Dephosphorizing flux and method for preparing same

Abstract

Provided is a dephosphorizing flux configured to adjust a phosphorous component contained in molten steel, the dephosphorizing flux includes a main material including BaCO.sub.3 and a supplementary material, wherein the supplementary material includes a first material containing either of NaHCO.sub.3 or Na.sub.2CO.sub.3 and a second material containing CaF.sub.2. Thus, in accordance with a dephosphorizing flux and a method for preparing the same of the present disclosure, the plugging of a lower blowing nozzle that blows a carrier gas during dephosphorization may be prevented while improving a dephosphorization ratio. In addition, since environment polluting substances are not used as in conventional arts, environment pollution risk may be reduced, and the cost burden due to the facility for pollution prevention and harmful substance management may be alleviated.

Claims

1. A dephosphorizing flux to adjust a phosphorous component contained in molten steel, the dephosphorizing flux comprising a main material comprising BaCO.sub.3 and a supplementary material, wherein the supplementary material comprises a first material comprising NaHCO.sub.3 and a second material comprising CaF.sub.2.

2. The dephosphorizing flux of claim 1, wherein the first material comprises NaHCO.sub.3 such that a content ratio of CaF.sub.2 wt %/NaHCO.sub.3 wt % of the second material to the first material is greater than 0 and not greater than 2.3.

3. The dephosphorizing flux of claim 2, wherein the first material comprises NaHCO.sub.3 such that the content ratio (CaF.sub.2 wt%/NaHCO.sub.3 wt%) of the second material to the first material is greater than 0 and not greater than 1.4.

4. The dephosphorizing flux of claim 3, wherein the first material comprises NaHCO.sub.3 such that the content ratio of CaF.sub.2 wt %/NaHCO.sub.3 wt % of the second material to the first material is 0.5 to 1 inclusive.

5. The dephosphorizing flux of claim 1, wherein the supplementary material is greater than 0 wt % and not greater than 30 wt % with respect to the total of the dephosphorizing flux.

6. The dephosphorizing flux of claim 5, wherein the supplementary material is greater than 0 wt % and not greater than 20 wt % with respect to the total of the dephosphorizing flux.

7. The dephosphorizing flux of claim 1, wherein the second material is at least 2 wt % with respect to the total of the supplementary material.

8. A method for preparing a dephosphorizing flux to adjust a phosphorous component contained in molten steel, the method comprising: preparing BaCO.sub.3 which is a main material; preparing a supplementary material comprising a first material comprising NaHCO.sub.3 and a second material comprising CaF.sub.2; and mixing the main material and the supplementary material.

9. The method of claim 8, wherein in the preparing of the supplementary material, when the first material comprises NaHCO.sub.3, the content ratio of CaF.sub.2 wt %/NaHCO.sub.3 wt % of the second material to the first material is configured to be greater than 0 and not greater than 2.3.

10. The method of claim 9, wherein in the preparing of the supplementary material, when the first material comprises NaHCO.sub.3, the content ratio of CaF.sub.2 wt %/NaHCO.sub.3 wt % of the second material to the first material is configured to be greater than 0 and not greater than 1.4.

11. The method of claim 10, wherein in the preparing of the supplementary material, when the first material comprises NaHCO.sub.3, the content ratio of CaF.sub.2 wt %/NaHCO.sub.3 wt % of the second material to the first material is configured to be 0.5 to 1 inclusive.

12. The method of claim 8, wherein in the mixing of the main material and the supplementary material, the supplementary material is added to be at most approximately 30 wt % with respect to the total of the dephosphorizing flux.

13. The method of claim 12, wherein in the mixing of the main material and the supplementary material, the supplementary material is added to be at most 20 wt % with respect to the total of the dephosphorizing flux.

14. The method of claim 8, wherein in the preparing the supplementary material, the second material is added to be at least 2 wt % with respect to the total of the supplementary material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a flowchart showing a method for preparing a dephosphorizing flux in accordance with an exemplary embodiment.

MODE FOR CARRYING OUT THE INVENTION

(2) Hereinafter, exemplary embodiments will be described in detail with reference to the accompanying drawings. The present disclosure may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present disclosure to those skilled in the art.

