Kawasaki Steel Corporation

Susumu Okada

Susumu Satoh

Masahiko Morita

Toshiyuki Kato

Tsuguhiko Nakagawa

Hideo Abe

Hideo Kuguminato

Makoto Aratani

Susumu Masui

Kouichi Hirata

Susumu Sato

Kei Sakata

Takashi Obara

Akio Tosaka

Kozo Tsunoyama

Keiji Nishimura

Makoto Imanaka

Masatoshi Shinozaki

Masatoshi Aratani

Yoshio Yamazaki

Osamu Furukimi

Kaneharu Okuda

Fumimaru Kawabata

Eiko Yasuhara

Hajime Takada

Masuto Shimizu

Norio Ohta

Hidenori Miyake

Masato Iri

Yasuo Tomura

Koushi Kuramoto

Toshihiro Sasaki

Tojiro Ikeda

Jun-ichi Mano

Yukio Kobata

Nobuaki Hanazono

Jun Morozumi

Naotoshi Ryu

A flaw detecting method and apparatus for continuously testing a strip that is continuously carried through a liquid includes features for reducing air bubble generation in a liquid. The apparatus includes a liquid, carrying rolls for passage of the strip through the liquid, and ultrasonic testing probes arranged in the liquid for testing the strip. A carrying roll in contact with the liquid is fully immersed. Air bubble generation is inhibited to improve the testing reliability by at least one of (a) shielding the liquid dropping from the portion of the strip leaving the liquid, (b) reducing the dropping force of the liquid onto the liquid surface by inclining the strip, (c) installing the fully immersed carrying roll at a depth of at least 5 mm in the liquid, and (d) using a carrying speed of less than about 200 m/min. Upon manufacturing steel strips, testing is carried out in the stage of hot-rolled steel sheet, or, preferably, in pickling equipment.

Method and apparatus for detecting flaws in strip, method of manufacturing cold-rolled steel sheet and pickling equipment for hot-rolled steel strip

A hot rolled steel sheet with improved formability and producing method therefor, which can be easily produced with general hot strip mills, having less anisotropy of mechanical properties and final ferrite grain diameter of less than 2 &mgr;m that could not be achieved by the prior art. The hot rolled steel sheet comprises a ferrite phase as a primary phase, and has an average ferrite grain diameter of less than 2 &mgr;m, with the ferrite grains having an aspect ratio of less than 1.5. The hot rolled steel sheet is obtained by carried out a reduction process under a dynamic recrystallization conditions through reduction passes of not less than 5 stands in the hot finish rolling.

Hot rolled steel plate to be processed having hyper fine particles, method of manufacturing the same, and method of manufacturing cold rolled steel plate

At least both ends of a sheet bar in the length direction, which is obtained by roughly rolling a steel slab including 0.1 wt % or less of C, 0.5 wt % or less of Si, 1.0 wt % or less of Mn, 0.1 wt % or less of P, 0.05 wt % or less of S, 0.20 wt % or less of Al, and 0.015 wt % or less of N, are heated so that the temperature at both ends of the sheet bar in the length direction is 15&deg; C. or more higher than the temperature of the remainder of the sheet bar. The rolling finish temperature is Ar,&plus;20&deg; C. to Ar,&plus;100&deg; C. in both end portions of the sheet bar in the length direction, and Ar,&plus;10&deg; C. to Ar,&plus;60&deg; C. in the remainder, and the rolling finish temperature in the both end portions in the length direction is 10&deg; C. or more higher than that of the remainder, so that a steel strip after cold rolling and annealing has r values within &plusmn;0.3 of the average r value, and &Dgr;r within &plusmn;0.2 of the average &Dgr;r in the region of 95% or more of each of the total length and total width of the steel strip.

