Nkk Corporation

Other

Toru Inazumi

Tadashi Inoue

Sadanori Imada

Yasunobu Nagataki

Yoichi Motoyashiki

Fusato Kitano

Hiroyasu Kikuchi

Yoshimasa Funakawa

Hiroshi Matsuda

Takeshi Fujita

Yuji Yamasaki

Kohei Hasegawa

Yasuhide Ishiguro

Yoshihiro Hosoya

Masaya Morita

Moriaki Ono

Hiroshi Nakata

Akio Kobayashi

Naoki Matsui

Kunikazu Tomita

Toshiaki Urabe

Hiroshi Sawada

Shogo Sato

Kenichi Mitsuzuka

Akira Hiura

Shunsaku Node

Takeshi Nakahara

Satoshi Ishijima

Jun Taniai

A method for manufacturing a steel sheet comprising continuously casting a steel containing 0.04 to 0.2 wt. % C, 0.25 to 2 wt. % Si, 0.5 to 2.5 wt. % Mn, and 0.1 wt. % or less Al to form a slab; hot-rolling by rough-rolling the slab to form a sheet bar and finish-rolling the sheet bar with a reduction in thickness at the final stand of less than 30%, the finish-rolling being completed at a temperature from the Ar transformation point to the Ar transformation point &plus;60&deg; C.; primary-cooling the hot-rolled steel sheet, the primary cooling being started within 1 second after the completion of hot-rolling and conducting the cooling at a cooling speed of higher than 200&deg; C./sec down to a temperature of Ar &minus;30&deg; C. to the Ar transformation point; slow cooling or air-cooling the primary-cooled steel sheet at a temperature of the Ar transformation point to the Ar transformation point at 10&deg; C./sec or less for 2 seconds or more; secondary-cooling the steel sheet after the slow cooling or the air-cooling at 30&deg; C./sec or more; and coiling the secondary-cooled steel sheet at 300&deg; C. or less.

Method for manufacturing a steel sheet

A high strength 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 a balance of substantially Fe and inevitable impurities, and having an n value of not less than 0.21 calculated from two points (1% and 10%) of nominal strain determined by the uniaxial tensile test, and a method for manufacturing the cold rolled steel sheet. The high strength cold rolled steel sheet has excellent combined formability, resistance to embrittlement during secondary operation, formability at welded portions, and anti-burring performance, and has a desirable surface appearance and uniformity of material in a coil, and thus can be desirably used for automobile exterior panels.

High strength cold rolled steel sheet and method for manufacturing the same

The method for manufacturing steel sheet comprises the steps of: rough-rolling to form a sheet bar; finish-rolling the sheet bar to form a steel strip; applying primary cooling and secondary cooling to the finish-rolled steel strip; and coiling the secondary-cooled steel strip. The primary cooling is conducted at cooling speeds of 120&deg; C./sec or more down to the temperatures of from 500 to 800&deg; C. The secondary cooling is conducted at cooling speeds of less than 60&deg; C./sec.

Steel sheet and method for manufacturing the same

High tensile strength hot-rolled steel sheet and method for manufacturing the same

The method for manufacturing cold-rolled steel sheet comprises the steps of: rough-rolling a slab using a rough-rolling unit; finish-rolling the sheet bar using a continuous hot finishing-rolling mill; cooling the hot-rolled steel strip on a runout table; coiling thus cooled hot-rolled steel strip; and applying picking, cold-rolling the hot-rolled steel strip, and final annealing to the cold-rolled steel strip.

Method for manufacturing cold-rolled steel sheet

The present invention relates to a very low C&mdash;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.

A hot-dip galvanized steel sheet is produced by rough rolling a steel, finish rolling the rough rolled steel at a temperature of Ar3 point or more, coiling the finish rolled steel at a temperature of 700&deg; C. or less, and hot-dip galvanizing the coiled steel at a pre-plating heating temperature of Ac1 to Ac3. A continuous hot-dip galvanizing operation is performed by soaking a pickled strip at a temperature of 750 to 850&deg; C., cooling the soaked strip to a temperature range of 600&deg; C. or less at a cooling rate of 1 to 50&deg; C. per second, hot-dip galvanizing the cooled strip, and cooling the galvanized strip so that the residence time at 400 to 600&deg; C. is within 200 seconds. The steel sheet has a structure consisting essentially of ferrite and martensite.

Hot-dip galvanized steel sheet and method for producing the same

A soft cold-rolled steel sheet contains: 0.06 wt. % or less C, 0.1 wt. % or less Si, 0.5 wt. % or less Mn, 0.03 wt. % or less P, 0.03 wt. % or less S, 0.006 wt. % or less N, 0.009 wt. % or less B and the balance being Fe. The method comprises the steps of: continuously casting a steel to produce a slab; hot-rolling the slab to form a hot-rolled steel sheet; cold-rolling the hot-rolled steel sheet to produce a cold-rolled steel sheet; and continuously annealing the cold-rolled steel sheet.

Soft cold-rolled steel sheet and method for making the same

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Ann Arbor, MI, United States of America

Toru Inazumi