A large steel mill produces stainless 420R, which is very hard: 220HV (by comparison, 316L stainless is 140HV and carbon steel typically ranges from 50HV to 120HV). It is also rather brittle, hence it cannot be acid pickled in a continuous line; it must be run on a push-pull type line.
However, success with pickling using hydrochloric acid (HCl) is difficult. Full scale removal is not consistently achieved, and the mill does not wish to pursue using the more aggressive (and more expensive) HF-based acid pickling. Instead, it wanted to investigate first running the 420R stainless through the EPS process and then through the push-pull HCl pickling line.
Two coils of the martensitic 420R stainless were processed on an EPS Coil Line. In each case, full scale removal was achieved and the coils continued on through cold rolling and batch annealing to complete their metallurgical processing. It was not necessary to run the coils through the HCl acid tanks to ‘finish’ their scale removal.
This reinforces the pickler’s thought that their best arrangement for the future may be to install a single EPS Cell in front of their acid pickling tanks. The EPS Cell would remove enough of the toughest scale that the duty on the acid tanks is reduced. This would allow them to greatly enhance their pickling speed and capacity, thereby enhancing the value of their investment in their existing acid pickling line. To learn more about using EPS technology to speed up an acid pickling line, visit the Using EPS Cells to Speed Up An Acid Pickling Line page of the EPS web site.