Civil Engineering Reference
In-Depth Information
Effects of electricity in
EAF
Decrease flow stress
Increase formability
Localized heating
Larger strains achieved
Decrease forming load
and interface pressure
More severe tribological
conditions
Better tribological
conditions
Fig. 9.30
Tribological effects of EAF [
13
,
14
]. As the electricity is applied to the manufacturing
process, it increases the formability of the part; however, it can also have negative effects on the
tribological effects at the die/workpiece interfaces
favors evaporation and chemical decomposition of the lubricant. Thus, the reduced
quantity of lubricant and possible modified
chemical
attributes are not able to con-
tinue providing sufficient separation. Metal-to-metal contact between the asperi-
ties of the dies and workpiece occurs, resulting in higher friction, die wear, and
poor surface quality. In conclusion, one requirement for a good metal forming
lubricant for EAF is the capacity of retaining its lubricity at elevated temperatures
and in the presence of electric current fields. The objective of this subsection is to
present the challenges brought by this process, and to screen the performance of a
few selected lubricants through electrically assisted ring compression tests.
9.2.2 Experimental Setup and Procedure (Ring Tribo-Tests)
To evaluate the performance of the three selected lubricants, the ring compression
tribo-test was used. This is a relatively simple test that can mimic the medium-to-
severe deformation occurring in an actual forming operation. The testing setup for
these experiments is shown in Fig.
9.31
. The insulated dies, consisting of a combi-
nation of A2 steel and reinforced plastics, are securely gripped by the top/bottom
platens of the 250-kN-capacity Instron hydraulic testing machine. Electrical cables
are fastened to the top and bottom dies, and the insulation ensures electricity flows
through the dies/workpiece in a closed loop. The electricity is applied continu-
ously from the beginning to the end of each test.
The ring compression specimens used in this work were manufactured from a
rod of 304 Stainless Steel. The rod was received as precision ground to a diameter
of 4.763 mm, and cut to a height of 2.10 mm using a wire EDM. Then, a drilling
operation was performed using a CNC lathe to create the 2.38 mm inner diameter.
Careful measures were taken to ensure the repeatability and flatness of all speci-
men surfaces in contact with the dies.
