Almost every morning the assistant manager of cold rolling mill entered the office of the hot rolling mill with broken strips for tin coil and threw them on my desk and shouted “ Stop the breakage problem ! “ The office of the hot strip mill was on the first floor and that of the cold rolling mill was on the second floor in the same building. I was the engineer in charge of the hot strip mill product quality. In those days pickling lines belonged to the hot strip mill. So I have the responsibility for the pickled coils with the defects that had been the starting point of the strip breakage. The breakage was called scab-breakage, because the starting point of the breakage looked like scabs or double layered defects after cold rolled. Scabs/double layered defects on the hot coil were usually originated from slab defects, such as cracks, hand scarfing residue, something adhered to the surface of slabs and so on. So cold rolling people called those breakages as scab-breakage.

But some breakage samples did not look like scabs and looked like heavy scratches. We checked pickled coils outer wraps and found heavy scratches on them. We recognized some breakages were due to scabs and some breakages were due to heavy scratches.

Over 40 years ago coil transfer of the hot coils ware done by lift trucks. When production amount increased, handling amount of lift tracks increased also and then handling procedure became rough, which increased scratches at inner wraps and outer wraps. And breakage problem increased at cold rolling mill.

On one occasion the breakage suddenly began to increase. We could not find the reason. Production had not increased at that time. No change in coil handling procedure. Finally we found the cause of the increased breakage. The assistant manager of the pickling line had reduced the removed length at both ends of coils without talk with technical group. He was a highly motivated person and had decided to increase product yield by decreasing the scrap length. Removed length at both ends was turned back to normal and breakages were reduced to normal.

Nowadays coil transfer between hot strip mill and pickling line is done by transfer tables and/or coil car system and this problem has ceased.