CaO-SiO2-Al2O3-Na2O-CaF2 Slag

Name: CaO-SiO2-Al2O3-Na2O-CaF2
Diagram No.: 1157
Type of diagram: TTT
Chemical composition in weight %: See the tables
Group: Slags
Note: The obtained TTT and CCT curves for beginning of crystallization for GR-5030, S-A, and STSP 816 are shown in Figures 58, 59 and 60, respectively.

It can be seen that the onset of crystallization occurs much faster for the isothermal experiments than for the continuous cooling experiments for GR-5030, and S-A. These two TTT curves are similar to the TTT curve obtained for Sample E3, which has almost the same basicity and contents of Na2O and Al2O3. The nose position for the isothermal experiments was determined to be at 1020C and 4.7s for GR-5030, and at 1000C and 3.3s for S-A. The critical cooling rates for glass formation are 45C/s and 54.5C/s for GR-5030 and S-A, respectively. However, during continuous cooling, no visible crystallization occurred at cooling rates over 6C/s for both Samples. It is obvious that the crystallization kinetics drastically change with a transient thermal field. An odd result, especially for Sample S-A is that the crystallization temperature for 1C/s cooling is above the maximum crystallization temperature measured during the isothermal experiments. The reason for this is the fluorine vaporization. In the isothermal experiments, the Sample is quickly melted and held for approximately 30s at 1400C before cooling to the experimental temperature. For the 1C/s experiment, the Sample is also quickly melted and held 30s at 1400C before the cooling starts. However, while the temperature of the isothermal Sample drops fast, the 1C/s Sample spends some significant time at temperatures above the maximum crystallization temperature measured for the isothermal experiments. It is well known that the fluorine vaporization increases with increasing temperature, and therefore more fluorine escapes the 1C/s Sample. Fluorides are fluxing agents, reducing the liquidus point, and so loss of fluorine will increase the crystallization temperature.

It was observed that crystallization of GR-5030, S-A, and STSP-816 occurred at a higher temperature for experiments with a low cooling rate than that observed during the isothermal experiment. This phenomenon might be due to fluoride vaporization, which would change the composition, and subsequently the thermal region for crystallization. The starting temperature for the experiments, before cooling, was the same for the isothermal and continuously cooled tests. At low cooling rates, the Sample spends a longer time at an elevated temperature, and would, therefore, lose more fluorine increasing the liquidus temperature of the Sample. The starting temperature for the continuously cooled experiments was decreased by 100C for S-A, and the generated CCT curve was compared with the original CCT curve. The results are shown in Figure 61.

The time for the onset of crystallization decreases naturally when the start temperature is decreased from 1400C to 1300C. The crystallization temperature decreased with decreasing start temperature for cooling rates of 1C/s and 3C/s. However, for higher cooling rates of 5C/s and 6C/s, the crystallization temperature was the same. It was also found that the start temperature did not affect the critical cooling rate for glass formation.

It was expected that LV 905/BC and M481 would show a similar behavior to STSP-816. M481 and STSP-816 have almost the same basicity, but M481 has twice the amount of Na2O. LV 905/BC had the lowest basicity of all the Samples, but contained the highest content of CaF2, and almost as much Na2O as M481. The results from both the isothermal experiments and the continuously cooled experiments are shown in Figures 62 and 63 for M481 and LV 905/BC, respectively.

The isothermal data are very scattered for both Samples, but M481 seems to exhibit a first nose between 1220C and 1100C. The data shown in Figures 62 are average data from results closest to each other. The determined crystallization temperatures remain scattered for isothermal experiments even with the average data. It was first thought that the Samples were not well mixed, and that compositional differences existed between specimens. However, both M481 and LV/905BC were prefused Samples. Additional mixing of the powder had no effect in reducing the scatter in the results. The fluorine vaporization was suspected to cause the scatter and great care was taken to minimize the time at elevated temperatures. Unfortunately, the minimization of exposure time to elevated temperatures did not reduce the scatter in data.

The results from continuously cooled experiments are less scattered, and CCT curves could be obtained. In the case of M481, the critical cooling rate was found to be 6C/s and for LV 905/BC, 15C/s. The critical cooling rates (Rc) for glass formation of the investigated industrial Samples have been summarized in Table 2.

Reference: Not shown in this demo version.

Transformation Diagram

Price: 30.00 US $
Buy Online Transformation Diagram

Other Steel Data links
Carbides in Steel
Etchants Database
Hardenability Diagrams of Steels
Macro Defects in Steel
Non-Metallic Inclusions in Steel
Tempering Diagrams of Steels
CCT and TTT Diagram Calculating Service
Transformation Diagrams of Non-Ferrous Alloys

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.