With Working Patents (Class 148/602)
  • Patent number: 6589369
    Abstract: A compound structure steel sheet excellent in burring workability made of a steel containing, by mass, 0.01 to 0.3% of C, 0.01 to 2% of Si, 0.05 to 3% of Mn, 0.1% or less of P, 0.01% or less of S, and 0.005 to 1% or Al, and having the microstructure being a compound structure having ferrite as the main phase and martensite or retained austenite mainly as the second phase, the quotient of the volume percentage of the second phase divided by the average grain size of the second phase being 3 or more and 12 or less, and the quotient of the average hardness of the second phase divided by the average hardness of the ferrite being 1.5 or more and 7 or less; or a compound structure steel sheet excellent in burring workability made of a steel containing, by mass, 0.01 to 0.3% of C, 0.01 to 2% of Si, 0.05 to 3% of Mn, 0.1% or less of P, 0.01% or less of S, and 0.
    Type: Grant
    Filed: July 25, 2001
    Date of Patent: July 8, 2003
    Assignee: Nippon Steel Corporation
    Inventors: Tatsuo Yokoi, Manabu Takahashi, Hiroyuki Okada, Toshimitsu Aso
  • Publication number: 20030121576
    Abstract: The present invention relates to a steel sheet that consists essentially of 0.10 to 0.37% C, 1% or less Si, 2.5% or less Mn, 0.1% or less P, 0.03% or less S, 0.01 to 0.1% sol.Al, 0.0005 to 0.0050% N, 0.0003 to 0.0050% B, by mass, and balance of Fe, [14B/(10.8N)] being 0.5 or more, average particle size of precipitate BN being 0.1 &mgr;m or more, and grain size of prior austenite after the hardening treatment being 2 to 25 &mgr;m. The steel sheet according to the present invention allows an inexpensive hardening treatment method to be applied to improve the strength to a level required for the structural components and the functional components of automobiles, while providing excellent toughness after the hardening treatment.
    Type: Application
    Filed: September 26, 2002
    Publication date: July 3, 2003
    Applicant: NKK CORPORATION
    Inventors: Takeshi Fujita, Kenichi Mitsuzuka, Nobuyuki Nakamura, Toshiaki Urabe, Katsutoshi Ito, Hideyuki Tsurumaru
  • Patent number: 6586117
    Abstract: A steel for forming a high strength steel sheet contains, in mass %, C: at most 0.04%, Si: at most 0.4%, Mn: 0.5-3.0%, P: at most 0.15%, S: at most 0.03%, Al: at most 0.50%, N: at most 0.01%, and Mo: 0.01-1.0%. Steel sheet formed from the steel is suitable for use as automotive panels.
    Type: Grant
    Filed: October 19, 2001
    Date of Patent: July 1, 2003
    Assignee: Sumitomo Metal Industries, Ltd.
    Inventors: Shigeki Nomura, Hiroyuki Nakagawa, Yoshiaki Nakazawa
  • Patent number: 6554918
    Abstract: A high-strength hot-rolled steel sheet superior in stretch flange formability which comprises C (0.01-0.10 mass %), Si (no more than 1.0 mass %), Mn (no more than 2.5 mass %), P (no more than 0.08 mass %), S (no more than 0.005 mass %), Al (0.015-0.050 mass %), and Ti (0.10-0.30 mass %), with the remainder being substantially Fe, said hot-rolled steel sheet having a structure composed mainly of ferrite in which the unit grain is surrounded by grains such that adjacent grains differ in orientation more than 15°, the unit grain having an average particle diameter (d) no larger than 5 &mgr;m. This steel sheet is produced by the steps of heating, rolling, cooling, and coiling under the following conditions. Heating temperature: 1150-1300° C.; reduction in rolling at 900-840° C.: no less than 70%; cooling rate: no less than 60° C./s; and coiling temperature: 300-500° C. or 600-750° C.
    Type: Grant
    Filed: July 23, 2001
    Date of Patent: April 29, 2003
    Assignee: Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.)
    Inventors: Takahiro Kashima, Shunichi Hashimoto
  • Patent number: 6544354
    Abstract: The object of the present invention is to provide high-strength steel sheets exhibiting high impact energy absorption properties, as steel sheets to be used for shaping and working into such parts to front side members which absorb impact energy upon collision, as well as a method for their production.
    Type: Grant
    Filed: July 28, 1999
    Date of Patent: April 8, 2003
    Assignee: Nippon Steel Corporation
    Inventors: Osamu Kawano, Junichi Wakita, Yuzo Takahashi, Hidesato Mabuchi, Manabu Takahashi, Akihiro Uenishi, Yukihisa Kuriyama, Riki Okamoto, Yasuharu Sakuma
  • Publication number: 20030063996
    Abstract: The present invention relates to a high strength hot rolled steel sheet containing 0.15% or less C, 0.02 to 0.35% Ti, and 0.05 to 0.7% Mo by weight percentage and consisting essentially of a matrix of ferrite structure single phase and fine precipitates with a grain size of smaller than 10 nm dispersed in the matrix, for example, a high strength hot rolled steel sheet which consists essentially of 0.06% or less C, 0.5% or less Si, 0.5 to 2.0% Mn, 0.06% or less P, 0.005% or less S, 0.1% or less Al, 0.006% or less N, 0.02 to 0.10% Ti, 0.05 to 0.6% Mo by weight percentage, and the balance being Fe, wherein fine precipitates with a grain size of smaller than 10 nm are dispersed in a matrix of ferrite structure single phase at a number per unit volume of 5×104/&mgr;m3 or higher. This steel sheet, which has tensile strength of not lower than 550 MPa, high elongation and excellent stretch flangeability, is suitable for intricately shaped automotive chassis parts such as a suspension arm.
    Type: Application
    Filed: March 28, 2002
    Publication date: April 3, 2003
    Applicant: NKK CORPORATION
    Inventors: Yoshimasa Funakawa, Tsuyoshi Shiozaki, Kunikazu Tomita, Takanobu Saito, Hiroshi Nakata, Kaoru Sato, Minoru Suwa, Tetsuo Yawamoto, Yasuhiro Murao, Eiji Maeda
  • Patent number: 6540846
    Abstract: Disclosed herein is a high-strength hot-rolled steel sheet superior in stretch-flanging properties and fatigue properties which comprises (in mass %) 0.01-0.10% C, less than 2% Si (including 0%), 0.5-2% Mn, less than 0.08% P (including 0%), less than 0.01% S (including 0%), less than 0.01% N (including 0%), 0.01-0.1% Al, and at least one of 0.1-0.5% Ti and less than 0.8% Nb (including 0%), with the granular bainitic structure accounting for more than 80% (by area) in its sectional metallographic structure. Disclosed also herein is a process for producing said steel sheet.
