An Evaluation of Critical Strain for Internal Crack Formation in Continuously Cast Slabs

Abstract

An in-situ melt-bending test method has been developed, which permits the simple evaluation of the critical strain for the internal crack initiation in continuously cast slabs. In this testing method, the center of the top surface of a specimen in the form of rectangular parallelepiped is melted by high-frequency induction heating and the heating current is then lowered to form a solidified layer about 20mm in thickness. The specimen under this condition is deformed by bending. The amount of strain applied to the solid-liquid interface is changed by changing the amount of bending. This test is conducted in an argon gas atmosphere. After the test, the internal cracking in the specimen is investigated and the critical strain for the internal crack initiation is determined by comparing the cracking condition with the amount of the strain applied. The critical strain was measured in six carbon steels by the above-mentioned method. It has been found that the difference in the critical strain among the steel grades is correlated to the difference between the calculated liquidus temperature and the calculated solidus temperature and that the greater the difference, the smaller the critical strain will be. It is also revealed that the critical strain values obtained by the other researchers show the same tendency.