摘要:
A heat-treatment-hardenable cold-rolled steel sheet having a high r value, comprising 0.010% or less of carbon, 0.05 to 0.5% of manganese, 1.0% or less of silicon, 0.001 to 0.030% of sulfur, 0.03% or less of phosphorus, 0.0050% or less of nitrogen, 0.005 to 0.10% of sol. aluminum, and 0.8 to 2.2% of copper with the balance being iron and unavoidable elements and, optionally incorporated therein, either or both of titanium and niobium and further nickel and optionally boron. The steel sheet can be manufactured by subjecting a cold-rolled steel sheet having this composition to recrystallization annealing at a temperature of 750.degree. C. or above and then heat-treating the steel sheet at a temperature ranging from 450.degree. to 700.degree. C. for 1 minute or longer. Alternatively, after the recrystallization annealing, the sheet can be cooled to a temperature of 450.degree. C. or below within 1 minute, followed by work deformation and heat-treating the work-deformed product at a temperature of 450.degree. C. or above to increase the strength of the steel sheet.
摘要:
A zinc-plated steel sheet with an ageing resistance is produced from an Al-killed steel by hot dip type, continuous zinc plating including recrystallization and annealing, where after recrystallization and grain growth, the steel sheet is quenched at a cooling rate of 30.degree..about.250.degree. C/sec from 720.degree..about.600.degree. C. to 310.degree..about.200.degree. C.; after keeping the steel sheet at the same temperature for 0 to 15 seconds, the steel sheet is reheated to a molten zinc bath temperature; then the steel sheet is dipped into the molten zinc bath for zinc-plating; and then the steel sheet is cooled at a cooling rate of 250 to 5.degree. C./sec from that temperature to 350.degree. C.; and then the steel sheet is cooled at a specific average cooling rate in a temperature region of 350.degree. C. to 300.degree. C. and at a specific average cooling rate in a temperature region of from 300.degree. C. to 285.degree..about.220.degree. C.
摘要:
A heat-treatment hardenable hot-rolled steel sheet having remarkably excellent cold workability comprising 0.0005 to 0.015% of carbon, 0.05 to 0.5% of manganese, 0.001 to 0.030% of sulfur, 1.0 to 2.2% of copper, 0.100% or less of phosphorus, 1.0% or less of silicon, 0.0050% or less of nitrogen, and 0.002 to 0.10% of sol. aluminum with the balance being iron and unavoidable elements and substantially comprising a ferritic single phase structure free from occurrence of pearlite. The steel may also contain 0.01 to 0.2% titanium, 0.005 to 0.2% niobium, 0.15 to 0.45% nickel and/or 0.0001 to 0.0030% boron. The steel sheet is produced by hot-rolling the steel at a temperature above the Ar.sub.3 point and coiling the hot-rolled steel strip at a temperature of, preferably, 350.degree. C. or below. The resultant steel sheet is relatively easy to work, and its strength can be dramatically increased by heat treatment for a short period of time after working.
摘要:
In a method for producing a cold-rolled steel sheet by continuously casting, hot-rolling, cold-rolling, and continuously annealing Al-killed steel, it is known to coil a hot-rolled strip at a coiling temperature of 630.degree. C. to 710.degree. C. so as to attain satisfactory precipitation of AlN in the hot-rolling step. When the direct-rolling of a continuously cast strand (DR method) is employed to produce a cold-rolled strip, it is impossible to attain satisfactory precipitation of AlN even by carrying out the known coiling method. The present invention is characterized in that an extremely high coiling temperature of at least 780.degree. C. is used to essentially prevent aging due to the precipitation of AlN, and, further, the carbon content of a continuously cast slab is 0.005% at the highest so as to essentially prevent the occurrence of orange peel. Heat conservation due to use of the DR method and excellent properties of the cold-rolled steel strip are simultaneously attained.
