Aluminum-based melting speed regulator for casting powder and preparation method of continuous casting powder

Abstract

The invention relates to an aluminum-based melting speed regulator for covering slag and a preparation method of continuous casting covering slag, the aluminum-based melting speed regulator is composed of metal aluminum powder and MnO powder, and the aluminum-based melting speed regulator comprises, by mass, 90%-95% of Al and 1%-10% of MnO. The aluminum-based melting speed regulator can regulate convergence of molten drops of casting powder of a sintering layer and a liquid slag layer, so that the melting speed of the protected slag is regulated on the whole, the carbon content in the continuous casting powder is effectively reduced, and recarburization of low-carbon molten steel is reduced from the source.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of continuous casting, in particular to an aluminum-based melting rate regulator for a protective slag used in the production of low-carbon steel and a preparation method of the continuous casting protective slag. BACKGROUND

[0002] The continuous casting protective slag plays the following roles in the casting process: (1) isolates air to prevent secondary oxidation of the molten steel; (2) absorbs non-metallic inclusions to purify the molten steel; (3) forms a lubricating film between the billet shell and the crystallizer wall; (4) improves the heat transfer effect between the crystallizer and the billet shell; (5) insulates and keeps warm to reduce the heat loss of the molten steel. The melting point and melting rate of the continuous casting protective slag are important performance indicators in its use process, and the melting rate determines the melting speed of the protective slag, which has an important influence on the reasonable distribution of the sintered layer and the liquid slag layer of the protective slag, as well as the lubrication and heat conduction of the casting billet. For a long time, the regulation of the melting speed of the continuous casting protective slag has been achieved by relying on the preparation of carbonaceous materials, and other ways are rarely involved. With the wide application and research of ultra-low carbon steel, the carbon control of molten steel is very prominent, and the carbon increase in each link will affect the quality of the finished steel, therefore, it is necessary to study the carbon-free speed regulation of the continuous casting protective slag.

[0003] The existing technology about the melting rate regulation of the continuous casting protective slag is listed as follows:

[0004] In the document "Influence Mechanism of Carbon Content in Continuous Casting Protective Slag on Melting Speed" (Yang Chunmei et al., Shanxi Metallurgy, May 2010), the main control factor of the melting speed of the protective slag, the oxidation mechanism of the carbon deposition layer, is elaborated in detail, the burning loss mechanism of free carbon and combined carbon is analyzed, and then the formation of the molten slag pool and the difference in the melting speed of the round billet and slab protective slag are discussed.

[0005] In the document "Research on Silicon Carbide as Melting Rate Regulator of Continuous Casting Crystallizer Protective Slag for Ultra-low Carbon Steel" (Li Ning et al., Journal of Shaoguan University, No. 3, 1998), the characteristics and mechanism of silicon carbide as a melting rate regulator of the protective slag are studied. In the use process of the protective slag, silicon carbide reacts with carbon monoxide gas to decompose into carbon and silicon monoxide gas at high temperature, and the silicon monoxide gas reacts with carbon monoxide gas again to form silicon dioxide during its upward process, and the gas-deposited silicon dioxide will cause the densification process of the surface layer of the protective slag particles, leading to the excessive development of the sintered layer, which is one of the shortcomings of silicon carbide as a melting rate regulator.

[0006] In the paper "Influence of melting rate regulator on melting rate of continuous casting protective slag" (You Jiegang et al., Refractories, No. 3, 2006), the influence of base slag basicity and the adding form and amount of three kinds of melting rate regulators, i.e. graphite, carbon black and silicon carbide, on the melting rate of the protective slag is studied. The results show that: (1) the melting rate of the protective slag is smaller when the graphite and carbon black are added together than when they are added separately, especially when m (carbon black) : m (graphite) = 1:3, the melting rate of the protective slag is the smallest; (2) the influence of the addition of silicon carbide alone on the melting rate of the protective slag is not great, but when the silicon carbide and carbon black are added together in a ratio of m (silicon carbide) : m (carbon black) = 1:3, the melting rate of the protective slag is smaller than when the carbon black is added alone; (3) the multiple linear regression of the test data shows that the mass fraction of the carbon black in the composite melting rate regulator has the most significant influence on the melting rate of the protective slag, followed by the adding amount of the melting rate regulator, and then the mass fraction of the graphite in the composite melting rate regulator, the mass fraction of the silicon carbide in the composite melting rate regulator and the basicity of the slag.

