OBRABOTKAMETALLOV technology Vol. 24 No. 4 2022 During cutting of C1220 copper specimens with thickness of 40 mm it was found that, despite the large thickness of sheet, the size of heat-affected zone in the specimens is at a sufficiently low level (Fig. 10, a–c). The magnitude of deviation of macrogeometry of specimens cut is less than 0.7 mm. The size of the melting zone is up to 0.15 mm. The heat-affected zone is practically not visible on metallographic thin sections. Its grain structure is similar to that of the base metal (Fig. 10, b–d). There are a large number of pores, discontinuities and laminations in the melting zone (Fig. 10, e, f). The heat-affected zone was detected only when analyzing changes in the microhardness of the material in the cutting zone (Fig. 10, g, h). The size of the heat-affected zone is 0.5–3.0 mm, depending on the cutting mode. The smallest size is characteristic for the mode No. 7, which can be considered optimal from the viewpoint of the allowance for further machining. Fig. 10. Macro- and microstructure of typical specimen of copper with a thickness of 40 mm after plasma cutting: a –macrostructure; b, c –enlargedimagesoftheupperandlowerpartsofcutzone; d–f –microstructure of specific zones; g, h –microhardness variation; 1 – basemetal; 2 – heat-affected zone; 3 – pores; 4, 5 – lamination; 6, 7 – areas of microhardness testing
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