CaO–Al2O3 Eutectic Slag

Name: CaO–Al2O3 Eutectic Slag
Diagram No.: 1165
Type of diagram: TTT
Chemical composition in weight %: See the table
Group: Slags
Note: Figure 15 shows the TTT diagram under Ar–Ti atmosphere. In the case of lower partial pressure of oxygen, the nose position was moved to the high temperature region (1150°C), but the start time was almost the same (7 s). The line of starting crystallization also moved toward the high temperature region which meant the lower growth rate of crystal in comparison with Ar atmosphere. Figure 16 shows the TTT diagram under Ar–Ti–CaS atmosphere, which is resemble to the TTT under Ar–Ti atmosphere. This sample was not added the sulfur (CaS) directly, however, a small quantity of sulfur was originated from the gas phase as mentioned above. Since the small content of sulfur existed in the slag, a significant change of TTT diagram was not found. In the another paper) the CaS up to 10 mass% was added directly to the CAEU slag, and the changes of TTT diagrams were discussed.

Figure 17 shows the comparison of the TTT diagram (start of crystallization) among three different atmospheres (Ar, Ar–Ti and Ar–Ti–CaS). The start of crystallization in the lower temperature region below the nose position was almost the same among three conditions, while in the high temperature region, the crystallization in the Ar+Ti and Ar+Ti+CaS atmospheres started earlier than that of Ar atmosphere, for example, about 80 s to 20 s at 1250°C and about 2000 s to 200 s at 1 300°C. From the results of SEM observation, the formation of primary crystal of CA might related to this phenomenon caused by the lower oxygen partial pressure and the existence of sulfur. Since the sulfur content of sample under Ar–Ti–CaS was very low, it was difficult to discuss the effect of sulfur in details. The position of sulfur is not known exactly, for example, whether the sulfur exists in the crystals (CA or C3A) or segregates in the grain boundary or in the eutectic structure. 1 mass%, 5 mass% and 10 mass% of CaS (Table 1) were added to the mother slag (CAEU) and crystallization behaviors were measured under Ar.

Reference: Yoshiaki KASHIWAYA, Yasuaki KUSADA and Ryosuke O. SUZUKI, Atmosphere Controlled Hot Thermocouple Method and Crystallization Phenomenon of CaO–Al2O3 Eutectic Slag, ISIJ International, Vol. 51 (2011), No. 12, pp. 1967–1973.

Transformation Diagram

Figure 15: TTT diagram of CAEU under Ar–Ti. Click the image to enlarge the diagram.

Transformation Diagram

Figure 16: TTT diagram of CAEU under Ar–Ti–CaS. Click the image to enlarge the diagram.

Transformation Diagram

Figure 17: Comparison of TTT diagrams of CAEU under different atmospheres. Click the image to enlarge the diagram.

Composition of sample slag used and atmosphere

Click the table to enlarge the data.

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