Abstract: In a cooling zone of a continuous annealing line engineered to continuously process longitudinally travelling steel strip, the strip is first slowly cooled to a desired temperature at a rate of not higher than 20.degree. C./sec. by means of a jet stream of cooling gas ejected against the surface of the strip and subsequently quenched to a desired temperature at a rate of not lower than 70.degree. C./sec. Thinner strip is quenched by high-speed gas-jet cooling that is effected by ejecting a jet stream of cooling gas against its surface, while heavier strip is quenched by bringing it into contact with the perimeter of cooling rolls cooled by a coolant. Namely, quenching is achieved either by high-speed gas-jet cooling or roll cooling depending on the thickness of the strip being processed.

Abstract: A strip cooling apparatus for a continuous annealing furnace for continuously treating longitudinally fed steel strip has a pair of cooling gas chambers attached to the furnace walls on both sides of the strip so that the front of each chamber faces the strip. Each cooling gas chamber has nozzles having round outlets opening toward the strip surface on its front side to shoot forth a cooling gas jet against the strip furnace. The nozzle is separated from the strip by a distance z not larger than 70 mm and projected from the front of the cooling gas chamber by a length of not less than (100--z) z) mm. The cooling apparatus also has a pair of rotatably holding rolls reciprocatably attached to the furnace walls to press the strip at a right angle thereto. The holding rolls holds the strip and prevents the occurrence of fluttering.

Abstract: In controlledly cooling steel strip in a continuous annealing line, the heat transfer rate needed for attaining the desired cooling rate is calculated from an equation including strip thickness, the cooling starting and finishing temperatures, and the desired cooling rate, and the obtained heat transfer rate is corrected according to the effect of natural cooling in idle-pass zones preceding and following the coolant spray zone. The flow rate of coolant is determined and set by using an equation expressing the predetermined relationship between the heat transfer rate and coolant flow rate. The length of the coolant spraying region extending in the direction of strip travel is calculated from the running speed of the strip, the cooling starting and finishing temperatures, and the desired cooling rate. The nozzles are set to turn on and off so that the coolant is sprayed from such a number of nozzles as correspond to the length of the spraying region thus calculated.

Abstract: A surface treatment apparatus for producing a steel strip having an enhanced phosphatizing property, has a plurality of guide rolls for guiding the strip along a predetermined path, a pickling vessel having nozzles for spraying a pickling liquid onto the surface of the strip, a first rinsing vessel having nozzles for spraying water onto the strip surface, an electrolytic treating vessel having an anode and a temperature control for the electrolytic treating liquid, a second rinsing vessel having nozzles for spraying water onto the strip surface, and a voltage supply for applying a voltage between an anode and a cathode consisting of a guide roll located beside and close to the electrolytic treating liquid contained in the electrolytic treating vessel.

Abstract: Method and apparatus for cooling a steel strip in a continuous annealing line, which has a first cooling step in which the steel strip immediately after an overageing treatment is cooled from the overageing temperature to a temperature in the range of from about 95.degree. C. to 60.degree. C., a temperature which prevents a surface oxidation but allows self-drying of the strip, in a protective atmosphere using a liquid coolant; and a second cooling step in which the steel strip is cooled to a temperature suitable for a subsequent temper rolling using liquid coolant at a temperature no higher than 40.degree. C.

Abstract: A method and apparatus for controlling a temper-rolled profile of a cold rolled steel strip after continuous annealing, comprising subjecting the continuously annealed cold rolled steel strip simultaneously to temper-rolling and profile controlling by use of a six-high rolling mill of intermediate roll shifting type in the same production line.