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On Adequacy of Parameters of Strip Cross-Section Profile. Part 2. Local Thickenings and Thinnings

Abstract

At present, the cross-section profile of the rolled strip is characterized by geometrical parameters such as wedging, convexity, difference of thickness, displacement of convexity, and edge wedging. Some of these parameters are redundant. The values of these parameters are calculated by known and generally accepted methods. However, some of the features of the cross-section profile of rolled strips, such as local thickenings/thinnings are calculated by unconventional methods. Practically every scientific school of rolling mill operators or rolling production specialists uses their own techniques, which often provide different results for the same cross-section profiles. The identification and calculation of the local thickenings/thinnings parameters of the cross-section profile of rolled strips consists in defining a so-called zero level, the excess/understatement of which is a sign of local thickening/thinning. The paper continues analyzing for the calculation of the parameters of the cross-section profile of rolled strips regarding local thickenings/thinnings for accuracy and adequacy. A new method based on statistical methods is proposed. The target function, the thickness distribution across the width of the rolled strip, is a symmetrical quadratic parabola. However, the actual distribution is always different from the target one for several reasons, such as ring wear of work rolls. In the first step of the proposed technique, strip thickness values dramatically different from the target distribution are eliminated as emissions by the Walter-Shewhart procedure (control charts). However, this procedure cannot be applied without excluding the nonlinear (parabolic) component of the measured cross-section profile and, therefore, applies to the first derivative of the function of the cross-section profile thickness distribution. To determine zero level, all of the thicknesses associated with these emissions are eliminated after calculating the upper and lower limits of the allowed values of the first derivative. The result of the repetitive process is zero level according to which the local thickening/thinning parameters are calculated.

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Funding

The work was supported by the Russian Foundation for Basic Research, project no. 19-38-90 257.

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Correspondence to S. M. Bel’skii.

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Translated by S. Kuznetsov

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Bel’skii, S.M., Shopin, I.I. & Shkarin, A.N. On Adequacy of Parameters of Strip Cross-Section Profile. Part 2. Local Thickenings and Thinnings. Steel Transl. 52, 76–80 (2022). https://doi.org/10.3103/S0967091222010041

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  • DOI: https://doi.org/10.3103/S0967091222010041

Keywords:

  • thin sheet rolling
  • strip’s cross-section profile
  • local thickening
  • Walter–Shewhart procedure
  • predictive interval