Patent ID: 7448430

Claim:
A manufacturing method for a continuously cast product of steel comprising the steps of: detecting a position of a crater end of said product by using a method for measuring a solidification state of the continuously cast product by a sensor arranged so as to have a liftoff of about 3.5 mm to 13 mm and thereby be in a non-contact manner with said product; and controlling at least one condition selected from the conditions of casting speed and quantity of secondary cooling water based on said detected position of crater end, said method for measuring a solidification state of the continuously cast product comprising the steps of: cooling said product until a surface layer portion thereof is α transformed; transmitting transverse waves of electromagnetic ultrasonic waves by use of magnetostriction effect to said cooled product as a transmitting signal; receiving a signal after said transmitting signal propagates in said product as a receiving signal; and judging the solidification state of said product based on said receiving signal.