# US 2014/0193667 A1 · High-strength cold-rolled steel sheet having excellent stretch flangeability and precision punchability and manufacturing method thereof > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0193667 A1 - Document ID: US20140193667A1 - Status: Published application - Kind: A1 - Application number: 14/235,009 - Filed: 2012-07-27 - Published: 2014-07-10 - Earliest claimed: 2011-07-27 - Assignees: Nippon Steel & Sumitomo Metal Corporation - Inventors: Hiroshi Shuto; Nobuhiro Fujita; Tatsuo Yokoi; Riki Okamoto; Kazuaki Nakano; Shinichiro Watanabe - Web page: https://patentgrep.com/patent/US20140193667A1 ## CPC - C22C 38/38: with more than 1.5% by weight of manganese - C21D 8/0263: {following hot rolling} - C21D 8/0426: {Hot rolling} - C21D 8/0436: {Cold rolling} - C21D 8/0473: {Final recrystallisation annealing} - C22C 38/001: {containing N} - C22C 38/002: {containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60} - C22C 38/005: {containing rare earths, i.e. Sc, Y, Lanthanides} - C22C 38/008: {containing tin} - C22C 38/02: containing silicon - C22C 38/04: containing manganese - C22C 38/06: containing aluminium - C22C 38/08: containing nickel {(C22C38/105 takes precedence)} - C22C 38/10: containing cobalt - C22C 38/12: containing tungsten, tantalum, molybdenum, vanadium, or niobium - C22C 38/14: containing titanium or zirconium - C22C 38/16: containing copper - C22C 38/22: with molybdenum or tungsten - C22C 38/28: with titanium or zirconium - C22C 38/32: with boron - C21D 2201/05: Grain orientation - C21D 2211/005: Ferrite - Y10T 428/12799: Next to Fe-base component [e.g., galvanized] - C22C: ALLOYS (treatment of alloys C21D, C22F) - 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) - Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION ## Abstract A high-strength cold-rolled steel sheet having excellent stretch flangeability and precision punchability containing predetermined components and a balance being composed of iron and inevitable impurities, in which in a range of ⅝ to ⅜ in sheet thickness from the surface of the steel sheet, an average value of pole densities of the {100}<011> to {223}<110> orientation group represented by respective crystal orientations of {100}<011>, {116}<110>, {114}<110>, {113}<110>, {112}<110>, {335}<110>, and {223}<110> is 6.5 or less, and a pole density of the {332}<113> crystal orientation is 5.0 or less, and a metal structure contains, in terms of an area ratio, greater than 5% of pearlite, the sum of bainite and martensite limited to less than 5%, and a balance composed of ferrite. ## Claims ### Claim 1 A high-strength cold-rolled steel sheet having excellent stretch flangeability and precision punchability comprising: in mass %, C: greater than 0.01% to 0.4% or less; Si: not less than 0.001% nor more than 2.5%; Mn: not less than 0.001% nor more than 4%; P: 0.001 to 0.15% or less; S: 0.0005 to 0.03% or less; Al: not less than 0.001% nor more than 2%; N: 0.0005 to 0.01% or less; and a balance being composed of iron and inevitable impurities, wherein in a range of ⅝ to ⅜ in sheet thickness from the surface of the steel sheet, an average value of pole densities of the {100}<011> to {223}<110> orientation group represented by respective crystal orientations of {100}<011>, {116}<110>, {114}<110>, {113}<110>, {112}<110>, {335}<110>, and {223}<110> is 6.5 or less, and a pole density of the {332}<113> crystal orientation is 5.0 or less, and a metal structure contains, in terms of an area ratio, greater than 5% of pearlite, the sum of bainite and martensite limited to less than 5%, and a balance composed of ferrite. ### Claim 2 (depends on 1) The high-strength cold-rolled steel sheet having excellent stretch flangeability and precision punchability according to claim 1, wherein further, Vickers hardness of a pearlite phase is not less than 150 HV nor more than 300 HV. ### Claim 3 (depends on 1) The high-strength cold-rolled steel sheet having excellent stretch flangeability and precision punchability according to claim 1, wherein further, an r value in a direction perpendicular to a rolling direction (rC) is 0.70 or more, an r value in a direction 30° from the rolling direction (r30) is 1.10 or less, an r value in the rolling direction (rL) is 0.70 or more, and an r value in a direction 60° from the rolling direction (r60) is 1.10 or less. ### Claim 4 (depends on 1) The high-strength cold-rolled steel sheet having excellent stretch flangeability and precision punchability according to claim 1, further comprising: one type or two or more types of in mass %, Ti: not less than 0.001% nor more than 0.2%, Nb: not less than 0.001% nor more than 0.2%, B: not less than 0.0001% nor more