Sumitomo Rubber Industries Limited

Kobe Steel, Ltd.

Shinshu Tlo Co., Ltd.

Kenji Saito

Akira Kajikawa

Kazuo Asano

Toshio Murakami

Shushi Ikeda

Hideo Hata

Koichi Sugimoto

Fumio Yuse

Tadao Murata

Akira Ibano

Hirokazu Natsumeda

Shunichi Hashimoto

Yoichi Mukai

Hiroshi Akamizu

Yukihiro Utsumi

Muneaki Ikeda

Koichi Makii

Atsushi Yamahira

Hiroyuki Noma

Akihiro Nakatani

Kazuhiko Kawamura

Atsuhiro Shiraki

Kosuke Shibata

Takahiro Ozawa

Toshiya Nakata

Saneto Saito

Disclosed is a high-strength sheet containing: C: 0.15% by mass to 0.35% by mass, a total of Si and Al: 0.5% by mass to 3.0% by mass, Al: 0.01% by mass or more, N: 0.01% by mass or less, Mn: 1.0% by mass to 4.0% by mass, P: 0.05% by mass or less, and S: 0.01% by mass or less, with the balance being Fe and inevitable impurities, wherein the steel structure satisfies that: a ferrite fraction is 5% or less, the total fraction of tempered martensite and tempered bainite is 60% or more, the amount of retained austenite is 10% or more, MA has an average size of 1.0 &#x3bc;m or less, retained austenite has an average size of 1.0 &#x3bc;m or less, retained austenite having a size of 1.5 &#x3bc;m or more accounts for 2% or more of the total amount of retained austenite, and the amount of solute nitrogen in a steel sheet is 0.002% by mass or less.

High-strength steel sheet and method for producing same

The present invention relates to a high-strength steel sheet which satisfies a specific chemical component composition, and which is configured such that: when the metal structure thereof is observed with a scanning electron microscope, polygonal ferrite is 30 to 60% by area; when the metal structure thereof is observed with an optical microscope, MA mixed structure is 21% by area or less; when the metal structure thereof is measured by an X-ray diffraction method, retained austenite is 8% by volume or more; an area ratio of polygonal ferrite having a circle equivalent diameter of 35.0 &#x3bc;m or more is 0% and an area ratio of polygonal ferrite having a circle equivalent diameter of 10.0 &#x3bc;m or more and less than 35.0 &#x3bc;m is 10% or less in the polygonal ferrite; and connectivity as defined by a specific relational expression is 10% or more.

High-strength steel sheet, high-strength galvanized steel sheet, method for producing high-strength steel sheet, and method for producing high-strength galvanized steel sheet

Disclosed is a high-strength sheet containing: C: 0.15% by mass to 0.35% by mass, a total of Si and Al: 0.5% by mass to 3.0% by mass, Mn: 1.0% by mass to 4.0% by mass, P: 0.05% by mass or less (including 0% by mass), S: 0.01% by mass or less (including 0% by mass), and Ti: 0.01% by mass to 0.2% by mass, with the balance being Fe and inevitable impurities, wherein the steel structure satisfies that: a ferrite fraction is 5% or less, a total fraction of tempered martensite and tempered bainite is 60% or more, a retained austenite fraction is 10% or more, a fresh martensite fraction is 5% or less, retained austenite has an average grain size of 0.5 &#x3bc;m or less, retained austenite having a grain size of 1.0 &#x3bc;m or more accounts for 2% or more of the total amount of retained austenite, and a prior austenite grain size is 10 &#x3bc;m or less.

High-strength steel sheet and production method for same

Provided is an ultra-high-strength steel sheet having a component composition that includes specific amounts of each of C, Mn, and Al and a remainder of iron and unavoidable impurities, and in which the amounts of each of P, S, and N among the unavoidable impurities are limited to a specific amount. The ultra-high-strength steel sheet includes 2 area% or more of a region having a structure that includes 90% or more of martensite and 0.5% or more of residual austentite by area ratio relative to the entire structure, the local Mn concentration in said region being at least 1.1 times that of the Mn content of the entire steel sheet. The ultra-high-strength steel sheet has a tensile strength of 1470 MPa or more.

Ultra-high-strength steel sheet having excellent delayed fracture resistance at cut end thereof

A cold-rolled steel sheet of the present invention which has a composition containing, in terms of % by mass, C: 0.05-0.30%, Si: 3.0% or less (including 0%), Mn: 0.1-5.0%, P: 0.1% or less (including 0%), S: 0.010% or less (including 0%), and Al: 0.001-0.10%, and remainder being mainly iron, and which has a structure comprising, in terms of area ratio, 10-80% ferrite, less than 5% (including 0%) of the sum of retained austenite and martensite, and a hard phase as the remainder. The steel sheet gives a KAM value frequency distribution curve in which the relationship between the proportion of frequency having a KAM value &#x2266;0.4, X, and the area ratio of ferrite, Vsatisfies X/V&#x2267;0.8 and the proportion of frequency having a KAM value in the range of 0.6-0.8, Xis 10-20%. In the hard phase adjoining the ferrite, cementite, grains having an equivalent circle diameter of 0.1 &#x3bc;m or larger exist so that three or less such cementite grains are dispersed per &#x3bc;mof the hard phase. The steel sheet has improved balance between elongation and stretch flangeability and has better formability.

