دانلود رایگان مقاله شکستگی نوار در رولینگ دستگاه تختال نازک ریخته گری

ABSTRACT

In this paper, a case of severe strip breakage in rolling mill of Thin Slab Casting and Rolling (TSCR) shop of TATA Steel, Jamshedpur is presented. Visual observation revealed complete splitting with material missing along the central axis of the strip. Presence of defects in form of white stringers, white patches and holes were observed along the same axis just ahead of split location. Metallurgical analysis revealed association of these defects with slag type foreign materials in the rolled strip. The entrapments of un-deformable materials like slag in slab resulted in the formation of surface discontinuities on the strip on account of differential rolling. The discontinuities manifested in form of holes at lower strip thickness in the later stands of the mill. Inhomogeneous deformation about such holes also resulted in material overlapping. In summary, the breakage of the strip was found to have a strong correlation with the presence of heavy chunk of foreign inclusions from secondary steelmaking sources.

8. Conclusions

Following conclusions can be drawn from this study: (1) Presence of foreign materials in form of secondary steelmaking slag is observed at the strip breakage site in the strip. (2) Rolling strips to low thickness exposed the foreign materials complete which get removed subsequently because of lack of deformability forming holes. (3) Material overlapping occurred due to the presence of holes in the strip which allows unconstrained deformation. (4) The splitting at the centreline is related to the presence of heavy chunk of such foreign slag in this location. (5) It is recommended to keep the slag detection system activated during ladle teeming in order to avoid slag carryover. If such cases accidentally occur, it is recommended to roll slabs to lower thicknesses.