, the heating was stopped and N 2 gas alone was continuously fed at 550°C to cool down the furnace. When the atmosphere temperature had dropped to 100°C or lower, the specimens were taken out of the furnace.
- Effluent gas from the furnace was branched off to have a portion of the effluent gas absorbed in a 2 wt.% aqueous solution of caustic soda, and an analysis was performed for HCN. From the analysis results of the HCN-absorbed solution, the average HCN concentration in the furnace atmosphere during the CO gas injection period was 1,000 mg/m 3 .
- Some of the SUS304 specimens were weighed to determine a weight increase after the nitriding treatment. As a result, the weight increase was determined to be 18 g/m 2 .
- Some of the SUS304 specimens were cut, and their cut surfaces were polished, etched with Marble's solution, and then observed under an optical microscope. Nitrided layers of 45- ⁇ m uniform thickness were found to be formed. Some of the remaining specimens were measured for surface hardness at 5 points by a Vickers hardness tester. All the values (Hv) distributed between 1,200 and 1,250.
- SUS304 plates were set in the Muffle furnace employed in Example 1, NH 3 gas and N 2 gas were fed at flow rates of 200 L/H, respectively, and the furnace atmosphere was heated from room temperature to 550°C in 75 minutes. At the time point that the atmosphere temperature had reached 100°C in the course of the heating (at the 18 th minute after the initiation of the heating), an injection of C 2 H 4 gas was initiated at 5 L/hr. After heated to 550°C, the atmosphere temperature was maintained for 2 hours. At that time point, the injection of C 2 H 4 gas was terminated and instead, NH 3 gas and N 2 gas were then fed at 550°C for 4 hours to allow nitriding to proceed. Subsequently, the heating was stopped and N 2 gas alone was continuously fed to cool down the furnace. When the atmosphere temperature had dropped to 100°C or lower, the specimens were taken out of the furnace.
- Effluent gas from the furnace was branched off to have a portion of the effluent gas absorbed in a 2 wt.% aqueous solution of caustic soda, and an analysis was performed for HCN. From the analysis results of the HCN-absorbed solution, the average HCN concentration in the furnace atmosphere during the C 2 H 4 gas injection period was 1,200 mg/m 3 .
- Some of the SUS304 specimens were weighed to determine a weight increase after the nitriding treatment. As a result, the weight increase was determined to be 18 g/m 2 .
- Some of the SUS304 specimens were cut, and their cut surfaces were polished, etched with Marble's solution, and then observed under an optical microscope. Nitrided layers of 45- ⁇ m uniform thickness were found to be formed. Some of the remaining specimens were measured for surface hardness at 5 points by a Vickers hardness tester. All the values (Hv) distributed between 1,200 and 1,250.
- SUS304 plates were set in the Muffle furnace employed in Example 1, NH 3 gas and N 2 gas were fed at flow rates of 200 L/H, respectively, and the furnace atmosphere was heated from room temperature to 550°C in 75 minutes. At the time point that the atmosphere temperature had reached 100°C in the course of the heating (at the 18 th minute after the initiation of the heating), an injection of C 4 H 10 gas was initiated at 5 L/hr. After heated to 550°C, the atmosphere temperature was maintained for 2 hours. At that time point, the injection of C 4 H 10 gas was terminated and instead, NH 3 gas and N 2 gas were then fed at 550°C for 4 hours to allow nitriding to proceed. Subsequently, the heating was stopped and N 2 gas alone was continuously fed to cool down the furnace. When the atmosphere temperature had dropped to 100°C or lower, the specimens were taken out of the furnace.
- Effluent gas from the furnace was branched off to have a portion of the effluent gas absorbed in a 2 wt.% aqueous solution of caustic soda, and an analysis was performed for HCN. From the analysis results of the HCN-absorbed solution, the average HCN concentration in the furnace atmosphere during the C 4 H 10 gas injection period was 600 mg/m 3 .
- Some of the SUS304 specimens were weighed to determine a weight increase after the nitriding treatment. As a result, the weight increase was determined to be 18 g/m 2 .
- Some of the SUS304 specimens were cut, and their cut surfaces were polished, etched with Marble' s solution, and then observed under an optical microscope. Nitrided layers of 45- ⁇ m uniform thickness were found to be formed. Some of the remaining specimens were measured for surface hardness at 5 points by a Vickers hardness tester. All the values (Hv) distributed between 1,200 and 1,250.
- SUS304 plates were set in the Muffle furnace employed in Example 1, NH 3 gas and N 2 gas were fed at flow rates of 200 L/H, respectively, and the furnace atmosphere was heated from room temperature to 550°C in 75 minutes. After heated to 550°C, the atmosphere temperature was maintained for 6 hours. NH 3 gas and N 2 gas were continuously fed to allow nitriding to proceed. Subsequently, the heating was stopped and N 2 gas alone was continuously fed to cool down the furnace. When the atmosphere temperature had dropped to 100°C or lower, the specimens were taken out of the furnace.
- Effluent gas from the furnace was branched off to have a portion of the effluent gas absorbed in a 2 wt.% aqueous solution of caustic soda, and an analysis was performed for HCN. From the analysis results of the HCN-absorbed solution, HCN was not detected at all, thereby ascertaining that HCN did not exist at all in the furnace atmosphere.
- Some of the SUS304 specimens were weighed to determine a weight increase after the nitriding treatment. As a result, the weight increase was determined to be 10 g/m 2 .
- Some of the SUS304 specimens were cut, and their cut surfaces were polished, etched with Marble's solution, and then observed under an optical microscope.
- Nitrided layers of uneven thicknesses of from 8 to 18 ⁇ m were found to be formed (a 500x micrograph is shown in FIG. 3 ). Some of the remaining specimens were measured for surface hardness at 5 points by a Vickers hardness tester. The values (Hv) considerably varied from 500 to 1,100, and their absolute values were found to be lower compared with the corresponding values of the examples.
- a passivated film on a surface of a high-alloy steel member makes it difficult to apply diffusion treatment, such as gas nitriding or gas carburizing, that forms a nitrided layer, carburized layer or carbonitrided layer on the surface of the steel member.
