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41. 发明专利

JP2002363644A METHOD FOR MANUFACTURING HIGH-TENSILE STEEL WITH EXCELLENT TOUGHNESS AND FATIGUE STRENGTH 失效
公开(公告)号：JP2002363644A
公开(公告)日：2002-12-18
申请号：JP2001175091
申请日：2001-06-11
申请人： NIPPON STEEL CORP
发明人： HASEGAWA TOSHINAGA , MINAGAWA MASANORI , SHIRAHATA HIROYUKI
IPC分类号： B21B3/00 , C21D8/02 , C22C38/00 , C22C38/06 , C22C38/58
摘要： PROBLEM TO BE SOLVED: To provide a method for attaining an ultrafine-grained structure of 1-3 μm average ferrite grain size over the whole thickness of steel and obtaining high-tensile steel combinedly having extremely excellent toughness, brittle crack arrest property, and fatigue characteristics of welded joint and having about >=490 MPa class tensile strength. SOLUTION: A manufacturing method wherein, as a basic requirement, the temperature of the steel during rolling stands within the range from (Ac1 transformation point - 50 deg.C) to (Ac3 transformation point - 50 deg.C) is applied to the steel having a microstructure with a prescribed component composition when the steel is heated to a temperature between 300 deg.C and rolling temperature at (0.1 to 50) deg.C/s temperature-rise rate and rolling is started in the course of temperature raise from the Ac1 transformation point to (Ac3 transformation point - 100 deg.C) or after holding at this temperature for 1-60 s and then rolling of 50-90% cumulative draft is applied. By this method, the ultrafine-grained structure of 1-3 μm minimal in the degree of duplex grain can be obtained, and extremely excellent toughness, brittle crack arrest property, and fatigue characteristics at welded joint can be attained.

42. 发明专利

JP2002105534A METHOD FOR MANUFACTURING HIGH-TENSILE STEEL HAVING EXCELLENT FRACTURE RESISTANCE 失效
公开(公告)号：JP2002105534A
公开(公告)日：2002-04-10
申请号：JP2000294879
申请日：2000-09-27
申请人： NIPPON STEEL CORP
发明人： HASEGAWA TOSHINAGA , MINAGAWA MASANORI , SHIRAHATA HIROYUKI
IPC分类号： C21D8/02 , C22C38/00 , C22C38/14 , C22C38/58
摘要： PROBLEM TO BE SOLVED: To produce high-tensile steel in which the safety of structures against fracture is increased by raising energy absorption in the shifting process from the occurrence and propagation of ductile fracture to brittle fracture and which has excellent fracture resistance. SOLUTION: In this method for manufacturing the high-tensile steel having excellent fracture resistance, a steel bloom containing specific components, having =750 deg.C finishing temperature and 50-95% cumulative draft. Successively, accelerated cooling at (5 to 100) deg.C/s cooling rate is started at =600 deg.C. By this procedure, high uniform elongation characteristics, high ductile crack propagation resistance and high toughness can simultaneously be provided.

43. 发明专利

JP2002003942A METHOD FOR PRODUCING TOUGH LOW YIELD RATIO STEEL HAVING SMALL QUALITY DEVIATION 失效
公开(公告)号：JP2002003942A
公开(公告)日：2002-01-09
申请号：JP2000179035
申请日：2000-06-14
申请人： NIPPON STEEL CORP
发明人： SHIRAHATA HIROYUKI , MINAGAWA MASANORI , HASEGAWA TOSHINAGA
IPC分类号： C21D8/02 , C21D1/18 , C22C38/00 , C22C38/06 , C22C38/58
摘要： PROBLEM TO BE SOLVED: To provide a method by which tough low yield ratio steel having small quality deviation can efficiently be produced. SOLUTION: In this method for producing tough low yield ratio steel having small material deviation, steel having a composition containing, by mass, 0.02 to 0.25% C, 0.02 to 2.5% Si, 0.30 to 3.5% Mn and 0.002 to 0.10% Al, and the balance Fe with inevitable impurities is subjected to rolling and cooling under the prescribed conditions. In a tempering stage thereafter, molten salt heated to Acl to Acl+80 deg.C is sprayed to rapidly and uniformly heat the steel sheet at a temperature rising rate of >=2 deg.C/s. Preferably, one or more metals selected from Ti, Nb, Zr, Ta, Cu, Ni, Cr, Mo, Co, W, V, B, Ca, Mg and rare earth metals are further added to the steel sheet by suitable amount.