    Type: Grant
    Filed: February 27, 2001
    Date of Patent: April 1, 2003
    Assignee: Kabushiki Kaisha Kobe Seiko Sho
    Inventors: Takahiro Kashima, Shunichi Hashimoto
  • Patent number: 6537394
    Abstract: A hot-dip galvanized high-strength steel sheet having superior workability and galvanizability containing: 0.01% to 0.20% by weight of C; 1.0% by weight or less of Si; more than 1.5% to 3.0% by weight of Mn; 0.10% by weight or less of P; 0.05% by weight or less of S; 0.10% by weight or less of Al; 0.010% by weight or less of N; 0.010% to 1.0% by weight in total of at least one element selected from the group consisting of Ti, Nb, and V; and the balance being Fe and incidental impurities; in which the steel sheet has the metal structure in which the areal rate of the ferrite phase is 50% or more, the ferrite phase has an average grain diameter of 10 &mgr;m or less, and the thickness of a band-like structure composed of the second phase satisfies the relationship Tb/T≦0.005, where Tb is the average thickness in the sheet thickness direction of the band-like structure and T is the thickness of the steel sheet, and a method for producing the same.
    Type: Grant
    Filed: June 21, 2001
    Date of Patent: March 25, 2003
    Assignee: Kawasaki Steel Corporation
    Inventors: Kazunori Osawa, Kei Sakata, Osamu Furukimi, Yoshitsugu Suzuki, Akio Shinohara
  • Patent number: 6533876
    Abstract: Process for producing a steel strip or sheet, in which liquid steel is cast in a continuous-casting machine to form a thin plate and, while making use of the casting heat, is fed through a furnace device, is roughed in a roughing stand to a pass-over thickness and is rerolled in a finishing rolling stand to form a steel strip or sheet of the desired final thickness, in which (a) to produce a ferritically rolled steel strip, the strip, the plate or a part thereof is fed without interruption at least from the furnace device, at speeds which essentially correspond to the speed of entry into the roughing stand and the following reductions in thickness, from the roughing stand to a processing device which is disposed downstream of the finishing rolling stand, the strip coming out of the roughing stand being cooled to a temperature at which the steel has an essentially ferritic structure; (b) to produce an austenitically rolled steel strip, the strip coming out of the roughing roll is brought to or held at a temper
    Type: Grant
    Filed: September 3, 1999
    Date of Patent: March 18, 2003
    Assignee: Corus Staal
    Inventors: Marcus Cornelis Maria Cornelissen, Aldricus Maria Groot, Huibert Willem Den Hartog
  • Publication number: 20030041932
    Abstract: The present invention provides a high tensile strength hot-rolled steel sheet having superior strain aging hardenability, which has high formability and stable quality characteristics, and in which satisfactory strength is obtained when the steel sheet is formed into automotive components, thus enabling the reduction in weight of automobile bodies. Specifically, a method for producing a high tensile strength hot-rolled steel sheet having superior strain aging hardenability with a BH of 80 MPa or more, a &Dgr;TS of 40 MPa or more, and a tensile strength of 440 MPa or more includes the steps of heating a steel slab to 1,000° C. or more, the steel slab containing, in percent by mass, 0.15% or less of C, 2.0% or less of Si, 3.0% or less of Mn, 0.08% or less of P, 0.02% or less of S, 0.02% or less of Al, 0.0050% to 0.0250% of N, and optionally 0.1% or less in total of at least one of more than 0.02% to 0.1% of Nb and more than 0.02% to 0.1% of V, the ratio N (mass %)/Al (mass %) being 0.
    Type: Application
    Filed: October 2, 2001
    Publication date: March 6, 2003
    Inventors: Akio Tosaka, Sinjiro Kaneko, Yoichi Tominaga, Noriyuki Katayama, Nobutaka Kurosawa, Kei Sakata, Osamu Furukimi
  • Patent number: 6527882
    Abstract: A method and an installation for the endless production of hot-rolled, flat products from thin cast strip. The installation includes a casting machine for producing cast strip, a device for cooling the cast strip under inert gas, a single-stand roughing train, a multi-stand finishing train, a device for cooling, heating or maintaining the temperature of the hot-rolled strip, according to choice, between the roughing train and the finishing train, shears for separating the hot-rolled strip from coil to coil, a delivery roller table with devices for cooling the hot-rolled strip and with coiling machines arranged downstream of the finishing train for coiling up the finished strip.
    Type: Grant
    Filed: August 15, 2000
    Date of Patent: March 4, 2003
    Assignees: SMS Demag AG, Salzgitter AG
    Inventors: Harald Wehage, Ulrich Skoda-Dopp, Horst Jacobi
  • Publication number: 20030034593
    Abstract: The present invention provides an effective method for mechanically removing iron oxide films formed on surfaces of a hot rolled steel strip with a high temperature.
    Type: Application
    Filed: August 26, 2002
    Publication date: February 20, 2003
    Inventor: Jae-Kon Lee
  • Publication number: 20030019550
    Abstract: A method is provided for producing medium carbon steel sheet and strip with enhanced uniform elongation for deep drawing applications. In one embodiment, a steel slab containing carbon 0.30/0.70%, manganese 0.75/2.0%, silicon up to 1.0% max., total aluminum 0.020/0.10%, the balance iron and incidental impurities is hot rolled to strip at a finishing temperature within the range of 839° C. (1542° F.) to 773° C. (1424° F.) and spheroidize annealed at a temperature below the A1 temperature. In a second embodiment, a steel slab containing 0.40 minimum/0.70% maximum carbon, 0.50/1.50% manganese, up to 1.0% silicon, 0.020/0.10% total aluminum, the balance iron and incidental impurities is hot rolled, cold rolled and spheroidize annealed, with various combinations of manganese and silicon within the above ranges providing lower yield strength at levels of 60 ksi, 70 ksi, and 80 ksi with minimum 14% uniform elongation.
