A roll-bending approach to suppress the edge cracking of silicon steel in the cold rolling process

Abstract

The range of roll-bending that inhibits the edge cracking of high-silicon (3.0 wt%) steel strip during cold rolling was investigated by performing a pilot cold rolling test. In the rolling test, roll-bending was emulated by lathe-machining the work roll surface to be concave (corresponding to negative roll-bending) or convex (corresponding to positive roll-bending). Crack growth length that propagated during rolling and crack growth direction were measured. Three-dimensional finite element analysis coupled with ductile fracture criterion was conducted to predict the crack growth length and crack growth direction. The reliability of the finite element analysis was verified by comparing the predictions with measurements. A series of finite element simulations were then conducted with different levels of roll-bending, expressed as the ratio of the radius of curvature of work roll surface ( R) to its barrel length ( L).The difference between the measurements and the predictions of the crack growth length and crack growth direction was 6.5% and 8.3%, respectively, when the initial notch length was 6 mm. Even if a high reduction ratio for a given pass was applied to the silicon steel strip, edge cracking did not occur if the L/ R ratio was less than −0.15, with a negative value corresponding to a concave surface profile, representing negative bending.

Numerical Analysis of Edge Cracking in High-Silicon Steel during Cold Rolling with 3D Fracture Locus

“…The elastic modulus of the strip was 190 GPa, the density was 7650 kg/m 3 , and Poisson's ratio was 0.3. Byon et al [8] showed that the pilot cold rolling test and FE analysis results were consistent when the element size in the x and z-directions around the notch tip of high silicon steel strip was 0.05 mm, respectively. Hence, mesh convergence test in this study was performed to determine the appropriate number of elements in the strip thickness direction.…”

“…Kang et al [41] calibrated a two-parameter ductile fracture model through tension test and FE analysis for stress triaxiality due to various notch changes in tensile specimens. Unlike the tension test, since the range of stress triaxiality in rolling is −1.2 to 1.2 [8], the effect on fracture is affected not only by stress triaxiality but also by the Lode parameter [42,43]. Therefore, a ductile fracture criterion that reflects the Lode parameter is required, and related models [10,29,34,44] are the maximum shear model [44], the modified Mohr-Coulomb (MMC) fracture criterion [10] and so on.…”

“…Recently, Byon et al [8] conducted FE analysis coupled with the Johnson-Cook ductile fracture (DF) criterion [9] to predict the length of crack growth and crack growth direction in the strip during cold rolling. They verified the reliability of the FE analysis by comparing the predictions with those measured from a pilot cold rolling test that used a 25-mm wide 3.0 wt% silicon strip being rolled.…”

“…In previous studies [4,5,7,8], the width of the strip used in the rolling test was limited to 25-100 mm. These widths are too small for the results of their research to be applied to actual cold rolling scenarios.…”

Effect of process parameters on porosity defects in Al-Si alloy hot rolling

“…Some scholars have investigated machining and rolling via finite element analysis. Byon et al 10 used finite element software to simulate the cold rolling process of steel strips, predicted the length and direction of strip edge crack extension with the ductile fracture criterion, and performed cold plate rolling test to validate the reliability of finite element analysis. The result shows that using a concave profile which corresponds to a negative roll can reduce the occurrence of edge cracks in the strip during cold rolling.…”