PSI - Issue 18

Christoph Bleicher et al. / Procedia Structural Integrity 18 (2019) 46–62 Author name / Structural Integrity Procedia 00 (2019) 000–000

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by Riposan et al. (2008), show reductions in fatigue strength of 19 to 33 %, while Starkey et al. (1982) report 20 % if Dross fractions are present close to the rim zone of a cast component. The results determined so far in literature therefore show no clear reduction factor that can be applied for the assessment of a Dross-affected component. Furthermore, no information is provided with regard to the loss in stiffness of the material when Dross is present. In this context, a safe and clear reduction factor, both for fatigue strength and stiffness, needs to be determined on each inspected cast iron component in the Dross region, in order to perform a correct reassessment ensuring a safe usage of the component as well as avoiding unnecessary rework in the foundry. 2.2. Material During the research activities, EN-GJS-400-15, used in many engineering applications, was used to perform non destructive and destructive tests on sound and on Dross-affected material conditions. For this purpose and to achieve a comparable microstructure, thick-walled cast blocks, with a size of 500 mm x 500 mm x 500 mm, were cast with Dross in the upper side, Fig. 1. To induce as much Dross as possible, the casting system was created to have a high pouring height, enabling the melt to absorb as much oxygen for the later Dross formation as possible. The pouring temperature ϑ was 1520 °C at the pouring basin, Fig. 2. The resulting chemical composition of the blocks, as well as the determined quasi-static material properties, are given in Table 1 and Table 2, respectively. The results of the tensile tests exceed the required values for tensile and yield strength as well as for elongation for EN-GJS-400-15 according to GINA (2012). The tensile specimens were removed from the cast blocks at depths of 60 and 100 mm, measured from the Dross side.

Fig. 1. Cast block.

Fig. 2. Cast system.

Table 1. Chemical composition of the cast blocks material

carbon C silicon Si manganese Mn phosphor P sulphur S magnesium Mg [wt. %] [wt. %] [wt. %] [wt. %] [wt. %] [wt. %]

EN-GJS-400-15

3.65

2.35

0.23

0.025

0.010

0.070

Table 2. Quasi-static material properties of the sound material condition Tensile strength R m [MPa] 384.7 yield strength R p0,2 [MPa] 257.1 elongation A [%] 19.5 yield ratio [-] 0.7 given values as mean of 23 tensile tests