| ArticleName |
Parameters of evaluation of shape cross section of hot-rolled steel strips. Message 2. The saddle coefficient |
| Abstract |
The work rolls of the stands of hot rolling mills are mostly worn out at places corresponding to the edges of the rolled strips. At hot rolling mills that are not equipped with devices for axial shifting of work rolls, it happens due to a violation of rolling sequence from wide strips to narrow strips. At hot rolling mills equipped with axial shifting of work rolls, it happens, as a rule, at the end of the assembly lot, when the value of the axial shifting of the work rolls, compensating for wear and thermal bulge, has reached the limit value, and then the work rolls are in place. As a result, the profile of the cross-section of the rolled strips acquires a characteristic «saddle-shaped» form: local thickenings appear on the edges of the strip. Analysis of the results of cold rolling revealed the following feature: if one of two strips of the same size, rolled at different times with similar values of the determination coefficient R2, has a flatness violation, then the profile of the cross section of this strip usually has a «saddle-shaped» form. To characterize the profile of the cross-section of hot-rolled strips with edge thickenings, the term «saddle» and the coefficient KS of «saddle» were introduced. Calculation of the value of this coefficient is carried out by analogy with the calculation of the central moment of the distribution of any value. In Message 1, a mathematical model of a cross-section profile with edge features, including thickenings, was described. With the help of the developed mathematical model, the saddle coefficients KS were calculated for different ratios of the convexity P of the cross-section profile, the height and length of the edge thickenings. Calculations have shown that the value of KS increases monotonically with the increase of the height and the length of the areas of the edge thickenings. The saddle coefficient KS is suitable for estimating of the edge thickenings of the cross-section profiles of hot-rolled strips. |
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