Method of producing can steel strip

This invention aims at providing a method of continuously carburizing a metal strip, which is capable of providing industrially optimum carburization conditions while attaining non-soot-generating atmospheric data, desired carburization concentration distribution and desired carburization rate, in a case where a strip passed through a carburization furnace is carburized continuously in a surface reaction rate-governing area in which the carbon concentration in a superficial layer of the strip has not yet reached an equilibruim level with respect to the time. The method consist of carburization concentration distribution (S7), on the basis of the carburization conditions including given specification data for the steel plate, furnace temperature and composition of the atmospheric gas, outputting the concentration of the components of the atmospheric gas, feed and discharge rates and other carburization conditions when the set carburization rate and an actual carburization rate are equal (S8-S15), and correcting the set carburization rate when a difference between the set carburization rate and an actual carburization rate is large, and correcting the strip feed rate while correcting the composition of the atmospheric gas when a difference between the predetermined carburization rate and set carburization rate is large (S9).

Method of continuously carburizing metal strip

Extremely-thin steel sheets and method of producing the same

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. The method includes hot-rolling a steel slab containing the above components, cooling at a rate of between 5 to not more than 20.degree. C./sec., and then coiling at a temperature ranging from over 550.degree. C. to 700.degree. C.

Hot-rolled steel sheet and method for forming hot-rolled steel sheet

A high tensile steel sheet excelling in workability and stretch flanging formability, which is of a composite texture composed of a ferrite phase and a 2nd phase selected from the group consisting of martensite, bainite, pearlite, retained austenite and cold-transformed ferrite, wherein the volume fraction of the 2nd phase is hoe less than about 1.3 times higher at an outer region of the steel sheet than the volume fraction of the 2nd phase in a central region of the sheet thickness.

Method of producing a high tensile steel sheet having excellent stretch

The present invention provides a steel sheet for press working that exhibits excellent stiffness and satisfactory press workability. The steel sheet for press working includes: a composition of C+N+B=0.007 to 1.0 wt % in a region from the surface of the steel sheet to a position of 5% of the thickness in a direction of the thickness in at least either of the surface layers; a pole intensity of [{321}+{211}]/{100}.gtoreq.1.2 in a vertical direction to the sheet surface realized at a 3% thickness position in the direction of the thickness from the surface; and a composition of C+N+B=0.010 wt % less than in the central portion 40% except for two 30% portions of the two surface layers in the direction of the thickness.

Steel sheet for press working that exhibits excellent stiffness and

The invention relates to a high strength cold rolled steel sheet having excellent non-aging property at room temperature and excellent drawability, said steel sheet having a dual-phase structure composed of a high-temperature transformed ferrite phase and a low-temperature transformed ferrite phase having high dislocation density. The invention also relates a high strength cold rolled steel sheet having excellent non-aging property at room temperature and bake hardenability, as well as excellent drawability. This steel sheet is produced by preparing a hot-rolled steel sheet, cold rolling the hot-rolled steel sheet at a rolling reduction not smaller than 60%, annealing the cold rolled steel sheet at a temperature which is not lower than the .gamma. transformation start temperature but below the A.sub.c3 transformation temperature, and cooling the annealed steel sheet at a rate not smaller than 5.degree. C./sec but not greater than 100.degree. C./sec.

High strength cold rolled steel sheet having excellent non-aging

A high tensile steel sheet excelling in workability and stretch flanging formability, which is of a composite texture composed of a ferrite phase and a 2nd phase selected from the group consisting of martensite, bainite, pearlite, retained austenite and cold-transformed ferrite, wherein the volume fraction of the 2nd phase is not less than about 1.3 times higher at an outer region of the steel sheet than the volume fraction of the 2nd phase in a central region of the sheet thickness.