- diffusion treatment such as gas nitriding or gas carburizing
- an activating treatment method is provided for the surface of the metal member. This method is not accompanied by problems of conventional activation treatment with a halide, such as furnace deposits, furnace wall erosion and effluent gas detoxification treatment, and is useful as pretreatment for diffusion treatment.
- the passivated surface of the high-alloy steel member can be activated by using a gas commonly employed in gas heat treatment, and forming HCN gas in a heating furnace while making use of catalytic action of the steel member or a surface of the furnace.
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)
Description
- The invention of the present application relates to a method for the pretreatment of a metal member to activate a surface of the metal member before applying diffusion treatment such as nitriding or carburizing to the metal member.
- To improve mechanical properties such as abrasion resistance and fatigue strength, gas nitriding or gas carburizing that forms a nitrided layer or carburized layer in a surface of a metal member is widely applied primarily to members made of iron-based material.
- Upon applying such treatment to a surface of a member made of alloy steel, especially high-alloy steel, the penetration and diffusion of nitrogen or carbon into the surface of the metal member is prevented by a passivated film (an oxide or the like) which exists on the surface of the member, thereby possibly resulting in the occurrence of poor treatment or uneven treatment of the member as a problem. Before such diffusion treatment, activation treatment is hence applied to the surfaces of metal members. It is methods making use of chloride compounds, led by Malcomizing, that are most widely adopted as such surface activation treatment. As the chloride compounds, vinyl chloride resin, ammonium chloride, methylene chloride and the like are used.
- Such a chloride is placed together with a metal member in a treatment furnace and is heated there. By this heating, the chloride is decomposed to form HCl, and the thus-formed HCl decomposes a passivated film on a surface of the metal member to activate the surface so that diffusion treatment such as nitriding or carburizing as a next step is assured.
- However, the surface activation of a metal member by such a chloride results in the erosion of a furnace wall made of bricks or a metal by HCl formed through decomposition, and in gas nitriding or gas softnitriding, HCl so formed reacts with ammonia as atmosphere gas to form ammonium chloride, which not only deposits in the furnace or an exhaust system to cause troubles but also remains on the surface of the metal member (work) to induce reductions in the corrosion resistance and fatigue strength of the member.
- As a substitute method for the above-de scribed methods making use of chlorides, an activation method of the surface of a metal member with a compound of fluorine which belongs to the same halogen group, NF3, has been put into practical use in recent years (for example, Patent Document 1). Upon heating, NF3 is decomposed to form fluorine, and the thus-formed fluorine converts a passivated film on the surface of the metal member into a fluoride film to activate the surface of the metal member. The activation method of the surface of the metal member with the fluorine compound (NF3), however, requires sophisticated treatment for the detoxification of NF3 and HF contained in effluent gas, which prevents the wide-spread adoption of the method.
- The above-described activation methods for the surfaces of metal members, which make use of halides, respectively, involves problems such as troublesome furnace deposits, furnace wall erosion and the need for detoxification treatment facilities for effluent gas. From the foregoing background, developments of activation methods for the surfaces of metal members, said methods making use of no halide, are under way.
- The ammonia gas nitriding method disclosed in Patent Document 2 reductively activates a passivated film on a surface of a high-chromium alloy steel member by forming reducing radicals and CO at the surface of the alloy steel member through the pyrolysis of acetone. According to this method, acetone is pyrolyzed on the heated surface of the high-chromium alloy steel member in accordance with the below-described formula (1) so that reducing radicals and CO are formed at the surface of the high-chromium alloy steel member.
2(CH3)CO → 2CH3 · + CO (1)
An oxide film (MO) on the surface of the metal member is reduced in accordance with the following formula (2):
5MO + 2CH3 · → 5M + 2CO + 3H2O (2)
As the principal component of the surface oxide film of the high-chromium alloy steel member is Cr2O3,
5Cr2O3 + 6CH3 · → 10Cr + 6CO + 9H2O (3)
The CO formed in accordance with the formulas (1) to (3) reacts with ammonia as atmosphere gas, and forms HCN in accordance with the following formula (4):
CO + NH3 → HCN + H2O (4)
The HCN formed in accordance with the formula (4) reduces the passivated film on the surface of the high-chromium alloy steel member in accordance with the following formula:
Cr2O3 + 6HCN → 2Cr(CN)3 + 3H2O (5)
The Cs and Ns in the resulting Cr(CN)3 diffuse into the surface of the high-chromium alloy steel member, and contribute to carburizing and nitriding so that no residue is formed on the surface of the member. - The above-described chloride-dependent activation method of a surface of a high-chromium alloy steel member, on the other hand, can be expressed by the following formula (6) :
Cr2O3 + 6HCl → 2CrCl3 + 3H2O (6)
The chromium chloride remains on the surface of the member, and acts as a causative substance for the corrosion of the member.
Patent Document 1:JP-A-3-44457
Patent Document 2: Japanese Patent Application No.9-38341 - As has been described above, the method disclosed in Patent Document 2 is good in that it has theoretically solved the problems of the chloride-dependent activation method for a surface of a metal member as disclosed in Patent Document 1. Nonetheless, the method disclosed in Patent Document 2 is accompanied by a drawback that the use of acetone, which is liquid at normal temperature and pressure, requires facilities for the introduction of acetone vapor and the difficult flow rate control of acetone makes it hard to obtain a metal member having an evenly-activated surface.
- With a view to solving the above-described problems, the present inventors have struggled to develop a method that makes use of a compound, which is gaseous at normal temperature and pressure, in place of acetone involving the problems in handling, leading to the completion of the present invention.
Described specifically, the present invention provides:
1. A method for activating a surface of a metal member, which comprises heating a mixed gas of a carbon donor compound, which is gaseous at normal temperature and pressure, and ammonia as essential components to at least 300°C in a metal-made heating furnace to formHCN under catalytic action of the metal member, a metal-made inner wall of the furnace or a metal-made jig in the thus-heated mixed gas, and causing the thus-formed HCN to act on the surface of the metal member. - 2. A method as described above under 1., wherein the carbon donor compound is at least one compound selected from acetylene, ethylene, propane, butane and carbon monoxide.
