The present invention provides an ultra high strength cold rolled steel sheet having excellent spot weldability and formability. The ultra high strength cold rolled steel sheet, according to one embodiment of the present invention, comprises, in weight percent,: 0.05% to 0.09% of carbon (C); 0.5% to 1.0% of silicon (Si); 2.0% to 2.8% of manganese (Mn); 0.2% to 0.5% of aluminum (Al); 0.8% to 1.2% of chromium (Cr); 0.05% to 0.10% of molybdenum (Mo); 0.03% to 0.06% of titanium (Ti); 0.001% to 0.003% of boron (B); 0.02% to 0.05% of antimony (Sb); 0.001% to 0.015% of phosphorus (P); more than 0% to 0.003% of sulfur (5); 0.004% to 0.006% of nitrogen (N); and a balance of iron (Fe) and other inevitable impurities, and the ultra high strength cold rolled steel sheet comprises a microstructure comprising ferrite and low hardness martensite.

The present invention provides an ultra high strength cold rolled steel sheet having excellent spot weldability and formability. The ultra high strength cold rolled steel sheet, according to one embodiment of the present invention, comprises, in weight percent,: 0.05% to 0.09% of carbon (C); 0.5% to 1.0% of silicon (Si); 2.0% to 2.8% of manganese (Mn); 0.2% to 0.5% of aluminum (Al); 0.8% to 1.2% of chromium (Cr); 0.05% to 0.10% of molybdenum (Mo); 0.03% to 0.06% of titanium (Ti); 0.001% to 0.003% of boron (B); 0.02% to 0.05% of antimony (Sb); 0.001% to 0.015% of phosphorus (P); more than 0% to 0.003% of sulfur (5); 0.004% to 0.006% of nitrogen (N); and a balance of iron (Fe) and other inevitable impurities, and the ultra high strength cold rolled steel sheet comprises a microstructure comprising ferrite and low hardness martensite.

A high-strength hot-dip galvanized steel sheet contains predetermined amounts of C, Si, Mn, P, S, N, O, sol. Al, Ti, and B, 0.1 to 1.5 mass % of Cr+2×Mo, and a balance in a form of Fe and inevitable impurities. A steel structure includes, in area %, ferrite: 1 to 50%, martensite: 20 to 70%, residual austenite: 0 to 5%, pearlite: 0 to 5%, MA and cementite having 0.2 μm or more grain size: 0 to 5% in total, and a balance in a form of bainite. A number density of MA or cementite having 0.2 μm or more grain size and isolated in ferrite or bainite grains is 100 pcs/1000 μm.sup.2 or less, and an average hardness of martensite is in a range from 330 to 500 Hv.

Method of producing a low interfacial contact resistance material for use in batteries or connectors and a low interfacial contact resistance material for use in batteries or connectors produced thereby.

In a metal coated steel sheet, a chemical composition contains, in mass %, at least C: 0.03% to 0.70%, Si: 0.25% to 2.50%, Mn: 1.00% to 5.00%, P: 0.100% or less, S: 0.010% or less, sol. Al: 0.001% to 2.500, N: 0.020% or less, and a balance composed of iron and impurities, a metal structure contains greater than 5.0 vol % of retained austenite and greater than 5.0 vol % of tempered martensite, and satisfies a C content in the retained austenite being 0.85 mass % or more.

A high strength steel strip having medium amounts of C, Mn, Si, Cr and Al, wherein the steel strip has a microstructure consisting of, in vol. %: ferrite and bainite together 50-90%, martensite<15%, retained austenite 5-15%, the remainder being pearlite, cementite, precipitates and inclusions together up to 5%.

The invention relates to a method for rolling a metal product (1), wherein the metal product is subjected to a rolling operation at a first station (2), which rolling operation is controlled by a control device (3), wherein the product (1) is subject to a measurement at a second station (4), wherein the product (1) is subjected to a further processing operation at a third station (6), and wherein the product (1) is in a specified quality at a fourth station (7). In order to increase the quality of the produced strip, the invention provides that the method has the following steps: a) measuring the value of a material property (IW) that the second station (4); b) feeding the value measured at the second station (4) to the control device (3), comparing the measured value with a value (SW) stored in the control device (3), and adjusting a parameter (PPI) if the measured value deviates from the stored value (SW), e) measuring a value of a quality material property (Q) at the fourth station (7); d) comparing the measured value with a stored value, and initiating a measure to influence the quality material property (Q) if the measured value deviates from the stored value beyond a permissible tolerance.

A hot-stamping formed body has a predetermined chemical composition and a microstructure including, by area ratio, 90% to 100% of martensite and 0% to 10% of a remainder in the microstructure. In the microstructure, a region in which an average GAIQ value in a unit grain is 60,000 or more is 30 area % or more, and a number density of carbides having a circle equivalent diameter of 0.20 μm or more is 50/mm.sup.2 or less.

The present invention provides a method for forming an aluminum alloy thin-walled curved part by ultra-low temperature gradient drawing. This method includes: placing the aluminum alloy sheet on a die, and closing a blank holder to hold the aluminum alloy sheet in a flange zone; filling a cavity of a die with an ultra-low temperature medium to cool a die cavity zone of the aluminum alloy sheet to a set low temperature, and forming an ultra-low temperature gradient in which the temperature of the die cavity zone is lower than the temperature in the flange zone; applying a set blank holder force to the blank holder, and controlling a punch to move downwards to form a deep-cavity thin-walled curved part; and controlling the punch to move upwards, opening the blank holder, and taking out the formed deep-cavity thin-walled curved part.

Provided is a high-strength hot-rolled coated steel sheet having a TS of 980 MPa or more, excellent bulging formability and stretch flange formability, and excellent coatability. The high-strength hot-rolled coated steel sheet includes a steel sheet having a chemical composition containing, by mass %, C: 0.03% to 0.09%, Si: 0.01% to 1.60%, Mn: 2.20% to 3.60%, P: 0.100% or less, S: 0.0100% or less, Ti: 0.05% to 0.18%, B: 0.0005% to 0.0050%, Al: 0.005% to 0.40%, N: 0.010% or less, and a balance of Fe and inevitable impurities, in which a CSM value expressed by the equation 33.8[% C][% Mn]+12.4[% Si]/[% Mn] is 3.3 to 12.0, and a steel microstructure containing bainite in an amount of 85% or more in terms of area fraction and martensite in an amount of 2.0% or more and 15.0% or less in terms of area fraction and includes a coating layer or an alloyed coating layer on a surface of the steel sheet.