CASTING POWDER, CASTING SLAG AND METHOD FOR CASTING STEEL

Abstract

Improved casting powders and improved casting slags enable production of steels having high aluminum contents of greater than or equal to 1% by weight and, in some cases, high manganese content of greater than or equal to 15% by weight. In some examples, such steels may also or alternatively include greater than or equal to 0.2% by weight titanium. The casting slag may result from a casting powder that comprises CaO and Al.sub.2O.sub.3 components essentially in the form of prefused calcium aluminate. Methods for casting steel, including methods for continuously casting steel, are also disclosed based on the use of the disclosed casting powders or casting slags.

Claims

1.-20. (canceled)

21. A casting powder, wherein aside from volatile constituents the casting powder comprises: 40-60% by weight prefused calcium aluminate; 10-30% by weight fluoride-containing component; 3-6.5% by weight SiO.sub.2; 5-15% by weight Na.sub.2O; 2-5.5% by weight Li.sub.2O; less than or equal to 10.5% by weight Al.sub.2O.sub.3; less than or equal to 15% by weight carbon, wherein a ratio of CaO to Al.sub.2O.sub.3 in the prefused calcium aluminate is in a range of 0.6 to 1.1.

22. The casting powder of claim 21 further comprising at least one of less than or equal to 5.0% by weight TiO.sub.2; less than or equal to 5.0% by weight MgO; less than or equal to 3.0% by weight MnO; less than or equal to 1.0% by weight Fe.sub.2O.sub.3; or less than or equal to 1.0% by weight FeO.

23. The casting powder of claim 21 comprising: 40-60% by weight of the prefused calcium aluminate; 15-25% by weight of the fluoride-containing component; 3-6% by weight of the SiO.sub.2; 7-12% by weight of the Na.sub.2O; 2-5.5% by weight of the Li.sub.2O; less than or equal to 10% by weight of the Al.sub.2O.sub.3; less than or equal to 15% by weight of the carbon; less than or equal to 3.0% by weight TiO.sub.2; less than or equal to 1.0% by weight MgO; less than or equal to 1.0% by weight MnO; less than or equal to 1.0% by weight Fe.sub.2O.sub.3; and less than or equal to 1.0% by weight FeO.

24. The casting powder of claim 21 wherein the fluoride-containing component is CaF.sub.2.

25. The casting powder of claim 21 comprising less than or equal to 6.0% by weight of the SiO.sub.2.

26. The casting powder of claim 21 further comprising 1.5-3% by weight TiO.sub.2.

27. The casting powder of claim 21 comprising 3-5% by weight of the SiO.sub.2 and 1.5-3% by weight TiO.sub.2.

28. A casting slag comprising: 30-50% by weight CaO; 20-45% by weight Al.sub.2O.sub.3; 7-15% by weight F.sup. (fluorine ions); 3-6.5% by weight SiO.sub.2; 5-15% by weight Na.sub.2O; and 2-5% by weight Li.sub.2O.

29. The casting slag of claim 28 further comprising at least one of less than or equal to 5.0% by weight TiO.sub.2; less than or equal to 5.0% by weight MgO; less than or equal to 3.0% by weight MnO; or less than or equal to 2.0% by weight FeO.

30. The casting slag of claim 28 comprising: 33-48% by weight of the CaO; 23-43% by weight of the Al.sub.2O.sub.3; 8-13% by weight of the F.sup. (fluorine ions); 3-6.5% by weight of the SiO.sub.2; 7-12% by weight of the Na.sub.2O; 2-5% by weight of the Li.sub.2O; less than or equal to 3% by weight TiO.sub.2; less than or equal to 1.5% by weight MgO; less than or equal to 1.0% by weight MnO; and less than or equal to 1% by weight FeO.

