# US 2020/0399734 A1 · A manufacturing process of press hardened parts with high productivity > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2020/0399734 A1 - Document ID: US20200399734A1 - Status: Published application - Kind: A1 - Application number: 16/968,880 - Filed: 2019-03-05 - Published: 2020-12-24 - Earliest claimed: 2018-03-09 - Assignees: ArcelorMittal - Applicants: Arcelormittal - Inventors: Alexandre BLAISE; Pascal DRILLET; Thierry STUREL - Web page: https://patentgrep.com/patent/US20200399734A1 ## CPC - C21D 9/48: deep-drawing sheets - C21D 1/673: for die quenching - C21D 8/0484: {Application of a separating or insulating coating} - C23C 2/12: Aluminium or alloys based thereon - C23C 2/261: {in a gas atmosphere, e.g. inert or reducing atmosphere} - C23C 2/28: Thermal after-treatment, e.g. treatment in oil bath - C23C 2/29: {Cooling or quenching} - C23C 2/40: Plates; Strips - C23C 8/14: Oxidising of ferrous surfaces - C23C 8/80: After-treatment - C21D 2211/004: Dispersions; Precipitations - C21D 2211/005: Ferrite - C21D 2211/009: Pearlite - Y02P 10/25: Process efficiency - 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) - 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) - Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS ## Abstract A process for manufacturing a non-stamped prealloyed steel coil, sheet or blank, comprising the following successive steps of: providing a non-stamped precoated steel coil, sheet or blank composed of a steel substrate covered by a precoating of aluminum, or aluminum-based alloy, or aluminum alloy, wherein the precoating thickness is comprised between 10 and 35 micrometers on each side of the steel coil, sheet or blank, then heating the non-stamped steel coil, sheet or blank in a furnace under an atmosphere containing at least 5% oxygen, up to a temperature θ1 comprised between 750 and 1000° C., for a duration t1 comprised between t1min and t1max, wherein: t1min=23500/(θ1−729.5) and t1max=4.946×1041×θ1−13.08, t1 designating the total duration in the furnace, θ1 being expressed in ° C. and t1min and t1max being expressed in seconds, then cooling the non-stamped steel coil, sheet or blank at a cooling rate Vr1 down to a temperature θi, then maintaining the non-stamped steel coil, sheet or blank at a temperature θ2 comprised between 100 and 500° C., for a duration t2 comprised between 3 and 45 minutes, so to obtain a diffusible hydrogen less than 0.35 ppm. ## Claims ### Claim at position 1 1-26. (canceled) ### Claim 27 A method for manufacturing a non-stamped prealloyed steel coil, sheet or blank, comprising the following successive steps: providing a non-stamped precoated steel coil, sheet or blank composed of a heat treatable steel substrate covered by a precoating of aluminum or an aluminum-based alloy, the aluminum-based alloy being defined as an alloy wherein aluminum is the main element in weight percentage, the precoating resulting directly from a hot-dip aluminizing process without additional heat treatment, wherein a thickness of the precoating thickness is between 10 and 35 micrometers on each side of the steel coil, sheet or blank, then heating the non-stamped steel coil, sheet or blank in a furnace under an atmosphere containing at least 5% oxygen, up to a temperature θ1 between 750 and 1000° C., for a duration t1 comprised between t1min and t1max, wherein: t1min=23500/(θ1−729.5) and t1max=4.946×1041×θ1−13.08 t1 designating a total duration in the furnace, θ1 being expressed in ° C. and t1min and t1max being expressed in seconds, then cooling the non-stamped steel coil, sheet or blank at a cooling rate Vr1 down to a temperature θi, then maintaining the non-stamped steel coil, sheet or blank at a temperature θ2 comprised between 100 and 500° C., for a duration t2 between 3 and 45 minutes, so as to obtain a diffusible hydrogen content less than 0.35 ppm. ### Claim 28 (depends on 27) The method as recited in claim 27 wherein the aluminum-based alloy is an aluminum alloy, the aluminum alloy defined by an alloy wherein the aluminum is higher than 50% in weight. ### Claim 29 (depends on 27) The method as recited in claim 27 wherein the non-stamped prealloyed steel coil, sheet or blank includes an interdiffusion layer between the steel substrate and the coating, with a thickness between 2 and 16 micrometers, the interdiffusion layer being a layer with an α(Fe) ferritic structure, having Al and Si in solid solution. ### Claim 30 (depends on 27) The method as recited in claim 27 wherein the non-stamped prealloyed steel coil, sheet or blank comprises an alumina-containing oxide layer atop with a thickness higher than 0.10 μm. ### Claim 31 (depends on 27) The method as recited in claim 27 wherein the cooling rate Vr1 is selected so that a sum of the area fractions of bainite and martensite is less than 30% in the steel substrate, after the cooling and before subsequent heating. ### Claim 32 (depends on 27) The method as recited in claim 27 wherein the cooling rate Vr1 is selected so as to obtain a ferrite-pearlite structure in the steel substrate after the cooling and before subsequent heating. ### Claim 33 (depends on 27) The method as recited in claim 27 wherein said temperature θ2 is higher than or equal to 100° C. and lower than 300° C. ### Claim 34 (depends on 27) The method as recited in claim 27 wherein said temperature θ2 is higher than or equal to 300° C. and lower than or equal to 400° C. ### Claim 35 (depends on 27) The method as recited in claim 27 wherein said temperature θ2 is higher than 400° C. and less than or equal to 500° C. ### Claim 36 (depends on 27) The method as recited in claim 27 wherein the duration t2 is between 4 and 15 minutes. ### Claim 