MICROGEOMETRY OF GALVANIZED ROLLING METAL. PART 2. DEVELOPMENT OF TECHNOLOGICAL MODES OF TEXTURE

Abstract

The study presents the results of developing a production technology for galvanized sheet steel that ensures guaranteed compliance with automotive manufacturers' requirements for peak count standardization. The research revealed a correlation: reducing the number of passes leads to an increase in peak count (NP) by approximately 15 cm⁻¹. However, it should be noted that decreasing the number of texturing passes results in a reduction of roughness parameters (Ra and NP) by the end of the campaign, likely due to decreased surface wear resistance. To determine the optimal parameters for the final reverse-polarity pass, work rolls with a nominal roughness of 2.2 μm were prepared in 3 passes. The settings of the EDT (Electro-Discharge Texturing) machine during experimental roll preparation corresponded to standard parameters: pulse-on time – 13 μs, pulse-off time – 14 μs, current – 11 A, and “+” polarity. The influence of the chromium plating process on Ra and RPc values was established: chromium plating reduces Ra by approximately 0.1–0.2 μm and RPc by 10–20 peaks/cm. The best experimental result in terms of achieving Rsk = 0 while maintaining Ra was determined. Based on the optimal experimental parameters, two pairs of work rolls were prepared to assess galvanized strip roughness variation and to test samples in an automotive manufacturer's laboratory. The results obtained at PJSC “Severstal” and the manufacturer's laboratory were comparable.