Quality and Efficiency Analysis of Edge Preparation in S355j2n Steel For Welding Applications

The process of edge preparation for welding plays a crucial role in ensuring the quality of welded structures, affecting both their mechanical properties and overall economic efficiency. The aim of this article is to present a comparative analysis of traditional oxy-fuel cutting and modern milling methods for edge preparation of S355J2N low-alloy steel, focusing on surface quality, microstructural changes, as well as economic aspects. The study was conducted on plates with thicknesses ranging from 8 to 20 mm, using bevel angles of 30° and 45°. Both straight and curved beveled edges were investigated, utilizing a self-propelled OMCA 900 beveling machine, Gerima MMB 400B and SMA 60 BER milling machines, and a PERUN PC-211A/Y11 gas torch. Surface roughness measurements, macroscopic analysis of the edges, and HV1 microhardness testing were performed. Operation times were recorded to enable a cost analysis.

The results demonstrated that milling significantly reduces edge roughness—Ra values decreased by a factor of 6 to 10 compared to oxy-fuel cutting. In the case of oxy-fuel cutting, a heat-affected zone approximately 2–3 mm thick and localized surface hardening up to 250–450 HV1 were observed, while milling did not cause changes in hardness. Cost analysis showed that under Polish labor rates, the total beveling costs were comparable for both methods (approximately 2 EUR/m), whereas under average EU labor rates, milling became the more economically viable solution.