1979 Volume 65 Issue 12 Pages 1702-1711
The influence of alloying elements on uneven solidification in a continuous casting mould has been investigated by emptying unsolidified steel out of flat mould composed of water-cooled copper plate and sand. The following results are obtained:
(1) In this experiment withou twithdrawal of strand and without use of powder, the solidified shell is formed as unevenly as in continuous casting mould, for specific alloying elements and contents.
(2) In carbon steel, the unevenness of solidified shell has the maximum value at 0.11-0.13%C, and decreases rapidly when the carbon content deviates slightly away from this range. This tendency is the same as in longitudinal cracking of continuously cast slab.
Also in SUS 304, Fe-11.6%Mn, Fe-10.1%Ni, and Fe-5.6% Si steels, the uneven solidification has been observed.
(3) A formation model of the uneven solidification has been proposed. Namely, bending force towards liquid steel is potentially exerted at upper part of shell by the difference of amount of shrinkage between water-cooled copper plate side and liquid steel side of shell during solidifying and cooling. This force is encouraged by additional shrinkage accornpanying δ→γ transformation near solid-liquid interface of the shell. When high-temperature strength of shell is good and this force overcomes the ferrostatic pressure, the shell bends actually towards liquid steel and air gap is formed between the shell and mould. In this way, retardation of solidification is generated locally, and shell is formed unevenly.