# US 11,242,594 B2 · Low pressure carbonitriding method and furnace > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,242,594 B2 - Document ID: US11242594B2 - Status: Granted - Kind: B2 - Application number: 15/532,270 - Filed: 2015-12-10 - Published: 2017-12-14 - Granted: 2022-02-08 - Earliest claimed: 2014-12-11 - Assignees: ECM Technologies - Applicants: Ecm Technologies - Inventors: Yves Giraud; Hubert Mulin - Web page: https://patentgrep.com/patent/US11242594B2 ## CPC - C23C 8/34: more than one element being applied in more than one step - C21D 1/06: Surface hardening - C21D 1/76: Adjusting the composition of the atmosphere - 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 (making metal-coated products by extrusion B21C23/22; covering with metal by connecting pre-existing layers to articles, see the relevant places, e.g. B21D39/00, B23K; metallising of glass C03C; metallising mortars, concrete, artificial stone, ceramics or natural stone C04B41/00; enamelling of, or applying a vitreous layer to, metals C23D; treating metal surfaces or coating of metals by electrolysis or electrophoresis C25D; single-crystal film growth C30B; by metallising textiles D06M11/83; decorating textiles by locally metallising D06Q1/04) - 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 (surface treatment of metallic material involving at least one process provided for in class C23 and at least one process covered by this subclass C23F17/00; unidirectional solidification of eutectic materials or unidirectional demixing of eutectoid materials C30B) ## Abstract A method for carbonitriding of a steel part arranged in a chamber comprises first steps and second steps, a carburizing gas being injected into the chamber during the first steps only and a nitriding gas being injected into the chamber during the second steps only, at least one of the second steps being situated between two first steps, the pressure in the chamber during at least one part of said two first steps being maintained at a first value and the pressure in the chamber during at least one part of said second step situated between said two first steps being at a second value that is strictly greater than the first value. ## Claims ### Claim 1 A method of carbonitriding a steel part arranged in a chamber, comprising first steps and second steps, a carburizing gas being injected into the chamber only during the first steps and a nitriding gas being injected into the chamber only during the second steps, at least one of the second steps taking place between two of the first steps, the pressure in the chamber during at least part of said two first steps being maintained at a first value and the pressure in the chamber during at least part of said second step taking place between said two first steps being at a second value greater than the first value, the pressure in chamber being kept lower than 500 hPa all along the carbonitriding process. ### Claim 2 (depends on 1) The method of claim 1, wherein the first value is in the range from 0.1 hPa to 20 hPa. ### Claim 3 (depends on 1) The method of claim 1, wherein the second value is in the range from 10 hPa to 250 hPa. ### Claim 4 (depends on 1) The method of claim 1, wherein the carburizing gas is propane or acetylene. ### Claim 5 (depends on 1) The method of claim 1, wherein the nitriding gas is ammonia. ### Claim 6 (depends on 1) The method of claim 1, further comprising third steps, each third step taking place between two of the first steps, between two of the second steps, or between one of the first steps and one of the second steps, a neutral gas being injected into the chamber during each third step. ### Claim 7 (depends on 6) The method of claim 6, further comprising first, second, and third successive phases, and wherein the first phase only comprises first steps alternating with third steps, wherein the second phase comprises the successive repetition of a cycle successively comprising a second step, a third step, a first step, and a second step, and wherein the third phase only comprises second steps alternating with third steps. ### Claim 8 (depends on 6) The method of claim 6, wherein at least one of the third steps directly precedes one of the second steps and wherein the pressure is increased from the first value to the second value during said third step before the beginning of said second step. ### Claim 9 (depends on 6) The method of claim 6, wherein at least one of the third steps directly precedes one of the second steps and wherein the pressure is maintained at the first value until the end of said second step and is increased from the first value to the second value after the beginning of said third step. ### Claim 10 (depends on 1) The method of claim 1, wherein the part is maintained at a temperature hold stage. ### Claim 11 (depends on 10) The method of claim 10, wherein the temperature hold stage is in the range from 800° C. to 1,050° C. ### Claim 12 (depends on 11) The method of claim 11, wherein the temperature hold stage is greater than 900° C. ### Claim 13 (depends on 6) The method of claim 6, wherein the pressure in the chamber during at least part of said third steps is maintained at the first value. ### Claim 14 (depends on 6) The method of claim 6, wherein at least one of the third steps directly follows one of the second steps and wherein the pressure is decreased from the second value to the first value during said second step before the beginning of said third step. ### Claim 15 (depends on 6) The method of claim 6, wherein at least one of the third steps directly follows one of the second steps and wherein the pressure is maintained at the second value until the end of said second step and is decreased from the second value to the first value after the beginning of said third step.