A major steel mill that produces a number of specialty high strength steels recently had several sheets of 100K yield steel processed through the EPS Sheet Line at TMW. The sheets were 1500 mm x 3000 mm across and 12 mm (0.4725 inch) thick. All sheets were thoroughly de-scaled and emerged with a very uniform surface appearance.
The mill representative was impressed. He explained that this high yield strength steel presents two persistent problems for acid pickling:
(1) The hardness of the material makes it difficult to loop through the acid tanks;
(2) It has a harder surface scale which requires longer acid immersion to remove.
This makes the acid pickling result more difficult to predict.
The results of this EPS trial are representative of past trials on material such as 6150 that is very difficult to acid pickle. It is important to note that since the EPS process is not a ‘dissolving’ process like acid pickling, EPS line speeds do not vary that much whether you’re processing commercial quality material or these very hard grades.
This particular mill produces 100K yield material up to 1 inch thick and its options for acid pickling such coils are very limited. It is encouraged that EPS may be a better way to “pickle” this very heavy gauge high strength material.