44. 发明专利

JPH09271806A THICK PLATE WITH UNIFORM SCALE HAVING SATISFACTORY ADHESION AND ITS MANUFACTURE 失效
公开(公告)号：JPH09271806A
公开(公告)日：1997-10-21
申请号：JP8034996
申请日：1996-04-02
申请人： NIPPON STEEL CORP
发明人： YOSHIE ATSUHIKO , CHIJIIWA RIKIO , SHIRAHATA HIROYUKI
IPC分类号： B21B1/38 , B21B3/00 , C21D1/00 , C21D8/02 , C21D9/00 , C22C38/00 , C22C38/06
摘要： PROBLEM TO BE SOLVED: To provide the thick plate with uniform scale having satisfactory adhesion, which can be used it is without performing painting, plating or a surface treatment. SOLUTION: This thick plate contains prescribed quantities of C, Si, Mn and Al as essential components. also contains one kind or more of prescribed quantities of Nb, Ti, Cu, Ni, Cr, Mo, Co, W, V, B, Rem and Ca as selected components. The scale thickness of this thick plate is 30μ or below over the whole plate, and a difference between the maximum scale thickness and the minimum scale thickness is within 5μ, and thick plate has scale components whose weight ratio of Fe3 O4 occupying to the whole scale is 60% or over, and has uniform scale with satisfactory adhesion. After completing the hot rolling of a steel consisting of the chemical compositions at 700 deg.C or over, the steel is immediately cooled by jetting molten salt at 350 deg. to 580 deg.C.

45. 发明专利

JPH08283838A PRODUCTION OF LOW YIELD RATIO, HIGH DUCTILITY STEEL EXCELLENT IN STRENGTH, TOUGHNESS AND DUCTILITY 失效
公开(公告)号：JPH08283838A
公开(公告)日：1996-10-29
申请号：JP11406095
申请日：1995-04-17
申请人： NIPPON STEEL CORP
发明人： FUJIOKA MASAAKI , FUJITA TAKASHI , SHIRAHATA HIROYUKI , MABUCHI HIDESATO
IPC分类号： C21D8/00 , C22C38/00 , C22C38/06 , C22C38/14 , C22C38/54 , C22C38/58
摘要： PURPOSE: To produce a steel having a low yield ratio and excellent in ductility and toughness. CONSTITUTION: A slab contg., by weight, 0.01 to 0.4% C, 0.02 to 3.0% Mn, 0.001 to 0.75% Si and 0.001 to 0.1% Al, and the balance Fe with inevitable impurities is cast. After that, hot rolling is started without executing cooling, or after once executing cooling, it is heated again to the Ac3 point or above, subsequently, hot rolling is started and is finished at the Ar3 point or above, and after that, air cooling is executed. As for the subsequent cooling stage, it is executed from a temp. of the Ar3 -10 deg.C or below to >=700 deg.C at a cooling rate of 20 to 50 deg.C/sec to 0 to 350 deg.C, after that, its temp. is moreover raised to 750 to 850 deg.C, and it is held for 0 to 60min and is air-cooled or is cooled to 0 to 350 deg.C at a cooling rate of 0.1 to 50 deg.C/sec.

