WATER QUENCHING OF COLD ROLLED STEEL STRIP

摘要

In a continuous annealing operation of a cold rolled steel strip involving water quenching and over-aging treatments, a method and apparatus employing a cooling system comprising a pair of rolls arranged to contact the surfaces of a steel strip, a pair of cooling water spray units arranged in symmetrical positions on both sides of the steel strip and a storage tank connected to the spray units, whereby when a steel strip heated to a temperature between 500 and 800'C is water quenched, the distortion of the strip during the water quenching is inhibited and the surface oxidation is reduced to such an extent that no supplementary pickling is required. Each of these cooling water spray units comprises a rear portion sonstituting a rear wall having a semicircular cross section, a damping screen built integral in the central portion or the unit, a nozzle plate mounted at the front portion of the unit and including a plurality of slits, and a water supply pipe having a C-shaped cross section and opened at a position opposite to the rear wall, whereby water sprays of uniform flow with a spray impact pressure between 40-and-170 mmHg are directed against each surface of the steel strip from the cooling water spray units.