# US 2021/0276065 A1 · Low density press-hardening steel having enhanced mechanical properties > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2021/0276065 A1 - Document ID: US20210276065A1 - Status: Published application - Kind: A1 - Application number: 17/251,655 - Filed: 2018-06-19 - Published: 2021-09-09 - Earliest claimed: 2018-06-19 - Assignees: GM Global Technology Operations LLC - Applicants: GM Global Technology Operations LLC - Inventors: Jiachen PANG; Qi LU; Jianfeng WANG - Web page: https://patentgrep.com/patent/US20210276065A1 ## CPC - B21D 22/022: {by heating the blank or stamping associated with heat treatment (C21D takes precedence)} - B32B 15/012: {one layer being formed of an iron alloy or steel, another layer being formed of aluminium or an aluminium alloy} - B32B 15/013: {one layer being formed of an iron alloy or steel, another layer being formed of a metal other than iron or aluminium} - C21D 1/19: by interrupted quenching - C21D 1/673: for die quenching - C21D 1/76: Adjusting the composition of the atmosphere - C21D 6/005: {containing Mn} - C21D 8/00: Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment (hardening articles or materials formed by forging or rolling with no further heating beyond that required for the formation C21D1/02) - C21D 9/0068: {for particular articles not mentioned below} - C22C 21/02: with silicon as the next major constituent - C22C 38/04: containing manganese - C22C 38/06: containing aluminium - C22C 38/08: containing nickel {(C22C38/105 takes precedence)} - C22C 38/12: containing tungsten, tantalum, molybdenum, vanadium, or niobium - C22C 38/14: containing titanium or zirconium - C22C 38/16: containing copper - C23C 8/14: Oxidising of ferrous surfaces - C21D 1/26: Methods of annealing - C21D 2211/001: Austenite - C21D 2211/008: Martensite - C21D 2261/00: Machining or cutting being involved - B21D: WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL (working or processing of wire B21F) - B32B: LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM - 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) - C22C: ALLOYS (treatment of alloys C21D, C22F) - 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) ## Abstract A method of forming a shaped steel object is provided. The method includes cutting a blank from an alloy composition including 0.05-0.5 wt. % carbon, 4-12 wt. % manganese, 1-8 wt. % aluminum, 0-0.4 wt. % vanadium, and a remainder balance of iron. The method also includes heating the blank until the blank is austenitized to form a heated blank, transferring the heated blank to a press, forming the heating blank into a predetermined shape to form a stamped object, and decreasing the temperature of the stamped object to a temperature between a martensite start (Ms) temperature of the alloy composition and a martensite final (Mf) temperature of the alloy composition to form a shaped steel object comprising martensite and retained austenite. ## Claims ### Claim 1 A method of forming a shaped steel object, the method comprising: cutting a blank from an alloy composition, the alloy composition comprising: carbon (C) at a concentration of greater than or equal to about 0.05 wt. % to less than or equal to about 0.5 wt. % of the alloy composition, manganese (Mn) at a concentration of greater than or equal to about 4 wt. % to less than or equal to about 12 wt. % of the alloy composition, aluminum (Al) at a concentration of greater than or equal to about 1 wt. % to less than or equal to about 8 wt. % of the alloy composition, vanadium (V) at a concentration of greater than 0 wt. % to less than or equal to about 0.4 wt. % of the alloy composition, and a balance of the alloy composition being iron (Fe); heating the blank until the blank is austenitized; transferring the heated blank to a press; forming the heated blank into a predetermined shape defined by the press to generate a stamped object; and decreasing the temperature of the stamped object to a temperature between a martensite start (Ms) temperature of the alloy composition and a martensite final (Mf) temperature of the alloy composition to form a shaped steel object comprising martensite and retained austenite. ### Claim 2 (depends on 1) The method according to claim 1, wherein the alloy composition further comprises: zirconium (Zr) at a concentration of greater than 0 wt. % to less than or equal to about 0.5 wt. % of the alloy composition. ### Claim 3 (depends on 2) The method according to claim 2, wherein the alloy composition further comprises at least one of: nickel (Ni) at a concentration of greater than 0 wt. % to less than or equal to about 5 wt. % of the alloy composition, molybdenum (Mo) at a concentration of greater than 0 wt. % to less than or equal to about 0.5 wt. % of the alloy composition, niobium (Nb) at a concentration of greater than 0 wt. % to less than or equal to about 0.2 wt. % of the alloy composition, copper (Cu) at a concentration of greater than 0 wt. % to less than or equal to about 3 wt. % of the alloy composition, titanium (Ti) at a concentration of greater than 0 wt. % to less than or equal to about 0.1 wt. % of the alloy composition, nitrogen (N) at a concentration of greater than 0 wt. % to less than or equal to about 0.01 wt. % of the alloy composition, and boron (B) at a concentration of greater than 0 wt. % to less than or equal to about 0.005 wt. % of the alloy composition. ### Claim 4 (depends on 1) The method according to claim 1, wherein the Mn is at a concentration of greater than or equal to about 6 wt. % to less than or equal to about 10 wt. % and the Al is at a concentration of greater than or equal to about 2 wt. % to less than or equal to about 5 wt. %. ### Claim 5 (depends on 1) The method according to claim 1, wherein the C is at a concentration of greater than or equal to about 0.1 