31. The casting slag of claim 28 wherein a content of the F.sup. (fluorine ions) is adjusted by way of CaF.sub.2.

32. The casting slag of claim 28 comprising less than or equal to 6% by weight of the SiO.sub.2.

33. The casting slag of claim 28 further comprising 1.5-3% by weight TiO.sub.2.

34. The casting slag of claim 28 comprising 3-5% by weight of the SiO.sub.2 and 1.5-3% by weight TiO.sub.2.

35. A method of casting steel, the method comprising: using a casting powder that comprises: 40-60% by weight prefused calcium aluminate, 10-30% by weight fluoride-containing component, 3-6.5% by weight SiO.sub.2, 5-15% by weight Na.sub.2O, 2-5.5% by weight Li.sub.2O, less than or equal to 10.5% by weight Al.sub.2O.sub.3, and less than or equal to 15% by weight carbon, wherein a ratio of CaO to Al.sub.2O.sub.3 in the prefused calcium aluminate is in a range of 0.6 to 1.1; or using a casting slag that comprises: 30-50% by weight CaO, 20-45% by weight Al.sub.2O.sub.3, 7-15% by weight F.sup. (fluorine ions), 3-6.5% by weight SiO.sub.2, 5-15% by weight Na.sub.2O, and 2-5% by weight Li.sub.2O.

36. The method of claim 35 wherein the method is a continuous casting method.

37. The method of claim 35 further comprising producing steel with an aluminum content of greater than or equal to 1% by weight.

38. The method of claim 35 further comprising producing steel with a manganese content of greater than or equal to 15% by weight.

39. The method of claim 35 further comprising producing steel with a titanium content of greater than or equal to 0.2 percent by weight.

40. The method of claim 39 wherein the produced steel includes greater than or equal to 1% by weight aluminum and greater than or equal to 0.2% by weight titanium.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0094] FIG. 1 shows advantageous compositions of the components CaO, Al.sub.2O.sub.3, and CaF.sub.2.

[0095] FIG. 2 shows the viscosity of a number of casting slags as a function of temperature, measured using a high-temperature rotary viscometer from Bhr, for different flux contents.

[0096] FIG. 3 shows the measured viscosity of a number of casting slags on reduction of the SiO.sub.2 fraction and increase of the TiO.sub.2 fraction (Pr.9 and Pr.25 with around 5 wt % SiO.sub.2; Pr.42 and Pr.44 with around 4 wt % SiO.sub.2 and around 2 wt % TiO.sub.2).

[0097] The invention is elucidated below with examples. The elucidations are given merely by way of example and do not restrict the general concept of the invention.

EXAMPLE

[0098] Various casting powders with the compositions indicated in table 1 were investigated. The C-containing samples Pr. 5, 19, 32, 40, and 44 were precalcined at 600 C. for 8 hours and melted at 1500 C. under an argon atmosphere. The C-free samples were not precalcined, being instead melted directly at 1500 C. under an argon atmosphere. After having been melted, the samples were each held at 1500 C. for 15 minutes and were subsequently cast onto a steel substrate, which was at room temperature, at room temperature in air for cooling. The cooled samples had thicknesses of up to 15 mm, which varied over the sample surface. For the subsequent investigations, locations were selected at which the solidified slag layer was 5 to 7 mm thick. At these locations, the fraction with amorphous and/or crystalline solidification in the sample cross section was determined with the aid of a light microscope.

[0099] Table 2 indicates the chemical compositions and also the amorphous fraction of the resulting slags. The chemical composition of the casting powders and of the casting slags was determined in triplicate in each case on samples by means of an X-ray fluorescence method. The content of fluorine ions was determined by hydropyrolysis to DIN 51723 and DIN 51727, with subsequent ion chromatography to DIN EN ISO 10304. The Na.sub.2O concentration was determined after appropriate sample preparation, by means of an ICPOS measurement to DIN EN ISO 11885.

[0100] Furthermore, casting powder samples with the composition of samples 31, 40, and 48 were brought into contact with selected melts and held under an argon atmosphere at 1450 C.-1550 C. for 15 minutes (cf. table 3). Slag and melt were then cast separately and each analyzed. The associated liquidus temperatures were determined by means of differential thermal analysis (DTA). The casting slag compositions which came about, and the fraction of amorphous casting slag, are identical with the results for samples 31, 40, and 48 in table 2. It was therefore demonstrated that the casting slag systems analyzed previously are also representative on contact with steel melts.