- 3. A method as described above under 1., wherein the metal-made inner wall of the heating furnace or the metal-made jig contains at least one metal selected from Fe, Ni, Co, Cu, Cr, Mo, Nb, V, Ti and Zr.
- 4. A method as described above under 1., wherein HCN is formed to at least 100 mg/m3 in the furnace and a furnace atmosphere gas has a dew point not higher than 5°C.
- A passivated film on a surface of a high-alloy steel member makes it difficult to apply diffusion treatment, such as gas nitriding or gas carburizing, that forms a nitrided layer, carburized layer or carbonitrided layer on the surface of the steel member. According to the present invention, an activating treatment method is provided for the surface of the metal member. This method is not accompanied by problems of conventional activation treatment with a halide, such as furnace deposits, furnace wall erosion and effluent gas detoxification treatment, and is useful as pretreatment for diffusion treatment. According to this method, the passivated surface of the high-alloy steel member can be activated by using a gas commonly employed in gas heat treatment, and forming HCN gas in a heating furnace while making use of catalytic action of the steel member or a surface of the furnace.
- The present invention will next be described in more detail based on best modes for carrying out the invention.
According to Patent Document 2 referred to in the above, CH3· (methyl radicals) formed by the pyrolysis of acetone in the formula (1) reduce an oxide film on a surface of a metal member. The CO formed in the above-described formula (1) and (2) reacts with ammonia as atmosphere gas on the metal surface to form HCN. HCN acts on the metal oxide film in accordance with the above-described formula (5). - From a comparison between the formula (2) and the formula (5), the CH3· formed by the pyrolysis of acetone and HCN (the reaction product of CO, the other pyrolyzate, with ammonia as atmosphere gas) are similar to each other in their action on the passivated film. The present inventors, therefore, presumed that the existence of both CH3· and HCN would be a sufficient condition for the activation of the surface of a high-chromium alloy steel member but would not absolutely be a necessary condition. Paying attention to HCN, the present inventors, therefore, endeavored to develop a method for the formation of HCN on a metal surface and also to ascertain effects of HCN for the activation of the surface of a metal member.
- An investigation was conducted on the formation of HCN by introducing a nitriding atmosphere gas (NH3:N2 = 1:1 by molar ratio) together with gases selected from various carbon-containing compounds, which are gaseous at normal temperature and pressure, respectively into a Muffle furnace made of SUS310S and heating them to 550°C. As a result, it has been clearly ascertained that carbon monoxide, carbon dioxide, acetylene, ethylene, propane and butane each forms HCN when combined with ammonia.
- An experiment was then conducted in a similar manner as described above except that the inner wall of the Muffle furnace was replaced by bricks, and an analysis was performed for the amount of HCN formed. In each case, HCN was not detected. From those results, it has become evident that the catalytic action of a metal surface is an essential condition for the HCN-forming reactions between ammonia and these gases.
- The HCN-forming reactions between ammonia and the above-mentioned carbon-containing compounds can be expressed by the following formulas, respectively:
NH3 + CO → HCN + H2O (7)
2NH3 + 2CO2 → 2HCN + H2O + O2 (8)
2NH3 + C2H2 → 2HCN + 3H2 (9)
2NH3 + C2H4 → 2HCN + 4H2 (10)
3NH3 + C3H8 → 3HCN + 7H2 (11)
4NH3 + C4H10 → 4HCN + 9H2 (12)
- To compare the amounts of HCN to be formed by the reactions between the nitriding atmosphere gas (NH3:N2 = 1:1 by molar ratio) and the gases selected from the various carbon-containing compounds, the reactions of the above-described formulas (7) to (12) were each conducted by incorporating the corresponding carbon-containing compound at 1% in terms of equivalent ratio in the nitriding atmosphere gas (NH3:N2 = 1:1 by molar ratio), introducing the resultant mixed gas into a Muffle furnace the inner wall of which was made of SUS310S, and then heating the mixed gas at 550°C for 30 minutes. As a result, the amounts of HCN formed from the respective carbon-containing compounds decreased in the following order:
C2H2 > CO > C2H4 > C4H10 > C3H8 > CO2
- With respect to these carbon-containing compounds ascertained to form HCN through their reactions with the nitriding atmosphere gas, these compounds were each introduced into a heating furnace at an initial stage of nitriding treatment and then assessed with an SUS304 plate to determine whether or not they have activating effect. As a result, compared with control nitriding treatment without introduction of any carbon-containing compound, C2H2, CO, C2H4, C4H10 and C3H8 have been found to be equipped with profound effects on such SUS304 plates in both the evenness of nitriding and the weight increase by the penetration of nitrogen. When CO2 was used, on the other hand, no difference was observed from the control nitriding treatment in both the evenness of nitriding treatment and the weight increase of the specimen. Concerning CO2, no activating effect was, therefore, recognized for the surface of the SUS304 plate.
- The availability of no activating effect for the surface of the SUS304 plate despite the formation of HCN in the furnace by the introduction of CO2 is presumably attributed to the re-oxidation of the surface of the SUS304 plate under the oxidation action of O2 and H2O, the byproducts of the HCN-forming reaction in the formula (8). Concerning CO, HCN is formed as mentioned above. This is inconsistent with the phenomenon that stainless steel is not evenly nitrided in a gas softnitriding atmosphere in which ammonia and CO-containing RX gas exist. This inconsistency may be explained by reasons to be described below. It is to be noted that the term "RX gas" means a gas, which is formed by mixing substantially equal chemical equivalents of a hydrocarbon gas (for example, propane gas, butane gas, or natural gas) and air and causing them to decompose in a catalyst layer maintained at 1, 000°C, contains CO and H2(N2) as a primary component and small amounts of CO2 and H2O, and is widely used as a nitriding gas.
