Oxide Behaviour in Hot Rolling

Mechanical behaviour of iron oxide scale: Experimental and numerical study

“…In the bite, cracks opened before entry tend to open more widely and fresh metal is "micro-extruded" in the gaps between the fragments (figure 3b,c), in accordance with the results obtained before by [1]. Note that this requires extremely fine elements at the corners of the oxide scale fragments.…”

“…It has been shown that toughness (i.e. small strain plasticity) increases with temperature, with a transition around 700°C as expected [1].…”

“…As expected [1], breaking of the oxide layer occurs even before the roll bite, because of the tensile stress associated with the bending of the surface there ( figure 3a). Transverse cracks open in a quasi-periodic way : each crack opening relaxes the surrounding stress, until further advance has created enough stress for the criterion (equation 4) to be met.…”

“…Although the thickest and most brittle, "primary scale" layers are removed by mechanical -thermal descaling [1], possible oxide residuals and fast re-oxidation are able to reform a 10 to 30 µm thick layer at the entry of the finishing Hot Strip Mill. At the strip surface temperature imposed by the contact with the cooled rolls, the oxide is most of the time much more brittle than the metal; co-deformation thus often leads to fracture of the oxide under the elongation imposed by rolling (figure 1).…”

“…The literature points to three micro-mechanisms [1][2][3] and proposes stress or strain criteria for their occurrence : interfacial sliding, transverse fracture and interfacial fracture (delamination). In the following, the main thrust will be on pre-bite transverse cracks linked with longitudinal tension.…”