(3) The present disclosure herein provides a dephosphorizing flux used for lowering the content of phosphorous (P) in a ferro-manganese (FeMn) molten steel and a method for producing the same. More specifically, the present disclosure herein provides a dephosphorizing flux which is capable of lowering the melting point of a dephosphorizing flux and slag and improving the dephosphorization efficiency of the ferro-manganese while securing fluidity, has a few environment-polluting elements, and is capable of reducing production costs, and a method for producing the same. As a more specific example, the present disclosure provides a dephosphorizing flux with which dephosphorization is performed with regard to a high-carbon ferro-manganese (FeMn) molten steel having a carbon content of 5-7 wt %, and a method for producing the same.

(4) In addition, the present disclosure herein also provides a dephosphorizing flux which has a dephosphorization ratio due to the dephosphorizing flux is at least 30% and is capable of causing no-plugging of a lower blowing nozzle or preventing the occurrence of plugging of the lower blowing nozzle, and a method for producing the same.

(5) The dephosphorizing flux in accordance with an exemplary embodiment includes at least any one among BaCo3, NaHCO.sub.3 or Na.sub.2CO.sub.3, which is a highly alkaline material, and CaF.sub.2.

(6) Meanwhile, when the dephosphorizing flux including BaCO.sub.3, which is a highly alkaline material is added into a ferro-manganese molten steel, phosphorous (P) in the ferro-manganese and oxygen react to form a phosphate (P.sub.2O.sub.5), and the phosphate (P.sub.2O.sub.5) is collected by the highly alkaline material and transits into a stable phase. Here, when a highly alkaline oxide is used for the dephosphorizing flux, since the oxide should be present in a liquid phase sate in order to promote a reaction with the phosphate (P.sub.2O.sub.5), a flux is used for lowering the melting point of slag. In addition, it is necessary to use an additive for improving the dephosphorization ratio.

(7) The dephosphorizing flux in accordance with an exemplary embodiment is configured to contain, with respect to the total wt % (100 wt %) of the dephosphorizing flux, at least 70 wt % of a main material and at most 30 wt % of supplementary materials. More favorably, at least 80 wt % of main material and at most 20 wt % of supplementary materials are configured to be contained. Here, the main material may be BaCO.sub.3, and the supplementary materials include at least any one of NaHCO.sub.3 or Na.sub.2CO.sub.3, and CaF.sub.2.

(8) FIG. 1 is a flowchart showing a method for preparing a dephosphorizing flux in accordance with an exemplary embodiment.

(9) Hereinafter referring to FIG. 1, a method for preparing a dephosphorizing flux in accordance with an exemplary embodiment will be described.

(10) Referring to FIG. 1, a method for preparing a dephosphorizing flux in accordance with an exemplary embodiment includes: preparing BaCO.sub.3, which is a main material (S110); preparing supplementary materials (S120); and mixing the main material and the supplementary materials (S200).

(11) The preparing of the supplementary materials (120) includes preparing a first material and a second material (S121 and S122). Here, the first material includes either of NaHCO.sub.3 or Na.sub.2CO.sub.3, and the second material includes CaF.sub.2. NaHCO.sub.3 or Na.sub.2CO.sub.3, functions as a flux for lowering the melting points of the dephosphorizing flux and slag. In addition, CaF.sub.2 functions as an additive for improving the dephosphorization efficiency.

(12) In the mixing of the main material and the supplementary material (S200), the supplementary materials are added so as to be at most 30 wt %, more favorably, at most 20 wt % with respect to the total of the dephosphorizing flux. For example, when the supplementary materials exceed 30 wt %, there is a problem in that the highly alkaline effect due to the use of BaCO.sub.3 is reduced, and the dephosphorization ratio decreases.

(13) The supplementary material is a mixture of the first material and the second material, and NaHCO.sub.3 or Na.sub.2CO.sub.3 are used as the first material and CaF.sub.2 is used as the second material. That is, the supplementary material in accordance with an exemplary embodiment may be configured to include, for example, NaHCO.sub.3 and CaF.sub.2 or to include Na.sub.2CO.sub.3 and CaF.sub.2.

(14) Thus, the dephosphorizing flux in accordance with an exemplary embodiment may be configured to include, for example, NaHCO.sub.3 and CaF.sub.2 or to include Na.sub.2CO.sub.3 and CaF.sub.2.