    Type: Application
    Filed: August 16, 2002
    Publication date: January 30, 2003
    Inventors: Craig O. Hlady, Todd M. Osman
  • Publication number: 20020179206
    Abstract: The present invention relates to a very low C-Nb cold rolled steel sheet giving 340 to 440 MPa of tensile strength. For example, the cold rolled steel sheet consists essentially of 0.0040 to 0.01% C, not more than 0.05% Si, 0.1 to 1.0% Mn, 0.01 to 0.05% P, not more than 0.02% S, 0.01 to 0.1% sol.Al, not more than 0.004% N, 0.01 to 0.14% Nb, by weight, and balance of substantially Fe and inevitable impurities, and has not less than 0.21 of n value calculated from two points (1% and 10%) of nominal strain determined by the uniaxial tensile test, and relates to a method for manufacturing the cold rolled steel sheet. The present invention provides a high strength cold rolled steel sheet for automobile exterior panels having excellent combined formability, resistance to embrittlement during secondary operation, formability at welded portions, anti-burring performance, good surface appearance, and uniformity of material in a coil.
    Type: Application
    Filed: April 15, 2002
    Publication date: December 5, 2002
    Applicant: NKK CORPORATION
    Inventors: Takeshi Fujita, Fusato Kitano, Yoshihiro Hosoya, Toru Inazumi, Yuji Yamasaki, Masaya Morita, Yasunobu Nagataki, Kohei Hasegawa, Hiroshi Matsuda, Moriaki Ono
  • Patent number: 6488790
    Abstract: A method of making a high-strength low-alloy (HSLA) hot rolled steel. A high-strength low-alloy steel is made by hot rolling a steel slab of a specified composition. The hot rolling step is carried out at an austenitic hot roll finishing temperature. The hot rolled steel is coiled at a temperature ranging from 1120° F. to 1180° F. The steel is characterized by a yield strength of at least 110 ksi. The steel may be further characterized by a ferrite-bainite microstructure.
    Type: Grant
    Filed: January 22, 2001
    Date of Patent: December 3, 2002
    Assignee: International Steel Group Inc.
    Inventors: John E. Hartmann, R. Devesh K. Misra, A. John Boucek
  • Publication number: 20020162613
    Abstract: Disclosed herein is a high-strength hot-rolled steel sheet superior in stretch-flanging properties and fatigue properties which comprises (in mass %) 0.01-0.10% C, less than 2% Si (including 0%), 0.5-2% Mn, less than 0.08% P (including 0%), less than 0.01% S (including 0%), less than 0.01% N (including 0%), 0.01-0.1% Al, and at least one of 0.1-0.5% Ti and less than 0.8% Nb (including 0%), with the granular bainitic structure accounting for more than 80% (by area) in its sectional metallographic structure. Disclosed also herein is a process for producing said steel sheet.
    Type: Application
    Filed: February 27, 2001
    Publication date: November 7, 2002
    Applicant: Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.)
    Inventors: Takahiro Kashima, Shunichi Hashimoto
  • Patent number: 6475308
    Abstract: Process for the production of a hot rolled metal strip of very high strength, usable for shaping and particularly for stamping, characterized in that a steel of the following weight composition: carbon, 0.12-0.25%; manganese, 1-2%; aluminum, 0.03-2.5%; silicon, 0.03-2%; chromium, 0.04-2%; phosphorus, 0.02-0.09%; sulfur optionally up to 0.01%; titanium up to 0.15%; niobium up to 0.15%; vanadium up to 0.15%; is subjected to: rolling at a temperature below 880° C.; a first short cooling, carried out over a time less than 10 seconds, a second controlled cooling with a cooling speed V ref1 comprised between 20° C./sec. and 150° C./sec., the temperature at the end of the second cooling being comprised between 700° C. and 750° C., holding at a temperature level, a third cooling, also controlled, whose speed is comprised between 20° C./sec. and 150° C./sec., the temperature at the end of the third cooling being comprised between 350° C and 550° C.
    Type: Grant
    Filed: November 13, 2000
    Date of Patent: November 5, 2002
    Assignee: Unisor
    Inventors: Christophe Issartel, Christian Marteau, Christian Giraud
  • Patent number: 6410163
    Abstract: The present invention provides a high strength thin excellent workability and galvanizability, having a composition comprising from 0.01 to 0.20 wt. % C, up to 1.0 wt. % Si, from 1.0 to 3.0 wt. % Mn, up to 0.10 wt. % P, up to 0.05 wt. % S, up to 0.10 wt. % Al, up to 0.010 wt. % N, up to 1.0 wt. % Cr, from 0.001 to 1.00 wt. % Mo, and the balance Fe and incidental impurities, wherein a band structure comprising a secondary phase has a thickness satisfying the relation Tb/T≦0.005 (where, Tb: average thickness of the band structure in the thickness direction of steel sheet; T: steel sheet thickness), and a manufacturing method thereof, and a manufacturing method of a high strength hot-dip galvanized steel sheet or a high strength galvannealed steel sheet applying hot-dip galvanizing or further galvannealing, and giving an excellent workability, a high tensile strength, and excellent galvanizability, coating adhesion and corrosion resistance.
    Type: Grant
    Filed: May 30, 2000
    Date of Patent: June 25, 2002
    Assignee: Kawasaki Steel Corporation
    Inventors: Yoshitsugu Suzuki, Kazunori Osawa, Chiaki Kato, Yoichi Tobiyama, Kei Sakata, Osamu Furukimi, Akio Shinohara
  • Patent number: 6395108
    Abstract: A flat product made of multiphase steel and a method for preparing the steel includes hot rolling at a temperature at which the austenite phase is stable, then tempering to form a C and Mn-enriched phase in a matrix, followed by a heat treatment to form austenite islands and/or enriching in Mn the already formed austenite and cooling down to room temperature so as to obtain a final product with a ferrite matrix containing residual austenite, bainite and/or martensite islands.
