Abstract: In a continuous annealing process for a cold reduced steel strip substantially including a rapid cooling stage and a carbon precipitation treating stage into said process, the rapid cooling rate which is obtained by initial heating to above the recrystallization temperature and then slowly cooled for about 100 seconds to be above 200.degree. C./sec; and the starting temperature is controlled to be between 500.degree. C. and lower than 600.degree. C., thereby to obtain good press-formability of the continuously annealed steel strip.

Abstract: When an Al-killed steel consisting of, specially, 0.005% .ltoreq. [N] .ltoreq. 0.007%; 10 .times. [N] .ltoreq. Sol.Al. .ltoreq. 0.12%; and the ratio Sol.Al.%/[N]% controlled within the range of 10 to 20, is continuously cast, hot rolled, coiled at a high temperature, cold reduced and finally continuously annealed under special requirements, the steel strip is not at all inferior to the commercial base strip in mechanical properties and is made under high productivity and exhibits excellent uniformity in qualities.

Abstract: A high tension Al-killed steel of which the yield point is more increased by the ensuing heat treatment after press-forming than that of the properties in which the tensile strength is above 40 to 80 Kg/mm.sup.2, is made by the following main steps:1. the chemical composition of steel is substantially controlled at the range of 0.04 to 0.12% C, 0.10 to 1.60% Mn, and 0.010 to 0.200% Sol.Al,2. the above steel is hot-rolled with a finishing temperature of more than 800.degree. C and a coiling temperature of less than 630.degree. C,3. after the above steel strip cold-reduced with the ordinary requirements is continuously heated up to 700.degree. to 900.degree. C and then rapidly cooled by a jet of water, said strip is reheated up to 150.degree. to 400.degree. C and held for 2 to 300 seconds at said temperature to partially remain solution carbon in steel.

Abstract: A steel consisting essentially of 0.04 to 0.10% C, 0.04 to 0.20% P, not more than 0.02% S, and [S]% .times. 10 to 0.7% Mn is conventionally hot and cold rolled. It is then subjected to the following continuous annealing:Recrystallization heating step: Ac.sub.1 to 900.degree. C. .times. 10 to 120 sec.;Quenching step: starting temperature of quench: Ac.sub.1 to 900.degree. C.; quenching method: jet stream of water;Tempering quenched steel: 200.degree. to 500.degree. C. .times. 10 to 180 sec.,And then conventional cooling and coiling. The steel has high tensile strength and excellent elongation and weldability characteristics.

Abstract: A steel being substantially made and adjusted within the range of 0.04 to 0.12% C, 0.50 to 2.00% Si, and 0.10 to 1.60% Mn, passed through ordinary hot and cold rolling processes, is subjected to a full continuous annealing process comprising the following steps:1. recrystallization heating step; rapid heating up to the range of 650.degree.C to 900.degree.C at a rate of 200.degree.C/min. and more;2. keeping and soaking step; holding for 10 to 120 sec. at the above heating temperature;3. ordinary cooling step; cooling to room temperature from the holding temperature;4. and then ordinary cooling step;Becomes a utility cold reduced steel having the most suitable mechanical properties required as a safe countermeasure for an automobile and similar vehicles.