(15) When adding a powder-state dephosphorizing flux including NaHCO.sub.3 is added into molten steel, a reaction such as the following reaction formula 1 from a low temperature of 60° C. and a large quantity of H.sub.2O and CO.sub.2 are generated simultaneously with blowing. Due to this gas, there is an effect of improving agitating capability of the molten steel, and thus, an additional effect of increasing dephosphorization efficiency may be exhibited. In addition, finally generated Na.sub.2CO.sub.3 is a material having a low melting point of 851° C., and functions as a flux that lowers the melting point of generated dephosphorization slag.
2NaHCO.sub.3-->Na.sub.2CO.sub.3+H.sub.2O+CO.sub.2  Reaction formula 1)

(16) Even when directly using Na.sub.2CO.sub.3 as the first material, the same effect may be generated. That is, the supplementary material may include Na.sub.2CO.sub.3 as the first material, and CaF.sub.2 as the second material. When directly using Na.sub.2CO.sub.3, an effect of increasing the ratio of Na element itself by two times than NaHCO.sub.3 is generated, and an effect is exhibited in which Na.sub.2CO.sub.3 is mixed into the dephosphorization slag by a higher content than NaHCO.sub.3. Thus, an effect of further increasing the function as a flux is exhibited and thus, a dephosphorization effect which is equal to or similar to that of NaHCO.sub.3 is exhibited.

(17) When using the dephosphorizing flux in accordance with the exemplary embodiments, the dephosphorization ratio may be improved by at least 30%. In addition, since the melting points of the dephosphorizing flux and the slag may be lowered and a high fluidity may thereby be maintained, a reaction efficiency with molten steel is high, and since being provided under a converter, the plugging of lower blowing nozzle that blows a carrier gas may be prevented.

(18) In addition, in mixing the main material and the supplementary material including the first material and the second material, the dephosphorization ratio may further be improved by appropriately adjusting the weight ratio of the second material to the first material.

(19) For example, when using NaHCO.sub.3 as the first material, it is effective that the weight ratio (that is, CaF.sub.2 wt %/NaHCO.sub.3 wt %) of the second material (CaF.sub.2) to the first material (NaHCO.sub.3) is adjusted to be greater than 0 and not greater than 2.3. Favorably, the weight ratio (that is, CaF.sub.2 wt %/NaHCO.sub.3 wt %) of the second material (CaF.sub.2) to the first material (NaHCO.sub.3) is adjusted to be greater than approximately 0 and not greater than 1.4, or more favorably, to be 0.5 to 1 inclusive. The weight ratio (that is, CaF.sub.2 wt %/NaHCO.sub.3 wt %) of the second material (CaF.sub.2) to the first material (NaHCO.sub.3) may be adjusted by adjusting the adding amount of the first material, or adjusting the adding amount of the second material.

(20) In addition, in order to improve the dephosphorization efficiency, it is effective to add the second material (CaF.sub.2) to be at least 2 wt % with respect to the total of the supplementary material. That is, there is a tendency that a higher dephosphorization ratio is exhibited when the weight ratio (that is, CaF.sub.2 wt %/NaHCO.sub.3 wt %) of the second material (CaF.sub.2) to the first material (NaHCO.sub.3) is greater than 0 and not greater than 2.3, than that when the second material (CaF.sub.2) is at least 2 wt %, and thus, it is more effective that the second material (CaF.sub.2) is added to be at least 2 wt % with respect to the total of the supplementary material.

(21) Meanwhile, when the second material (CaF.sub.2) is less than 2 wt %, there is a method of increasing the content of the first material (NaHCO.sub.3) in order to adjust the weight ratio (that is, CaF.sub.2 wt %/NaHCO.sub.3 wt %) of the second material (CaF.sub.2) to the first material (NaHCO.sub.3) to be at most 2.3. However, in this method, the dephosphorization ratio is relatively low than that when the second material (CaF.sub.2) is at least 2 wt % and the weight ratio (that is, CaF.sub.2 wt %/NaHCO.sub.3 wt %) of the second material (CaF.sub.2) is adjusted to be at most 2.3. Accordingly, while adjusting the second material (CaF.sub.2) having a larger direct influence to be at least 2 wt %, the weight ratio (that is, CaF.sub.2 wt %/NaHCO.sub.3 wt %) of the second material (CaF.sub.2) to the first material (NaHCO.sub.3) to be at most 2.3, favorably greater than 0 and not greater than 1.4, and more favorably, 0.5 to 1 inclusive.

