Method for inhibiting high-temperature fluidity deterioration of high-aluminum steel casting powder

Abstract

The invention relates to the technical field of steelmaking continuous casting, in particular to a method for inhibiting high-temperature fluidity deterioration of high-aluminum steel casting powder. According to the method, the casting powder comprises the following effective components in percentage by weight: 2 to 4 percent of CaO, 34.84 to 39.94 percent of CaF2, 7.8 to 9.3 percent of NaCl, less than 0.5 percent of Na2O + K2O, 1 to 5 percent of Li2O, less than 1 percent of Al2O3, less than 1.5 percent of MgO and 3 to 5 percent of C. The mass percentage content of SiO2 should meet the formula # imgabs0 #, and WSiO2WCaF2 and WCaO are the mass percentage contents of SiO2, CaF2 and CaO in the casting powder respectively, namely%; w [Al] is the mass percentage content of [Al] in the cast steel. The casting powder of the system can guarantee that the high-temperature flow characteristic of the casting powder is stable when high-aluminum steel with the aluminum content being 2-7% is cast, and the problems of casting blank quality and continuous casting smoothness caused by viscosity change of the casting powder are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of steelmaking and continuous casting, and in particular to a method for inhibiting the deterioration of high-temperature fluidity of high-aluminum steel protection slag. Background Art

[0002] As an indispensable functional material in the continuous casting process, mold powder plays a vital role in the smooth progress of continuous casting and the quality of the ingot. The physical properties of the mold powder include melting point, melting rate, viscosity and crystallization temperature. The viscosity of the mold powder directly determines the uniformity and thickness of the slag film in the gap between the ingot and the wall of the crystallizer. If the viscosity is too high, the flowability of the mold powder will deteriorate, resulting in less liquid slag flowing into the gap between the primary shell and the water-cooled crystallizer wall, and the slag film will also become thinner, affecting the heat transfer and lubrication performance. If the viscosity is too low, the flowability of the mold powder will be stronger, resulting in more liquid slag flowing into the gap between the primary shell and the water-cooled crystallizer wall, making the slag film thicker and uneven, which will also affect the heat transfer and lubrication performance, thereby affecting the quality of the ingot.

[0003] When molten steel contains a high content of Al, the SiO2 in the mold slag reacts with it, causing Al2O3 to replace SiO2. This increases the alkalinity of the slag, and some Al2O3 acts as a network former, causing the network structure to aggregate. This leads to a sharp increase in the viscosity of the mold slag, poor slag fluidity, and impacting casting. Current research on mold slags for high-aluminum steels focuses on two main areas. The first is the use of low-reactivity CaO-Al2O3-based mold slags. These slags aim to achieve favorable casting conditions by inhibiting slag reactions, but they fail to consider the changes in mold slag properties after Al2O3 inclusions are adsorbed, and therefore have not been widely adopted. The second is the low-alkalinity CaO-SiO2-based mold slags currently widely used by steelmakers. These mold slags perform well in the early stages of casting, but as casting time increases, the viscosity of the mold slag increases, preventing the mold slag from flowing properly into the slag channel. This significantly degrades lubrication of the ingot and impacts its smooth casting. So far, there has been no report on the research on stabilizing the high-temperature fluidity of protective slag. Therefore, it is urgent to develop a method to inhibit the deterioration of the high-temperature fluidity of high-aluminum steel protective slag and solve the problem of sudden change in the high-temperature viscosity of the protective slag caused by steel slag reaction.

[0004] This invention provides a method for suppressing the deterioration of high-temperature fluidity in mold slag for high-aluminum steel. This method effectively addresses the problem of a significant increase in mold slag viscosity at high temperatures (1200-1300°C) after slag reaction. This ensures good high-temperature fluidity in the mold slag, thereby enabling smooth continuous casting of high-aluminum steel. Summary of the Invention

[0005] The purpose of the present invention is to address the above-mentioned problems and provide a method for inhibiting the deterioration of high-temperature fluidity of high-aluminum steel protection slag.