Cold-rolled steel sheet and method for producing the same

The invention provides a high-strength cold-rolled steel sheet which is improved in elongation and stretch-flangeability and exhibits more excellent formability. The high-strength cold-rolled steel sheet has a composition which contains by mass C: 0.03 to 0.30%, Si: 0.1 to 3.0%, Mn: 0.1 to 5.0%, P: 0.1% or below, S: 0.005% or below, N: 0.01% or below, and Al: 0.01 to 1.00% with the balance consisting of iron and unavoidable impurities. The high-strength cold-rolled steel sheet has a structure which comprises at least 40% (up to 100% inclusive) in terms of area fraction of tempered martensite having a hardness of 300 to 380 Hv and the balance ferrite. The cementite particles in the tempered martensite take such dispersion that 10 or more cementite particles having equivalent-circle diameters of 0.02 to less than 0.1 &#x3bc;m are present per one &#x3bc;mof the tempered martensite and three or fewer cementite particles having equivalent-circle diameters of 0.1 &#x3bc;m or above are present per one &#x3bc;mof the tempered martensite.

High-strength cold-rolled steel sheet

A high-strength cold rolled steel sheet contains: 0.10 to 0.28% of C, 1.0 to 2.0% of Si, 1.0 to 3.0% of Mn, and 0.03 to 0.10% of Nb in terms of % by mass, Al is controlled to 0.5 or less, P is controlled to 0.15% or less, and S is controlled to 0.02% or less, and residual austenite accounts for 5 to 20%, bainitic ferrite accounts for 50% or more, and polygonal ferrite accounts for 30% or less (containing 0%), of the entire structure, and a mean number of residual austenite blocks is 20 or more as determined when the random area (15 &#x3bc;m&#xd7;15 &#x3bc;m) is observed by EBSP (electron back scatter diffraction pattern).

High-strength cold rolled steel sheet having excellent formability, and plated steel sheet

The present invention provides a high strength steel used for spring steel that has excellent hydrogen embrittlement resistance. The high strength steel which spring steel having excellent hydrogen embrittlement resistance comprises 0.20 to 0.60% of C, 1.0 to 3.0% of Si, 1.0 to 3.5% of Mn, higher than 0% and not higher than 1.5% of Al, 0.15% or less P, 0.02% or less S, and balance of iron and inevitable impurities and the structure includes:

High strength spring steel having excellent hydrogen embrittlement resistance

A belted radial ply tire which comprises a bead core disposed in each bead portion, a carcass extending between the bead portions and turned up around the bead cores, and a belt comprising at least two cross plies disposed radially outside the carcass and inside the tread, and in a state that the tire is mounted on its regular rim and inflated to its regular inner pressure but loaded with no tire load, the effective belt width BW of the effective belt part BE of the belt, the belt edge camber height CH of the belt, and the tire section width TW satisfy 2.50(BW/TW)-1.25&lt;CH&lt;13.3(BW/TW)-4.65.

Radial tire with even wear at tread shoulders

A pneumatic radial tire has a tread surface extending along a specific curvature plane which includes a first arc with the radius R1 having a center on the tire's equatorial plane and passing through the tire's equatorial point, a second arc with the radius R2 having a center on the tire's equatorial plane and intersecting with the first arc at an intersection distant from the tire's equatorial plane by 0.2 to 0.25 times the tire width SW, and a third arc with the radius R3 passing through a ground contact outer edge point of the ground contact surface, when a standard load is applied, and a belt intermediate height point on the tread surface. In the specific curvature plane, the curvature radius ratio R2/R3 is set in a range from 4 to 12, and the curvature radius ratio R1/R2 is set in a range from 1.2 to less than 1.6 when the aspect ratio H/SW is 0.70 or more. The tread surface is provided with a main circumferential groove, preferably having a groove width of 0.06 to 0.10 times the tire width SW, extending near the intersection of the first arc and the second arc in the tire circumferential direction for dividing the tread surface into the crown part and an outer shoulder part. Narrow lateral grooves crossing the tire circumferential direction divide the crown part and shoulder part into blocks.

