Hot rolling is a process in which a steel billet, heated above its re-crystallization temperature, is passed through a set of rolls. During hot rolling, the billet remains in a ductile and workable state, allowing a large degree of deformation. Hot rolling is therefore the obvious choice to obtain spectacular levels of deformation when rolling wire.
At OCAS, hot rolling of wire is performed on a reversible rolling mill that has been equipped and extended with dedicated systems to guide and control steel billets during the consecutive rolling passes. During these different steps, a bar is gradually rolled to a wire with a diameter of 5.5 mm. For this, a set of pair of grooved rolls is used.
Pass design know-how
The shape of each roll pass sequence is specifically engineered to induce the right degree of reduction and keep an optimum, homogeneous deformation throughout the cross-section. For the latter purpose, it is common to use various shape transformations such as square-to-oval or oval-to-diamond.
During rolling, various sensors monitor the exact position of the wire while pyrometers scan the temperature of the bar at each intermediate step. Manipulation of the bar in between two steps is performed manually, allowing the operator to evaluate the appearance of the bar at each step of the process. With the quality checked and all system parameters automatically adjusted by the mill controller, the next step of the rolling process is started by moving the bar through a dedicated guiding system that accurately positions the rod for the next pass of the rolling sequence.
Multiple successful bar rolling campaigns have been carried out, using different compositions including non-ferrous alloys, and shaping various geometries.
“The hot rolling of bars into wires is quite different than plate rolling and requires a good insight into the forming mechanisms of this process”
“By modifying our lab hot rolling mill, we can now offer the full range of geometries: heavy gauge, flat and bar”
