At Chiba works of Kawasaki steel, No.1 HSM rolled tin plate hot coil, stainless steel, Si steel and high carbon steel after No.2 HSM was introduced. The barrel length of WR at No.1 HSM was 1422mm and so it was focused to roll narrow material.
We struggled with severe demands from high carbon steel customers constantly. Main demands were good surface appearance and small crown (transverse thickness deviation). As for small crown we could meet the demand from customers by applying taper crown WR. In surface appearance demand we, I and all operators at No.1 HSM, struggled for many years. Especially high carbon steel containing Ni was very difficult to produce without rolled in scale. I surveyed documents and books. No way to solve the problem was presented. Only remarks that Ni containing steel has a notorious scale was written. I examined the English meaning “notorious” by the dictionary and found the meaning in Japanese. I found this rolled in scale is very difficult to solve.
We increased furnace temperature as high as we could. One week we had less rolled in scale, and next week we had more rolled in scale.
Furnace temperature was so high, maybe 1320-1340℃ at soaking zone from my remembrance, and sometimes we could see the melted surface scale through the side window of reheating furnace. To get good result high temperature is good as far as surface scale was not melted. But this operation was difficult actually. When we reduced furnace temperature much lower, the condition of rolled in scale was stable, but we could not have good surface. There existed some amount of rolled in scale in every time.

Our understanding about this rolled in scale is clear today. Originally rolled in scale of Ni containing high carbon steel is notorious, difficult to remove, but after all new FSB with higher descaling pressure and short distance between nozzles and sheet bar surface solved the problem. We could produce Ni containing high carbon strip without any rolled in scale after the installation of new FSB.