CN113953473B - Covering slag for continuous casting crystallizer and preparation method thereof - Google Patents

Abstract

The application relates to the field of cast steel, and particularly discloses a covering slag for a continuous casting crystallizer and a preparation method thereof. The continuous casting crystallizer casting powder comprises the following components of SiO ₂ 24.00-31.00 parts of CaO26.00-33.00 parts of Al ₂ O ₃ 5.40-5.70 parts of Fe ₂ O ₃ Not more than 3.00 parts of MgO not more than 3.00 parts of Na ₂ O and Li ₂ 6.50-10.50 parts of O and CaF ₂ 3.50-7.50 parts of ZrO ₂ 4.5-5.5 parts of Y ₂ O ₃ 3.5-4.5 parts; the preparation method comprises the following steps: the components are uniformly mixed and ground to obtain the finished product of the covering slag powder slag, and the covering slag powder slag has the advantage of good heat insulation effect.

Description

Mold powder for continuous casting mold and preparation method thereof

technical field

The application relates to the field of steel casting, and more specifically, it relates to a mold flux for continuous casting molds and a preparation method thereof.

Background technique

Mold slag is a functional material that affects the quality of the billet and the stability of the continuous casting process. During the molten steel casting process, granular or powdery slag is continuously added to the molten steel surface of the mold. Due to the high temperature of the molten steel, The mold powder forms a three-layer structure, namely liquid slag layer, sintered layer and powder slag layer. The basic functions of mold powder are: (1) to insulate the exposed molten steel; (2) to prevent secondary oxidation of molten steel; (3) to absorb inclusions floating to the surface of molten steel; The gap is filled with liquid liquid film to play the role of lubrication (5) Control the heat transfer from the slab to the mold. Mold slag can effectively improve problems such as longitudinal cracks, depressions and steel breakouts on the billet surface.

At present, because the heat insulation effect of mold slag is not good enough, the cooling from the outer wall of the mold to the slab is too fast, resulting in longitudinal cracks in the slab, which affects the quality of the slab. It is very common that the mold slag can be effectively controlled by adding carbon black. However, due to the changeable composition of molten steel, it is not easy to calculate the proportion of carbon black added. If the proportion of carbon black is too high, carbon black will easily enter the slab, which will increase the carbon content on the surface of the slab and affect the quality of the slab. The proportion of carbon black Too low, the heat transfer process is difficult to control.

Contents of the invention

In order to improve the heat insulation effect of the mold flux, the application provides a continuous casting mold flux and a preparation method thereof.

A continuous casting mold powder and its preparation method provided by the application adopt the following technical scheme:

In the first aspect, a mold flux for a continuous casting mold, comprising the following components: SiO ₂ 24.00-31.00 parts, CaO 26.00-33.00 parts, Al ₂ O ₃ 5.40-5.70 parts, Fe ₂ O ₃ ≤ 3.00 parts, MgO ≤ 3.00 parts parts, Na ₂ O and Li ₂ O 6.50-10.50 parts, CaF ₂ 3.50-7.50 parts, ZrO ₂ 4.5-5.5 parts, Y ₂ O ₃ 3.5-4.5 parts.

By adopting the above technical scheme, zirconia has the advantages of high melting point, not easy to oxidize, etc., and has stable chemical properties, good heat insulation effect, good corrosion resistance and oxidation resistance, non-volatile and pollution-free in a specific high-temperature environment. Good refractory material,

When the mold slag is added to the molten steel surface, the mold slag is melted due to the high temperature of the molten steel, and the mold slag forms a three-layer structure, which are liquid slag layer, sintered layer and powder slag layer. Due to the sloshing of the mold, a gap is formed between the billet and the wall of the mold, and the liquid slag layer flows into the gap between the billet and the wall of the mold to lubricate and control heat transfer. , zirconia has high temperature resistance, stable chemical properties, and good heat insulation performance, which can better reduce the heat transfer efficiency of mold slag and reduce the possibility of cracks in the casting slab due to excessive cooling speed. , It also avoids the phenomenon of mold slag carburizing to the surface of the slab.

The mold flux is added with zirconia, which can better control the heat transfer efficiency of the mold flux, but the zirconia increases the viscosity of the mold flux liquid slag layer, which is not conducive to the liquid slag layer penetrating into the gap between the mold and the billet, thus As a result, the cast slab is not easy to pull out from the crystallizer, and even causes sticky steel breakout accidents. In addition, zirconia is unstable above 1200°C, so yttrium oxide is added to mold flux. The performance of yttrium oxide is stable at high temperatures, and it is It can reduce the viscosity of the protective liquid slag layer. In addition, yttrium oxide can also stabilize zirconia at high temperature, making the performance of zirconia more stable.