- The CO contained in NH3:RX gas = 1:1 by molar ratio, a typical composition for gas softnitriding, amounts to about 10% in terms of volume percentage. HCN, which is required for the activation of a surface of a metal member, is therefore presumed to exist sufficiently in a gas soft nitriding furnace. In an RX gas the dew point of which is not controlled, however, there are a significant amount of H2O (around 2 vol.%) and about 0.5 vol.% of CO2. It is, therefore, judged that by their oxidizing action, the activated surface of the SUS304 plate is re-oxidized to prevent the penetration of nitrogen into the surface of the plate.
- When CO gas is selected as a carbon donor compound for the activation of a surface of a metal member, it is thus desired to use CO gas singly instead of RX gas. Because the amount of CO gas required to be injected in the present invention is as little as 1/10 (by volume) or so of a gas softnitriding atmosphere, the effects of H2O and CO2 in RX gas are reduced so that RX gas may be used as a CO source in some instances.
- Judging from the formulas on the right-hand sides in the reaction formulas (7) to (12), the byproducts in the case of CO2 have the highest oxidizing action among these compounds having cyan-forming effect, followed by CO, and the hydrocarbon compounds all form reducing hydrogen. To avoid re-oxidation, it is, therefore, desired to choose a hydrocarbon compound as a carbon donor compound.
- The activating effect for the surface of the alloy steel member in the present invention is attributed to HCN. The above-described activating effect is dependent on the concentration of HCN in the furnace atmosphere. To obtain satisfactory activating effect, the concentration of HCN can appropriately be in a range of from 100 to 30, 000 mg/m3. At an HCN concentration lower than 100 mg/m3, the above-described activating effect cannot be expected. At an HCN concentration higher than 30,000 mg/m3, on the other hand, the above-described activating effect is saturated, resulting not only in an economical disadvantage but also in the occurrence of sooting (the formation of carbon in the furnace) by pyrolysis of the carbon donor compound. Therefore, HCN concentrations outside the above-described range are not preferred.
Further, the dew point of the furnace atmosphere gas may preferably be 5°C or lower. If the dew point is higher than 5°C, the metal surface activated by HCN gas is re-oxidized with H2O in the atmosphere and accordingly, is passivated back again. - The method according to the present invention is also advantageous from the environmental standpoint in that as explained in the reaction formula (5), the HCN attributed to the activation of the surface of the metal member is absorbed into the member and attributes to the nitriding and carburizing of the member to leave no residue on the surface of the member and the HCN discharged as effluent gas without any contribution to the reaction can be readily burned and detoxified in an ammonia combustion facility arranged as an attachment for the nitriding facility to obviate any new additional facility.
- A further advantage of the present invention is that the time of nitriding treatment can be shortened owing to the smooth progress of the steps in the nitriding treatment process. Gas nitriding of a metal member is generally conducted in such a schedule as will be described below.
- The metal member is set in a furnace, and subsequent to vacuum purging or nitrogen gas replacement of the air in the furnace, the temperature is raised to a nitriding temperature of the metal member and is then maintained constantly at the temperature, both while introducing the nitriding atmosphere gas (NH3 + N2) at a rate as much as 1 to 10 times the internal volume of the furnace per hour. During the treatment, the internal pressure of the furnace is maintained at atmospheric pressure + 0.5 kPa or so by a pressure control valve, and the force-out effluent gas is caused to burn and decompose in an effluent gas combustion facility.
- According to the method disclosed in Patent Document 1 and making use of the fluorine-based gas, it is necessary, subsequent to the introduction of the fluorine-based gas and the activation treatment of the member, to exhaust the fluorine-based gas and then to introduce the nitriding atmosphere gas into the furnace as disclosed in the examples of the specification of Japanese Patent No.
2,501,925 - In the present invention, on the other hand, the carbon donor compound is introduced into the nitriding atmosphere gas during the step in which the metal member is heated to the nitriding treatment temperature. As a consequence, HCN is formed to activate the surface of the metal member, and the subsequent termination of the introduction of the carbon donor compound makes it possible to advance directly to the nitriding step. As a result, the treatment time of the nitriding step is substantially shortened, thereby making it possible to fundamentally eliminate the re-oxidation phenomenon of the surface of the metal member which has until now remained as a problem in the conventional treatment upon advancing from the activation step to the nitriding step.
- The present invention has such technical features and advantageous effects as described above. A description will hereinafter be made about certain preferred embodiments of the present invention. In the treatment furnace for use in the present invention, the inner wall can preferably be made of metal. Even if the inner wall is not made of metal, the present invention can still be practiced provided that the metal member to be treated acts as a catalyst for the formation of HCN or a jig adapted to hold the metal member within the furnace is made of metal. The metal that makes up the metal-made inner wall, metal member or jig may preferably contain, for example, one or more metals selected from Fe, Ni, Co, Cu, Cr, Mo, Nb, V, Ti and Zr.
- Examples of metal members which can be subjected to surface activation treatment by the method of the present invention include members of cold-working die steel, hot-working die steel, plastic die steel, high-speed tool steel, powder metal high-speed tool steel, chrome-molybdenum steel, maraging steel, austenitic stainless steel, ferritic stainless steel, martensitic stainless steel, martensitic heat-resisting steel, austenitic heat-resisting steel or nickel-based superalloys. In the above-described treatment furnace, these metal members are held by suitable jigs and are subjected to surface activation treatment in a manner known per se in the art.
- The surface treatment gases to be fed into the furnace are the carbon donor compound, which is gaseous at normal temperature and pressure, and ammonia, which are fed from their own gas cylinders into the furnace. After the metal member is set in the furnace and the internal air of the furnace is purged under vacuum or is replaced with nitrogen gas, the nitriding atmosphere gas (ammonia alone, ammonia + nitrogen gas, or ammonia + nitrogen gas + hydrogen gas) is introduced into the furnace to establish a reducing atmosphere. Subsequently, heating is initiated, followed by the introduction of the carbon donor compound useful in the present invention. The ammonia gas and carbon donor compound form HCN under the catalytic action of the metal surface when they are heated to 300°C or higher in the furnace. The ratio of the flow rate of ammonia as a nitriding atmosphere gas to that of the introduced carbon donor compound should be controlled within a range of from 1:0.0001 to 1:0.1. If the flow rate of the carbon donor compound is so low that the flow rate ratio becomes smaller than 1:0.0001, HCN is formed too little to bring about its activating effect. If the flow rate of the carbon donor compound is so high that the flow rate ratio becomes greater than 1:0.1, on the other hand, the activating effect is saturated to result in an economical disadvantage.
