Many of the largest users of flat roll sheet and plate purchase hot roll black (HRB) carbon steel. Think of ConAg equipment OEMs, railcar manufacturers and the like, plus makers of equipment that stays indoors and is sheltered from the weather. For many of their large fabrications, HRPO isn’t economical plus they lack the paint pre-treatment systems to remove the oil from HRPO.
Most HRB has a heavy layer of mill scale that leaves an obnoxious dust as the material makes its way through a production facility. It fouls the warehouse, processing machinery . . . pretty much everything. HRB also limits the speed of laser cutting machines because the scale presents an inconsistent surface to the laser beam. And because many HRB users don’t have a paint pre-treatment system, they spend a lot of time and money wiping down their fabrications prior to painting.
Is EPS a good alternative to HRB for these manufacturers? It absolutely can be. Most think of EPS processing as a replacement for acid pickling – which, of course, it is – and, therefore think of EPS’d material as a replacement for HRPO and pickled dry. But limiting the application of EPS this way misses some big opportunities for savings with HRB users.
|To put this discussion in context look at the sheet of 0.187″ HRB at the left. The dark surface shows the customary heavy mill scale. The inset photo is a closeup of a napkin after wiping it across the HRB sheet. It picks up the loose, heavy scale that HRB users must content with in their material storage, their work centers and all throughout their operations.
Now, running this material through an EPS line at standard ‘full scale removal’ settings will remove the mill scale to the same level as acid pickling. The resulting sheet appearance is remarkably clean, as shown in the next photo (below) of material from the same 0.187″ HRB coil after standard EPS processing and a cut-to-length processing. The napkin is spotless. What’s more, the surface is very uniform in both appearance and texture, providing excellent conditions for paint adhesion and smoothness (see the full EPS surface paint testing analysis report).
|This is the EPS material you’re used to – a complete replacement for HRPO with a superior surface AND NO OIL. For manufacturers with processes that tolerate no surface scale at all – aggressive stamping, forming or drawing, galvanizing, plating or coating – ‘standard’ EPS has the advantage that there’s no oil to remove prior to painting.
The interesting alternative to standard EPS for many HRB users is a type of EPS processing where the line is run at a much higher speed than normal. This accomplishes removal of most of the surface scale – certainly all the loose, heavy scale – but does not remove all the tight scale bound to the surface. An example of material run this way from the same 0.187″ coil is shown in the photo below. The surface is much, much cleaner than HRB, as the napkin indicates, but is not ‘spotless’ like standard EPS. It also retains a slightly darker color than standard EPS, indicating some residual scale remains.
|The point is this material underwent EPS processing at THREE TIMES THE SPEED of normal EPS. At 3X throughput, this is a very inexpensive way to produce a clean, dry replacement for HRB with a lot less hot roll dust, faster laser cutting speeds, and much less time and money spent to prepare fabrications for painting.
Many manufacturers order HRPO to make certain parts and HRB to make others. By switching to EPS, they can eliminate that practice, using standard EPS to replace HRPO and ‘high speed’ EPS to replace HRB. That does much more than simplify ordering and materials management. It keeps the twin burdens of oil and heavy, dirty scale out of their operations completely.