MICROGEOMETRY OF GALVANIZED ROLLING METAL. PART 1. STUDY OF THE POSSIBILITY OF OBTAINING THE MAXIMUM NUMBER OF PEAKS

Abstract

The paper presents the results of studies of the required level of peak density of galvanized rolled products (RPc) of global automobile manufacturers, which should be at least 50–60 units/cm for rolled products intended for the manufacture of front parts of car bodies. It was revealed that foreign manufacturers of automotive sheet steel provide an average value of the number of peaks on galvanized rolled products at the level of 70 units/cm, the preparation of rolls is carried out by the method of electric discharge texturing. In view of the various methods of roll preparation, it is interesting to determine the method of roll preparation, for this purpose, selective samples of foreign manufacturers were examined using an X-ray electron microscope. A study of the microgeometry of galvanized rolled products of PAO Severstal was conducted, according to the results it was established that the actual roughness values correspond to the world level. A study of the change in microgeometry along the length of the campaign of auto sheet production was carried out, the nature of the change in frequency characteristics depending on the operating time of the rolls was established. During the production of automotive sheet, the roughness and density of peaks were changed over the campaign (at the beginning of the campaign – after rolling 50 tons from the moment of transshipment, in the middle of the campaign – 500 tons and at the end of the campaign – 1000 tons), the influence of the PDS forces on Ra, RPc, mechanical properties, flatness of galvanized rolled products was revealed. The surface of the working roll of the straightening and tempering mill was prepared on a 36-channel electric discharge texturing machine HERKULES. A method was determined for stably obtaining the same number of peaks throughout the campaign (at least 70 units/cm) due to an increase in the specific tempering force at the end of the campaign. The effect of the tempering value on the change in the yield strength of galvanized automotive sheet IF steel was determined.