# US 7,608,155 B2 · High strength, hot dip coated, dual phase, steel sheet and method of manufacturing same > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,608,155 B2 - Document ID: US7608155B2 - Status: Granted - Kind: B2 - Application number: 11/527,918 - Filed: 2006-09-27 - Published: 2008-03-27 - Granted: 2009-10-27 - Earliest claimed: 2006-09-27 - Assignees: Nucor Corporation - Inventors: Weiping Sun - Web page: https://patentgrep.com/patent/US7608155B2 ## CPC - C22C 38/002: {containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60} - C22C 38/02: containing silicon - C22C 38/04: containing manganese - C22C 38/06: containing aluminium - C22C 38/18: containing chromium - C22C 38/22: with molybdenum or tungsten - C22C 38/40: with nickel - C23C 2/02: Pretreatment of the material to be coated, e.g. for coating on selected surface areas (C23C2/30 takes precedence) - C23C 2/0224: {Two or more thermal pretreatments} - C23C 2/024: {by cleaning or etching} - C23C 2/28: Thermal after-treatment, e.g. treatment in oil bath - C23C 2/29: {Cooling or quenching} - Y10T 428/12799: Next to Fe-base component [e.g., galvanized] - Y10T 428/12972: Containing 0.01-1.7% carbon [i.e., steel] - 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) - Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION ## Abstract A galvanized steel sheet having (a) a dual phase microstructure with a martensite phase and a ferrite phase and (b) a composition containing by percent weight: carbon in a range from about 0.01% to about 0.18%; manganese in a range from about 0.2% to about 3%; silicon ≦ about 1.2%; aluminum in a range from about 0.01% to about 0.1%; one or both of chromium and nickel in a range from about 0.1% to about 3.5%; calcium in a range from about 0.0003% to about 0.01%; phosphorus ≦ about 0.01%; sulfur ≦ about 0.03%; nitrogen ≦ about 0.02%; molybdenum ≦ about 1%; copper ≦ about 0.8%; one or more of niobium, titanium, and vanadium ≦ about 1%; and boron ≦ about 0.006% by weight; and with the balance of the composition being iron and incidental ingredients. In one embodiment, the steel sheet is both galvanized and galvannealed. ## Claims ### Claim 1 A method of making a galvanized steel sheet, comprising: (I) at a temperature in a range between about (Ar3-60)° C. and about 980° C. (about 1796° F.), hot rolling a steel slab into a hot band, wherein the steel slab comprises a composition comprising: carbon in a range from about 0.01% by weight to about 0.18% by weight, manganese in a range from about 0.2% by weight to about 3% by weight, silicon ≦ about 1.2% by weight, aluminum in a range from about 0.01% by weight to about 0.1% by weight, chromium or nickel or a combination thereof in a range from about 0.1% by weight to about 3.5% by weight, calcium in a range from about 0.0003% by weight to about 0.01% by weight, phosphorus ≦ about 0.01% by weight, sulfur ≦ about 0.03% by weight, nitrogen ≦ about 0.02% by weight, molybdenum ≦ about 1% by weight, copper ≦ about 0.8% by weight, niobium or titanium or vanadium or a combination thereof ≦ about 1% by weight, and boron ≦ about 0.006% by weight, and with the balance of said composition comprising iron and incidental ingredients; (II) cooling the hot band at a mean rate of at least about 3° C./s (about 5.4° F./s) to a temperature not higher than about 800° C. (about 1472° F.) obtaining a steel sheet comprising a dual phase microstructure comprising a martensite phase at least 3% by volume embedded in a ferrite matrix phase; (III) coiling the cooled band to form a coil; (IV) galvanizing the steel sheet by heating to a temperature higher than about 600° C. (1112° F.), holding the temperature in a soaking zone of a galvanizing line while using a line speed or process speed faster than about 30 m/min, cooling the steel sheet to a temperature close to the temperature in the galvanizing bath in a range between about 400° C. (about 752° F.) and about 550° C. (about 1022° F.), passing the steel sheet through the galvanizing bath to coat the steel sheet with a zinc coating or