Welding with flux-cored wire containing a thermite additive
摘要
The effect of a flux-cored welding wire based on thermite mixture (Al, Fe2O3) containing ferroalloy additions (FeMn, FeSi) on the structure and properties of welded joints in St3sp steel sheets was investigated. Welding parameters that allow welded joints to meet GOST requirements were identified. The structure and properties of the joints were examined by metallography using optical microscopy, scanning electron microscopy, and X-ray microanalysis. The welds were free of defects, and the fusion zone exhibited a ferrite–pearlite microstructure. Fractographic examination showed mixed brittle–ductile fracture in all specimens, with nonmetallic inclusions (NMIs) present on the fracture surface. No differences were found in NMI composition or size between the brittle and ductile regions of the fracture surface. NMIs were studied on transverse sections of the fusion zone, which was preliminarily divided into four height segments, while all inclusions were classified into four size groups. All inclusions were rounded and contained alumina; the maximum inclusion diameter reached 70 μm. The highest inclusion density was observed in the upper segment of the fusion zone, mainly due to large exogenous inclusions formed with the participation of the flux. Endogenous inclusions up to 10 μm in size were high-alumina and contained Mn, Si, and Fe.