[0006] The object of the present invention is achieved in this way: a method for inhibiting the deterioration of high-temperature fluidity of high-aluminum steel protective slag, wherein the percentage content of the effective ingredients of the protective slag is as follows: CaO: 2-4%, CaF2: 34.84-39.94%, NaCl: 7.8-9.3%, Na2O+K2O <0.5%, Li2O: 1-5%, Al2O3: <1%, MgO: <1.5%, C: 3-5%, and the rest is SiO2 and unavoidable impurities.

[0007] The mass percentage content of SiO2 satisfies the formula: Among them, W SiO2 W is the mass percentage of SiO2 in the protective slag, %; CaF2 W is the mass percentage of CaF2 in the mold slag, %; CaO W is the mass percentage of CaO in the mold slag, %; [Al] is the mass percentage of Al element in the cast steel, %.

[0008] The aluminum content in the high-aluminum steel is 2% to 7%.

[0009] The high temperature fluidity, ie the high temperature flow stability, refers to the viscosity fluctuation of the mold slag before and after the slag reaction within a temperature range of 1200-1300°C within 0.06 Pa.s.

[0010] The beneficial effects of the present invention are: (1) The present invention effectively stabilizes the high-temperature fluidity of the protective slag based on CaF2 as the main base material.

[0011] (2) The present invention accurately provides the mass percentage ratio of SiO2 in the protective slag based on the content of Al element in the molten steel, so that the viscosity of the protective slag of the CaF2-SiO2 system after Al2O3 replaces SiO2 and the CaF2-Al2O3 system after the same replacement remains consistent.

[0012] (3) NaCl was used to replace Na2O in the traditional protective slag, which greatly improved the stability of the high-temperature flow of the protective slag. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The present invention will be further described below in conjunction with the accompanying drawings.

[0014] Figure 1 This is a diagram showing the change in high-temperature fluidity of mold slag before and after slag reaction under traditional technology; Figure 2 This is a diagram showing the change in high-temperature fluidity of the protective slag before and after the steel slag reaction under the technology of the present invention. DETAILED DESCRIPTION

[0015] This invention addresses the problem of viscosity degradation in mold slag for high-aluminum steel caused by shortcomings in existing technologies. It proposes a method for suppressing the deterioration of high-temperature fluidity in mold slag for high-aluminum steel. This method effectively addresses the problem of sudden changes in high-temperature viscosity of mold slag under existing technology by adjusting the slag composition, using CaF2 as the base material, adding NaCl and Li2O as fluxes, and adding SiO2 in a quantitative manner based on the [Al] element in high-aluminum steel. The technical solution of the invention is as follows.

[0016] 1. The percentage content of the active ingredients in the mold slag is as follows: CaO: 2-4%, CaF2: 34.84-39.94%, NaCl: 7.8-9.3%, Na2O+K2O <0.5%, Li2O: 1-5%, Al2O3: <1%, MgO: <1.5%, C: 3-5%. The remainder is SiO2 and unavoidable impurities.

[0017] 2. Furthermore, the mass percentage of SiO2 is closely related to the [Al] element in high-aluminum steel. The higher the Al content, the lower the effective basicity of the mold slag required, and the higher the mass percentage of SiO2. This is to ensure that there is enough SiO2 after the slag reaction to compensate for the viscosity of the mold slag, thereby achieving the purpose of stabilizing the high-temperature fluidity of the mold slag. The mass percentage of SiO2 should satisfy the formula: Among them, W SiO2 W is the mass percentage of SiO2 in the protective slag, %; CaF2 W is the mass percentage of CaF2 in the mold slag, %; CaO W is the mass percentage of CaO in the mold slag, %; [Al] is the mass percentage content of [Al] element in the cast steel, %.

[0018] 3. Furthermore, the aluminum content in the high aluminum steel continuous casting is 2% to 7%.

[0019] 4. Furthermore, the physical properties of high aluminum steel protection slag are: melting point 950-1060℃, viscosity at 1300℃: 0.1-0.23Pa.s.