a zinc alloy coating, and cooling the galvanized steel sheet; and (V) obtaining a galvanized steel sheet comprising (a) a dual phase microstructure comprising a martensite phase and a ferrite phase, (b) said composition, and (c) one or more of a property chosen from (i) a weldability superior to that of known galvanized steel sheet having a dual phase microstructure of a martensite phase and a ferrite phase, (ii) an impact energy ≧ about 1200 g-m, measured on a V-notch Charpy specimen of about 1.5 mm thickness, or (iii) a yield strength/tensile strength ratio ≦ about 70%. ### Claim 2 (depends on 1) The method according to claim 1, wherein after step (IV), the steel sheet is galvannealed by reheating to a temperature in a range from about 450° C. (about 842° F.) to about 650° C. (about 1202° F.), and cooling the steel sheet, to obtain a resultant steel sheet that is both galvanized and galvannealed. ### Claim 3 (depends on 1) The method according to claim 1, wherein after coiling and prior to galvanizing, the method further comprises one or both of: (i) pickling the coil, or (ii) cold rolling the coil to a desired steel sheet thickness, with a total reduction of at least about 30%. ### Claim 4 (depends on 1) The method according to claim 1, wherein the martensite phase comprises from about 3% by volume to about 35% by volume of the microstructure. ### Claim 5 (depends on 1) The method according to claim 1, wherein: the carbon ranges from about 0.02% by weight to about 0.12% by weight, the manganese ranges from about 0.3% by weight to about 2.8% by weight, the silicon ≦ about 1% by weight, the aluminum ranges from about 0.015% by weight to about 0.09% by weight, the chromium or the nickel or a combination thereof ranges from about 0.2% by weight to about 3% by weight, the calcium ranges from about 0.0005% by weight to about 0.009% by weight, the phosphorus ≦ about 0.08% by weight, the sulfur ≦ about 0.02% by weight, the nitrogen ≦ about 0.015% by weight, the molybdenum ≦ about 0.8% by weight, the copper ≦ about 0.6% by weight, the niobium or the titanium or the vanadium or a combination thereof ≦ about 0.8% by weight, or the boron ≦ about 0.003% by weight, or a combination thereof. ### Claim 6 (depends on 1) The method according to claim 1, wherein: (I) hot rolling into the hot band is performed at a temperature in a range between about (Ar3-30)° C. and about 930° C. (about 1706° F.); (II) cooling the hot band is performed at a mean rate of at least about 5° C./s (about 9° F./s); III) coiling the cooled band to form a coil of the steel sheet is performed at a temperature in a range between about 400° C. (about 752° F.) and about 750° C. (about 1382° F.); and (IV) galvanizing the steel sheet is performed by heating to a temperature in a range between about 650° C. (1202° F.) and about 950° C. (about 1742° F.), holding the temperature in a soaking zone of a galvanizing line while using a line speed or process speed in a range from about 50 m/min to about 150 m/min, and cooling the steel sheet to a temperature close to the temperature in the galvanizing bath in a range between about 425° C. (about 797° F.) and about 500° C. (about 932° F.). ### Claim 7 (depends on 6) The method according to claim 6, wherein heating during galvanizing is to a temperature in a range between about 700° C. (about 1292° F.) to about 925° C. (about 1697° F.). ### Claim 8 (depends on 1) The method according to claim 1, wherein galvanized steel sheet of (V) has properties of (i) a weldability superior to that of known galvanized steel sheet having a dual phase microstructure of a martensite phase and a ferrite phase, (ii) a yield strength/tensile strength ratio ≦ about 70%, (iii) an impact energy ≧ about 1200 g-m, measured on a V-notch Charpy specimen of about 1.5 mm thickness, (iv) an elongation about 20%, and (v) an excellent n-value. ### Claim 9 A method of making a galvanized steel sheet, comprising: (I) at a temperature in a range between about (Ar3-30)° C. and about 930° C. (about 1706° F.), hot rolling a steel slab having