- The carbon donor compound is composed of one or more gaseous compounds selected from acetylene, ethylene, propane, butane and carbon monoxide as described above, and can be fed into the treatment furnace concurrently with the ammonia-containing gas as mentioned above. It is preferred for the efficient utilization of the carbon donor compound to initiate the introduction of the carbon donor compound at the time point that the temperature of the ammonia-containing gas within the furnace has reached about 300°C. To raise the concentration of the carbon donor compound in the furnace atmosphere at such an early stage as permitting shortening the treatment time, however, it is desired to introduce the carbon donor compound at the same time as the initiation of heating and to assure the formation of HCN from the initial stage.
- Based on examples and a comparative example, the present invention will hereinafter be described more specifically. It is to be noted that the following examples and comparative example were conducted using a treatment furnace of the construction illustrated in
FIG. 1. FIG. 1 shows a Muffle furnace 1, an outer shell 2 of the Muffle furnace, aheater 3, an internal container (retort) 4, a gas inlet pipe 5, an exhaust pipe 6, amotor 7, afan 8, a metal-madejig 9, a gas guide cylinder 10, an inverted funnel 11, avacuum pump 12, an effluentgas combustion facility 13, a carbon donorcompound gas cylinder 14, anammonia gas cylinder 15, anitrogen gas cylinder 16, ahydrogen gas cylinder 17, aflowratemeter 18, and agas control valve 19. - Using the SUS310S Muffle furnace of 100-L internal capacity shown in
FIG. 1 , SUS304 plates were set in the furnace, NH3 gas and N2 gas were fed at flow rates of 200 L/H, respectively, and the furnace atmosphere was heated from room temperature to 550°C in 75 minutes. At the time point that the atmosphere temperature had reached 100°C in the course of the heating (at the 18th minute after the initiation of the heating), an injection of acetylene gas was initiated at 2 L/hr. After heated to 550°C, the atmosphere temperature was maintained for 2 hours. At that time point, the injection of acetylene gas was terminated and instead, NH3 gas and N2 gas were then fed at 550°C for 4 hours to allow nitriding to proceed. Subsequently, the heating was stopped and N2 gas alone was continuously fed to cool down the furnace. When the atmosphere temperature had dropped to 100°C or lower, the specimens were taken out of the furnace. - Effluent gas from the furnace was branched off to have a portion of the effluent gas absorbed in a 2 wt.% aqueous solution of caustic soda, and an analysis was performed for HCN. From the analysis results of the HCN-absorbed solution, the average HCN concentration in the furnace atmosphere during the acetylene gas injection period was 8,000 mg/m3. Some of the SUS304 specimens were weighed to determine a weight increase after the nitriding treatment. As a result, the weight increase was determined to be 20 g/m2. Some of the SUS304 specimens were cut, and their cut surfaces were polished, etched with Marble's solution, and then observed under an optical microscope. Nitrided layers of 50-µm uniform thickness were found to be formed (a 500x micrograph is shown in
FIG. 2 ). Some of the remaining specimens were measured for surface hardness at 5 points by a Vickers hardness tester. All the values (Hv) distributed between 1,200 and 1,250. - SUS304 plates were set in the Muffle furnace employed in Example 1, NH3 gas and N2 gas were fed at flow rates of 200 L/H, respectively, and the furnace atmosphere was heated from room temperature to 550°C in 75 minutes. At the time point that the atmosphere temperature had reached 100°C in the course of the heating (at the 18th minute after the initiation of the heating), an injection of propane gas was initiated at 5 L/hr. After heated to 550°C, the atmosphere temperature was maintained for 2 hours. At that time point, the injection of propane gas was terminated and instead, NH3 gas and N2 gas were then fed at 550°C for 4 hours to allow nitriding to proceed. Subsequently, the heating was stopped and N2 gas alone was continuously fed to cool down the furnace. When the atmosphere temperature had dropped to 100°C or lower, the specimens were taken out of the furnace.
- Effluent gas from the furnace was branched off to have a portion of the effluent gas absorbed in a 2 wt.% aqueous solution of caustic soda, and an analysis was performed for HCN. From the analysis results of the HCN-absorbed solution, the average HCN concentration in the furnace atmosphere during the propane gas injection period was 400 mg/m3. Some of the SUS304 specimens were weighed to determine a weight increase after the nitriding treatment. As a result, the weight increase was determined to be 18 g/m2. Some of the SUS304 specimens were cut, and their cut surfaces were polished, etched with Marble's solution, and then observed under an optical microscope. Nitrided layers of 45-µm uniform thickness were found to be formed. Some of the remaining specimens were measured for surface hardness at 5 points by a Vickers hardness tester. All the values (Hv) distributed between 1,200 and 1,250.
- SUS304 plates were set in the Muffle furnace employed in Example 1, NH3 gas and N2 gas were fed at flow rates of 200 L/H, respectively, and the furnace atmosphere was heated from room temperature to 550°C in 75 minutes. At the time point that the atmosphere temperature had reached 100°C in the course of the heating (at the 18th minute after the initiation of the heating), an injection of CO gas was initiated at 5 L/hr. After heated to 550°C, the atmosphere temperature was maintained for 2 hours. At that time point, the injection of CO gas was terminated and instead, NH3 gas and N2 gas were then fed for 4 hours to allow nitriding to proceed. Subsequently, the heating was stopped and N2 gas alone was continuously fed at 550°C to cool down the furnace. When the atmosphere temperature had dropped to 100°C or lower, the specimens were taken out of the furnace.
- Effluent gas from the furnace was branched off to have a portion of the effluent gas absorbed in a 2 wt.% aqueous solution of caustic soda, and an analysis was performed for HCN. From the analysis results of the HCN-absorbed solution, the average HCN concentration in the furnace atmosphere during the CO gas injection period was 1,000 mg/m3. Some of the SUS304 specimens were weighed to determine a weight increase after the nitriding treatment. As a result, the weight increase was determined to be 18 g/m2. Some of the SUS304 specimens were cut, and their cut surfaces were polished, etched with Marble's solution, and then observed under an optical microscope. Nitrided layers of 45-µm uniform thickness were found to be formed. Some of the remaining specimens were measured for surface hardness at 5 points by a Vickers hardness tester. All the values (Hv) distributed between 1,200 and 1,250.
