Silicon Steel: Hot Working Constitutive Behaviour and Multistage Rolling Simulation

Abstract

From torsion testing of silicon steel over the range 600 to 900 °C and 0.1-5 s^-1, the constitutive analysis was performed by the sin h law to establish activation energies. As the temperature rose and strain rate declined, the fracture strain increased to as much as 14.3 and the subgrains in the elongated grains became larger. These results are shown graphically to agree with data from a wide collection of published reports on Si steels. The strengths were intermediate between those of 409 (11Cr) and 434 (16Cr-1Mo) that indicated Si has a strengthening effect almost 4 times that of Cr per unit weight; however, the activation energies of 409 and 434 were higher. Simulation of multistage rolling was done with T declining from 900 to 600 °C, pass strains of 0.2 or 0.3, strain rate of 1 s^-1 and intervals of 20 or 40 seconds. Because of the short intervals, the pass flow curves did not exhibit the yield points of isothermal tests so that it was not possible to calculate fractional softening in the intervals at a declining temperature. Two new measures were suggested: a) the relative softening during an interval that decreased as temperature fell and b) relative reduction of the maximum pass stress relative to isothermal peak stress that increased at a decreasing rate as temperature declined.

From torsion testing of silicon steel over the range 600 to 900 °C and 0.1-5 s^-1, the constitutive analysis was performed by the sin h law to establish activation energies. As the temperature rose and strain rate declined, the fracture strain increased to as much as 14.3 and the subgrains in the elongated grains became larger. These results are shown graphically to agree with data from a wide collection of published reports on Si steels. The strengths were intermediate between those of 409 (11Cr) and 434 (16Cr-1Mo) that indicated Si has a strengthening effect almost 4 times that of Cr per unit weight; however, the activation energies of 409 and 434 were higher. Simulation of multistage rolling was done with T declining from 900 to 600 °C, pass strains of 0.2 or 0.3, strain rate of 1 s^-1 and intervals of 20 or 40 seconds. Because of the short intervals, the pass flow curves did not exhibit the yield points of isothermal tests so that it was not possible to calculate fractional softening in the intervals at a declining temperature. Two new measures were suggested: a) the relative softening during an interval that decreased as temperature fell and b) relative reduction of the maximum pass stress relative to isothermal peak stress that increased at a decreasing rate as temperature declined.

On a effectué l'analyse constitutive avec la loi du sinh pour établir les énergies d'activation à partir d'essai de torsion d'acier au silicium, dans la gamme de 600 à 900 °C et de 0.1-5 s^-1. À mesure que la température s'élevait et que la vitesse de déformation déclinait, la déformation de rupture augmentait jusqu'à autant que 14.3 et les sous-grains dans les grains allongés grandissaient. On montre graphiquement que ces résultats sont en accord avec les données provenant d'une grande collection de rapports publiés sur les aciers au Si. Les résistances étaient intermédiaires entre celles de 409 (11Cr) et 434 (16Cr-1Mo), ce qui indiquait que le Si a un effet de renforcement de presque 4 fois celui du Cr, par unité de poids; cependant, les énergies d'activation de 409 et 434 étaient plus élevées. On a effectué une simulation du laminage à plusieurs étages avec T diminuant de 900 à 600 °C, des déformations de passe de 0.2 ou 0.3, une vitesse de déformation de 1 s^-1 et des intervalles de 20 ou 40 secondes. À cause des intervalles courts, les courbes d'écoulement de passe n'ont pas montré les limites d'élasticité des essais isothermes, de telle sorte qu'il n'était pas possible de calculer l'adoucissement fractionnel dans les intervalles à température en déclin. On a suggéré deux nouvelles mesures: a) l'adoucissement relatif lors d'un intervalle qui diminuait à mesure que la température tombait et b) la réduction relative de la contrainte maximale de passe par rapport à la contrainte de pointe isotherme qui augmentait à une vitesse décroissante à mesure que la température diminuait.