High tensile steel sheet having excellent stretch flanging formability

A high-tension steel sheet suitable for deep drawing and having superior surface treatment characteristics is made of a steel consisting essentially of, by weight: 0.001 to 0.05% of C; not more than 1.0% of Si; not more than 2.5% of Mn; 0.05 to 1.0% of Mo; one or both of 0.001 to 0.2% of Nb and not more than 0.3% of Ti, wherein Ti*%+(48/93)Nb%.gtoreq.(48/12)C% in which Ti*%=Ti%-(48/32) S%-(48/14)N%, wherein, when Ti*%&lt;0, Ti*% is regarded as being 0; 0.0005 to 0.01% of B; 0.01 to 0.10% of Al; not more than 0.15% of P; not more than 0.010% of S; not more than 0.006% of N; Si, Mn and P meeting the condition of 0.2&lt;(Si%+10P%)/Mn%&lt;3.3; and the balance substantially Fe and incidental impurities. This steel sheet is produced by a process which includes: hot-rolling the steel slab to obtain a hot rolled steel strip at a final hot-rolling temperature not lower than the Ar.sub.3 transformation temperature; coiling the steel strip at a temperature not lower than 300.degree. C. but not higher than 615.degree. C. when Nb is not contained and not lower than 500.degree. C. but not higher than 700.degree. C. when Nb is contained; cold-rolling the steel strip to obtain a cold rolled steel strip at a rolling reduction not smaller than 65%; and recrystallization-annealing the cold rolled strip at a temperature not lower than the recrystallization temperature but below the Ac.sub.3 transformation temperature.

Cold-rolled high-tension steel sheet having superior deep drawability

A method of producing a high-strength cold-rolled steel sheet suitable for working uses which utilizes a steel material having the following composition: not more than 0.006 wt % of C, not more than 0.5 wt % of Si, not more than 2.0 wt % of Mn, and not less than 0.01 wt % but not more than 0.10 wt % of Ti, the Ti, C and N contents being determined to meet the condition of Ti&gt;(48/12) C wt %+(48/14) N wt %, the steel also consisting essentially of not less than 0.0010 wt % but not more than 0.0100 wt % of Nb, not less than 0.0002 wt % but not more than 0.0020 wt % of B, not less than 0.03 wt % but not more than 0.20 wt % of P, not more than 0.03 wt % of S, not less than 0.010 wt % but not more than 0.100 wt % of Al, not more than 0.008 wt % of N, not more than 0.0045 wt % of O, and the balance substantially Fe and incidental inclusions. The steel material is cast and hot-rolled and then subjected to a cold rolling conducted at a sheet temperature not higher than 300.degree. C. under such a condition that the sum of the rolling reductions of passes which meet the following condition between said sheet temperature (T .degree.C.) and the strain rate .epsilon. (S-1) is 50% or greater:

Method of producing high-strength cold-rolled steel sheet suitable for

A formable thin steel sheet such as hot rolled sheet, cold rolled sheet or surface treated sheet comprises not more than 0.003 wt % of C, not more than 1.0 wt % of Si, not more than 1.0 wt % of Mn, not more than 0.15 wt % of P, not more than 0.020 wt % of S, not more than 0.0045 wt % of O, not more than 0.0020 wt % of N, not more than 0.15 wt % of Al provided that a ratio of Al/N is not less than 30, and the balance being Fe and inevitable impurities, and has not only improved formability for press forming, deep drawing or the like but also improved fatigue resistance as a welded joint.

Method of producing formable thin steel sheets

An extra-low carbon cold rolled steel sheet useful for use in automobiles and the like, having an improved spot weldability is obtained by combining and adding Ti, Nb and B in predetermined amounts to an extra-low carbon steel to control the amount of fine Ti precipitate dispersed in steel to within a specified reasonable range. Furthermore, the spot weldability is improved by controlling the production conditions of the extra-low carbon steel sheet to within specified reasonable ranges.

Cold rolled steel sheets having improved spot weldability

A formable thin steel sheet such as hot rolled sheet, cold rolled sheet or surface treated sheet comprises not more than 0.003 wt. % of C, not more than 1.0 wt % of Si, not more than 1.0 wt % of Mn, not more than 0.15 wt % of P, not more than 0.020 wt % of S, not more than 0.0045 wt % of O, not more than 0.0020 wt % of N, not more than 0.15 wt % of Al provided that a ratio of Al/N is not less than 30, and the balance being Fe and inevitable impurities, and has not only improved formability for press forming, deep drawing or the like but also improved fatigue resistance as a welded joint.

Growing community of inventors

Chiba, Japan

Susumu Okada