(22) In another example, when using Na.sub.2CO.sub.3 as the first material, the weight ratio (that is, CaF.sub.2 wt %/Na.sub.2CO.sub.3 wt %) of the second material (CaF.sub.2) to the first material (Na.sub.2CO.sub.3) is favorably adjusted to greater than 0 and not greater than 4, and more favorably adjusted to be 0.7 to 2 inclusive. The weight ratio (that is, CaF.sub.2 wt %/Na.sub.2CO.sub.3 wt %) of the second material (CaF.sub.2) to the first material (Na.sub.2CO.sub.3) may be adjusted by adjusting the adding amount of the first material, or adjusting the adding amount of the second material.

(23) Also in this case, it is effective to add the second material (CaF.sub.2) to be at least 2 wt % with respect to the total of the supplementary material. That is, there is a tendency that a higher dephosphorization ratio is exhibited when the weight ratio (that is, CaF.sub.2 wt %/Na.sub.2CO.sub.3 wt %) of the second material (CaF.sub.2) to the first material (NaHCO.sub.3) is at most 4 than that when the second material (CaF.sub.2) is less than 2 wt %, and thus, it is effective that the second material (CaF.sub.2) is added to be at least 2 wt % with respect to the total of the supplementary material.

(24) Meanwhile, when the second material (CaF.sub.2) is less than 2 wt %, there is a method of increasing the content of the first material (Na.sub.2CO.sub.3) in order to adjust the weight ratio (that is, CaF.sub.2 wt %/Na.sub.2CO.sub.3 wt %) of the second material (CaF.sub.2) to the first material (Na.sub.2CO.sub.3) to be at most 4. However, in this method, the dephosphorization ratio is relatively low than that when the second material (CaF.sub.2) is at least 2 wt % and the weight ratio (that is, CaF.sub.2 wt %/Na.sub.2CO.sub.3 wt %) of the second material (CaF.sub.2) is adjusted to be at most 4. Accordingly, while adjusting the second material (CaF.sub.2) having a larger direct influence to be at least 2 wt %, the weight ratio (that is, CaF.sub.2 wt %/Na.sub.2CO.sub.3 wt %) of the second material (CaF.sub.2) to the first material (Na.sub.2CO.sub.3) to be greater than 0 and not greater than 4, and more favorably, 0.7 to 2 inclusive.

(25) Hereinafter, this will be described through specific and various examples and comparative examples of exemplary embodiments.

(26) Table 1 shows the composition of the dephosphorizing fluxes in accordance with first to sixth comparative examples, and Table 3 shows the dephosphorization ratio when using the dephosphorizing fluxes in accordance with the first to sixth comparative examples and shows whether a lower blowing nozzle provided under a converter is plugged.

(27) Table 2 shows the composition of the dephosphorizing fluxes in accordance with first to ninth examples, and Table 4 shows the dephosphorization ratio when using the dephosphorizing fluxes in accordance with the first to ninth examples and shows whether a lower blowing nozzle provided under a converter is plugged.

(28) The first comparative example is a dephosphorizing flux (BaCO.sub.3 100 wt %) which includes only BaCO.sub.3, does not include NaHCO.sub.3 or Na.sub.2CO.sub.3, and does not include CaF.sub.2. In addition, the second comparative example is a dephosphorizing flux which includes BaCO.sub.3 and 10 wt % of NaHCO.sub.3, and does not include CaF.sub.2. In addition, the third and fourth comparative examples are dephosphorizing fluxes which include BaCO.sub.3 and Na.sub.2CO.sub.3, the third comparative example contains 10 wt % of Na.sub.2CO.sub.3, and the fourth example contains 20 wt % of Na.sub.2CO.sub.3. In addition, the fifth and sixth comparative examples are dephosphorizing fluxes which include BaCO.sub.3 and CaF.sub.2, and do not include NaHCO.sub.3 or Na.sub.2CO.sub.3. Here, the content of CaF.sub.2 are different in the fifth and sixth comparative examples

(29) In addition, the dephosphorizing fluxes in accordance with the first to ninth comparative examples each include BaCO.sub.3 as the main material, NaHCO.sub.3 or Na.sub.2CO.sub.3 as the first material for the supplementary material, and CaF.sub.2 as the second material. Here, the dephosphorizing fluxes in accordance with the first to fifth comparative examples each include BaCO.sub.3, NaHCO.sub.3, and CaF.sub.2, and each have different composition contents of respective components. In addition, the dephosphorizing fluxes in accordance with the sixth to ninth comparative examples each include BaCO.sub.3, Na.sub.2CO.sub.3, and CaF.sub.2, and each have different composition contents of respective components.

