Critical hot plasticity and transverse cracking in continuous slab casting with particular reference to composition.

Abstract

The influence of alloy and residual elements on transverse rebend cracking at continuous slab casting was studied. Statistical evaluation of one year's production comprising 35 530 slabs is set in relation to the hot plasticity of the steels. Thermomechanical simulation of the cooling and the rebend strain cycle on a Gleeble machine was used to evaluate plasticity in the critical temperature range. Generally elements that increase transverse cracking negatively influence hot plasticity, which demonstrates that the simulation technique can be used to predict transverse cracking susceptibility.Elements as Nb, Al, Al+N, V appear to be detrimental, while N according to the Gleeble studies had no detrimental effect except when in combination with Al. Due possibly to a scavenging effect Ti improves plasticity of Al+N containing steels. High contents of P improve plasticity and production statistics gave similar indications. Further a raised content o f C within the range might improve resistance to transverse cracking. Statistics as well as hot plasticity testing point towards a beneficial influence of B. Also the influence of Cu and Mo was studied. The significant detrimental influence of S obtained from production statistics was not reflected by a similar drop of plasticity at Gleeble simulation. The results are discussed in terms of recent publications with due consideration to the influence of physical metallurgical factors.