BLOOMING METHOD FOR PRODUCTION OF CONSTANT-STRAIN STEEL

摘要

PROBLEM TO BE SOLVED: To provide a constant-strain steel capable of being controlled with a product strain after heat treatment by reducing a difference between strains in the outside and inside of the macro pattern through further increasing a draft rate while utilizing a center segregation control effect to the maximum extent whose positive and negative segregations near the final solidifying point are small by making a billet section rectangular. SOLUTION: A billet produced by a rectangular mold with an outside length- width ratio being over 1.2 is reduced down more than two times by strong screw down pass with a draft being more than 15% at a short side shown in Fig. 1. Then, the blooming is performed based on a pass schedule which presets the number of strong draft pass times at a long side to be the same number or less than that at a short side, and a constant-strain steel is produced by controlling a length-width ratio to be below 1.4.