OBRABOTKAMETALLOV technology Vol. 25 No. 4 2023 GOST 8713-79-S4 (for 5 mm thick workpieces) Specimen 6 (450 A, 27 V) Measurement point Start Center End Weld cap width e, mm 12.4 12.5 12.4 Root bead width e1, mm 8 8 8.6 Weld cap height g, mm 1.5 1 1 Root bead height g1, mm 0.5 0.5 0.5 Specimen 7 (500 A, 27 V) Measurement point Start Center End Weld cap width e, mm 11.7 12.5 11.2 Root bead width e1, mm 14.7 9.3 9.9 Weld cap height g, mm 2 2 2 Root bead height g1, mm 1 1 0.5 Specimen 8 (500 A, 27 V) (commercially available flux) Measurement point Start Center End Weld cap width e, mm 13.4 13.1 13.6 Root bead width e1, mm 10.6 10.2 9.2 Weld cap height g, mm 1 2 2 Root bead height g1, mm 1 0.5 1 Note: — acceptable — unsatisfactory characteristics T h e E n d Ta b l e 2 Table 2 shows that Specimens 1–5 fail to meet the GOST 8713-79 size requirements for weld type S4. Other Specimens 6–8 satisfy all of the above requirements. Radiographs of the resulting weld specimens are shown in fig. 3. Radiographic inspection of the welds (fig. 3) revealed the defects in specimen 1, 2, and 5 (discontinuities) that had been earlier detected by visual inspection. Specimen 4 had a 17 mm long lack of fusion at the start of the weld. Except for the above irregularities, all the specimens have solid weld metal with no hidden subsurface defects (porosity or cracking). Fig. 4 shows the computer processing results for the 3D weld specimen models generated by laser scanning and demonstrating its overall residual strain profile. Fig. 4 shows that Specimens 1 and 3–8 have a common longitudinal strain that is evident from an upward curvature of the specimen face that is highest at the cross section of the weld’s center, while Specimens 2 and 5 have a downward curvature in the weld root direction. Specimen 2 shows a higher lateral strain that is highest at the start and end of the weld. Specimens 3 and 6 show twisting distortion, that is, the cross section is twisted around the longitudinal centerline due to the hybrid nature of the strain. Strain is lowest in Specimens 4 and 6–8. Strain behavior of Specimens 4 and 8 is similar with respect to the maximum strain area width. Specimen 6 shows the best performance. Consequently, high arc energy (600A/37 V, (2,466 kJ/mm)) using the tested flux causes both longitudinal and lateral strain with a max. deflection of 5 mm. An intermediate energy input of 500 A/37 V (2,055.5 kJ/mm) results in an intricate strain rate pattern combining both longitudinal and lateral strain. 400 A/37 V (1,645 kJ/mm) produced lowest longitudinal strain and an unsatisfactory weld root formation. The best welding parameters for 5 mm thick sheet pieces using the tested flux with a ceramic backing are 450 A/27 V (1,350 kJ/mm) that will form a good bead both on the face and root to meet GOST 8713-79-S4 and minimize the residual strain of the welded component. Table 3 summarizes statistical modeling of the welding parameters effect on the resulting weld size using the tested flux.
RkJQdWJsaXNoZXIy MTk0ODM1