Mechanical properties and crack susceptibility of steel during solidification

The determination of high temperature mechanical properties is a necessity for the better understanding of defect formation during continuous casting of steel. Although a lot of studies have been performed on this topic, some aspects like the influence of cast structure on crack susceptibility are still unclear. The present paper focuses on the effect of carbon on high temperature strength and crack susceptibility. Tensile tests have been performed on steel shells with different carbon content during solidification. The results indicate an important influence of the orientation of the inhomogeneous cast structure towards main stress axis. The initial shell with a thickness of only a few millimetres is more sensitive to defect formation than commonly believed. The critical limits of straining range from about 0.15 to 0.4 %. With increasing shell thickness, the critical strain ascends up to 1.6 %. The detected segregated internal cracks form within the critical temperature range. The strength near solidus temperature is lower than in comparable hot tensile tests, which can also be attributed to the detrimental effect of the inhomogeneous structure. The strength at solidus temperature amounts to 2.5 MPa for higher carbon steels and about 1 MPa for low carbon steels.