Abstract
Having established that sulphur presence in the mould materials appears to have an important contribution in graphite degeneration at least in the casting surface layer, a research program is undertaken to explore the possible beneficial effect of sulphur diffusion blocking at the metal–mould interface. Test samples, with and without a thin steel sheet (up to 3 mm thickness) application on the inner surface of the mould cavity, before iron melt pouring, are considered for structure analysis. A higher nodulizing potential (0.048% Mgres, 0.015% Ceres, and 0.006% Lares) decreases the occurrence of surface graphite degeneration in castings obtained in rigid chemically bonded resin sand moulds, using P-toluol sulfonic acid (PTSA) hardener (S-including), but it is not enough to avoid this phenomenon (200–400 μm skin in present experimental conditions). The casting skin appears to have different values, depending on the evaluation technique (un- and Nital-etching direct measurement, or graphite parameters variation on the casting section). In the presence of a thin steel sheet at the metal–mould interface, the casting skin thickness decreases or is just excluded. It is supposed that it acts as a barrier, blocking S-diffusion from the mould media into the iron melt. Without this S-diffusion, the graphite degeneration in the casting surface layer could be avoided, or at least diminished. For industrial application, the increasing of residual content of nodulizing elements is a limited solution, and it is recommended to use barriers to block S transfer on the mould/metal surface, such as dense coatings or coatings with desulphurization capacity.
Highlights
According to Modern Casting Journal census [1], the world casting production in 2018 was over than 112 million metric tons, including around 70% cast iron, 10% cast steel, and 20% non-ferrous (17% Al) castings, respectively
Having established that sulphur presence in the mould materials appears to have an important contribution in graphite degeneration at least in the casting surface layer, a research program is undertaken to explore the possible beneficial effect of sulphur diffusion blocking at the metal–mould interface
A research program is undertaken to explore the possible beneficial effect of sulphur diffusion blocking at the metal–mould interface, on graphite degeneration at in Mg-treated iron castings
Summary
According to Modern Casting Journal census [1], the world casting production in 2018 was over than 112 million metric tons, including around 70% cast iron, 10% cast steel, and 20% non-ferrous (17% Al) castings, respectively. The iron, steel, and malleable foundries of the CAEF member states produce approximately 12.3 M tons of castings per year. For the both mould media, un-coating and mould coating moulds are tested. The applied coatings include sulphur bearing materials or MgO bearing material
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