than 0.005%, Mg: not less than 0.0001% nor more than 0.01%, Rem: not less than 0.0001% nor more than 0.1%, Ca: not less than 0.0001% nor more than 0.01%, Mo: not less than 0.001% nor more than 1%, Cr: not less than 0.001% nor more than 2%, V: not less than 0.001% nor more than 1%, Ni: not less than 0.001% nor more than 2%, Cu: not less than 0.001% nor more than 2%, Zr: not less than 0.0001% nor more than 0.2%, W: not less than 0.001% nor more than 1%, As: not less than 0.0001% nor more than 0.5%, Co: not less than 0.0001% nor more than 1%, Sn: not less than 0.0001% nor more than 0.2%, Pb: not less than 0.001% nor more than 0.1%, Y: not less than 0.001% nor more than 0.1%, and Hf: not less than 0.001% nor more than 0.1%. ### Claim 5 (depends on 1) The high-strength cold-rolled steel sheet having excellent stretch flangeability and precision punchability according to claim 1, wherein further, when the steel sheet whose sheet thickness is reduced to 1.2 mm with a sheet thickness center portion set as the center is punched out by a circular punch with Φ 10 mm and a circular die with 1% of a clearance, a shear surface percentage of a punched edge surface becomes 90% or more. ### Claim 6 (depends on 1) The high-strength cold-rolled steel sheet having excellent stretch flangeability and precision punchability according to claim 1, wherein on the surface, a hot-dip galvanized layer or an alloyed hot-dip galvanized layer is provided. ### Claim 7 A manufacturing method of a high-strength cold-rolled steel sheet having excellent stretch flangeability and precision punchability, comprising: on a steel billet containing: in mass %, C: greater than 0.01% to 0.4% or less; Si: not less than 0.001% nor more than 2.5%; Mn: not less than 0.001% nor more than 4%; P: 0.001 to 0.15% or less; S: 0.0005 to 0.03% or less; Al: not less than 0.001% nor more than 2%; N: 0.0005 to 0.01% or less; and a balance being composed of iron and inevitable impurities, performing first hot rolling in which rolling at a reduction ratio of 40% or more is performed one time or more in a temperature range of not lower than 1000° C. nor higher than 1200° C.; setting an austenite grain diameter to 200 μm or less by the first hot rolling; performing second hot rolling in which rolling at a reduction ratio of 30% or more is performed in one pass at least one time in a temperature region of not lower than a temperature T1 determined by Expression (1) below +30° C. nor higher than T1+200° C.; setting the total reduction ratio in the second hot rolling to 50% or more; performing final reduction at a reduction ratio of 30% or more in the second hot rolling and then starting pre-cold rolling cooling in such a manner that a waiting time t second satisfies Expression (2) below; setting an average cooling rate in the pre-cold rolling cooling to 50° C./second or more and setting a temperature change to fall within a range of not less than 40° C. nor more than 140° C.; performing cold rolling at a reduction ratio of not less than 40% nor more than 80%; performing heating up to a temperature region of 750 to 900° C. and performing holding for not shorter than 1 second nor longer than 300 seconds; performing post-cold rolling primary cooling down to a temperature region of not lower than 580° C. nor higher than 750° C. at an average cooling rate of not less than 1° C./s nor more than 10° C./s; performing retention for not shorter than 1 second nor longer than 1000 seconds under the condition that a temperature decrease rate becomes 1° C./s or less; and performing post-cold rolling secondary cooling at an average cooling rate of 5° C./s or less. T1(° C.)=850+10×(C+N)×Mn+350×Nb+250×Ti+40×B+10×Cr+100×Mo+100×V (1) Here, C, N, Mn, Nb, Ti, B, Cr, Mo, and V each represent the content of the element (mass %). t≦2.5×t1 Expression (2) Here, t1 is obtained by Expression (3) below. t1=0.001×((Tf−T1)×P1/100)2−0.109×((Tf−T1)×P1/100)+3.1 Expression (3) Here, in Expression (3) above, Tf represents the temperature of the steel billet obtained after the final reduction at a reduction ratio of 30% or more, and P1 represents the reduction ratio of the final reduction at 30% or more. ### Claim 8 (depends on 7) The manufacturing method of the high-strength cold-rolled steel sheet having excellent stretch flangeability and precision punchability according to claim 7, wherein the total reduction ratio in a temperature range of lower than T1+30° C. is 30% or less. ### Claim 9 (depends on 7) The manufacturing method of the high-strength cold-rolled steel sheet having excellent stretch flangeability and precision punchability according to claim 7, wherein the waiting time t second further satisfies Expression (2a) below. t