(30) In addition, in the composition of the first to sixth comparative examples and the first to seventh comparative examples, although the BaCO.sub.3 content is not described, the BaCO.sub.3 content is the remaining content excluding the supplementary material with respect to total dephosphorizing flux of 100 wt %.

(31) TABLE-US-00001 TABLE 1 Second material (CaF.sub.2)/ Second material (CaF.sub.2) First material content + first material Dephosphorizing (NaHCO.sub.3 or N.sub.2CO.sub.3) (NaHCO.sub.3 or N.sub.2CO.sub.3) flux composition ratio content (wt %) First BaCO.sub.3 —  0 wt % comparative example Second BaCO.sub.3 + — 10 wt % comparative NaHCO.sub.3 (10 wt %) (NaHCO.sub.3 10 wt %) example Third BaCO.sub.3 + — 10 wt % comparative Na.sub.2 CO.sub.3 (10 wt %) (Na.sub.2 CO.sub.3 10 wt %) example Fourth BaCO.sub.3 + — 20 wt % comparative Na.sub.2 CO.sub.3 (20 wt %) (Na.sub.2 CO.sub.3 20 wt %) example Fifth BaCO.sub.3 + —  5 wt % comparative CaF.sub.2 (5 wt %) (CaF.sub.2 5 wt %) example Sixth BaCO.sub.3 + — 10 wt % comparative CaF.sub.2 (10 wt %) (CaF.sub.2 10 wt %) example

(32) TABLE-US-00002 TABLE 2 Second material (CaF.sub.2)/ Second material (CaF.sub.2) First material content + first material Dephosphorizing (NaHCO.sub.3 or N.sub.2CO.sub.3) (NaHCO.sub.3 or N.sub.2CO.sub.3) flux composition ratio content (wt %) First BaCO.sub.3 + 1.4 12 wt % comparative NaHCO.sub.3 (5 wt %) + (NaHCO.sub.3 5 wt % ++ example CaF.sub.2 (7 wt %) CaF.sub.2 7 wt %) Second BaCO.sub.3 + 1 14 wt % comparative NaHCO.sub.3 (7 wt %) + (NaHCO.sub.3 7 wt % + example CaF.sub.2 (7 wt %) CaF.sub.2 7 wt %) Third BaCO.sub.3 + 0.58 19 wt % comparative NaHCO.sub.3 (12 wt %) + NaHCO.sub.3 12 wt % ++ example CaF.sub.2 (7 wt %) CaF.sub.2 7 wt %) Fourth BaCO.sub.3 + 2 15 wt % comparative NaHCO.sub.3 (5 wt %) + (NaHCO.sub.3 5 wt % + example CaF.sub.2 (10 wt %) CaF.sub.2 10 wt %) Fifth BaCO.sub.3 + 2.3 10 wt % comparative NaHCO.sub.3 (3 wt %) + NaHCO.sub.3 3 wt % ++ example CaF.sub.2 (7 wt %) CaF.sub.2 7 wt %) Sixth BaCO.sub.3 + 0.71 12 wt % comparative Na.sub.2 CO.sub.3 (7 wt %) + Na.sub.2 CO.sub.3 7 wt % + example CaF.sub.2 (5 wt %) CaF.sub.2 5 wt %) Seventh BaCO.sub.3 + 2.3 10 wt % comparative Na.sub.2 CO.sub.3 (3 wt %) + Na.sub.2 CO.sub.3 3 wt % + example CaF.sub.2 (7 wt %) CaF.sub.2 7 wt % Eighth BaCO.sub.3 + 4 15 wt % comparative Na.sub.2 CO.sub.3 (3 wt %) + Na.sub.2 CO.sub.3 3 wt % + example CaF.sub.2 (12 wt %) CaF.sub.2 12 wt %) Ninth BaCO.sub.3 + 2 15 wt % comparative Na.sub.2 CO.sub.3 (5 wt %) + Na.sub.2 CO.sub.3 5 wt % + example CaF.sub.2 (10 wt %) CaF.sub.2 10 wt %)

(33) TABLE-US-00003 TABLE 3 Dephosphorization Dephosphorization Dephosphorization Lower blowing initial stage completion ratio nozzle [P] (wt %) [P] (wt %) [P] (wt %) plugging First 0.106 0.065 39 Plugging comparative occurs example Second 0.112 0.088 21.8 Plugging does comparative not occur example Third 0.104 0.085 18.1 Plugging does comparative not occur example Fourth 0.118 0.091 22.6 Plugging does comparative not occur example Fifth 0.101 0.061 39.2 Plugging comparative occurs example Sixth 0.107 0.058 45.4 Plugging comparative occurs example