    Type: Grant
    Filed: April 30, 2001
    Date of Patent: May 28, 2002
    Assignee: Recherche et Developpement du Groupe Cockerill Sambre
    Inventors: Klaus Eberle, Philippe Harlet, Pierre Cantinieaux
  • Patent number: 6391126
    Abstract: In order to provide a cost-effective, time saving method for producing aging-resistant strip consisting of aluminum-killed steel, for which, initially, a strip is produced in the usual manner by rolling and the rolled strip is annealed continuously, the still hot strip is wound into a coil and cooled to room temperature, the strip, cooled in the coil, being finally finished.
    Type: Grant
    Filed: September 28, 2000
    Date of Patent: May 21, 2002
    Assignee: Thyssen Krupp Stahl AG
    Inventors: Bernhard Engl, Klaus-Dieter Horn
  • Patent number: 6364968
    Abstract: The invention provides a thin high-strength hot-rolled steel sheet with a thickness of not more than 3.5 mm which has excellent stretch flangeability and high uniformity in both shape and mechanical properties of the steel sheet, as well as a method of producing the hot-rolled steel sheet. A slab containing C: 0.05-0.30 wt %, Si: 0.03-1.0 wt %, Mn: 1.5-3.5 wt %, P: not more than 0.02 wt %, S: not more than 0.005 wt %, Al: not more than 0.150 wt %, N: not more than 0.0200 wt %, and one or two of Nb: 0.003-0.20 wt % and Ti: 0.005-0.20 wt % is heated at a temperature of not higher than 1200° C. The slab is hot-rolled at a finish rolling end temperature of not lower than 800° C., preferably at a finish rolling start temperature of 950-1050° C. A hot-rolled sheet is started to be cooled within two seconds after the end of the rolling, and then continuously cooled down to a coiling temperature at a cooling rate of 20-150° C./sec. The hot-rolled sheet is coiled at a temperature of 300-550° C.
    Type: Grant
    Filed: June 2, 2000
    Date of Patent: April 2, 2002
    Assignee: Kawasaki Steel Corporation
    Inventors: Eiko Yasuhara, Akio Tosaka, Osamu Furukimi, Takao Uchiyama, Nobuo Yamada
  • Publication number: 20020036035
    Abstract: A high-strength hot-rolled steel sheet superior in stretch flange formability which comprises C (0.01-0.10 mass %), Si (no more than 1.0 mass %), Mn (no more than 2.5 mass %), P (no more than 0.08 mass %), S (no more than 0.005 mass %), Al (0.015-0.050 mass %), and Ti (0.10-0.30 mass %), with the remainder being substantially Fe, said hot-rolled steel sheet having a structure composed mainly of ferrite in which the unit grain is surrounded by grains such that adjacent grains differ in orientation more than 15°, said unit grain having an average particle diameter (d) no larger than 5 &mgr;m. This steel sheet is produced by the steps of heating, rolling, cooling, and coiling under the following conditions. Heating temperature: 1150-1300° C.; reduction in rolling at 900-840° C.: no less than 70%; cooling rate: no less than 60° C./s; and coiling temperature: 300-500° C. or 600-750° C.
    Type: Application
    Filed: July 23, 2001
    Publication date: March 28, 2002
    Applicant: Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.)
    Inventors: Takahiro Kashima, Shunichi Hashimoto
  • Publication number: 20020029828
    Abstract: A high tensile strength hot-rolled steel sheet comprises 0.04 to 0.09% C, 0.1% or less Si, 0.5 to 1.5% Mn, 0.02% or less P, 0.01% or less S, 0.1% or less Al, 0.001 to 0.008% N, and 0.01 to 0.
    Type: Application
    Filed: May 24, 2001
    Publication date: March 14, 2002
    Applicant: NKK CORPORATION
    Inventors: Hiroshi Nakata, Tadashi Inoue, Hiroyasu Kikuchi, Sadanori Imada, Akira Hiura, Takeshi Nakahara, Satoshi Ishijima, Yoshimasa Funakawa, Toru Inazumi
  • Publication number: 20020007882
    Abstract: The method for manufacturing steel sheet comprises the steps of: forming a sheet bar; forming a steel strip; primary-cooling; air-cooling; secondary-cooling; and coiling. The sheet bar is finish-rolled at finish temperatures of (Ar3 transformation point−20° C.) or more. The primary cooling cools the finish-rolled steel strip at cooling speeds of more than 120° C./sec down to the temperatures ranging from 500 to 800° C.
    Type: Application
    Filed: April 19, 2001
    Publication date: January 24, 2002
    Applicant: NKK CORPORATION
    Inventors: Tadashi Inoue, Yoichi Motoyashiki, Hiroyasu Kikuchi, Yoshimasa Funakawa, Hiroshi Nakata, Sadanori Imada, Toru Inazumi
  • Publication number: 20020000266
    Abstract: The present invention relates to a high strength steel sheet consisting essentially of 0.04 to 0.1% C, 0.5% or less Si, 0.5 to 2% Mn, 0.05% or less P, 0.005% or less 0, 0.005% or less S, by weight, having 10 &mgr;m or less of average ferritic grain size, and 20 mm/mm2 or less of generation frequency A, which generation frequency A is defined as the total length of a banded secondary phase structure observed per 1 mm2 of steel sheet cross section along the rolling direction thereof. The steel sheet is manufactured by, for example, a method comprising the steps of: hot-rolling a continuously cast slab having the composition described above at temperatures of Ar3 transformation point or above directly or after reheating thereof; and cooling the hot-rolled steel sheet within 2 seconds down to the temperatures of from 600 to 750° C. at cooling speeds of from 100 to 2,000° C. /sec, followed by coiling the cooled steel sheet at temperatures of from 450 to 650° C.
    Type: Application
    Filed: April 5, 2001
    Publication date: January 3, 2002
    Applicant: NKK CORPORATION
    Inventors: Tadashi Inoue, Yoichi Motoyashiki, Hiroyasu Kikuchi, Sadanori Imada, Takayuki Odake, Yasunobu Nagataki, Toru Inazumi
  • Patent number: 6328826
    Abstract: The invention provides a method of fabricating “TRIP” steel in the form of thin strip, wherein: a strip from 1.5 to 10 mm thick, preferably from 1 to 5 mm thick, is cast directly from liquid steel having the composition (in weight percent) C % from 0.05 to 0.25, (Mn+Cu+Ni) % from 0.5 to 3, (Si+Al) % from 0.1 to 4, (P+Sn+As+Sb) % not greater than 0.1, (Ti+Nb+V+Zr+rare earths) % less than 0.3, Cr % less than 1, Mo % less than 1, V % less than 1, the remainder being iron and manufacturing impurities; said strip is hot rolled on-line in one or more passes at a temperature higher than the Ar3 temperature of said steel and with a reduction ratio from 25 to 70%; first forced cooling of said strip is carried out at a cooling rate from 5 to 100° C./s; the strip remains at temperatures from 550 to 400° C.
