Salzgitter increases capacity for index grades

With the help of an investment in the logistics for special grades, Salzgitter is reacting to the current bottleneck in index grades.

Index goods are exacting special grades. They feature a high alloy content and can therefore easily tend to develop stress cracks. If the slabs cool too rapidly, they can break. To limit the temperature drop, after the strand casting these special grades must be transported as quickly as possible to the hot-rolling mill for further processing.

Until now, only direct use of the slabs was possible at Salzgitter Flachstahl. The throughput in the hot-rolling mill is greater than the continuous casting system's output, bringing the logistics to its limits. To counteract this logistic bottleneck, it is expedient to store grades temporarily, either in hot boxes or by storage in slab stacks for selected grades.

In order to boost index grade production, the capacities for the controlled stack cooling were increased by expanding the building and the outdoor storage area in the finishing line. Two hot boxes, each with a capacity of 1,400 tons, were also built for temporary storage.

In addition to magnetic loading, the investment also includes a modified crane gripper. This makes it possible to move warm slabs that are above the Curie temperature. At a temperature around 600° C, the slabs are placed into the hot boxes where they remain warm longer. The slabs can be stored like this for up to five days and then further processed in the hot-rolling mill.

Thanks to this investment in the finishing line, Salzgitter Flachstahl can meet the lively demand for special grades and achieve greater flexibility in its production planning. Up to 6,000 additional tons of index grades can be rolled weekly.