The effect of rolling condition on the annihilation process of loose structure in large slab ingot was investigated to clarify the possibility of getting sound heavy steel plate by rolling. The most important parameters for annihilating the loose structure were found to be reduction ratio, rolling shape factor, and deformation resistance ratio. The following formulae were derived to predict the rolling conditions required for annihilating loose structure.
a=∑n1=1ψi(Δh/Ho)i≥1,
ψ=(Δb/bo)/(Δh/Ho)=3[1-0.14/1d/hm·exp{-4·(1d/hm)0.77·Pav/koc}]
where a : Critical closing hole index ψ : Rate of closing hole
Δh : Reduction 1d/hm : Rolling shape factor
Ho : Initial thickness koc : Deformation resistance at the center of thickness
Pav : Average of hydrostatic stress
Δb : Reduction of hole diameter bo : Initial hole diameter
