HOT ROLLED STEEL SHEET HAVING EXCELLENT BLANKING PROPERTIES AND UNIFORMINTY, AND MANUFACTURING METHOD THEREOF

• Main Authors: KIM, Dong-Wan, KIM, Sung-Il
• Format: Patent
• Language: English; French; Korean
• Published: 24.06.2021
• Subjects: ALLOYS; CHEMISTRY; FERROUS OR NON-FERROUS ALLOYS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUSMETALS OR ALLOYS; MAKING METAL MALLEABLE BY DECARBURISATION, TEMPERING OR OTHERTREATMENTS; METALLURGY; METALLURGY OF IRON; MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; TREATMENT OF ALLOYS OR NON-FERROUS METALS

The present invention provides a high-strength hot-rolled steel sheet comprising, in percentage by weight: C: 0.10-0.30%; Si: 0.001-1.0%; Mn: 0.5-2.5%; Cr: 0.001-1.5%; Mo: 0.001-0.5%; Al: 0.001-0.5%; P: 0.001-0.01%; S: 0.001-0.01%; N: 0.001-0.01%; B: 0.0001-0.004%; Ti: 0.001-0.1%; Nb: 0.001-0.1%; and the balance consisting of Fe and inevitable impurities, and satisfying relational expression (1) as stated below, and a microstructure thereof includes a columnar phase comprising: a martensite phase; a bainite phase, wherein the fraction of the martensite phase is 50% to 90%, the fraction of the bainite phase is 5% to 50%, the sum of the fractions of the martensite phase and the bainite phase is 90% or more; and the balance thereof consisting of a ferrite phase. [Relational Expression (1)] CL < 1 CL = -0.692 - 0.158×[Mn] + 0.121×[Mn]2 + 0.061×[Cr]2 - 0.319×[Mo] + 0.035×[Hardness_HRC] ] (where CL is an effective crack occurrence index, [Mn], [Cr], and [Mo] are the percentages by weight of respective corresponding alloy elements, and [Hardness_HRC] is Rockwell hardness (HRC).) La présente invention concerne une tôle d'acier laminée à chaud à résistance élevée comprenant, en pourcentage en poids : du C : 0,10-0,30 % ; du Si : 0,001-1,0% ; du Mn : 0,5-2,5% ; du Cr : 0,001-1,5% ; du Mo : 0,001- 0,5 % ; de l'Al : 0,001-0,5 % ; du P : 0,001-0,01 % ; du S : 0,001-0,01 % ; du N : 0,001-0,01 % ; du B : 0,0001-0,004 % ; du Ti : 0,001-0,1 % ; du Nb : 0,001-0,1 % ; et le reste étant constitué de Fe et d'impuretés inévitables, et satisfaisant l'expression relationnelle (1) telle que citée ci-dessous, et une microstructure de celle-ci comprend une phase en colonnes comprenant : une phase de martensite ; une phase de bainite, la fraction de la phase martensite étant de 50 % à 90 %, la fraction de la phase de bainite étant de 5 % à 50 %, la somme des fractions de la phase de martensite et de la phase de bainite étant de 90 % ou plus ; et le reste de celle-ci étant constituée d'une phase ferrite. [Expression Relationnelle (1)] CL < 1 CL = -0,692 - 0,158×[Mn] + 0,121×[Mn]2 + 0,061×[Cr]2 - 0,319×[Mo] + 0,035×[Dureté_HRC] ] (où CL est un indice d'apparition de fissure effectif, [Mn], [Cr], et [Mo] sont les pourcentages en poids d'éléments d'alliage correspondants respectifs, et [Dureté_HRC] est une dureté Rockwell (HRC).) 본 발명은 중량%로, C: 0.10~0.30%, Si: 0.001~1.0%, Mn: 0.5~2.5%, Cr: 0.001~1.5%, Mo: 0.001~0.5%, Al: 0.001~0.5%, P: 0.001~0.01%, S: 0.001~0.01%, N: 0.001~0.01%, B: 0.0001~0.004%, Ti: 0.001~0.1%, Nb: 0.001~0.1% 및 잔부가 철 및 불가피한 불순물을 포함하고, 하기 관계식 (1) 을 만족하며, 미세조직이, 주상은 마르텐사이트 상과 베이나이트 상으로 이루어지며, 상기 마르텐사이트 상의 분율은 50% 이상 90% 미만이고, 상기 베이나이트 상의 분율은 5% 이상 50% 이하이며, 상기 마르텐사이트 상과 상기 베이나이트 상의 분율의 합이 90% 이상이고, 잔부는 페라이트 상으로 이루어진 고강도 열연강판을 제공한다. [관계식 (1)] CL < 1 CL = -0.692 - 0.158×[Mn] + 0.121×[Mn] 2 + 0.061×[Cr] 2 - 0.319×[Mo] + 0.035×[Hardness_HRC] (여기서, CL 은 유효크랙발생지수이며, [Mn], [Cr], [Mo] 는 해당 합금원소의 중량%, [Hardness_HRC]는 로크웰 경도(HRC)이다.)