The present invention relates to a rack steel plate with a thickness up to 177.8 mm by a continuous casting slab, the constituents and mass percentages including C0.11˜0.15%, Si0.15˜0.35%, Mn0.95˜1.25%, P≤0.010%, S≤0.002%, Cr0.45˜0.75%, Mo0.4˜0.6%, Ni1.3˜2.6%, Cu0.2˜0.4%, Al0.06˜0.09%, V0.03˜0.06%, Nb≤0.04%, N≤0.006%, B0.001˜0.002%, the balance is Fe and unavoidable impurity elements. The manufacture method includes, in sequence, KR molten steel pretreatment, converter smelting, LF refining, RH refining, continuous casting through a straight-arc continuous casting machine, shielding the continuous casting slab a cover and slowly cooling, cleaning the continuous casting slab, heating, high-pressure water descaling, control rolling, straightening, slowly cooling, quenching and tempering treatment. The rack steel plate of large thickness in present invention has advantages of high strength, good plasticity and excellent toughness at a low temperature, the process method has advantages of simple process, low cost and efficiently quick etc.

The invention relates to sheet steel, more particularly a coated sheet steel, which is skin-pass rolled with a deterministic surface structure, and to a method for producing this steel.

A high-strength galvanized steel sheet is excellent in the external appearance of plating and the hydrogen brittleness resistance, and has a high yield ratio, and a method for manufacturing the same. The high-strength galvanized steel sheet including a steel sheet having a specific component composition and a specific steel structure, the amount of diffusible hydrogen in the steel sheet being 0.20 mass ppm or less; and a galvanizing layer provided on a surface of the steel sheet, the galvanizing layer having a content amount of Fe of 8 to 15% in mass %, and an attachment amount of plating per one surface of 20 to 120 g/m.sup.2, wherein the amount of Mn oxides contained in the galvanizing layer is 0.050 g/m.sup.2 or less; and the high-strength galvanized steel sheet has a yield strength of 700 MPa or more and a yield strength ratio of 65% or more and less than 85%.

A method and system solution heat treat, at an elevated first temperature, a coil of aluminum alloy sheet to form a heat-treated coil and while at least a portion of the heat-treated coil is being solution heat treated, uncoil a heat-treated portion of the aluminum alloy sheet from the heat-treated coil and continuously quenching the uncoiled heat-treated portion to form a quenched sheet.

A steel sheet includes, by mass %: C: 0.020% to 0.080%; Si: 0.01% to 0.10%; Mn: 0.80% to 1.80%; and Al: more than 0.10% and less than 0.40%; and further includes: Nb: 0.005% to 0.095%; and Ti: 0.005% to 0.095%, in which a total amount of Nb and Ti is 0.030% to 0.100%, and the steel sheet includes, as a metallographic structure, ferrite, bainite, and other phases, an area fraction of the ferrite is 80% to 95%, an area fraction of the bainite is 5% to 20%, a total fraction of the other phases is less than 3%, a tensile strength is 590 MPa or more, and a fatigue strength ratio as a fatigue strength to the tensile strength is 0.45 or more.

The invention relates to a method for manufacturing strips of stainless steel, comprising hot rolling in an initial process (A) and subsequently cold rolling in a cold rolling line (B). The hot rolling is stopped when the strip thickness has been reduced to a thickness between 2.0 mm and 6.5 mm. The subsequent cold rolling is passed at least one time through said cold rolling line, which comprises in the following order: At least one cold rolling mill (11-13) in the initial part of the line, at least one annealing section (17), a scale breaking step (21), a shot blasting step (23) and at least one pickling section (26, 27) utilizing a mixture of nitric acid HNO.sub.3, hydrofluoric acid HF and optionally sulphuric acid H.sub.2SO.sub.4.

A high strength steel sheet according to the present invention contains a predetermined chemical composition, a metallographic structure includes, by an area ratio, ferrite: 20% to 70%, residual austenite: 5% to 40%, fresh martensite: 0% to 30%, tempered martensite and bainite: 20% to 75% in total, and pearlite and cementite: 0% to 10% in total, in a range of a ⅛ thickness to a ⅜ thickness from a surface, a number proportion of residual austenite having an aspect ratio of 2.0 or more with respect to the number of all residual austenite is 50% or more, at a sheet thickness ¼ position of a cross section parallel to a rolling direction and perpendicular to the surface, a standard deviation of area ratios of ferrite measured at 10 points every 50 mm along a width direction is less than 10%, and a tensile strength is 780 MPa or more.

The present invention relates to a steel for a mold, including 0.070≤C≤0.130 mass %, 0.01≤Si≤0.60 mass %, 0.02≤Mn≤0.60 mass %, 0.003≤P≤0.150 mass %, 0.005≤Cu≤1.50 mass %, 0.005≤Ni≤0.80 mass %, 7.50≤Cr≤8.40 mass %, 0.70≤Mo≤1.20 mass %, 0.01≤V≤0.30 mass %, 0.010≤Al≤0.120 mass %, and 0.015≤N≤0.095 mass %, with the balance being Fe and unavoidable impurities. The steel for a mold according to the present invention satisfies all of 6 properties of SA property, tempering hardness, residual stress, machinability, impact value and corrosion resistance.

Disclosed is an electro-galvanized super-strength dual-phase steel resistant to delayed cracking. A matrix structure thereof is ferrite+tempered martensite and the steel contains the following chemical elements in the following mass percentages: C:0.07-0.1%, Si: 0.05-0.3%, Mn: 2.0-2.6%, Cr: 0.2-0.6%, Mo: 0.1-0.25%, Al: 0.02-0.05%, Nb: 0.02-0.04%, and V: 0.06-0.2%. Also disclosed is a method for manufacturing the electro-galvanized super-strength dual-phase steel resistant to delayed cracking, the method comprising the steps of: smelting and continuous casting, hot rolling, cold rolling, annealing, tempering, leveling and electroplating. The electro-galvanized super-strength dual-phase steel resistant to delayed cracking according to the present invention not only has better mechanical properties, but also has excellent delayed cracking resistance and low initial hydrogen content.

This high-strength steel sheet contains predetermined chemical components, in a range from a surface to 1/10 of a sheet thickness in a sheet thickness direction, an average pole density of an orientation group 1 that is an orientation group expressed by ϕ1=0° to 90°, Φ=50° to 60° and ϕ2=45° in terms of an Euler angle is 1.5 or less, an average pole density of an orientation group 2 that is an orientation group expressed by ϕ1=450 to 85°, Φ=85° to 90° and ϕ2=45° in terms of the Euler angle is 1.5 or more, an S value that indicates a degree of randomness of surface properties is 7.5 or less, an E value that indicates a degree of concentration of the surface properties is 0.04 or more, and a tensile strength is 590 MPa or more.