    Type: Grant
    Filed: July 21, 2000
    Date of Patent: December 11, 2001
    Assignee: Usinor
    Inventors: Thierry Iung, Odile Faral, Michel Faral, Michel Babbit, Christophe Issartel
  • Patent number: 6309482
    Abstract: The in-line combination of a reversing rolling mill (Steckel mill) and its coiler furnaces with accelerated controlled cooling apparatus immediately downstream thereof and associated method permits steel to be sequentially reversingly rolled to achieve an overall reduction of at least about 3:1, imparted by a first reduction while the steel is kept at a temperature above the Tnr by the coiler furnaces so as to preserve an optimum opportunity for controlled recrystallization of the steel after each rolling pass, and a second reduction while the temperature of the steel drops from about the Tnr to about the Ar3. The second reduction is preferably of the order of 2:1 as a result of which the steel reaches a final plate thickness.
    Type: Grant
    Filed: May 17, 2000
    Date of Patent: October 30, 2001
    Inventors: Jonathan Dorricott, William R. Frank
  • Patent number: 6284069
    Abstract: The invention relates to a process for producing strips of homogenous structures and characteristics made of non-alloyed and low-alloyed steel by continuous hot rolling in several roll passes in the austenitic region and subsequently in the ferritic region, as well as coiling. The invention is characterised in that continuous-cast strip and/or strip rough rolled in the austenitic region, starting with a temperature T≧Ar3+30° C., with a total degree of deformation of eh≧30% is rolled in two or several roll passes in the austenitic region and in that the rolling stock is intensively cooled after every roll pass until the ferritic transformation has been completed, after which the rolling stock is end rolled to final thickness in the ferritic range in several passes with a total degree of deformation eh≧60%.
    Type: Grant
    Filed: December 28, 1999
    Date of Patent: September 4, 2001
    Assignee: Thyssen Krupp Stahl AG
    Inventors: Hans Pircher, Manfred Espenhahn, Rudolf Kawalla, Waldemar Wolpert
  • Patent number: 6284063
    Abstract: The invention concerns hot-rolled steel strip no more than 5 mm thick, optionally less than 2 mm thick, made of high-tensile steel, that contains 0.08%-0.25% carbon, 1.20% to 2.0% manganese, and 0.02% to 0.05% aluminum, and optionally up to 1.0% chromium, up to 0.1% copper, up to 0.5% molybdenum, up to 0.1% nickel, up to 0.009% nitrogen, up to 0.0025% B, and optionally a stoichiometric amount of titanium in relation to nitrogen. The steel strip has a greater than 95% martensitic structure, and a tensile strength of 800 to 1400 N/mm2.
    Type: Grant
    Filed: February 25, 1999
    Date of Patent: September 4, 2001
    Assignee: Thyssen Stahl AG
    Inventors: Manfred Espenhahn, Thomas Heller, Jürgen Esdohr
  • Patent number: 6264769
    Abstract: Apparatus for the production and heat treatment of coiled elongated metal product of relatively small cross section, such as rods, bars and wire-rod material, is described. The elements required for the conduct of a variety of heat treatments can be performed on coiled product in a substantially continuous manner through the use of a ring conveyor with which the coilers of various process lines and a heat treating furnace communicate. Methods for performing various heat treatments using the described apparatus are also disclosed.
    Type: Grant
    Filed: May 21, 1999
    Date of Patent: July 24, 2001
    Assignee: Danieli Technology, Inc.
    Inventor: Gianpietro Benedetti
  • Patent number: 6264767
    Abstract: A steel rolling mill including a Steckel mill is provided with an in-line upstream quench station located downstream of the caster and upstream of the reheat furnace, a shear located downstream of the Steckel mill, and a temperature reduction station downstream of the shear. The upstream quench station has spray nozzles that quench a surface layer of the steel to transform same from an austentitic to a non-austentitic microstructure. The shear provides a precise transverse vertical face on the leading end of the steel. The temperature reduction station applies cooling fluid to the rolled steel so as to obtain a preferred microstructure that may be either bainite or martensite. If bainite, the temperature reduction station includes laminar-flow cooling apparatus; if martensite, the station also includes an initial rapid quench, in which latter case the station is followed by a tempering furnace.
    Type: Grant
    Filed: July 9, 1999
    Date of Patent: July 24, 2001
    Assignee: IPSCO Enterprises Inc.
    Inventors: William R. Frank, Jonathan Dorricott, Laurie E. Collins, Joseph Duane Russo, Robert Joseph Boecker, Brian H. Wales
  • Publication number: 20010007267
    Abstract: The invention is directed to a process for the production of hot-rolled steel strip from continuously cast precursor strip in at least two deformation stages, each deformation stage having one or more roll stands, wherein initial rolling is carried out in the first deformation stage at the output speed at which the precursor strip exits from the continuous casting plant and the intermediate strip thus produced is coiled prior to the second deformation stage at the output speed at which it exits from the first deformation stage, wherein the coil is uncoiled after reaching the coil weight and is supplied to the second deformation stage for finish rolling at the initial roll pass speed and is then coiled in the desired finished coil sizes.
    Type: Application
    Filed: December 4, 1998
    Publication date: July 12, 2001
    Inventors: JOACHIM SCHONBECK, HERBERT QAMBUSCH, HANS HOPPMANN
  • Patent number: 6258186
    Abstract: A method for manufacturing a hot rolled galvanized steel sheet at a high speed, with the pickling skipped, is disclosed, in which an intermediate rapid cooling is carried out at a predetermined temperature so as to make the wüstite component of the scales become 20% or more after a hot rolling, then a reducing heat-treatment is carried out, and then the steel sheet is dipped into a zinc bath containing a predetermined amount of Al, thereby realizing a superior coating adherence and a superior productivity. The hot rolled steel sheet is cooled at a usual cooling rate, and is coiled. Then an intermediate rapid cooling is carried out on the hot rolled steel sheet (thus coiled) to an intermediate rapid cooling temperature of 300-500° C. so as to make a wüstite component of scales become 20% or more. Then a reducing heat treatment is carried out at a temperature of 550-700° C. for 30-300 seconds under a 20% (or more) hydrogen atmosphere.