37 (depends on 27) The method as recited in claim 27 wherein the temperature θi is equal to room temperature and wherein the non-stamped steel coil, sheet or blank, after cooling at room temperature, is heated up to said temperature θ2. ### Claim 38 (depends on 27) The method as recited in claim 27 wherein said temperature θi is equal to the temperature θ2. ### Claim 39 (depends on 27) The method as recited in claim 27 further comprising, immediately after maintaining the non-stamped steel coil, sheet or blank at a temperature θ2 between 100 and 500° C. for a duration t2, cooling of the steel coil, sheet or blank down to room temperature. ### Claim 40 A non-stamped prealloyed steel coil, sheet or blank, comprising: a heat-treatable steel substrate covered by an alloyed precoating containing aluminum and iron, aluminum not being present as free aluminum; and an interdiffusion layer at an interface between the steel substrate and the precoating, with a thickness between 2 and 16 micrometers, the interdiffusion layer being a layer with an α(Fe) ferritic structure, having Al and Si in solid solution. ### Claim 41 (depends on 40) The non-stamped prealloyed steel coil, sheet or blank as recited in claim 40 further comprising an alumina-containing oxide layer atop the alloyed precoating, with a thickness higher than 0.10 μm. ### Claim 42 (depends on 40) The non-stamped prealloyed steel coil, sheet or blank as recited in claim 40 wherein diffusible hydrogen is less than 0.35 ppm. ### Claim 43 (depends on 40) The non-stamped prealloyed steel coil, sheet or blank as recited in claim 40 wherein a thickness of the steel coil, sheet or blank is comprised between 0.5 and 5 mm. ### Claim 44 (depends on 40) The non-stamped prealloyed steel coil, sheet or blank as recited in claim 40 wherein the steel substrate has a non-uniform thickness. ### Claim 45 (depends on 40) The non-stamped prealloyed steel coil, sheet or blank as recited in claim 40 wherein a sum of the area fractions of bainite and martensite is less than 30% in the steel microstructure. ### Claim 46 (depends on 40) The non-stamped prealloyed steel coil, sheet or blank as recited in claim 40 wherein the steel substrate has a ferrite-pearlite microstructure. ### Claim 47 (depends on 40) A method for manufacturing a press hardened coated steel part, wherein: providing the non-stamped prealloyed steel coil, sheet or blank as recited in claim 40; if the non-stamped prealloyed steel sheet, coil or blank is in the form of coil or sheet, cutting the coil or sheet so to obtain the prealloyed steel blank, then heating the non-stamped prealloyed steel blank such that the heating duration ΔT20-700° between 20 and 700° C., expressed in s, is less than ((26.22×th)−0.5), th being the thickness, expressed in millimeters, of the non-stamped prealloyed steel blank, up a temperature θ3, and maintaining the non-stamped prealloyed steel blank at said temperature θ3 for a duration t3 so to obtain partial or total austenitic structure in the steel substrate, then transferring the heated blank into a press, then hot press forming the heated blank so to obtain a part, then cooling the part while maintaining it in a press tooling, so as to obtain a microstructure in the steel substrate comprising at least martensite or bainite, and to obtain a press hardened coated part. ### Claim 48 (depends on 27) A method for manufacturing a press hardened coated steel part, wherein: providing the non-stamped prealloyed steel coil, sheet or blank according to the method as recited in claim 27; if the non-stamped prealloyed steel sheet, coil or blank is in the form of coil or sheet, cutting the coil or sheet so to obtain the prealloyed steel blank, then heating the non-stamped prealloyed steel blank such that the heating duration ΔT20-700° between 20 and 700° C., expressed in s, is less than ((26.22×th)−0.5), th being the thickness, expressed in millimeters, of the non-stamped prealloyed steel blank, up a temperature θ3, and maintaining the non-stamped prealloyed steel blank at said temperature θ3 for a duration t3 so to obtain partial or total austenitic structure in the steel substrate, then transferring the heated blank into a press, then hot press forming the heated blank so to obtain a part, then cooling the part while maintaining it in a press tooling, so as to obtain a microstructure in the steel substrate comprising at least martensite or bainite, and to obtain a press hardened coated part. ### Claim 49 (depends on 48) The method as recited in claim 48 wherein the non-stamped prealloyed steel blank is not cooled at room temperature between maintaining at said temperature θ2 and heating at said temperature θ3. ### Claim 50 (depends on 48) The method as recited in claim 48 wherein a difference ΔHdiff between the content of diffusible hydrogen in the press hardened coated part and the content of diffusible hydrogen in the non-stamped prealloyed blank, is less than 0.10 ppm. ### Claim 51 (depends on 48) The method as recited in claim 48 wherein the heating of the non-stamped prealloyed steel blank up a temperature θ3 is performed by a method selected among induction heating, resistance heating or conduction heating. ### Claim 52 (depends on 48) The method as recited in claim 48 wherein microstructure of the steel substrate of the press hardened coated part comprises more than 80% of martensite. ### Claim 53 (depends on 48) The method as recited in claim 48 wherein the press hardened coated part has a yield stress higher than 1000 MPa. ### Claim 54 (depends on 48) The method as recited in claim 48 wherein the press hardened coated part is used for the fabrication of structural or safety parts of vehicles.