wt. % to less than or equal to about 0.45 wt. %. ### Claim 6 (depends on 1) The method according to claim 1, wherein the alloy composition is in the form of a coil. ### Claim 7 (depends on 1) The method according to claim 1, wherein the heating the blank comprises heating the blank to a temperature of greater than or equal to about 900° C. to less than or equal to about 950° C. for a time period of greater than or equal to about 1 minute to less than or equal to about 60 minutes. ### Claim 8 (depends on 1) The method according to claim 1, wherein the temperature between the Ms temperature of the alloy composition and the Mf temperature of the alloy composition is ambient temperature. ### Claim 9 (depends on 1) The method according to claim 1, wherein the decreasing the temperature comprises decreasing the temperature at a rate of greater than or equal to about 5° C.s−1 to less than or equal to about 300° C.s−1. ### Claim 10 (depends on 1) The method according to claim 1, further comprising, prior to the heating the blank until the blank is austenitized: preoxidizing the alloy composition by heating the alloy composition to a temperature of greater than or equal to about 500° C. to less than or equal to about 600° C. for a time period of greater than or equal to about 1 minute to less than or equal to about 60 minutes. ### Claim 11 (depends on 1) The method according to claim 1, further comprising, after the decreasing the temperature: tempering the shaped steel object. ### Claim 12 (depends on 11) The method according to claim 11, wherein the tempering the shaped steel object comprises: heating the shaped steel object to a temperature greater than or equal to about 150° C. to less than or equal to about 300° C. for a time period of greater than or equal to about 1 minute to less than or equal to about 120 minutes, and cooling the shaped steel object to ambient temperature. ### Claim 13 (depends on 1) The method according to claim 1, wherein the shaped steel object has a higher strength and a lower weight relative to an equivalent shaped steel object formed from 22MnB5. ### Claim 14 A method of forming a shaped steel object, the method comprising: heating a blank to a temperature of greater than or equal to about 900° C. to less than or equal to about 950° C. for a time period of greater than or equal to about 1 minute to less than or equal to about 60 minutes to generate a heated blank, the blank being composed of an alloy composition comprising: carbon (C) at a concentration of greater than or equal to about 0.05 wt. % to less than or equal to about 0.5 wt. % of the alloy composition, manganese (Mn) at a concentration of greater than or equal to about 4 wt. % to less than or equal to about 12 wt. % of the alloy composition, aluminum (Al) at a concentration of greater than or equal to about 1 wt. % to less than or equal to about 8 wt. % of the alloy composition, vanadium (V) at a concentration of greater than 0 wt. % to less than or equal to about 0.4 wt. % of the alloy composition, zirconium (Zr) at a concentration of greater than 0 wt. % to less than or equal to about 0.5 wt. % of the alloy composition, and a balance of the alloy composition being iron (Fe); forming the heated blank into a predetermined shape in a press to generate a stamped object; quenching the stamped object by decreasing the temperature of the stamped object to about ambient temperature to form a shaped steel object comprising martensite and retained austenite; and tempering the shaped steel object by heating the shaped steel object to greater than or equal to about 150° C. to less than or equal to about 300° C. for a time period of greater than or equal to about 1 minute to less than or equal to about 120 minutes and then decreasing the temperature of the shaped steel object to ambient temperature. ### Claim 15 (depends on 14) The method according to claim 14, wherein the shaped steel object is an automobile part selected from the group consisting of a pillar, a bumper, a roof rail, a rocker rail, a tunnel, a beam, and a reinforcement. ### Claim 16 An alloy composition comprising: carbon (C) at a concentration of greater than or equal to about 0.05 wt. % to less than or equal to about 0.5 wt. % of the alloy composition, manganese (Mn) at a concentration of greater than or equal to about 4 wt. % to less than or equal to about 12 wt. % of the alloy composition, aluminum (Al) at a concentration of greater than or equal to about 1 wt. % to less than or equal to about 8 wt. % of the alloy composition, vanadium (V) at a concentration of greater than 0 wt. % to less than or equal to about 0.4 wt. % of the alloy composition, zirconium (Zr) at a concentration of greater than 0 wt. % to less than or equal to about 0.5 wt. % of the alloy composition, and a balance of the alloy composition being iron (Fe). ### Claim 17 (depends on 16) The alloy composition according to claim 16, wherein the alloy composition has a higher strength and lower weight after press hardening relative to an equivalent 22MnB5 steel after press hardening. ### Claim 18 (depends on 16) The alloy composition according to claim 16, wherein after press hardening, the alloy composition comprises greater than or equal to about 80 wt. % to less than or equal to about 95 wt. % martensite and greater than or equal to about 5 wt. % to less than or equal to about 20 wt. % retained austenite. ### Claim 19 (depends on 18) The alloy composition according to claim 18, wherein after press hardening, the alloy composition has a martensite:retained austenite ratio that increases when a load is applied to the alloy composition. ### Claim 20 (depends on 16) An automobile part comprising the alloy composition according to claim 16, wherein the automobile part is a pillar, a bumper, a roof rail, a rocker rail, a tunnel, a beam, or a reinforcement.