    Type: Grant
    Filed: December 28, 1999
    Date of Patent: July 10, 2001
    Assignee: Pohang Iron & Steel Co., Ltd.
    Inventor: Jin Won Choi
  • Patent number: 6231696
    Abstract: A method of manufacturing microalloyed structural steels by rolling in a CSP plant or compact strip production plant, wherein the cast slab strand is supplied divided into rolling lengths through an equalizing furnace to a multiple-stand CSP rolling train and is continuously rolled in the rolling train into hot-rolled wide strip, wherein the strip is cooled in a cooling section and is reeled into coils, and wherein, for achieving optimum mechanical properties, a controlled structure development by thermomechanical rolling is carried out as the thin slab travels through the CSP plant. For manufacturing high-strength microalloyed structural steels with a yield point of ≧480 MPa, the available strengthening mechanisms are utilized in a complex manner in order to achieve an optimum property complex with respect to strength and toughness of the structural steels, by carrying out, in addition to the thermomechanical rolling with the method steps according to U.S. patent application Ser. No. 09/095,338 filed Jun.
    Type: Grant
    Filed: March 25, 1999
    Date of Patent: May 15, 2001
    Assignee: SMS Schloemann-Siemag Aktiengesellschaft
    Inventors: Karl-Ernst Hensger, Robert F. Davis
  • Patent number: 6217679
    Abstract: The invention provides hot-rolled steel strips which, after having been acid-pickled, can be directly used. The strips have no Cr-decreasing layer and no shot blasted marks on their surface and have good corrosion resistance. The invention also provides a technique of efficiently producing the hot-rolled steel strips. A steel slab having a Cr content of from 6.0 to 25.0 wt. % is hot-rolled, then coiled at a temperature not higher than 700° C., then optionally quenched in water immediately after the coiling, then annealing in a reducing atmosphere, and thereafter acid-pickled in a solution of nitric acid/hydrochloric acid.
    Type: Grant
    Filed: November 23, 1998
    Date of Patent: April 17, 2001
    Assignee: Kawasaki Steel Corporation
    Inventors: Masaaki Kohno, Kunio Fukuda, Kazuhide Ishii, Susumu Satoh, Hiroshi Yaginuma, Takumi Ujiro
  • Patent number: 6210501
    Abstract: When a hot-rolled steel strip 1 is rolled at a large rolling reduction by a cold-rolling mill 4, cracking and interlayer peeling occur in those mill-scales which can not keep up with the elongation of base steel so as to weaken the adhesiveness of the mill-scales to the base steel. When such a steel strip is then brushed, the threads of the brush penetrate into the cracks formed in the scale layer, whereby the mill-scales are removed from the steel strip. The rolling reduction R (%) is set to satisfy the formula of t×R≧150 in relation with the thickness t (&mgr;m) of the mill-scales. The mill-scales weakened in adhesiveness by the heavy-duty rolling are removed from the surface of the steep strip 1 by brush rolls 5 provided in the pass of the steel strip 1 between the cold-rolling mill 4 and the bridle rolls 5.
    Type: Grant
    Filed: August 21, 1997
    Date of Patent: April 3, 2001
    Assignee: Nisshin Steel Co., Ltd.
    Inventors: Tetsuhiko Okano, Toshinori Miki, Masaki Otsuka, Junya Hayakawa
  • Patent number: 6190469
    Abstract: A method for producing a high strength hot-rolled steel sheet with good formability applicable to automobiles, industrial machines and the like is disclosed. The basic composition of TRIP steel is adjusted wherein Cu is added to improve the strength by precipitation hardening of a fine &egr;—Cu. Other conditions are controlled to obtain a tensile strength of over 90 kg/mm2 with good formability. The steel is composed of 0.15-0.3% by weight of C, 1.5-2.5% by weight of Si, 0.6-1.8% by weight of Mn, 0.02-0.10% by weight of Al, 0.6-2.0% by weight of Cu, 0.6-2.0% by weight of Ni, the balance being Fe and inevitable impurities and has a microstructure of multi-phase structure consisting of ferrite, bainite, and retained austenite, or a granular structure (M-A constituents in bainitic ferrite matrix). The steel is finish rolled at a temperature of 750-880° C., water cooled from a water cooling initiation temperature of 680-740° C.
    Type: Grant
    Filed: July 1, 1998
    Date of Patent: February 20, 2001
    Assignee: Pohang Iron & Steel Co., Ltd.
    Inventors: Hyang Jin Koh, Nack Joon Kim, Sung Ho Park
  • Patent number: 6106638
    Abstract: The subject of the invention is a process for manufacturing ferritic stainless steel strip, in which a strip of a ferritic stainless steel, of the type containing at most 0.12% of carbon, at most 1% of manganese, at most 1% of silicon, at most 0.040% of phosphorus, at most 0.030% of sulfur and between 16 and 18% of chromium, is solidified, directly from liquid metal, between two close-together, internally-cooled, counterrotating rolls with horizontal axes, wherein said strip is then cooled or left to cool so as to avoid making it remain within the austenite to ferrite and carbides transformation range, wherein said strip is coiled at a temperature of between 600.degree. C. and the martensitic transformation temperature Ms, wherein the coiled strip is left to cool at a maximum rate of 300.degree. C./h down to a temperature of between 200.degree. C. and ambient temperature and wherein said strip then undergoes box annealing.
    Type: Grant
    Filed: May 11, 1998
    Date of Patent: August 22, 2000
    Assignee: Usinor
    Inventors: Philippe Paradis, Philippe Martin
  • Patent number: 6099665
    Abstract: This invention aims at producing a cold rolled thin sheet having excellent surface quality from a cast strip of a Cr--Ni type stainless steel cast strip by a thin casting method. The production method of the invention comprises the steps of continuously casting a Cr--Ni type stainless steel to a cast strip having a thickness of not greater than 10 mm by using a continuous casting machine the cast mold wall surface of which moves in synchronism with the cast strip; hot rolling the resulting cast strip at a temperature within the range of 900 to 1,200.degree. C. at a reduction ratio of 10 to 50%; carrying out, subsequently, heat-treatment at a temperature within the range of 1,200 to 900.degree. C. for at least 5 seconds; coiling the hot rolled cast strip at a temperature not higher than 600.degree. C.; descaling the rolled cast strip; cold rolling the cast strip; conducting annealing, pickling or bright annealing; and conducting skin pass rolling, whenever necessary.