- SUS304 plates were set in the Muffle furnace employed in Example 1, NH3 gas and N2 gas were fed at flow rates of 200 L/H, respectively, and the furnace atmosphere was heated from room temperature to 550°C in 75 minutes. At the time point that the atmosphere temperature had reached 100°C in the course of the heating (at the 18th minute after the initiation of the heating), an injection of C2H4 gas was initiated at 5 L/hr. After heated to 550°C, the atmosphere temperature was maintained for 2 hours. At that time point, the injection of C2H4 gas was terminated and instead, NH3 gas and N2 gas were then fed at 550°C for 4 hours to allow nitriding to proceed. Subsequently, the heating was stopped and N2 gas alone was continuously fed to cool down the furnace. When the atmosphere temperature had dropped to 100°C or lower, the specimens were taken out of the furnace.
- Effluent gas from the furnace was branched off to have a portion of the effluent gas absorbed in a 2 wt.% aqueous solution of caustic soda, and an analysis was performed for HCN. From the analysis results of the HCN-absorbed solution, the average HCN concentration in the furnace atmosphere during the C2H4 gas injection period was 1,200 mg/m3. Some of the SUS304 specimens were weighed to determine a weight increase after the nitriding treatment. As a result, the weight increase was determined to be 18 g/m2. Some of the SUS304 specimens were cut, and their cut surfaces were polished, etched with Marble's solution, and then observed under an optical microscope. Nitrided layers of 45-µm uniform thickness were found to be formed. Some of the remaining specimens were measured for surface hardness at 5 points by a Vickers hardness tester. All the values (Hv) distributed between 1,200 and 1,250.
- SUS304 plates were set in the Muffle furnace employed in Example 1, NH3 gas and N2 gas were fed at flow rates of 200 L/H, respectively, and the furnace atmosphere was heated from room temperature to 550°C in 75 minutes. At the time point that the atmosphere temperature had reached 100°C in the course of the heating (at the 18th minute after the initiation of the heating), an injection of C4H10 gas was initiated at 5 L/hr. After heated to 550°C, the atmosphere temperature was maintained for 2 hours. At that time point, the injection of C4H10 gas was terminated and instead, NH3 gas and N2 gas were then fed at 550°C for 4 hours to allow nitriding to proceed. Subsequently, the heating was stopped and N2 gas alone was continuously fed to cool down the furnace. When the atmosphere temperature had dropped to 100°C or lower, the specimens were taken out of the furnace.
- Effluent gas from the furnace was branched off to have a portion of the effluent gas absorbed in a 2 wt.% aqueous solution of caustic soda, and an analysis was performed for HCN. From the analysis results of the HCN-absorbed solution, the average HCN concentration in the furnace atmosphere during the C4H10 gas injection period was 600 mg/m3. Some of the SUS304 specimens were weighed to determine a weight increase after the nitriding treatment. As a result, the weight increase was determined to be 18 g/m2. Some of the SUS304 specimens were cut, and their cut surfaces were polished, etched with Marble' s solution, and then observed under an optical microscope. Nitrided layers of 45-µm uniform thickness were found to be formed. Some of the remaining specimens were measured for surface hardness at 5 points by a Vickers hardness tester. All the values (Hv) distributed between 1,200 and 1,250.
- SUS304 plates were set in the Muffle furnace employed in Example 1, NH3 gas and N2 gas were fed at flow rates of 200 L/H, respectively, and the furnace atmosphere was heated from room temperature to 550°C in 75 minutes. After heated to 550°C, the atmosphere temperature was maintained for 6 hours. NH3 gas and N2 gas were continuously fed to allow nitriding to proceed. Subsequently, the heating was stopped and N2 gas alone was continuously fed to cool down the furnace. When the atmosphere temperature had dropped to 100°C or lower, the specimens were taken out of the furnace.
- Effluent gas from the furnace was branched off to have a portion of the effluent gas absorbed in a 2 wt.% aqueous solution of caustic soda, and an analysis was performed for HCN. From the analysis results of the HCN-absorbed solution, HCN was not detected at all, thereby ascertaining that HCN did not exist at all in the furnace atmosphere. Some of the SUS304 specimens were weighed to determine a weight increase after the nitriding treatment. As a result, the weight increase was determined to be 10 g/m2. Some of the SUS304 specimens were cut, and their cut surfaces were polished, etched with Marble's solution, and then observed under an optical microscope. Nitrided layers of uneven thicknesses of from 8 to 18 µm were found to be formed (a 500x micrograph is shown in
FIG. 3 ). Some of the remaining specimens were measured for surface hardness at 5 points by a Vickers hardness tester. The values (Hv) considerably varied from 500 to 1,100, and their absolute values were found to be lower compared with the corresponding values of the examples. - A passivated film on a surface of a high-alloy steel member makes it difficult to apply diffusion treatment, such as gas nitriding or gas carburizing, that forms a nitrided layer, carburized layer or carbonitrided layer on the surface of the steel member. According to the present invention, an activating treatment method is provided for the surface of the metal member. This method is not accompanied by problems of conventional activation treatment with a halide, such as furnace deposits, furnace wall erosion and effluent gas detoxification treatment, and is useful as pretreatment for diffusion treatment. According to this method, the passivated surface of the high-alloy steel member can be activated by using a gas commonly employed in gas heat treatment, and forming HCN gas in a heating furnace while making use of catalytic action of the steel member or a surface of the furnace.
