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Measured Porosity of Solid Films

The presence of pores in solid film can affect film conductivity. A density method was developed to measure the overall closed porosity in films. The porosity of slag film can be calculated as follows:

P—porosity of slag film;

Dp—true density of pulverized slag film;

Ds—density of solid slag film.

The measured porosities of film samples (Fig. 6) show that the overall porosity of HB films is much higher than the TB films. The resulting lower effective thermal conductivity may have contributed to the thickness of these films. Cross-sections of the films (Fig. 7) show that in the TB films most of the pores formed close to the probe, thus the overall porosity decreased with increased film thickness. For HB films, the porosity increases with increased probe immersion times. The large lath-shaped crystals formed during solidification are associated with the large porosity in the crystalline layer of these films.

The porosity of slag film with different probe immersion times

Fig. 6 The porosity of slag film with different probe immersion times

The section features of HB a and TB b slag films (optical micrographs)

Fig. 7 The section features of HB a and TB b slag films (optical micrographs)

Table 2 quality statistic of slabs

Year

Total production, millions of tons

Longitudinal crack ratio, %

Scrap ratio, % (caused by Longitudinal cracks)

2012

5.29

5.32

0.13

2013

5.38

4.92

0.028

2014

3.82

2.15

0.00061

Table 3 Defect ratio (%) of final products caused by longitudinal surface cracks

Year

Section width of heavy and medium plates

4100 mm

2700 mm

1780 mm

2013

0.43

0.09

0.417

2014

0.14

0.03

0.065

 
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