Kawasaki Steel Corporation

Minoru Nishida

Takashi Obara

Susumu Satoh

Osamu Hashimoto

Hideo Suzuki

Nobuo Ohashi

Motoyuki Konishi

Yukio Inokuchi

Kei Sakata

Masahiko Morita

Hideo Kuguminato

Kazunori Osawa

Tomoo Tanaka

Junichi Mano

Syoichi Takizawa

Nobuo Aoyagi

A cold rolled dual-phase structure steel sheet having an excellent deep drawability is disclosed, which consists of ferrite phase and low temperature transformation product phase and comprises 0.001-0.008 wt % of C, not more than 1.0 wt % of Si, 0.05-1.8 wt % of Mn, not more than 0.15 wt % of P, 0.01-0.10 wt % of Al, 0.002-0.050 wt % of Nb and 0.0005-0.0050 wt % of B provided that the value of Nb(%)+10B(%) is in a range of 0.010-0.080%, and, if necessary, 0.05-1.00 wt % of Cr and the balance being substantially Fe with inevitable impurities. This steel sheet is manufactured by hot and cold rolling a steel slab with the above chemical composition and continuously annealing the resulting steel sheet in such a manner than the steel sheet is heated and soaked at a temperature from .alpha..fwdarw..gamma. transformation point to 1,000.degree. C. and then cooled at an average cooling rate of not less than 0.5.degree. C./sec but less than 20.degree. C./sec in a temperature range of from the soaking temperature to 750.degree. C., and subsequently at an average cooling rate of not less than 20.degree. C./sec in a temperature range of from 750.degree. C. to not more than 300.degree. C.

Method of making cold rolled dual-phase structure steel sheet having an

A cold rolled dual-phase structure steel sheet having an excellent deep drawability is disclosed, which consists of ferrite phase and low temperature transformation product phase and comprises 0.001-0.008 wt % of C, not more than 1.0 wt % of Si, 0.05-1.8 wt % of Mn, not more than 0.15 wt % of P, 0.01-0.10 wt % of Al, 0.002-0.050 wt % of Nb and 0.0005-0.0050 wt % of B provided that the value of Nb (%)+10B (%) is in a range of 0.010-0.080%, and, if necessary, 0.05-1.00 wt % of Cr and the balance being substantially Fe with inevitable impurities. This steel sheet is manufactured by hot and cold rolling a steel slab with the above chemical composition and continuously annealing the resulting steel sheet in such a manner than the steel sheet is heated and soaked at a temperature from .alpha..fwdarw..gamma. transformation point to 1,000.degree. C. and then cooled at an average cooling rate of not less than 0.5.degree. C./sec but less than 20.degree. C./sec in a temperature range of from the soaking temperature to 750.degree. C., and subsequently at an average cooling rate of not less than 20.degree. C./sec in a temperature range of from 750.degree. C. to not more than 300.degree. C.

Cold rolled dual-phase structure steel sheet having an excellent deep

Disclosed herein is a method of manufacturing a base steel sheet, which method comprises combined steps of: not rolling a steel slab containing not more than 0.0070% by weight of C (hereinafter referred to briefly as '%'), not more than 0.1% of Si, not more than 0.5% of Mn, 0.010 to 0.080% of Al, not more than 0.0050% of N, not more than 0.030% of S provided that the ratio of Mn/S is not less than 10, and not more than 0.030% of P while the hot rolling being terminated at a finish temperature of not less than 800.degree. C.; cold rolling thus obtained hot rolled steel sheet in an ordinary manner; continuously annealing the cold rolled steel sheet in which heating is done up to a temperature from a recrystallization temperature to 800.degree. C., followed by cooling; and then temper rolling the annealing steel sheet at a reduction of not less than 7% by using two or more stand rolling mill, whereby the thus obtained base sheet, to be surface-treated may be utilized for a tinplate or a tin free steel in which no stretcher strain is formed even after baking treatment.

Production of a base steel sheet to be surface-treated which is to

Method of producing cold rolled steel sheets for deep drawing

Method for producing hot-rolled steel sheets having a low yield ratio

A pretreatment of cold-rolled steel sheet for annealing so as to suppress graphite formation on the surface thereof and nitrogenization during the annealing for recrystallization, by causing an effective amount of sulfur, aluminum, tin, arsenic, lead, antimony, bismuth, selenium, and/or tellurium to exist on the steel sheet surface.

Process of pretreating cold-rolled steel sheet for annealing

Growing community of inventors

Chiba, Japan

Minoru Nishida