-
- [
FIG. 1 ] A diagram illustrating the construction of a treatment furnace useful in the present invention. - [
FIG. 2 ] A micrograph of a cut surface of a specimen of Example 1. - [
FIG. 3 ] A micrograph of a cut surface of a specimen of Comparative Example 1. -
- 1:
- Muffle furnace
- 2:
- Outer
- 3:
- Heater
- 4:
- Internal container (retort)
- 5:
- Gas inlet pipe
- 6:
- Exhaust pipe
- 7:
- Motor
- 8:
- Fan
- 9:
- Metal-made jig
- 10:
- Gas guide cylinder
- 11:
- Inverted funnel
- 12:
- Vacuum pump
- 13:
- Effluent gas combustion facility
- 14:
- Carbon donor compound gas cylinder
- 15:
- Ammonia gas cylinder
- 16:
- Nitrogen gas cylinder
- 17:
- Hydrogen gas cylinder
- 18:
- Flowratemeter
- 19:
- Gas control valve
Claims (4)
- A method for activating a surface of a metal member, which comprises heating a mixed gas of a carbon donor compound, which is gaseous at normal temperature and pressure, and ammonia as essential components to at least 300°C in a heating furnace to form HCN under catalytic action of said metal member, a metal-made inner wall of said furnace or a metal-made jig in the thus-heated mixed gas, and causing the thus-formed HCN to act on said surface of said metal member.
- A method according to claim 1, wherein said carbon donor compound is at least one compound selected from acetylene, ethylene, propane, butane and carbon monoxide.
- A method according to claim 1, wherein said metal-made inner wall of said heating furnace or said metal-made jig contains at least one metal selected from Fe, Ni, Co, Cu, Cr, Mo, Nb, V, Ti and Zr.
- A method according to claim 1, wherein HCN is formed to at least 100 mg/m3 in said heating furnace and a furnace atmosphere gas has a dew point not higher than 5°C.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2004012328 | 2004-01-20 | ||
PCT/JP2005/000607 WO2005068679A1 (en) | 2004-01-20 | 2005-01-19 | Method for activating surface of metal member |
Publications (3)
Publication Number | Publication Date |
---|---|
EP1707646A1 EP1707646A1 (en) | 2006-10-04 |
EP1707646A4 EP1707646A4 (en) | 2008-09-03 |
EP1707646B1 true EP1707646B1 (en) | 2009-08-12 |
Family
ID=34792370
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP05703844A Not-in-force EP1707646B1 (en) | 2004-01-20 | 2005-01-19 | Method for activating surface of metal member |
Country Status (7)
Country | Link |
---|---|
US (1) | US20070204934A1 (en) |
EP (1) | EP1707646B1 (en) |
JP (1) | JP4861703B2 (en) |
KR (1) | KR100858598B1 (en) |
CN (1) | CN1910303B (en) |
DE (1) | DE602005015934D1 (en) |
WO (1) | WO2005068679A1 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2011009463A1 (en) | 2009-07-20 | 2011-01-27 | Expanite A/S | A method of activating an article of passive ferrous or non-ferrous metal prior to carburising, nitriding and/or nitrocarburising |
Families Citing this family (11)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2006233261A (en) * | 2005-02-24 | 2006-09-07 | Nippon Techno:Kk | Gas nitriding method |
KR100902169B1 (en) * | 2007-07-24 | 2009-06-10 | 쳉-시엔 리우 | Method for improvement of hardness of martensite type stainless surface |
DK2462253T3 (en) | 2009-08-07 | 2021-05-31 | Swagelok Co | COOLING AT LOW TEMPERATURE UNDER LOW VACUUM |
US8961711B2 (en) | 2010-05-24 | 2015-02-24 | Air Products And Chemicals, Inc. | Method and apparatus for nitriding metal articles |
CN102168269A (en) * | 2011-03-16 | 2011-08-31 | 广州有色金属研究院 | Method for preparing accelerated carburizing plasma nitrocarburizing and titanium carbonitride composite membrane layer |
KR101245564B1 (en) * | 2011-05-06 | 2013-03-20 | 주식회사 삼락열처리 | Gas Nitriding Heat Treatment of the Stainless steel, Heat resisting steel and High alloy steel |
US9617632B2 (en) | 2012-01-20 | 2017-04-11 | Swagelok Company | Concurrent flow of activating gas in low temperature carburization |
TWI548778B (en) * | 2014-02-11 | 2016-09-11 | 國立臺灣大學 | Method for treating stainless steel surface and stainless steel treating system |
JP6357042B2 (en) * | 2014-07-18 | 2018-07-11 | 株式会社日本テクノ | Gas soft nitriding method and gas soft nitriding apparatus |
JP6516238B2 (en) * | 2015-03-30 | 2019-05-22 | 日鉄ステンレス株式会社 | Austenitic stainless steel and method for producing the same |
TWI798885B (en) | 2020-11-18 | 2023-04-11 | 日商帕卡熱處理工業股份有限公司 | Metal component processing method and processing device |
Family Cites Families (15)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US1984411A (en) * | 1933-06-08 | 1934-12-18 | Du Pont | Method of case hardening |
US2095565A (en) * | 1936-11-18 | 1937-10-12 | Electro Alloys Company | Carburizing box |
DE851810C (en) * | 1943-06-19 | 1952-10-09 | Bergwerksverband Zur Verwertun | Cementing of objects made of iron, steel and their alloys |
US2404060A (en) * | 1944-02-03 | 1946-07-16 | Westinghouse Electric Corp | High temperature furnace |
US3281517A (en) * | 1963-11-19 | 1966-10-25 | Melpar Inc | Vacuum furnace |
CA933073A (en) * | 1969-06-25 | 1973-09-04 | H. Podgurski Harry | Method for maintaining nitriding atmosphere |
JPS51105938A (en) * | 1975-02-28 | 1976-09-20 | Fujikoshi Kk | Ko chutetsuno teionshintanchitsukashorihoho |
JPS52145344A (en) * | 1976-05-31 | 1977-12-03 | Daido Steel Co Ltd | Method of preparing atmosphere gas for soft nitriding |
US4145232A (en) * | 1977-06-03 | 1979-03-20 | Union Carbide Corporation | Process for carburizing steel |
US4175986A (en) * | 1978-10-19 | 1979-11-27 | Trw Inc. | Inert carrier gas heat treating control process |
ZA812776B (en) * | 1980-05-02 | 1982-07-28 | African Oxygen Ltd | Heat treatment of metals |
JPH05202464A (en) * | 1992-01-27 | 1993-08-10 | Parker Netsushiyori Kogyo Kk | Method for partially nitriding parts |