46. 发明专利

JPH08253812A PRODUCTION OF THICK STEEL PLATE EXCELLENT IN BRITTLE CRACK ARREST PROPERTY 失效
公开(公告)号：JPH08253812A
公开(公告)日：1996-10-01
申请号：JP8346895
申请日：1995-03-16
申请人： NIPPON STEEL CORP
发明人： SHIRAHATA HIROYUKI , MABUCHI HIDESATO , YOSHIE ATSUHIKO
IPC分类号： C21D8/02 , C22C38/00 , C22C38/12 , C22C38/54
摘要： PURPOSE: To produce a thick steel plate excellent in brittle crack arrest property by subjecting a cast slab having a specific composition to respective treatments of heating, cooling, rolling, and recuperation in succession under respectively specified conditions. CONSTITUTION: A cast slab, having a composition consisting of, by weight, 0.01-0.30% C, 0.03-1.5% Si, 0.30-2.0% Mn, 0.002-0.10% Al, 0.005-1.0% V, 0.001-0.01% N, and the balance Fe with inevitable impurities, is subjected, after heating up to >=Ac3 or in the as-cast state, to cooling until the temp., in the part 1/20 to 1/2 of cast slab thickness from one surface or both surfaces of the cast slab in the central direction of the cast slab thickness, reaches a value in the range between 200 deg.C and Ar3 . Subsequently, rolling is started when the part 1/20 to 1/2 of cast slab thickness from one surface or both surfaces of the cast slab in the central direction of the cast slab thickness is in a state of ferritic phase or in a ferrite-austenite dual phase state, and recuperation is done to a temp. in the range between (Ac3 -100 deg.C) and (Ac3 +100 deg.C) over the whole region of the cast slab thickness in the course of rolling or after the completion of rolling, and the maximum hardness difference in the plate thickness direction of the steel plate after rolling and cooling is regulated to a value two or less times the plate thickness (mm) by Vickers hardness.

47. 发明专利

JPH08243621A MANUFACTURE OF HOT ROLLED STEEL SHEET MINIMIZED IN SEAM FLAW 失效
公开(公告)号：JPH08243621A
公开(公告)日：1996-09-24
申请号：JP5160295
申请日：1995-03-10
申请人： NIPPON STEEL CORP
发明人： FUJITA TAKASHI , MABUCHI HIDESATO , SHIRAHATA HIROYUKI
IPC分类号： B21B37/00 , B21B37/76 , C21D8/02
摘要： PURPOSE: To provide a rolling method that is free from seam flaw, to decrease a rate of incidence of repair and to improve yield. CONSTITUTION: In this rolling method, at the time of manufacturing a steel sheet by hot rolling, in rolling pass whose rolled shape ratio α is 0.6-0.8, the seam flaw is not generated by heating the ridge line parts of a base stock to be rolled within the temp. range of -20 deg.C+50 deg.C of the surface temp. in the middle part in the width direction. The rolled shape ratio a is expressed by the equation I. α=2R.(H1 -H2 )/(H1 -2 ) ...(I) Where, R: the radius of rolling roll, H1 : the thickness on the inlet side of rolling, H2 : the thickness on the outlet side of rolling.

48. 发明专利

JP2004010971A METHOD FOR PRODUCING STEEL SHEET HAVING EXCELLENT STRENGTH AND TOUGHNESS AND SATISFACTORY FLATNESS AT HIGH EFFICIENCY 审中-公开
公开(公告)号：JP2004010971A
公开(公告)日：2004-01-15
申请号：JP2002166580
申请日：2002-06-07
申请人： NIPPON STEEL CORP
发明人： SHIRAHATA HIROYUKI , MINAGAWA MASANORI , HASEGAWA TOSHINAGA
IPC分类号： C21D8/02 , C22C38/00 , C22C38/06 , C22C38/58
摘要： PROBLEM TO BE SOLVED: To provide a method for efficiently producing a steel member which has excellent strength, toughness and flatness without requiring complicated hot rolling stage and heat treatment stage in which productivity is low. SOLUTION: A slab having prescribed components is heated to the temperature range of 1,100 to 1,300°C, is subjected to rough rolling at 950 to 1,100°C at a cumulative draft of ≥50%, and is subjected to finish rolling so as to satisfy prescribed conditions. The steel is thereafter cooled at a mean cooling rate of 2 to 30°C/s in a sheet thickness direction till the surface temperature reaches the range of Ar3-120°C to Ar3-200°C, and is recuperated till the temperature reaches the range of Ar3 to Ar3+100°C. The steel is successively cooled at a mean cooling rate of 2 to 30°C/s in a sheet thickness direction by ≥40°C in a temperature difference, and the cooling is completed at a temperature of Ar3-200°C or higher. COPYRIGHT: (C)2004,JPO