    Type: Grant
    Filed: October 10, 1996
    Date of Patent: August 8, 2000
    Assignee: Nippon Steel Corporation
    Inventors: Shin-ichi Teraoka, Toshiyuki Suehiro, Eiichiro Ishimaru, Tetsurou Takeshita, Shunji Shoda, Takashi Arai, Hideki Oka, Yoshikatsu Nohara
  • Patent number: 6096146
    Abstract: Method for heat treating rolled stock leaving a rolling train (12), wherein the rolled stock (13) undergoes a rapid cooling treatment in a rapid cooling assembly (11) located immediately downstream of the last rolling pass, the first cooling step being followed by a temperature-equalisation step in air and at least by a second cooling treatment before being discharged and collected, the temperature-equalisation step in air and the at least second cooling treatment being set so as not to modify the surface and inner crystalline structure of the rolled stock (13) which has formed at the outlet of the first cooling treatment, the at least second cooling treatment being followed by a short segment of temperature-equalisation in air and then directly by the collection of the rolled stock (13) into compact form, such as rolls coils bundles or packs, wherein the slow cooling of the rolled stock (13) collected in compact form leads to the transformation of the crystalline structure in the stable structures.
    Type: Grant
    Filed: June 4, 1998
    Date of Patent: August 1, 2000
    Assignee: Danieli & C. Officine Meccanichi SpA
    Inventors: Alfredo Poloni, Matteo Bellina, Giuseppe Bordignon, Massimo Lestani
  • Patent number: 6063214
    Abstract: A method of producing a steel sheet useful for making cans. The method steps include hot-rolling a slab consisting of about 0.0005 to 0.01 wt % C, about 0.001 to 0.04 wt % N (the total of C and N is at least about 0.008 wt %), about 0.05 to 2.0 wt % Mn, about 0.005 wt % or less Al, about 0.01 wt % or less O at a finish rolling temperature within a temperature range of about the Ar.sub.3 point to about 950.degree. C., coiling the rolled material at a temperature range of about 400 to 600.degree. C., cold rolling the material, continuously annealing the material at a temperature higher than the recrystallization temperature, and then temper-rolling the material. The steel sheet exhibits good workability during can making and which can be formed into a can having high strength.
    Type: Grant
    Filed: August 8, 1994
    Date of Patent: May 16, 2000
    Assignee: Kawasaki Steel Corporation
    Inventors: Chikako Fujinaga, Akio Tosaka, Toshiyuki Kato, Kaku Sato, Hideo Kuguminato, Yoshihiro Okawa
  • Patent number: 6053996
    Abstract: A method for the manufacture of a strip of formable steel comprises the steps of (i) forming liquid steel by continuous casting into a slab having a thickness of not more than 100 mm, (ii) rolling the slab in the austenitic region into an intermediate slab having a thickness in the range 5 to 20 mm, (iii) cooling the intermediate slab to below the Ar.sub.3 temperature, (iv) holding the intermediate slab in an enclosure for temperature homogenisation, (v) rolling the intermediate slab into strip, with at least one rolling pass applying a thickness reduction of more than 50%, at a temperature below T.sub.t and above 200.degree. C., wherein T.sub.t is the temperature at which 75% of the steel is converted into ferrite, and (vi) coiling said strip at a temperature above 500.degree. C. Advantages of simplicity of the method and the plant required for it are obtained.
    Type: Grant
    Filed: April 15, 1998
    Date of Patent: April 25, 2000
    Assignee: Hoogovens Staal BV
    Inventors: Cornelis Pronk, Huibert Willem Den Hartog, Marcus Cornelis Maria Cornelissen
  • Patent number: 6030714
    Abstract: A zinc and zinc-alloy hot-dip-coated steel sheet and an alloyed zinc and zinc-alloy hot-dip-coated steel sheet, and a method for manufacturing these steel sheets, which steel sheets are used for automobiles. A zinc and zinc-alloy hot-dip-coated steel sheet which has oxides of readily oxidizable elements just under a coated layer and which shows a decreased number of bare spots and excellent coating adhesion. According to the method, the temperature for coiling during hot rolling is set to not less than 600.degree. C. and the cooling is conducted at a slow-cooling rate so that the-oxides remain after the following steps.
    Type: Grant
    Filed: September 12, 1997
    Date of Patent: February 29, 2000
    Assignee: Kawasaki Steel Corporation
    Inventors: Nobue Fujibayashi, Kazuaki Kyono, Motonori Miyaoka, Nobuo Totsuka
  • Patent number: 6030470
    Abstract: A method and a plant for rolling hot-rolled wide strip from continuously cast thin slabs of ferritic/pearlitic microalloyed structural steels with a microalloy with vanadium and/or with niobium and/or with titanium in a CSP plant or compact strip production plant, wherein the cast slab strand is supplied divided into rolling lengths through an equalizing furnace to a multiple-stand CSP rolling train and is continuously rolled in the CSP rolling train into hot-rolled wide strip, is then cooled in a cooling stretch and is reeled into coils. For achieving optimum mechanical properties in hot-rolled wide strip by thermomechanical rolling, a controlled structure development is carried out when the thin slabs travel through the CSP plant.
    Type: Grant
    Filed: June 10, 1998
    Date of Patent: February 29, 2000
    Assignee: SMS Schloemann-Siemag Aktiengesellschaft
    Inventors: Karl-Ernst Hensger, Robert Davis
  • Patent number: 5997664
    Abstract: Method for producing a galvannealed steel sheet wherein a slab consisting essentially of C in an amount of 0.004 wt. % or less, N in an amount of 0.004 wt. % or less, Ti in an amount of 0.01 to 0.15 wt %, Si in an amount of 0.05 wt. % or less, Mn in an amount up to 2.5 wt. %, P in an amount up to 0.1 wt. %, S in an amount of 0.015 wt. % or less, sol. Al in an amount of 0.02 to 0.1 wt. % and the balance being Fe, is soaked for at least 30 minutes at a specified temperature (range). The soaked slab is hot rolled to produce a hot-rolled steel sheet which is coiled at a temperature of 500 to 700.degree. C. The coiled hot-rolled steel sheet is cold rolled at a reduction ratio of 60% or more to produce a cold-rolled steel sheet which is annealed at a temperature of from recrystallization temperature to Ac3 transformation temperature. Galvanizing the annealed cold-rolled steel sheet and then galvannealing at a temperature of 450 to 600.degree. C.
