The Effect of Superheat on Micro- and Macrosegregation and Crack Formation in the Continuous Casting of Low-alloyed Copper

摘要

In continuous casting, the severity of centerline macrosegregation and internal crack formation is linked to the cast structure, which can be minimized by increasing the equiaxed zone. Thus all the factors which favour an equiaxed structure are useful to quality. These are: low superheat, electro magnetic stirring (EMS) in the mould, large section size and especially in the case of internal cracks, uniform heat transfer between the strand and the mould. Microsegregation, which is the primary reason for macrosegregation, is due to the distribution coefficient and the growth rate of the solidification front. It is known that superheat has an influence on the solidification structure on both the micro- and macro- levels. Research has confirmed that superheat also affects crack formation in the solidifying front. These observations are usually reported on steels but little has been reported on low-alloyed coppers. In our experimental studies we examined the effects of superheat and uneven heat transfer on segregation behavior of phosphorus and iron in round, deoxidized, high phosphorus (DHP) copper billets. Furthermore crack formation and the solidification structure on both the micro- and macro- levels were studied. Results were verified by optical emission spectrometry (OES) and scanning electron microscopy (SEM).