(34) TABLE-US-00004 TABLE 4 Dephosphorization Dephosphorization Dephosphorization Lower blowing initial stage completion ratio nozzle [P] (wt %) [P] (wt %) [P] (wt %) plugging First 0.109 0.047 49 Plugging does comparative not occur example Second 0.099 0.040 60 Plugging does comparative not occur example Third 0.118 0.049 58.5 Plugging does comparative not occur example Fourth 0.121 0.065 46.2 Plugging does comparative not occur example Fifth 0.132 0.077 41.7 Plugging does comparative not occur example Sixth 0.105 0.04 61.9 Plugging does comparative not occur example Seventh 0.105 0.071 32.4 Plugging does comparative not occur example Eighth 0.123 0.079 35.4 Plugging does comparative not occur example Ninth 0.095 0.054 42.8 Plugging does comparative not occur example

(35) For the experiment, dephosphorization was performed with respect to high-carbon ferro-manganese molten steel containing 5-7 wt % of carbon. In addition, the dephosphorization method was performed such that a lance was immersed in the ferro-manganese molten steel, and then while blowing a carrier gas through a lower blowing nozzle provided under a converter, a dephosphorizing flux was blown into the molten steel. In order to compare under the same conditions, the same unit of the flux of 140 kg/ton was blown, and the final temperature when completing the blowing of the dephosphorizing flux and completing a dephosphorization process were managed to be the same, that is, to be at most 1,310° C.

(36) The dephosphorizing fluxes in accordance with the first to sixth examples and ninth examples have higher dephosphorization ratio than the first comparative example. This is resulted in the example, by an effect of lowering the melting point due to NaHCo3 or Na.sub.2CO.sub.3, an effect of securing fluidity and improving agitating efficiency, and an effect of improving dephosphorization ratio due to CaF.sub.2. Meanwhile, in case of the first comparative example, since the dephosphorizing flux includes only BaCO.sub.3, which is highly alkaline substance and contains a large quantity of BaCO.sub.3, the melting points of the dephosphorizing flux and slag are raised, and thus, the fluidity is lowered. Therefore, the dephosphorization ratio is lower than those in the first to sixth examples and ninth examples.

(37) In addition, when comparing the second comparative example and the first to fifth examples which include NaHCO.sub.3 aside from BaCO.sub.3, the dephosphorization ratios in the first to fifth examples are 1.9 times higher than that in the second comparative example. More specifically, the dephosphorization ratio in the fifth example is 1.9 times higher than that in the first comparative example, and the dephosphorization ratios in the first to fourth examples are 2 times higher, and among these, those in the second and third examples are at least 2.5 times higher.

(38) Meanwhile, the dephosphorization ratio in the second comparative example is higher than that in the third comparative example including 10 wt % of Na.sub.2CO.sub.3, and is similar to that in the fourth comparative example including 20 wt % of Na.sub.2CO.sub.3, but is lower than those of the dephosphorizing fluxes in accordance with the first to ninth examples. This is because the second comparative example does not include CaF.sub.2 that directly affects the dephosphorization ratio.

(39) In addition, when comparing the third to fourth comparative examples and the sixth to ninth examples which include Na.sub.2CO.sub.3 aside from BaCO.sub.3, the dephosphorization ratio in the sixth to ninth examples are approximately 1.4 times higher than those in the third and fourth comparative examples. This is because the third and fourth comparative examples do not include CaF.sub.2, but the sixth to ninth examples include CaF.sub.2 aside from Na.sub.2CO.sub.3. In addition, the dephosphorizing fluxes (the third and fourth comparative examples) in which only Na.sub.2CO.sub.3 is added as the supplementary material functions as a flux in the initial dephosphorization stage, lowers the melting point of the dephosphorizing flux and maintains a molten state, but as the dephosphorization operation is performed, a phenomenon occurs in which the function as the flux may not be performed while Na.sub.2CO.sub.3 is volatized together with the generation of Mn oxides, and thus, the dephosphorization ratio decreases due to solidification of the dephosphorization slag.

(40) Meanwhile, when comparing dephosphorization ratios in accordance with the first comparative example, which does not include CaF.sub.2 and NaHCO.sub.3 or Na.sub.2CO.sub.3, and the fifth and sixth comparative examples which do not include NaHCO.sub.3 or Na.sub.2CO.sub.3, are higher than those in accordance with the seventh to eight examples which include Na.sub.2CO.sub.3 and CaF.sub.2. In addition, when comparing the fifth and sixth comparative examples, a tendency is shown in which the higher the CaF.sub.2 content, the higher the dephosphorization ratio.