said composition into a hot band, wherein the steel slab comprises a composition comprising: carbon in a range from about 0.02% by weight to about 0.12% by weight, manganese in a range from about 0.3% by weight to about 2.8% by weight, silicon ≦ about 1% by weight, aluminum in a range from about 0.0 15% by weight to about 0.09% by weight, chromium or nickel or a combination thereof in a range from about 0.2% by weight to about 3% by weight, calcium in a range from about 0.0005% by weight to about 0.009% by weight, phosphorus ≦ about 0.08% by weight, sulfur ≦ about 0.02% by weight, nitrogen ≦ about 0.015% by weight, molybdenum ≦ about 0.8% by weight, copper ≦ about 0.6% by weight, niobium or titanium or vanadium or a combination thereof ≦ about 0.8% by weight, and boron ≦ about 0.003% by weight, and with the balance of the composition comprising iron and incidental ingredients; (II) cooling the hot band at a mean rate of at least about 5° C./s (about 9° F./s) obtaining a steel sheet comprising a dual phase microstructure comprising a martensite phase from about 3% to about 35% by volume embedded in a ferrite matrix phase; (III) coiling the cooled band at a temperature in a range between 400° C. (about 752° F.) and about 750° C. (about 1382° F.) to form a coil of the steel sheet; (IV) pickling the coil; (V) cold rolling the pickled coil to a desired steel sheet thickness, with a total reduction of at least about 30%; (VI) galvanizing the steel sheet by heating to a temperature in a range between about 650° C. (1202° F.) and about 950° C. (about 1742° F.), holding the temperature in a soaking zone of a galvanizing line while using a line speed or process speed in a range from about 50 m/min to about 150 m/min, and cooling the steel sheet to a temperature close to the temperature in the galvanizing bath in a range between about 425° C. (about 797° F.) and about 500° C. (about 932° F.), passing the steel sheet through the galvanizing bath to coat the steel sheet with a zinc coating or a zinc alloy coating, and cooling the galvanized steel sheet; and (VII) obtaining a galvanized steel sheet comprising (a) a dual phase microstructure comprising a martensite phase and a ferrite phase, wherein the martensite phase comprises from about 3% by volume to about 35% by volume of the microstructure (b) said composition, and (c) properties of (i) a weldability superior to that of known galvanized steel sheet having a dual phase microstructure of a martensite phase and a ferrite phase, (ii) a yield strength/tensile strength ratio ≦ about 70%, (iii) an impact energy ≧ about 1200 g-m, measured on a V-notch Charpy specimen of about 1.5 mm thickness, (iv) an elongation ≧ about 20%, and (vii) an excellent n-value. ### Claim 10 (depends on 9) The method according to claim 9, wherein heating during galvanizing is to a temperature in a range between about 700° C. (about 1292° F.) to about 925° C. (about 1697° F.). ### Claim 11 A method of making a galvanized and galvannealed steel sheet, comprising: (I) at a temperature in a range between about (Ar3-60)° C. and about 980° C. (about 1796° F.), hot rolling a steel slab into a hot band, wherein the steel slab comprises a composition comprising: carbon in a range from about 0.01% by weight to about 0.18% by weight, manganese in a range from about 0.2% by weight to about 3% by weight, silicon ≦ about 1.2% by weight, aluminum in a range from about 0.01% by weight to about 0.1% by weight, chromium or nickel or a combination thereof in a range from about 0.1% by weight to about 3.5% by weight, calcium in a range from about 0.0003% by weight to about 0.01% by weight, phosphorus ≦ about 0.01% by weight, sulfur ≦ about 0.03% by weight, nitrogen ≦ about 0.02% by weight, molybdenum ≦ about 1% by weight, copper ≦ about 0.8% by weight, niobium or titanium or vanadium or a combination thereof ≦ about 1% by weight, and boron ≦ about 0.006% by weight, and with the balance of said composition comprising iron and incidental ingredients; (II) cooling the hot band at a mean rate of at least about 3° C./s (about 5.4° F./s) to a temperature not higher than about 800° C. (about 1472° F.) obtaining a steel sheet comprising a dual phase microstructure comprising a martensite phase from about 3% to about 35% by volume embedded in a ferrite matrix phase; (III) coiling the cooled band to form a coil; (IV) galvanizing the steel sheet by heating to a temperature higher than about 600° C. (about 1112° F.), holding the temperature in a soaking zone of a galvanizing line while using a line speed or process speed faster than about 30 m/min, cooling the steel sheet to a temperature close to the temperature in the galvanizing bath in a range between about 400° C. (about 752° F.) and about 550° C. (about 1022° F.), passing the steel sheet through the galvanizing bath to coat the steel sheet with a zinc coating or a zinc alloy coating, and cooling the galvanized steel sheet; (V) galvannealing the steel sheet by reheating to a temperature in a range from about 450° C. (about 842° F.) to about 650° C. (about 1202° F.) and cooling the steel sheet; and (VI) obtaining a galvanized and galvannealed steel sheet comprising (a) a dual phase microstructure comprising a martensite phase and a ferrite phase, wherein the martensite phase comprises from about 3% by volume to about 35% by volume of the microstructure, (b) said composition, and (c) one or more of a property chosen from (i) a weldability superior to that of known galvanized and galvannealed steel sheet having a dual phase microstructure of a martensite phase and a ferrite phase, (ii) an impact energy ≧ about 1200 g-m, measured on a V-notch Charpy specimen of about 1.5 mm thickness, or (iii) a yield strength/tensile strength ratio ≦ about 70%. ### Claim 12 (depends on 11) The method according to claim 11, wherein after coiling and prior to galvanizing, the method further comprises one or both of: (i) pickling the coil, or (ii) cold rolling the coil to a desired steel sheet thickness, with a total reduction of at least about 30%. ### Claim 13 (depends on 11) The method according to claim 11, wherein: the carbon ranges from about 0.02% by weight to about 0.12% by weight, the manganese ranges from about 0.3% by weight to about 2.8% by weight, the silicon ≦ about 1% by weight, the aluminum ranges from about 0.015% by weight to about 0.09% by weight, the chromium or the nickel or a combination thereof ranges from about 0.2% by weight to about 3% by weight, the calcium ranges from about 0.0005% by weight to about 0.009% by weight, the phosphorus ≦ about 0.08% by weight, the sulfur ≦ about 0.02% by weight, the nitrogen ≦ about 0.015% by weight, the molybdenum ≦ about 0.8% by weight, the copper ≦ about 0.6% by weight, the niobium or the titanium or the vanadium or a combination thereof ≦ about 0.8% by weight, or the boron ≦ about 0.003% by weight, or a combination thereof. ### Claim 14 (depends on 11) The method according to claim 11, wherein: (I) hot rolling into the hot band is performed at a temperature in a range between about (Ar3-30)° C. and about 930° C. (about 1706° F.); (II) cooling the hot band is performed at a mean rate of at least about 5° C./s (about 9° F./s); III) coiling the cooled band to form a coil of the steel sheet is performed at a temperature in a range between about 400° C. (about 752° F.) and about 750° C. (about 1382° F.); and (IV) galvanizing the steel sheet is performed by heating to a temperature in a range between about 650° C. (1202° F.) and about 950° C. (about 1742° F.), holding the temperature in a soaking zone of a galvanizing line while using a line speed or process speed in a range from about 50 m/min to about 150 m/min, and cooling the steel sheet to a temperature close to the temperature in the galvanizing bath in a range between about 425° C. (about 797° F.) and about 500° C. (about 932° F.); and (V) galvannealing the steel sheet is performed by reheating to a temperature in a range from about 500° C. (about 932° F.) to about 600° C. (about 1112° F.) and cooling the steel sheet. ### Claim 15 (depends on 14) The method according to claim 