Pneumatic radial tire with high cornering and steering stability

A pneumatic radial tire has a tread surface extending along a specific curvature plane which includes a first arc with the radius R1 having a center on the tire's equatorial plane and passing through the tire's equatorial point, a second arc with the radius R2 having a center on the tire's equatorial plane and intersecting with the first arc at an intersection distant from the tire's equatorial plane by 0.2 to 0.25 times the tire width SW, and a third arc with the radius R3 passing through a ground contact outer edge point of the ground contact surface, when a standard load is applied, and a belt intermediate height point on the tread surface. In the specific curvature plane, the curvature radius ratio R2/R3 is set in a range from 1.2 to less than 1.6 when the aspect ratio H/SW is 0.70 or more. The tread surface is provided with a main circumferential groove, preferably having a groove width of 0.06 to 0.10 times the tire width SW, extending near the intersection of the first arc and the second arc in the tire circumferential direction for dividing the tread surface into the crown part and an outer shoulder part. Narrow lateral grooves crossing the tire circumferential direction divide the crown part and shoulder part into blocks.

A pneumatic radial tire has a tread surface extending along a specific curvature plane which includes a first arc with the radius R1 having a center on the tire's equatorial plane and passing through the tire's equatorial point, a second arc with the radius R2 having a center on the tire's equatorial plane and intersecting with the first arc at an intersection distant from the tire's equatorial plane by 0.2 to 0.25 times the tire width SW, and a third arc with the radius R3 passing through a ground contact outer edge point of the ground contact surface, when a standard load is applied, and a belt intermediate height point on the tread surface. In the specific curvature plane, the curvature radius ratio R2/R3 is set in a range from 4 to 12, and the curvature radius ratio R1/R2 is set in a range from 1.6 to less than 2.6 when the aspect ratio H/SW is more than 0.55 and less than 0.70. The tread surface is provided with a main circumferential groove, preferably having a groove width of 0.06 to 0.10 times the tire width SW, extending near the intersection of the first arc and the second arc in the tire circumferential direction for dividing the tread surface into the crown part and an outer shoulder part. Narrow lateral grooves crossing the tire circumferential direction divide the crown part and shoulder part into blocks.

A pneumatic radial tire has a tread surface extending along a specific curvature plane which includes a first arc with the radius R1 having a center on the tire's equatorial plane and passing through the tire's equatorial point, a second arc with the radius R2 having a center on the tire's equatorial plane and intersecting with the first arc at an intersection distant from the tire's equatorial plane by 0.2 to 0.25 times the tire width SW, and a third arc with the radius R3 passing through a ground contact outer edge point of the ground contact surface, when a standard load is applied, and a belt intermediate height point on the tread surface. In the specific curvature plane, the curvature radius ratio R2/R3 is set in a range from 4 to 12, and the curvature radius ratio R1/R2 is set in a range from 2.6 to 4.6 when the aspect ratio H/SW is 0.55 or less. The tread surface is provided with a main circumferential groove, preferably having a groove width of 0.06 to 0.10 times the tire width SW, extending near the intersection of the first arc and the second arc in the tire circumferential direction for dividing the tread surface into the crown part and an outer shoulder part. Narrow lateral grooves crossing the tire circumferential direction divide the crown part and shoulder part into blocks.

A pneumatic radial tire has a tread surface extending along a specific curvature plane which includes a first arc with the radius R1 having a center on the tire's equatorial plane and passing through the tire's equatorial point, a second arc with the radius R2 having a center on the tire's equatorial plane and intersecting with the first arc at an intersection distant from the tire's equatorial plane by 0.2 to 0.25 times the tire width SW, and a third arc with the radius R3 passing through a ground contact outer edge point of the ground contact surface, when a standard load is applied, and a belt intermediate height point on the tread surface. The tread surface is provided with a main circumferential groove, preferably having a groove width of 0.06 to 0.10 times the tire width SW, extending near said intersection of the first arc and the second arc in the tire circumferential direction for dividing the tread surface into the crown part and an outer shoulder part. Narrow lateral grooves crossing the tire circumferential direction divide the crown part and shoulder part into blocks.

A pneumatic radial tire has a thread surface extending along a specific curvature plane which includes a first arc with the radius R1 having a center on the tire's equatorial plane and passing through the tire's equatorial point, a second arc with the radius R2 having a center on the tire's equatorial plane and intersecting with the first arc at an intersection distant from the tire's equatorial plane by 0.2 to 0.25 times the tire width SW, and a third arc with the radius R3 passing through a ground contact outer edge point of the ground contact surface, when a standard load is applied, and a belt intermediate height point on the tread surface. In the specific curvature plane, the curvature radius ratio R2/R3 is set in a range from 4 to 12, and the curvature radius ratio R1/R2 is set in a range from 2.6 to 4.6 when the aspect ratio H/SW is 0.55 or less. The tread surface is provided with a main circumferential groove, preferably having a groove width of 0.06 to 0.10 times the tire width SW, extending near the intersection of the first arc and the second arc in the tire circumferential direction for dividing the tread surface into the crown part and an outer shoulder part. Narrow lateral grooves crossing the tire circumferential direction divide the crown part and shoulder part into blocks.

Growing community of inventors

Kobe, Japan

Kenji Saito