(41) However, in case of the dephosphorizing flux including only BaCO.sub.3 (the first comparative example), or including only BaCO.sub.3 and CaF.sub.2 (the fifth and sixth comparative examples), the dephosphorization slag is solidified due to CaO generated while the dephosphorization progresses. Thus, the fluidity of the slag that covers a melt surface becomes very low, and this causes the plugging of a lower blowing nozzle which is provided under a converter and blows an inert gas or a carrier gas in order to move or agitate the powder-like dephosphorizing flux. Therefore, a scattering phenomenon of the molten steel remarkably occurs while the dephosphorization progresses, and in a severe case, a phenomenon of flooding outside a ladle also occurs, and thus, there is a problem of substantially degrading operability.

(42) In addition, in case of the first comparative example, and the fifth to sixth comparative examples, the reaction rate with the molten steel is decreased due to the degradation in the fluidity of the dephosphorizing flux, the dephosphorization ratio is lower than those of the first to sixth examples and the ninth example.

(43) Accordingly, the dephosphorizing fluxes in accordance with exemplary embodiments are configured to include BaCO.sub.3, NaHCO.sub.3 and CaF.sub.2 or to include BaCO.sub.3, Na.sub.2CO.sub.3 and CaF.sub.2, so that the lower blowing nozzle plugging phenomenon may be prevented while having a dephosphorization ratio of at least 30%.

(44) In addition, in accordance with exemplary embodiments, the dephosphorization ratio may further increased by adjusting the ratio of the first material to the second material (CaF.sub.2 wt %/NaHCO.sub.3 wt % or CaF.sub.2 wt %/Na.sub.2CO.sub.3 wt %) that constitutes the supplementary material.

(45) That is, when comparing the first to fifth examples, the dephosphorization ratios of the dephosphorizing fluxes in accordance with the first to third examples, in which the ratio of the first material to the second material (CaF.sub.2 wt %/NaHCO.sub.3 wt % or CaF.sub.2 wt %/Na.sub.2CO.sub.3 wt %) is greater than 0 and not greater than 1.4, exceed 1.4, and this is higher than those of the fourth to fifth examples in which dephosphorization ratio is at most 2.3. This is because the supplementary materials similarly include NAHCO.sub.3 and CaF.sub.2 in the first to fifth examples, but in case of the first to third examples the weight ratio of CaF.sub.2 to NaHCO.sub.3 (that is, CaF.sub.2 wt %/NaHCO.sub.3 wt %) is adjusted to be at most 1.4 while adjusting the NaHCO.sub.3 content corresponding to the CaF.sub.2 content. In other words, this is because in case of the first to third examples, the weight ratio of CaF.sub.2 to NaHCO.sub.3 (that is, CaF.sub.2 wt %/NaHCO.sub.3 wt %) is at most 1.4 while the adding ratio of CAF.sub.2 is reduced compared to those in the fourth to fifth examples, a larger melting point lowering effect due to NaHCO.sub.3 is exhibited in the first to third examples than those in the fourth to fifth examples.

(46) In addition, among the first to fifth example, the dephosphorization ratios of the dephosphorizing fluxes in accordance with the second to third examples, in which the ratio of the first material to the second material (CaF.sub.2 wt %/NaHCO.sub.3 wt %) is 0.5 to 1 inclusive, are higher than those in the first, fourth and fifth examples in which the ratio of the first material to the second material exceeds approximately 1. This is because in the case of the second and third examples, while the adding ratio of CaF.sub.2 decreases compared to the first, fourth, and fifth examples, the weight ratio of CAF.sub.2 to NaHCO.sub.3 (that is, CaF.sub.2 wt %/NaHCO.sub.3 wt %) is 0.5 to 1 inclusive, and thus, a larger melting point lowering effect due to NaHCO.sub.3 is exhibited in the second and third examples than those in the first, fourth and fifth examples.

(47) In addition, the third example shows the result in which dephosphorization was performed in the same manner after mixing NaHCO.sub.3 and CaF.sub.2 while the content ratio of NaHCO.sub.3 is increased up to 12 wt % with respect to the CaF.sub.2 content of 7 wt % in the same manner as the second example. As a result, it was confirmed that the third example exhibited the equal or a similar level of dephosphorization ratio to the second example.

