PSI - Issue 13

Guy Khosla et al. / Procedia Structural Integrity 13 (2018) 1447–1452 Guy Khosla/ Structural Integrity Procedia 00 (2018) 000–000

1450

4

a

b

Fig. 3. (a) 5x optical microscopy of sample taken 10 mm from the surface of the top of the slab after Charpy testing at 200 ° C. (b) 5x optical microscopy of sample 20 mm from the surface of the slab of high silicon steel after room temperature Charpy testing

XRF testing analyses the composition of specimens after being fractured from the Charpy machine. The composition of specimens 20 mm, 40 mm, and 70 mm (just above the slab bottom surface) are shown in Table 1. All values are quoted in percentage. As can be seen from the results a slightly higher composition of manganese is observed on the surface specimen, 70 mm, known to be detrimental to cracking due to the formation of MnS which pin the grain boundaries. No aluminium concentration is observed in 20 mm, however samples 40 mm and 70 mm see substantial quantities of aluminium. Aluminium is known to form AlN which is known to be detrimental to the formation of transverse cracking. The error in results are to be under 0.002%. Table 1: XRF results (normalized) from samples A, B and C through the thickness of the slab. All values are quoted in %. Compound 20 mm 40 mm 70 mm Al 0.00 1.05 0.95 Si 0.99 1.00 1.01 P 0.56 1.44 0.00 S 0.97 1.01 1.03 Cl 0.90 0.56 1.54 Ca 0.72 1.28 0.00 Mn 0.97 0.99 1.04 Fe 1.00 1.00 1.00 Ni 1.23 0.89 0.89 Cu 0.98 1.02 1.00 Zn 0.43 1.33 1.24 Sn 0.98 1.01 1.02 Energy Dispersive X-ray spectroscopy (EDX) analysis is completed on a sample 15mm from the top surface (see Fig. 4 The aim of this analysis is to pinpoint possible 2 nd phase particles that may be initiator of cracks during transverse cracking. As seen in Fig. 4 (b), a MnS particle is next to the grain boundary which already shows the initial signs of void formation. This is in the region of the grain boundary, where strain is likely concentrated during the

Spectrum 4

b

a

Spectrum 1

Spectrum 2

Spectrum 3

10μm

200μm

Fig. 4. (a) SEM image of a sample 20mm from the top surface of a high silicon as-cast slab used for EDX analysis of spectrum 1 and 2. (b) SEM image of sample 20mm from the top surface from a high silicon as-cast slab used for EDX analysis of spectrum 3and 4.