[0007] The research results of the above paper show that the carbon material plays a major role in the melting rate regulation, and the selection of other materials for the melting rate regulator also cannot be separated from the mechanism of the carbon material melting rate regulation (i.e. hindering the fusion of liquid drops in the high temperature zone of the protective slag and hindering the sintering of the protective slag in the low temperature zone). Along this line, the present application has researched and developed an aluminum-based melting rate regulator. SUMMARY

[0008] The present application provides an aluminum-based melting rate regulator for protective slag and a preparation method of continuous casting protective slag. The aluminum-based melting rate regulator can adjust the convergence of the sintering layer and the liquid slag layer of the protective slag, regulate the melting rate of the protective slag as a whole, effectively reduce the carbon content in the continuous casting protective slag, and reduce the carbon pickup of the low carbon steel molten steel from the root.

[0009] In order to achieve the above purpose, the present application adopts the following technical scheme:

[0010] The aluminum-based melting rate regulator for protective slag is composed of metal aluminum powder and MnO powder, and the content of Al in the aluminum-based melting rate regulator is 90% to 95% and the content of MnO is 5% to 10% by mass percentage.

[0011] The purity of the metal aluminum powder is ≥99% and the particle size is 0.5 to 1 mm; the purity of the MnO powder is ≥99% and the particle size is 0.2 to 1 mm.

[0012] The preparation method of the continuous casting protective slag comprises the following steps:

[0013] 1) grinding and mixing the base material of the protective slag, and the particle size after grinding is 0.06 to 0.1 mm; the maximum deviation of the chemical composition of the five-point sample is ≤0.2%;

[0014] 2) adding aluminum-based melting rate regulator into the protective slag base, the aluminum-based melting rate regulator is added in an amount of 1-6% of the protective slag base by mass percentage;

[0015] 3) preparing the continuous casting protective slag with a particle size of 1-4 mm after uniformly mixing the protective slag base and the aluminum-based melting rate regulator.

[0016] Compared with the prior art, the present application has the following beneficial effects:

[0017] 1) the aluminum-based melting rate regulator can adjust the convergence of the sintering layer and the liquid slag layer protective slag melt dripping, and overall regulate the melting rate of the protective slag;

[0018] 2) reducing the carbon content in the protective slag, and reducing the carbon pick-up of the molten steel from the root;

[0019] 3) simple preparation process, easy to implement. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is the action principle diagram of the protective slag added with the aluminum-based melting rate regulator according to the present application.

[0021] Figure 2 is the melting rate curve of the continuous casting protective slag 1 tested by the melting point melting rate instrument in the embodiment of the present application.

[0022] Figure 3 is the melting rate curve of the continuous casting protective slag 2 tested by the melting point melting rate instrument in the embodiment of the present application.

[0023] In the figure: 1. mold 2. molten steel 3. solidified shell 4. liquid slag layer 5. crystallization layer 6. glass layer 7. slag ring 8. aluminum oxide particles 9. melting layer 10. sintering layer 11. powder slag layer DETAILED DESCRIPTION

[0024] The aluminum-based melting rate regulator for the protective slag according to the present application is composed of metal aluminum powder and MnO powder, and the Al content in the aluminum-based melting rate regulator is 90-95% and the MnO content is 5-10% by mass percentage.

[0025] The purity of the metal aluminum powder is ≥99%, and the particle size is 0.5-1 mm; the purity of the MnO powder is ≥99%, and the particle size is 0.2-1 mm.

[0026] A preparation method of a continuous casting protective slag, the continuous casting protective slag is added with the aluminum-based melting rate regulator; specifically comprising the following steps:

[0027] 1) grinding and uniformly mixing the protective slag base, the particle size after grinding is 0.06-0.1 mm; the maximum deviation of the five-point sampling chemical composition is ≤0.2%;

[0028] 2) adding an aluminum-based melting rate regulator to the mold slag base material, wherein the amount of the aluminum-based melting rate regulator added is 1% to 6% of the mold slag base material by mass percentage;

[0029] 3) The mold slag base material and the aluminum-based melting rate regulator are evenly mixed to prepare a continuous casting mold slag with a particle size of 1 to 4 mm.

[0030] like Figure 1 As shown, in the crystallizer 1, the layers between the molten steel 2 and the sidewalls of the crystallizer 1 are, from the inside out, a solidified shell 3, a liquid slag layer 4, a crystallization layer 5, and a glass layer 6. A slag ring 7 forms on top of the glass layer 6. The top of the molten steel 2 is, from bottom to top, a liquid slag layer 4, a molten layer 9, a sintered layer 10, and a powdered slag layer 11. After using the aluminum-based melting rate regulator described in the present invention, aluminum particles enter the mold slag and form fine alumina particles 8 in the molten layer 9, which hinder the molten mold slag from merging and growing, slowing the melting of the mold slag, thereby adjusting the melting rate of the mold slag.