(48) In addition, the dephosphorization ratios of the dephosphorizing fluxes in accordance with the first and fourth examples, in which the weight ratio of CAF.sub.2 to NaHCO.sub.3 (that is, CaF.sub.2 wt %/NaHCO.sub.3 wt %) is greater than 1 and not greater than 2, are higher than those of the first to sixth comparative examples, and the plugging of the lower blowing nozzle does not occur.

(49) Comparing the sixth to ninth examples, the dephosphorization ratio of the dephosphorizing fluxes in accordance with the sixth example is higher than those of the dephosphorizing fluxes in accordance with the seventh to ninth examples. This is because in case of the dephosphorizing fluxes in accordance with the sixth example, the weight ratio of CaF.sub.2 to Na.sub.2CO.sub.3 is adjusted to be 0.7 to 2 inclusive, and the degree of increase in the melting point of slag due to an increase in CaO according to a progress in dephosphorization is relatively lower than those in the seventh to ninth examples, and the reaction efficiency is relatively high.

(50) In addition, it may be found that the sixth example, which includes BaCO.sub.3, Na.sub.2CO.sub.3 and CaF.sub.2 and in which the weight ratio of CaF.sub.2 to Na.sub.2CO.sub.3 is 0.7 to 2 inclusive, exhibits a dephosphorization ratio which is equal or similar to those of the second and third examples which includes BaCO.sub.3, NaHCO.sub.3 and CaF.sub.2 and in which the weight ratio of CaF.sub.2 to NaHCO.sub.3 is 0.5 to 1.4 inclusive.

(51) As such, according to the dephosphorizing flux in accordance with an exemplary embodiment, the plugging of the lower blowing nozzle that blows a carrier gas during dephosphorization may be prevented while securing a dephosphorization ratio of at least 30%. In addition, in configuring the supplementary material for the dephosphorizing flux,

(52) The occurrence of nozzle plugging may be prevented or suppressed while securing a dephosphorization ratio of at least 41% by adjusting the weight ratio (that is, CaF.sub.2 wt %/NaHCO.sub.3 wt %) of the second material (CaF.sub.2) to the first material (NaHCO.sub.3) to be greater than 0 and not greater than 2.3. In addition, favorably, the occurrence of nozzle plugging may be prevented or suppressed while securing a dephosphorization ratio of at least 49% by adjusting the weight ratio (that is, CaF.sub.2 wt %/NaHCO.sub.3 wt %) of the second material (CaF.sub.2) to the first material (NaHCO.sub.3) to be greater than 0 and not greater than 1.4. In addition, more favorably, the occurrence of nozzle plugging may be prevented or suppressed while securing a dephosphorization ratio of at least 55% by adjusting the weight ratio (that is, CaF.sub.2 wt %/NaHCO.sub.3 wt %) of the second material (CaF.sub.2) to the first material (NaHCO.sub.3) to be greater than 0.5 and not greater than 1.

(53) In addition, the occurrence of nozzle plugging may be prevented or suppressed while securing a dephosphorization ratio of at least 30% by adjusting the weight ratio (that is, CaF.sub.2 wt %/NaHCO.sub.3 wt %) of the second material (CaF.sub.2) to the first material (NaHCO.sub.3) to be greater than 0 and not greater than 4. More favorably, the occurrence of nozzle plugging may be prevented or suppressed while securing a dephosphorization ratio of at least 40% by adjusting the weight ratio (that is, CaF.sub.2 wt %/NaHCO.sub.3 wt %) of the second material (CaF.sub.2) to the first material (NaHCO.sub.3) to be 0.7 to 2 inclusive.

(54) In addition, since environment polluting substances are not used as in conventional arts, environment pollution risk may be reduced, and the cost burden due to the facility for pollution prevention and harmful substance management may be alleviated. In addition, there is a cost reduction effect by using NaHCO.sub.3 or Na.sub.2CO.sub.3 and CaF.sub.2 which are relatively cheap

INDUSTRIAL APPLICABILITY

(55) According to the dephosphorizing flux and a method for preparing the same in accordance with exemplary embodiments, the plugging of a lower blowing nozzle that blows a carrier gas during dephosphorization may be prevented while improving a dephosphorization ratio. In addition, since environment polluting substances are not used as in conventional arts, environment pollution risk may be reduced, and the cost burden due to the facility for pollution prevention and harmful substance management may be alleviated.