In ingot casting days we had a cold strip order for automotive outer panel. The order required good press performance and beautiful surface. To guarantee good press performance S content was very low and because of outer panel the strip width was wide, around 1600mm. We had consistently rolled in scale problem in every time we rolled the ordered coils. When the rolled in scales were very big and deep, we reduced the pickling speed to 30mpm and even 0mpm to remove them. The ordered coils were cold rolled use. If they were pickled completely, rolled in scale disappeared after cold rolled
We suffered the production long years. And one day continuous casting was introduced to the steel works.
Unexpectedly, changing to continuous casting solved the problem. Continuous casting largely helped hot strip mill in the stand point of rolled in scale.

In case of ingot casting slab surface layer was very pure and so S content there was much lower than the average S content described on the rolling order. We empirically knew the influence of S content to rolled in scale, that was “The less S content, the more rolled in scale.”  So we easily realized the effect of continuous casting to rolled in scale problem, because slab surface layer of CC slab was not so pure as that of IC slab.

In another aspect of this remembrance;
When I was a young engineer, I was wrapped up in my work as the engineer responsible for daily strip quality problem and I thought I must solve the quality problem with the existing equipment. I thought improving/installing equipment was out of my scope. If I was a free-thinking person who could get over the scope of work, I could have achieved more improvements in hot strip mill. Afterwards, increased descaling capacity almost solved the rolled in scale problem excluding finisher stands type rolled in scale.