[0101] The casting powder compositions of the invention as specified in table 1 are therefore outstandingly suitable for the production of the desired casting slags.

TABLE-US-00001 TABLE 1 Composition of the casting powders in wt %, excluding volatile constituents, and ratio of CaO to Al.sub.2O.sub.3 in the prefused calcium aluminate (dimensionless) CaO/Al.sub.2O.sub.3 Prefused in prefused calcium calcium Sample aluminate CaF.sub.2 Na.sub.2O Li.sub.2O Al.sub.2O.sub.3 SiO.sub.2 TiO.sub.2 C aluminate Pr. 4 47.3 28.7 10.6 5.0 2.6 5.6 0.0 0.0 0.80 Pr. 5 41.1 29.2 10.8 5.1 0.0 5.7 0.0 8.0 1.00 Pr. 9 42.1 29.1 10.8 2.5 9.7 5.7 0.0 0.0 0.90 Pr. 10 45.6 23.5 10.3 4.9 10.2 5.5 0.0 0.0 0.90 Pr. 17 57.6 21.2 10.6 2.5 2.6 5.6 0.0 0.0 1.00 Pr. 18 51.1 21.2 10.6 2.5 9.0 5.6 0.0 0.0 0.90 Pr. 19 47.1 19.8 9.9 2.3 9.1 5.2 0.0 6.7 0.80 Pr. 23 55.9 25.7 10.7 2.5 0.0 5.2 0.0 0.0 0.67 Pr. 25 57.1 21.4 10.7 2.5 3.1 5.1 0.0 0.0 1.00 Pr. 26 64.3 11.2 11.7 2.7 10.0 0.0 0.0 0.0 0.90 Pr. 28 55.9 20.9 10.4 4.7 3.1 5.0 0.0 0.0 1.00 Pr. 31 56.8 21.0 10.5 3.5 2.8 5.4 0.0 0.0 1.00 Pr. 32 50.9 19.8 9.9 3.3 5.0 5.0 0.0 6.1 1.00 Pr. 33 56.1 20.8 10.4 4.7 2.7 5.3 0.0 0.0 1.00 Pr. 34 55.5 22.2 10.5 3.5 2.8 5.4 0.0 0.0 1.00 Pr. 35 54.1 21.7 10.2 3.5 5.2 5.2 0.0 0.0 1.00 Pr. 36 50.4 21.0 10.5 3.5 9.1 5.4 0.0 0.0 0.90 Pr. 39 53.5 20.8 10.4 4.7 5.3 5.3 0.0 0.0 1.00 Pr. 40 50.3 20.1 9.5 3.2 4.9 4.9 0.0 7.1 1.00 Pr. 41 51.0 20.8 10.4 4.7 7.9 5.3 0.0 0.0 1.00 Pr. 42 57.1 21.4 10.7 2.5 3.1 3.3 1.8 0.0 1.00 Pr. 43 55.7 20.9 10.4 5.0 3.1 3.3 1.7 0.0 1.00 Pr. 44 50.2 19.5 9.7 4.7 5.0 3.3 1.6 6.0 1.00 Pr. 49 56.8 21.3 10.6 3.6 3.1 3.3 1.3 0.0 1.00 Pr. 50 53.7 20.9 10.4 3.5 5.3 3.6 2.6 0.0 1.00 Pr. 51 58.3 9.0 10.5 2.4 9.2 5.6 0.0 5.0 0.80 Pr. 52 59.7 7.5 10.8 2.5 9.7 5.7 0.0 4.0 0.80 Pr. 53 51.1 31.0 10.4 2.4 0.0 5.0 0.0 0.0 1.00