    Type: Grant
    Filed: June 6, 1997
    Date of Patent: December 7, 1999
    Assignee: NKK Corporation
    Inventors: Kenji Tahara, Junichi Inagaki, Toyofumi Watanabe, Masaaki Yamashita
  • Patent number: 5948183
    Abstract: The present invention provides a hot-rolled steel sheet having a low yield ratio, a high specific strength, and excellent toughness. The hot-rolled steel sheet comprises: 0.005 to less than 0.030 weight percent of carbon, 1.5 weight percent or less of silicon, 1.5 weight percent or less of manganese, 0.020 weight percent or less of phosphorus, 0.015 weight percent or less of sulfur, 0.005 to 0.10 weight percent of aluminum, 0.0100 weight percent or less of nitrogen, 0.0002 to 0.0100 weight percent of boron, at least one element selected from the group consisting of 0.20 weight percent or less of titanium and 0.25 weight percent or less of niobium in an amount to satisfy (Ti+Nb/2)/C.gtoreq.4, and balance iron and incidental impurities. The metal structure is selected from the group consisting of ferrite and bainitic ferrite. The amount of carbon dissolved in grains ranges from 1.0 to 4.0 ppm. The present invention also provides a method for producing a hot-rolled steel sheet.
    Type: Grant
    Filed: October 8, 1997
    Date of Patent: September 7, 1999
    Assignee: Kawasaki Steel Corporation
    Inventors: Susumu Okada, Masahiko Morita, Fumimaru Kawabata
  • Patent number: 5922149
    Abstract: A method for making steel wires, wherein an elongate shaped wire is produced by rolling or drawing steel consisting of 0.05-0.5% C, 0.4-1.5% Mn, 0-2.5% Cr, 0.1-0.6% Si, 0-1% Mo, no more than 0.25% Ni, and no more than 0.02% S and P, and a first heat treatment is performed on the shaped wire, including at least one step of quenching under predetermined conditions to achieve an HRC hardness of at least 32, a predominately martensitic and bainitic steel structure and a small amount of ferrite. A shaped wire and a flexible tube for conveying an H.sub.2 S-containing effluent are disclosed.
    Type: Grant
    Filed: November 4, 1997
    Date of Patent: July 13, 1999
    Assignees: Institut Francais du Petrole, Coflexip
    Inventors: Jose Mallen Herrero, Fran.cedilla.ois Ropital, Andre Sugier
  • Patent number: 5863361
    Abstract: A method is provided for Steckel mill rolling and finishing flat rolled steel having uniform mechanical properties, good surface quality, and ease of flattening whether in coil form or discrete sheet or plate by hot rolling a heated transfer bar in a Steckel mill and reverse rolling and optional coiling to achieve finished flat rolled product of a selected thickness and selected austenite finishing temperature. The finished product is water cooled to a ferrite transformation temperature and thereafter air cooled until transformation from austenite to ferrite is at least 70% completed. The product may be further water cooled to a temperature below the ferrite transformation temperature.
    Type: Grant
    Filed: May 1, 1997
    Date of Patent: January 26, 1999
    Assignee: Pennock Corporation
    Inventor: John H. Bucher
  • Patent number: 5853503
    Abstract: After a starting material of steel comprising C: 0.001-0.20 wt %, Si: 0.01-0.50 wt %, Mn: 0.05-2.0 wt %, P: not more than 0.05 wt %, S: not more than 0.05 wt %, sol.Al: 0.01-0.10 wt %, N: not more than 0.020 wt % and the balance being Fe and inevitable impurities is heated above AC.sub.3 point, rough rolling is completed within a temperature range of (Ar.sub.3 point+100.degree. C.)-(Ar.sub.3 point+50.degree. C.), and super-high pressure descaling is carried out under conditions satisfying a jetting pressure of not less than 25 kgf/cm.sup.2 and a liquid quantity density of not less than 0.002 liter/cm.sup.2, and subsequently finish rolling at a rolling reduction of not less than 80% above Ar.sub.3 point of a rolling completion temperature is started in 5 seconds and coiling is carried out below 700.degree. C., whereby hot rolled steel sheets having a surface roughness Ra of not more than 0.8 .mu.m and an average scale thickness of not more than 4 .mu.
    Type: Grant
    Filed: April 28, 1997
    Date of Patent: December 29, 1998
    Assignee: Kawasaki Steel Corporation
    Inventors: Kazuhiro Seto, Kei Sakata, Osamu Furukimi, Takashi Obara
  • Patent number: 5849116
    Abstract: A steel material and a steel pipe each exhibiting an excellent corrosion resistance in an environment containing a wet carbon dioxide and a small amount of hydrogen sulfide are produced at low cost and with high productivity, a steel slab which contains, in wt %, 0.01 to 0.6% of Si, 0.02 to 1.8% of Mn, 7.5 to 14.0% of Cr, 1.5 to 4.0% of Cu and 0.005 to 0.1% of Al, which reduces C to not more than 0.02%, N to not more than 0.02%, P to not more than 0.025% and S to not more than 0.01%, and whose balance consists of Fe and unavoidable impurities, is heated to a temperature of 1,100.degree. to 1,300.degree. C., hot rolling is finished at a rolling finish temperature of not less than 800.degree. C. and a cumulative rolling reduction quantity at a temperature not more than 1,050.degree. C. is at least 65%, and cooling is carried out at a cooling rate of less than 0.02.degree. C./sec to at least 500.degree. C. so as to substantially convert the metallic structure to ferrite.
    Type: Grant
    Filed: January 15, 1997
    Date of Patent: December 15, 1998
    Assignee: Nippon Steel Corporation
    Inventors: Akihiro Miyasaka, Masaaki Obata, Takashi Motoyoshi