[0031] In order to more intuitively embody the present invention, the embodiments of the present invention are further described in conjunction with examples. The following examples are only preferred specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any technical solution that can be obviously obtained by a person skilled in the art within the technical scope disclosed in the present invention, including simple changes or equivalent replacements, is within the scope of protection of the present invention.

[0032] [Example]

[0033] In this embodiment, a mold slag base material is obtained by decarburizing a conventional ultra-low carbon steel continuous casting mold slag (hereinafter referred to as continuous casting mold slag 1). An aluminum-based melting rate regulator is added to the mold slag base material to prepare a novel mold slag for continuous casting of ultra-low carbon steel (hereinafter referred to as continuous casting mold slag 2). The chemical composition of the conventional ultra-low carbon steel continuous casting mold slag is shown in Table 1:

[0034] Table 1 Chemical composition of conventional ultra-low carbon steel continuous casting mold slag (mass percentage, %)

[0035] CaO SiO2 Al2O3 Li2O3 Na2O Fixed carbon Fe2O3 40 38 6 2 9 2 3

[0036] The process of preparing the protective slag base material is as follows: decarburize 102g of traditional ultra-low carbon steel continuous casting protective slag, place it in a muffle furnace and heat it at a constant temperature of 900°C for 2 hours, then take it out to obtain the protective slag base material, and the protective slag base material weighs 100g.

[0037] The second continuous casting mold slag is prepared according to the method of the present invention, specifically as follows:

[0038] (1) Preparation of aluminum-based melting rate regulator, raw materials include aluminum powder (purity 99.2%, particle size 0.5-1mm) and MnO powder (purity 99.3%, particle size 0.2-1mm), after mixing, aluminum-based melting rate regulator is obtained, chemical composition is as follows: Al: 92%, MnO: 8% by mass percentage;

[0039] (2) After decarburization, the protective slag base is ground to a particle size of 0.08-0.09mm, then 5g of aluminum-based melting rate regulator is added and mixed, the chemical composition of five-point sampling is detected, the maximum deviation is 0.15%, which meets the requirements;

[0040] (3) The mixed material is prepared into continuous casting protective slag with a particle size of 2mm for standby.

[0041] As a comparative example, the melting point melting rate instrument is heated to 1300℃, then the cylindrical continuous casting protective slag one with a diameter of 3mm and a height of 5mm is sent into the constant temperature zone of the melting point melting rate instrument to start measurement, timing starts when the melting reaches 75% of the original height, timing ends when the melting reaches 25% of the original height, the measured time is the melting rate, the melting rate curve of the continuous casting protective slag one is shown in Figure 2 The melting rate of the continuous casting protective slag one tested by the melting point melting rate instrument is 100s.

[0042] As an example, the melting point melting rate instrument is heated to 1300℃, then the cylindrical continuous casting protective slag two with a diameter of 3mm and a height of 5mm is sent into the constant temperature zone of the melting point melting rate instrument to start measurement, timing starts when the melting reaches 75% of the original height, timing ends when the melting reaches 25% of the original height, the measured time is the melting rate, the melting rate curve of the continuous casting protective slag two is shown in Figure 3 The melting rate of the continuous casting protective slag two after adding the aluminum-based melting rate regulator is 125s.

[0043] Conclusion, the aluminum-based melting rate regulator can adjust the melting rate of the continuous casting protective slag.

[0044] The above is only the preferred specific embodiment of the present application, but the protection scope of the present application is not limited to this, any skilled person in the art can make equivalent replacement or change according to the technical solution and the inventive concept of the present application within the technical range disclosed by the present application, which should be covered in the protection scope of the present application.

Claims

1. An aluminum-based melting rate regulator for mold slag, characterized in that: The aluminum-based melting rate regulator consists of metal aluminum powder and MnO powder. Calculated by mass percentage, the aluminum-based melting rate regulator has an Al content of 90% to 95% and a MnO content of 5% to 10%.

2. The aluminum-based melting rate regulator for mold slag according to claim 1, characterized in that: The purity of the metal aluminum powder is ≥99%, and the particle size is 0.5-1 mm; the purity of the MnO powder is ≥99%, and the particle size is 0.2-1 mm.

3. A method for preparing a continuous casting mold slag, wherein the aluminum-based melting rate regulator according to claim 1 or 2 is added to the continuous casting mold slag; characterized in that: The specific steps include: 1) Grind and mix the mold slag base material to a particle size of 0.06-0.1 mm; the maximum deviation of the chemical composition of the five-point sampling is ≤0.2%; 2) adding an aluminum-based melting rate regulator to the mold slag base material, wherein the amount of the aluminum-based melting rate regulator added is 1% to 6% of the mold slag base material by mass percentage; 3) The mold slag base material and the aluminum-based melting rate regulator are evenly mixed to prepare a continuous casting mold slag with a particle size of 1 to 4 mm.

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