Lipetsk State Technical University (Lipetsk, Russia):

S. M. Belskiy, Dr. Eng., Prof., e-mail: Belsky-55@yandex.ru
A. N. Shkarin, Post-graduate Student

Novolipetsk Steel – NLMK (Lipetsk, Russia):

V. A. Pimenov, Cand. Eng., Senior Researcher, Chief Specialist

The shape of cross-sectional profile is the most important characteristic of the quality of hot rolled steel, because it is accurately reproduced after subsequent cold rolling and thereby has a significant effect on the flatness of cold rolled strips. Traditional method to evaluating the accuracy of cross-sectional profile by geometric dimensions is the least squares approximation of hot-rolled strip thickness by second order polynomial. A number of parameters that characterize the macro-features of hot-rolled strips’ profile are found from the obtained second order parabola coefficients; this is wedge, convexity, displacement, coefficient of determination and the recently introduced saddle-shape coefficient, showing the presence of edge thickenings. Edge thickenings are formed due to wear of the work rolls in the areas corresponding to the edges of the rolled strips. An analysis of the existing geometrical parameters of the cross-sectional profile of the hot-rolled strips showed that with their help in some cases it is practically impossible to predict the flatness of cold-rolled strips. Analysis of the flatness of cold-rolled strips has identifi ed four specific classes of cross-sectional profi les of hot rolled strips that have a significant effect on the shape of cold-rolled strips, and three of them negatively affect the flatness of cold rolled strips. Profiles with a concave middle and (or) nearedge areas lead to waviness, pike-shaped profiles cause warping.
The reported stady was funded RFBR, project number 9-38-90257.

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