Mold Flux

Name: Mold Flux
Diagram No.: 1130
Type of diagram: CCT, TTT
Chemical composition in weight %: See the table
Group: Slags
Note: The TTT diagrams of mold fluxes with different basicity were shown in Figure 1. In the experiment, the 5 vol% of crystallization was defined as the beginning of crystallization, and the 95 vol% of crystallization was defined as the end of crystallization. It could be observed from Figure 1 (a) to (d) that all the curves were double noses except the R=0.8. This indicated that there were two separate crystallization processes occurred at the low and high temperature zone individually, when the basicity of mold fluxes was larger than 0.8. The phase composition of crystals was further identified by X-ray diffraction, and results showed that the crystal phase of R=0.8 and R=1.0-1.2 at lower temperature zone was cuspidine (Ca4Si2O7F2). While, calcium silicate (CaO·SiO2) precipitated at higher temperature zone for R=1.0-1.2 series fluxes. The incubation time was a very important parameter to characterize the crystallization property, and a shorter incubation time suggested an easier crystallization process. Figure 1 (e) combined all the four series 5 vol% of crystallization TTT curves and it suggested that the incubation time was getting shorter with the increase of mold flux basicity. For example, when the temperature held at 1000 C, the incubation time for R=0.8 was about 1212 s. However, it was reduced to 77.4s, 2.0S and 0.1S, when basicity changed to 1.0, 1.1 and 1.2 respectively.
Figure 2 gave the CCT diagrams of the four series mold fluxes. It could be noticed that for the R=0.8 mold flux, the continuous cooling rates range was rather narrow, and the critical cooling rate was about 0.17 C/s, which indicated it was hard to form crystals during the operation of the industrial casting. However, when the basicity (NBO/T) value increased, the critical cooling rate was improved. The crystallization temperature was a strong function of both cooling rate and basicity. The increase of basicity tended to promote a higher crystallization temperature, and the crystallization temperature was increased from 956 to 1180, 1320 and 1402 C, when the continuous cooling rate for four serials mold fluxes was kept at 0.17 C/s. The cooling rate would also dramatically influence the mold flux crystallization. For example, the mold flux, R=1.0, its crystallization temperature decreased from 1202oC to 963oC, when the cooling rate increased from 0.17 C /s to 12 C /s (Figure 2 (b)). In figure 2(d), the crystallization temperature of mold flux R=1.2 was reduced linearly when the cooling rate changed from 20 C /s to 40 C /s. The reason may be due to the increase of molten slag viscosity with addition of cooling rate, and this required a larger driving force to initiate the crystallization. In other words, larger undercooling was needed.Therefore, the crystallization temperature decreased.
Reference: Wanlin WANG, Lejun ZHOU, Kezhuan GU and Fanjun MA, Study of basicity impact on mold flux crystallization and radiative heat transfer in continuous casting, PROCEEDINGS OF THE IX INTERNATIONAL CONFERENCE ON MOLTEN SLAGS, FLUXES AND SALTS, MOLTEN12, May 28 to 31, 2012, Beijing, China, pp. 1-15.

Transformation Diagram

TTT diagrams of mold fluxes with different basicity. Click the image to enlarge the diagram.

Transformation Diagram

CCT diagrams of mold fluxes with different basicity. Click the image to enlarge the diagram.

The Chemical Compositions of Pre-melted Mold Fluxes (in Mass Pct)

Click the table to enlarge the data.

Disclaimer: The information and data presented herein are typical or average values and are not a guarantee of maximum or minimum values. Applications specifically suggested for material described herein are made solely for the purpose of illustration to enable the reader to make his own evaluation and are not intended as warranties, either express or implied, of fitness for these or other puposes. There is no representation that the recipient of this literature will receive updated editions as the become available.

Copyright © 2019 by Steel Data. All Rights Reserved.