49. 发明专利

JP2003239036A THICK STEEL PLATE HAVING EXCELLENT FATIGUE STRENGTH AND PRODUCTION METHOD THEREFOR 审中-公开
公开(公告)号：JP2003239036A
公开(公告)日：2003-08-27
申请号：JP2002041389
申请日：2002-02-19
申请人： NIPPON STEEL CORP
发明人： HASEGAWA TOSHINAGA , MINAGAWA MASANORI , SHIRAHATA HIROYUKI
IPC分类号： C21D8/02 , C22C38/00 , C22C38/06 , C22C38/58
摘要： PROBLEM TO BE SOLVED: To obtain a thick steel plate for a welded structure which has excellent fatigue crack propagation resistance of a base material without depending on the addition of a large quantity of special or expensive alloy elements, or depending on a production method which is inferior in productivity or is complicated, or without the placement of large restrictions on tensile strength and steel plate thickness. SOLUTION: In the thick steel plate having a composition containing proper amounts of C, Si, Mn, Al and N, and, if required, containing Ni, Cu, Cr, Mo, W, Ti, V, Nb, Zr, Ta, B, Mg, Ca and rare earth metals, and having a structure consisting of ferrite and a hard secondary phase consisting of bainite or martensite or a mixed structure of both, by making the hard secondary phase in the cross-section parallel to the surface of the steel plate satisfy all conditions of a fraction of 20 to 80%, a mean Vickers hardness of 250 to 800, a diameter of the equivalent circle of 10 to 200 μm, and the maximum spacing between the hard secondary phases of ≤500 μm, the fatigue crack propagation of the base material is remarkably delayed, so that the fatigue strength of a joint is improved. COPYRIGHT: (C)2003,JPO

50. 发明专利

JP2001342520A METHOD FOR MANUFACTURING HIGH TENSION STEEL OF LOW YIELD RATIO AND SUPERIOR TOUGHNESS WITH LITTLE FLUCTUATION OF MATERIAL PROPERTY 失效
公开(公告)号：JP2001342520A
公开(公告)日：2001-12-14
申请号：JP2000165912
申请日：2000-06-02
申请人： NIPPON STEEL CORP
发明人： HASEGAWA TOSHINAGA , MINAGAWA MASANORI , SHIRAHATA HIROYUKI
IPC分类号： C21D8/02 , C22C38/00 , C22C38/06 , C22C38/58
摘要： PROBLEM TO BE SOLVED: To manufacture a steel plate with reduced fluctuation of material properties by DLT treatment and a low yield ratio characteristic. SOLUTION: A method for manufacturing a high tension steel of low yield ratio and superior toughness with a little fluctuation of material properties includes; heating a piece of steel with a particular component at Ac3 transformation temperature to 1300 deg.C; hot rolling which includes hot rolling at a starting temperature of 950 deg.C or less and a finishing temperature of 800 deg.C or more, and with an accumulated rolling reduction of 30-90%, and hot rolling at a starting temperature of 750 deg.C or less and a finishing temperature of 650 deg.C or more, and with an accumulated rolling reduction of 10-50%; and then starting an accelerated cooling at a cooling velocity of 1-100 deg.C/s from 700 deg.C or less, and stopping it at 500 deg.C or less.

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