Surface roughness of cold rolled sheets is an important parameter for the finishing process. Up to now, online roughness measurement was only possible with systems measuring in rolling direction. AMEPA developed a new optical system enabling a measurement under 45° or 90° – as stipulated by SEP 1940 and DIN EN 10049 – for all kinds of textures.
Increasing customer requirements, complex metal forming, the necessity to raise productivity and to guarantee high surface quality with low tolerances are some of the numerous problems facing the steel maker. Although major improvements have been achieved, the roughness factor is not yet subject to online control.
Integrated into the production line, the online roughness measuring System SRM measures along the whole length of the strip and leads to a better understanding of the influence of the various production parameters.
The targets of the SRM system are:
The surface roughness measurements system SRM uses the light sectioning principle – a two dimensional laser triangulation, developed and patented by the Centre for Research in Metallurgy (CRM, Liège). This noncontact measurement principle uses a very thin laser line which is projected under a defined angle onto the measured surface where the originally straight laser line is distorted because it follows the surface topography. Microscope optics with a high resolution camera is used to take the image of the distorted laser line. The surface profile can be directly calculated from the image of the laser line.
In addition to the roughness value Ra, also Rz, RPc and other statistical values can be calculated. The SRM system offers a wide range of possibilities for the visualization of the online and the stored data. The examples of screens shot show the online Ra results over the coil length with the latest microscopic picture and as second example the visualization of stored measurements which can be accessed by via network.
Based on customer pre-set thresholds, warnings and alarms are indicated immediately if the roughness is out of tolerance so that the operator can start proper countermeasures without losing any time.