摘要:
A thin ferritic steel sheet having an excellent shape fixability capable of being used for bending is provided, comprising: at least 0.027 to less than 0.05 mass % of C, 0.01 to 1.0 mass % of Si, 0.01 to 2.0 mass % of Mn, not more than 0.15 mass % of P, not more than 0.03 mass % of S, 0.01 to 0.1 mass % of Al, not more than 0.01 mass % of N, not more than 0.007 mass % of O, the balance being Fe and inevitable impurities, wherein a ratio of presence of {100} planes parallel with a face of the steel sheet to {111} planes is not less than 1.0, and TS×El, which represents a product of maximum tensile strength (TS) multiplied by rupture elongation (El) of the steel sheet, is at least 13,860 MPA %.
摘要:
A cold rolled steel sheet having a good ageing resistance is produced by subjecting a cold rolled steel sheet to continuous annealing including recrystallization, grain growth, quenching, supercooling, reheating and overageing according to inclinatory cooling, where after the recrystallization and the grain growth, the steel sheet is quenched at a cooling rate of 50 to 250.degree. C./sec from 720-600.degree. C. to 200-310.degree. C.; after retaining the steel sheet at the same temperature for 0 to 15 seconds, the steel sheet is reheated by at least 40.degree. C. up to 320-400.degree. C.; then the steel sheet is retained at the same temperature or cooled at a rate of not more than 0.7.degree. C./sec including the time for retaining the steel sheet at the same temperature; and then the steel sheet is cooled at an average cooling rate of not more than 10.degree. C./sec in a temperature zone of higher than 350.degree. C., at a specific average cooling rate in a temperature zone of 350.degree. C. to 300.degree. C. and at a specific average cooling rate down to 285-220.degree. C. in a temperature zone of lower than 300.degree. C.
摘要:
Disclosed is a process for producing titanium-containing cold rolled steel sheets and strips which can stand very severe press forming, which process comprising hot rolling, coiling at a temperature not lower than 700.degree. C., cold rolling and continuous annealing at a temperature, from 700.degree. to 900.degree. C., for 20 seconds to 2 minutes.
摘要:
A method of producing a non-ageing cold rolled steel strip having excellent deep-drawability, with a r value of 1.5 or higher and ageing index of not higher than 3 kg/mm.sup.2 from an Al-killed steel with a lowered carbon content between 0.001 and 0.0035% and with no special additives such as titanium by a relatively low temperature coiling in the hot rolling, and a short-time continuous annealing without over-ageing, thus over-coming the disadvantages caused by a high temperature coiling and by additional over-ageing.
摘要:
Provided are a cold-rolled steel sheet which undergoes a small load at the time of cold-rolling, has excellent press formability and high strength, and a method of manufacturing the cold-rolled steel sheet. A hot-rolled steel sheet having the composition comprising by mass %, 0.10 to 0.30 C, 0.2 or more Mn, 0.01 or more Ni, 0.5 to 2.5 Mn+Ni, 1.2 to 9.0 Cr, and Fe and unavoidable impurities as a balance, and has a tensile strength of 1000 MPa or less is subjected to pickling and, is subjected to cold rolling at a total rolling reduction of 60% or more thus forming a cold-rolled steel sheet. A final continuous annealing treatment is performed at a soaking temperature of 750° C. or above and at a cooling rate of 3° C./s to 100° C./s so that the cold-rolled steel sheet which has a tensile strength of 1280 MPa or more, breaking elongation of 3% or more, and a thickness of 0.05 to 0.60 mm is manufactured.
摘要:
The present invention provides a cold rolled steel sheet and a hot dip zinc-coated cold rolled steel sheet excellent in paint bake hardenability, non-aging properties and formability, and a process for producing the same. In the present invention, an extremely low carbon steel or extremely low carbon steel containing at least one element selected from the group consisting of Ti and Nb is used as a base steel, and Mn and Cr are positively added thereto, whereby the resultant steel has a mixed structure after annealing. Accordingly, there can be obtained a steel sheet having both a high paint bake hardenability and non-aging properties, and being excellent in formability such as an average r-value (deep drawability). With regard to the paint bake hardenability, the present invention may provide a cold rolled steel sheet and a hot dip zinc-coated cold rolled steel sheet to which paint bake hardening may be optionally imparted in an amount as large as about 10 kgf/mm.sup.2 and which also have non-aging properties.