# Analysis of the Influence of Segmented Rollers on Slab Bulge Deformation
## 5 Influences of Roller Spacing and Roller Diameter on Slab Bulge Deformation
### Results and Conclusions
#### 5.2.2 Influences of Roller Diameter on Bulge Deformation  
The influence of roller diameter was observed by using the deformation models under various roller diameters and a constant roller spacing. The roller spacing was defined as 300 mm. The roller diameters of the bulging model are shown in Table 5. The results of bulge deformation on the wide side under different roller diameters are listed in Table 7. It was found that the slab bulge deformation under the rigid rollers was almost unchanged with different roller diameters. This was because the rigid roller was established by a rigid body that did not reform in the continuous casting process, and the changing roller diameters had no influence on slab bulge deformation. The average deformation of the slab on the wide side decreased by about 0.08 mm when the elastic solid roller diameter increased by 20 mm. The influence of changing roller diameters on bulging deformation was relatively small due to the low stiffness of the elastic solid roller. However, the slab bulge deformation was effectively influenced by changing the segmented roller diameter by 20 mm, including the two-segment and three-segment rollers. The maximum reduction of bulging deformation was 0.24 mm, with the two-segment roller diameter changing from 250 to 270 mm, and the decrease remained around 21.8%. The minimum reduction was 0.1 mm with the three-segment roller diameter changing from 230 to 250 mm, and the decrease remained around 11.1%. This was because the elastic roller was deformed in the model, which resulted in a larger contact area between the slab and the roller as the roller diameter increased. In other words, the rigidity of the solidified shell was indirectly increased. The bulge deformation of the continuous casting slab was effectively controlled with the improved stiffness of the solidified shell and the casting roller. An analysis of variance (Table 7) showed that the value of variance ratio was 6.30 under different roller diameters, which was larger than the critical value of variance ratio (the critical value was 5.14). The roller diameter had a significant effect on slab bulging deformation.  
In general, the slab bulge deformation increased with the increased roller spacing and decreased with the increased roller diameter. The comparisons of average values of bulge deformation along the wide side are shown in Figure 11. When the roller spacing was 400 mm and the roller diameter was 230 mm, the maximum average value of bulge deformation along the wide side was 2.80 mm with the elastic solid rollers. When the roller spacing was 300 mm and the roller diameter was 270 mm, the minimum average value of bulge deformation along the wide side was 0.69 mm with the three-segment rollers; the difference was of 2.11 mm in comparison with the previous one. The bulge deformation was reduced by 75.4%. The optimized structural parameters could effectively control slab bulge deformation.  
\begin{table}
\begin{tabular}{c c c c c} \hline \multirow{2}{*}{**Roller Diameter**} & **Rigid** & **Elastic** & **Elastic Two-Segment** & **Elastic** \\  & **Solid Roller** & **Solid Roller** & **Roller** & **Three-Segment Roller** \\ \hline
230 mm & 0.82 mm & 1.43 mm & 1.28 mm & 0.90 mm \\
250 mm & 0.80 mm & 1.37 mm & 1.10 mm & 0.80 mm \\
270 mm & 0.80 mm & 1.25 mm & 0.86 mm & 0.69 mm \\ \hline \end{tabular}
\end{table}
Table 7: Bulge deformation on the wide side with different roller diameters.