WO1996030556A1 (en) * | 1995-03-29 | 1996-10-03 | Jh Corporation | Method and equipment for vacuum carburization and products of carburization |
JPH10219418A (en) * | 1997-02-06 | 1998-08-18 | Nippon Bell Parts Kk | Method for nitriding high-chromium alloy steel with gaseous ammonia |
JP3960697B2 (en) * | 1998-12-10 | 2007-08-15 | 株式会社日本テクノ | Carburizing and carbonitriding methods |
-
2005
- 2005-01-19 US US10/586,626 patent/US20070204934A1/en not_active Abandoned
- 2005-01-19 WO PCT/JP2005/000607 patent/WO2005068679A1/en active Application Filing
- 2005-01-19 KR KR1020067016535A patent/KR100858598B1/en active IP Right Grant
- 2005-01-19 EP EP05703844A patent/EP1707646B1/en not_active Not-in-force
- 2005-01-19 DE DE602005015934T patent/DE602005015934D1/en active Active
- 2005-01-19 JP JP2005517113A patent/JP4861703B2/en active Active
- 2005-01-19 CN CN2005800025506A patent/CN1910303B/en active Active
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2011009463A1 (en) | 2009-07-20 | 2011-01-27 | Expanite A/S | A method of activating an article of passive ferrous or non-ferrous metal prior to carburising, nitriding and/or nitrocarburising |
Also Published As
Publication number | Publication date |
---|---|
EP1707646A1 (en) | 2006-10-04 |
US20070204934A1 (en) | 2007-09-06 |
EP1707646A4 (en) | 2008-09-03 |
DE602005015934D1 (en) | 2009-09-24 |
KR20060114368A (en) | 2006-11-06 |
KR100858598B1 (en) | 2008-09-17 |
CN1910303B (en) | 2010-05-12 |
CN1910303A (en) | 2007-02-07 |
JPWO2005068679A1 (en) | 2007-12-27 |
JP4861703B2 (en) | 2012-01-25 |
WO2005068679A1 (en) | 2005-07-28 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
EP1707646B1 (en) | Method for activating surface of metal member | |
JP5650739B2 (en) | Low temperature carburization under low vacuum | |
KR930003031B1 (en) | Method of nitriding steel | |
KR102466065B1 (en) | Enhanced activation of self-passivating metals | |
EP2390378A1 (en) | Method and apparatus for nitriding metal articles | |
EP0551702B1 (en) | Method of nitriding nickel alloy | |
EP1712658B1 (en) | Method for surface treatment of metal material | |
US5650022A (en) | Method of nitriding steel | |
US6328819B1 (en) | Method and use of an apparatus for the thermal treatment, in particular nitriding treatment, of metal workpieces | |
JP2005232518A (en) | Surface hardening treatment method for engine valve | |
JP5758278B2 (en) | Nitriding method | |
JP2005036279A (en) | Surface hardening method for steel, and metallic product obtained thereby | |
KR20200049304A (en) | Low-Temperature Carburizing Method by Controlling Carbon Potential | |
EP3684961B1 (en) | Improved pre-treatment process of a surface of a metallic substrate | |
JP2918765B2 (en) | Nickel alloy products whose surface is nitrided and hardened | |
JPH10219418A (en) | Method for nitriding high-chromium alloy steel with gaseous ammonia | |
JP3396336B2 (en) | Method of nitriding steel | |
JP6072530B2 (en) | Soft nitriding method | |
KR20200049306A (en) | Low-Temperature Carburizing Method Using Native Oxide Removal Gas | |
Kula et al. | Information system support for vacuum furnaces and technology | |
JPH08193256A (en) | Method for nitriding steel |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
Free format text: ORIGINAL CODE: 0009012 |
|
17P | Request for examination filed |
Effective date: 20060712 |
|
AK | Designated contracting states |
Kind code of ref document: A1 Designated state(s): DE FR GB |
|
DAX | Request for extension of the european patent (deleted) | ||
RBV | Designated contracting states (corrected) |
Designated state(s): DE FR GB |
|
A4 | Supplementary search report drawn up and despatched |
Effective date: 20080806 |
|
GRAP | Despatch of communication of intention to grant a patent |
Free format text: ORIGINAL CODE: EPIDOSNIGR1 |
|
GRAC | Information related to communication of intention to grant a patent modified |
Free format text: ORIGINAL CODE: EPIDOSCIGR1 |
|
GRAC | Information related to communication of intention to grant a patent modified |
Free format text: ORIGINAL CODE: EPIDOSCIGR1 |
|
GRAS | Grant fee paid |
Free format text: ORIGINAL CODE: EPIDOSNIGR3 |
|
GRAA | (expected) grant |
Free format text: ORIGINAL CODE: 0009210 |
|
AK | Designated contracting states |
Kind code of ref document: B1 Designated state(s): DE FR GB |
|
REG | Reference to a national code |
Ref country code: GB Ref legal event code: FG4D |
|
REF | Corresponds to: |
Ref document number: 602005015934 Country of ref document: DE Date of ref document: 20090924 Kind code of ref document: P |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: FR Payment date: 20100209 Year of fee payment: 6 |
|
PLBE | No opposition filed within time limit |
Free format text: ORIGINAL CODE: 0009261 |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: GB Payment date: 20100121 Year of fee payment: 6 Ref country code: DE Payment date: 20100128 Year of fee payment: 6 |
|
26N | No opposition filed |
Effective date: 20100517 |
|
GBPC | Gb: european patent ceased through non-payment of renewal fee |
Effective date: 20110119 |
|
REG | Reference to a national code |
Ref country code: FR Ref legal event code: ST Effective date: 20110930 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: FR Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20110131 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: GB Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20110119 |
|
REG | Reference to a national code |
Ref country code: DE Ref legal event code: R119 Ref document number: 602005015934 Country of ref document: DE Effective date: 20110802 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: DE Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20110802 |