African Fusion June 2019

by the welder, it was possible to deposit a single continuous run along the circumference of the part. The arc time per bead averaged ten minutes. The welder was able to deposit an average of 1.04 kg of weld metal per hour totalling 47 kg in 45 hours of work, despite using exceptionally lowarc energies. Ultimately only three indications were detected that re- quired repair work. Conclusions Cold repairs of Inconel 625 can be successfully executed on mediumcarbonsteelswith transformation temperatures equal to or greater than 735 ᵒC using GMAW-P, provided a minimum of 1.5 mm of the original Inconel clad layer is retained. Viable welding parameters fall into a narrow operational band and must be strictly adhered to. Due to the fine control required to successfully perform cold repairs, the A c1 temperature of the carbon steel should be determined with dilatometry. The results obtained in this study indicate that the Rosen- thal equation is not well suited for cold repair applications unless heating and cooling rates can be determined for the carbon steel substrates and the delayed austenite transforma- tion as a result of superheating effects can be accounted for in the calculations. Acknowledgements: The assistance of One Eighty Integrated Engineering solutions and Helena Rossouw of the University of Pretoriawith themetallography is acknowledged. The financial support of the Southern African Institute of Welding for one of the authors (PP) is gratefully noted. 3C Metal agreed to the publication of this paper.

Figure 8: Change in hardness (HV 0.5) as a function of distance from the fusion line between the original clad layer and the medium carbon steel substrate, before (original weld) and after (repair weld) the repair weld was deposited.

References 1 American Society of Mechanical Engineers: 2017; ASME Boiler and Pressure Vessel Code Part II B; ASME BVPC. 2 ASTMA519/A519M– 17: Standard specification for seamless carbon and alloy steel mechanical tubing. 3 Trzaska J, 2016: Calculation of Critical Temperatures by Empirical Formulae; Arch. Metall. Mater. Vol 61, pp981-986. 4 ASM International, 1990: ASMHandbook – Purpose and Selection: Nonferrous Alloys and Special-PurposeMaterials; ASMHandbook. 5 Norwegian Technology Centre, 2008): NORSOKM-601; Welding and inspection of piping. Section 4.3.5 Corrosion testing.

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June 2019

AFRICAN FUSION