Identifikace vztahu topografie povrchu materiálu k technologickému procesu.

Abstract

This work is focused on surface roughness evaluation of sheets produced by longitudinal cold rolling process. This is concerned with the evaluation of surface topography of low carbon, deep drawing steel sheet of type KOHAL 697, interstitials free steel, microalloyed and refosforised steel. The surface topography of rolled sheets was measured using a contact profilometer Mitutoyo SurfTest SJ 401 and optical profilometer MicroProf FRT (Fries Research & Technology GmbH). A method of evaluation is based on comparison of surface profile height parameters of steel sheets with the technological parameters of the rolling mill DUO 210 SVa. The technological parameters are as follows: rolling force Froll, absolute rolling reduction in thickness Dh, number of revolutions of the rolls nroll and others. All these technological parameters have an impact both on the rolling process and the surface quality of rolled sheet. The surface quality is very important from both manufacturer's and customer's point of view. It is therefore important to have a great knowledge of the relationship between qualitative aspects of the rolled material and technological parameters of treatment. Based on theoretical knowledge, it has been developed a new procedure for determining the main technological parameters of rolling mill. The main difference between the current and proposed method of calculating is as follows: the proposed method is based on knowledge of deformation properties of materials, it also requires knowledge of the state of stress and strain as well as knowledge of the reduction in thickness at different stages of rolling process. Existing methods are based on static calculations using geometry relationships in rolling. This is related to parameters of the working roll and instantaneous sheet thickness in the roll gap. However, the calculations do not respect the true stress-strain characteristics of material of rolled sheets at a certain speed of rolls and rolling force and absolute rolling reduction. The proposal deals with the well - balanced system - material - absolute rolling reduction - rolling force- rolling speed. This enables to significantly increase operational efficiency and quality improvement of the rolling process.