[0020] 5. Furthermore, the high-temperature flow stability mentioned here refers to the fact that the viscosity of the protective slag before and after the slag reaction (the redox reaction between the Al element in the high-aluminum steel and the SiO2 in the protective slag) fluctuates within 0.06 Pa.s in the temperature range of 1200-1300°C.

[0021] 6. The present invention uses a relatively high content of CaF2 as the base material. This is because CaF2 does not react with the Al element in the steel, and its fluoride ions can effectively reduce the melting point and viscosity of the mold slag at high temperatures. When the CaF2 content is higher than 32%, the viscosity of the mold slag no longer decreases significantly, but instead maintains a relatively stable value. Moreover, at high temperatures (1200-1300°C), the viscosity of the CaF2-SiO2 system and the CaF2-Al2O3 system after equivalent substitution are almost the same. Therefore, even if Al2O3 replaces SiO2 in the mold slag, the high-temperature viscosity of the mold slag remains relatively stable.

[0022] 7. This invention uses NaCl instead of Na2O in conventional mold flux. On the one hand, NaCl does not react with the [Al] in the steel, resulting in excellent chemical stability. On the other hand, NaCl is more soluble in water at room temperature than sodium carbonate and is non-reactive. The addition of NaCl is primarily used to adjust the melting point and viscosity of the mold flux based on CaF2.

[0023] Example

[0024] Cast high aluminum steel with 2.3% aluminum content

[0025] 1. The percentage content of effective ingredients in the protective slag is as follows: CaO: 3.2%, CaF2: 37.2%, NaCl: 8.1%, Na2O+K2O=0.15%, Li2O: 4.1%, Al2O3: 0.8%, MgO: 1.2%, C: 3.5%.

[0026] 2. The mass percentage content of SiO2 should satisfy the formula:

[0027] 3. The melting point of the prepared protective slag is 1023℃, and the viscosity at 1300℃ is 0.19Pa.s.

[0028] Cast high aluminum steel with 6.5% aluminum content

[0029] (1) The percentage content of effective components of the protective slag is as follows: CaO: 2.0%, CaF2: 35.1%, NaCl: 8.5%, Na2O+K2O=0.15%, Li2O: 4.5%, Al2O3: 0.8%, MgO: 1.1%, C: 3.5%.

[0030] (2) The mass percentage content of SiO2 should satisfy the formula:

[0031] (3) The melting point of the prepared protective slag is 980℃, and the viscosity at 1300℃ is 0.13Pa.s.

[0032] The above description is only a specific embodiment of the present invention, but the structural features protected by the present invention are not limited thereto. Any changes or modifications made by any technician in this field within the scope of the present invention are included in the patent scope of the present invention.

Claims

1. A method for inhibiting the deterioration of high-temperature fluidity of high-aluminum steel mold slag, characterized by: The percentage content of effective ingredients in the protective slag is as follows: CaO: 2-4%, CaF2: 34.84-39.94%, NaCl: 7.8-9.3%, Na2O+K2O <0.5%, Li2O: 1-5%, Al2O3: <1%, MgO: <1.5%, C: 3-5%, and the rest are SiO2 and unavoidable impurities.

2. The method for suppressing the deterioration of high-temperature fluidity of high-aluminum steel mold slag according to claim 1, characterized in that: The mass percentage content of SiO2 satisfies the formula: Among them, W SiO2 W is the mass percentage of SiO2 in the protective slag, %; CaF2 W is the mass percentage of CaF2 in the mold slag, %; CaO W is the mass percentage of CaO in the mold slag, %; [Al] is the mass percentage of Al element in the cast steel, %.

3. The method for suppressing the deterioration of high-temperature fluidity of high-aluminum steel mold slag according to claim 1, characterized in that: The aluminum content in the high-aluminum steel is 2% to 7%.

4. The method for suppressing the deterioration of high-temperature fluidity of high-aluminum steel mold slag according to claim 1, characterized in that: The high temperature fluidity, ie the high temperature flow stability, refers to the viscosity fluctuation of the mold slag before and after the slag reaction within a temperature range of 1200-1300°C within 0.06 Pa.s.

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