14, wherein heating during galvanizing is to a temperature in a range between about 700° C. (about 1292° F.) to about 925° C. (about 1697° F.). ### Claim 16 (depends on 11) The method according to claim 11, wherein the galvanized and galvannealed steel sheet of (VI) has properties of (i) a weldability superior to that of known galvanized steel sheet having a dual phase microstructure of a martensite phase and a ferrite phase, (ii) a yield strength/tensile strength ratio ≦ about 70%, (iii) an impact energy ≧ about 1200 g-m, measured on a V-notch Charpy specimen of about 1.5 mm thickness, (iv) an elongation ≦ about 20%, (v) an excellent n-value, and (v) being robust under various hot dip coating processing conditions. ### Claim 17 A method of making a galvanized and galvannealed steel sheet, comprising: (I) at a temperature in a range between about (Ar3-30)° C. and about 930° C. (about 1706° F.), hot rolling a steel slab having said composition into a hot band, wherein the steel slab comprises a composition comprising: carbon in a range from about 0.02% by weight to about 0.12% by weight, manganese in a range from about 0.3% by weight to about 2.8% by weight, silicon ≦ about 1% by weight, aluminum in a range from about 0.0015% by weight to about 0.09% by weight, chromium or nickel or a combination thereof in a range from about 0.2% by weight to about 3% by weight, calcium in a range from about 0.0005% by weight to about 0.009% by weight, phosphorus ≦ about 0.08% by weight, sulfur ≦ about 0.02% by weight, nitrogen ≦ about 0.015% by weight, molybdenum ≦ about 0.8% by weight, copper ≦ about 0.6% by weight, niobium or titanium or vanadium or a combination thereof ≦ about 0.8% by weight, and boron ≦ about 0.003% by weight, and with the balance of the composition comprising iron and incidental ingredients; (II) cooling the hot band at a mean rate of at least about 5° C./s (about 9° F./s) obtaining a steel sheet comprising a dual phase microstructure comprising a martensite phase from about 3% to about 35% by volume embedded in a ferrite matrix phase; (III) coiling the cooled band at a temperature in a range between 400° C. (about 752° F.) and about 750° C. (about 1382° F.) to form a coil of the steel sheet; (IV) pickling the coil; (V) cold rolling the pickled coil to a desired steel sheet thickness, with a total reduction of at least about 30%; (VI) galvanizing the steel sheet by heating to a temperature in a range between about 650° C. (1202° F.) and about 950° C. (about 1742° F.), holding the temperature in a soaking zone of a galvanizing line while using a line speed or process speed in a range from about 50 m/min to about 150 m/min, and cooling the steel sheet to a temperature close to the temperature in the galvanizing bath in a range between about 425° C. (about 797° F.) and about 500° C. (about 932° F.), passing the steel sheet through the galvanizing bath to coat the steel sheet with a zinc coating or a zinc alloy coating, and cooling the galvanized steel sheet; (VII) galvannealing the steel sheet by reheating to a temperature in a range from about 500° C. (about 932° F.) to about 600° C. (about 1112° F.) and cooling the steel sheet; and (VIII) obtaining a galvanized and galvannealed steel sheet comprising (a) a dual phase microstructure comprising a martensite phase and a ferrite phase, wherein the martensite phase comprises from about 3% by volume to about 35% by volume of the microstructure (b) said composition, and (c) properties of (i) a weldability superior to that of known galvanized steel sheet having a dual phase microstructure of a martensite phase and a ferrite phase, (ii) a yield strength/tensile strength ratio ≦ about 70%, (iii) an impact energy ≧ about 1200 g-m, measured on a V-notch Charpy specimen of about 1.5 mm thickness, (iv) an elongation ≦ about 20%, and (vii) an excellent n-value. ### Claim 18 (depends on 17) The method according to claim 17, wherein heating during galvanizing is to a temperature in a range between about 700° C. (about 1292° F.) to about 925° C. (about 1697° F.).