TABLE-US-00002 TABLE 2 Composition of the laboratory slags in wt % (standardized) and fraction with amorphous solidification Amorphous Sample CaO Al.sub.2O.sub.3 SiO.sub.2 F.sup. Na.sub.2O Li.sub.2O MgO FeO MnO TiO.sub.2 fraction, % Pr. 4 38.98 26.37 5.64 12.87 10.30 4.81 0.68 0.30 0.02 0.03 85 Pr. 5 43.00 23.58 5.76 12.47 9.18 4.83 0.74 0.39 0.02 0.04 85 Pr. 9 39.19 30.27 5.36 10.44 10.84 2.52 0.72 0.21 0.02 0.03 90 Pr. 10 34.78 31.21 5.44 12.20 11.12 4.54 0.52 0.15 0.01 0.03 90 Pr. 17 42.43 27.41 6.27 9.91 10.21 2.73 0.69 0.29 0.02 0.04 85 Pr. 18 38.50 33.03 5.68 8.72 10.68 2.44 0.64 0.24 0.02 0.04 60 Pr. 19 35.14 35.73 5.66 9.55 10.59 2.47 0.56 0.24 0.01 0.03 60 Pr. 23 40.54 29.75 5.29 11.25 9.99 2.29 0.63 0.22 0.01 0.03 70 Pr. 25 43.63 29.32 5.39 8.92 9.25 2.34 0.79 0.30 0.02 0.04 90 Pr. 26 40.82 42.80 0.70 3.89 7.81 2.75 0.84 0.33 0.01 0.05 45 Pr. 28 42.91 29.45 5.19 8.51 8.23 4.65 0.73 0.27 0.01 0.04 95 Pr. 31 42.36 28.47 5.95 8.89 9.36 3.35 0.72 0.83 0.02 0.06 80 Pr. 32 41.37 29.53 5.70 9.25 9.49 3.62 0.67 0.30 0.02 0.05 70 Pr. 33 42.36 28.40 5.76 9.16 9.04 4.23 0.68 0.29 0.02 0.07 85 Pr. 34 42.78 27.74 5.72 9.97 9.44 3.34 0.66 0.28 0.02 0.05 70 Pr. 35 41.66 29.27 5.55 9.73 9.56 3.22 0.66 0.25 0.03 0.06 70 Pr. 36 38.33 32.55 5.61 8.89 10.50 3.24 0.58 0.23 0.02 0.06 65 Pr. 39 41.84 29.79 5.70 7.93 9.31 4.41 0.65 0.26 0.02 0.08 95 Pr. 40 42.02 29.17 5.46 9.78 9.31 3.26 0.66 0.25 0.03 0.07 85 Pr. 41 40.12 30.45 5.52 9.04 9.47 4.45 0.63 0.23 0.02 0.07 95 Pr. 42 42.75 29.12 3.85 9.50 9.54 2.43 0.78 0.30 0.01 1.71 70 Pr. 43 42.76 29.17 3.72 8.73 7.98 4.73 0.88 0.31 0.01 1.71 80 Pr. 44 41.30 29.68 3.94 8.96 8.30 4.98 0.75 0.32 0.01 1.75 95 Pr. 49 42.42 28.34 3.94 9.22 9.84 3.54 0.71 0.49 0.02 1.48 80 Pr. 50 41.37 29.51 3.86 9.17 8.97 3.28 0.64 0.29 0.02 2.89 70 Pr. 51 34.10 38.17 5.55 6.84 11.46 2.39 1.14 0.29 0.02 0.04 45 Pr. 52 33.63 40.89 6.04 5.05 10.53 2.75 0.78 0.28 0.02 0.04 10 Pr. 53 50.82 21.55 5.71 9.45 8.85 2.32 0.81 0.42 0.04 0.05 20

[0102] Slag sample 26 contains 0.7 wt % silicon dioxide, despite no silicon dioxide having been added actively to the associated casting powder sample. The reason for this is that a small amount of silicon dioxide was in the refractory material used for melting furnace and crucible, and was able to diffuse during the experiment into the melted casting slag.

TABLE-US-00003 TABLE 3 Examples of steel melts used within a contact experiment (steels based on iron, and the major alloying elements in wt %, liquidus temperature T.sub.liq in C.): Steel Composition of grade T.sub.liq. C Mn Al Ti laboratory slag Steel 1 1502 0.22 1.67 1.46 Pr. 40 (table 2) Steel 2 1420 0.40 18.80 1.20 Pr. 31 (table 2) Steel 3 1516 0.05 5.00 0.5 Pr. 48 (table 2)