METHOD AND DEVICE FOR COOLING STEEL STRIP

摘要

PURPOSE:To obtain a steel material having a good shape and desired quality without surface oxidation in the stage of subjecting a steel strip which is not subjected to an overaging treatment to a dip hardening treatment by administering the three points; the temp. control of a dipping bath, nozzle disposition of water sprayers and jet pressure control of the nozzles. CONSTITUTION:A heated steel strip 1 is dipped and cooled from above to below in a tank 3 filled therein with warm water 2 kept at the temp. of 60-75% the boiling temp. and is discharged to the outside of the tank by a sink roll 4. Water sprayers 5 are provided in multiple stages on both sides of the strip 1 in the water 2 and water ejecting nozzles 6 are provided in a way that jets are generated at each tip of each sprayer 5. When the space between the adjacent upper and lower nozzles is designated as A and the distance between the nozzles existing in the exactly opposite positions on the front and rear of the strip 1 is designated as B, the relation of A and B is set at A>B. As a result the jets generated by the nozzles 6 collide with each other on the strip 1 surfaces without generating turbulence. The steam films generated on the strip 1 surfaces are thus positively removed and the steel material having both excellent shape and surface quality is obtd. The width of the nozzles 6 is required to be set at the full width of the strip 1 or above.