Zirconia and yttrium oxide synergistically improve the heat transfer performance of the mold flux without weakening the viscosity of the mold flux liquid slag and reducing the possibility of cracks in the slab.

Optionally, the weight ratio of Na ₂ O to Li ₂ 0 is 1:1-2:1.

By adopting the above technical solution, Na ₂ O and Li ₂ O can destroy the chain structure of mold flux, reduce the viscosity of the mold flux liquid slag layer, and reduce the crystallization temperature at the same time. The weight ratio of Na ₂ O to Li ₂ 0 is greater than 2:1 , Mold slag is easy to precipitate nepheline, which is not conducive to lubrication. The weight ratio of Na ₂ O to Li ₂ 0 is less than 1:1, which affects the crystallization rate and vitrification degree of mold slag.

Optionally, the weight ratio of CaO to SiO ₂ is 0.95:1-1.15:1.

By adopting the above technical scheme, the weight ratio of CaO to _SiO2 is the alkalinity of the mold slag, which is an important indicator of the ability of the reaction mold slag to absorb inclusions in molten steel. Properly increasing the alkalinity is conducive to the absorption of mold slag in molten steel. inclusions.

On the other hand, a method for preparing mold flux for continuous casting molds, comprising SiO ₂ 24.00-31.00 parts, CaO 26.00-33.00 parts, Al ₂ O ₃ 5.40-5.70 parts, Fe ₂ O ₃ ≤ 3.00 parts, MgO ≤ 3.00 parts, Na ₂ O and Li ₂ O 6.50-10.50 parts, CaF ₂ 3.50-7.50 parts, ZrO ₂ 4.5-5.5 parts, Y ₂ O ₃ 3.5-4.5 parts, mix evenly, and grind to obtain the finished powder slag .

Optionally, the finished mold powder slag is dried.

By adopting the above technical solution, the moisture content in the mold flux is reduced, so as not to affect the quality of the cast slab.

Optionally, the grinding process uses a ball mill.

Optionally, the particle size of the finished mold powder slag corresponds to a mesh number of 100-200 mesh.

By adopting the above technical solution, the particle density is finer, which is beneficial to the melting of mold flux, but the particle density is too fine, which makes it difficult to control the heat transfer temperature after the liquid film passes.

Optionally, the finished mold powder is stored in a dry environment.

In summary, the application has the following beneficial effects:

1. When the mold slag is added to the molten steel surface, the mold slag is melted due to the high temperature of the molten steel, and the mold slag forms a three-layer structure, which are liquid slag layer, sintered layer and powder slag layer. Due to the sloshing of the mold, a gap is formed between the billet and the wall of the mold, and the liquid slag layer flows into the gap between the billet and the wall of the mold to lubricate and control heat transfer. , zirconia has high temperature resistance, stable chemical properties, and good heat insulation performance, which can better reduce the heat transfer efficiency of mold slag and reduce the possibility of cracks in the casting slab due to excessive cooling speed. , It also avoids the phenomenon of mold slag carburizing to the surface of the slab.

2. The weight ratio of CaO to SiO ₂ is the alkalinity of the mold slag, which is an important indicator of the ability of the mold slag to absorb inclusions in molten steel. Properly increasing the alkalinity is beneficial for the mold slag to absorb inclusions in molten steel.

detailed description

The following examples describe the application in further detail.

Example

Example 1

A continuous casting mold flux, including the following components: SiO ₂ 24.00kg, CaO 26.00kg, Al ₂ O ₃ 5.40kg, Fe ₂ O ₃ 3.00kg, MgO 3.00kg, Na ₂ O and Li ₂ 06.5kg, CaF ₂ 3.50-7.50 parts, ZrO ₂ 4.5-5.5 parts, Y ₂ O ₃ 3.5-4.5 parts, wherein the weight ratio of Na ₂ O to Li ₂ 0 is 1:1.

A preparation method of mold flux for continuous casting mold: 24.00kgSiO ₂ , 26.00kgCaO, 5.40kgAl ₂ O ₃ , 3.00kgFe ₂ O ₃ , 3.00kgMgO, 3.50kgCaF ₂ , 4.5kgZrO ₂ , 3.5kgY ₂ O ₃ , 6.50kg Mix kgNa ₂ O and Li ₂ 0 evenly, use a ball mill to grind, and dry to obtain the finished mold slag powder. The particle size of the finished mold slag powder slag corresponds to 100 meshes, and the weight ratio of Na ₂ O to Li ₂ 0 is 1:1, the weight ratio of CaO to _SiO2 is 1.08:1.

Embodiment 2-9 and comparative example 1-2

The difference between Examples 2-9 and Comparative Examples 1-2 and Example 1 is that the ratio of raw materials is different, and the specific ratio of raw materials is shown in Table 1-1 and Table 1-2.

Table 1-1 embodiment 2-9 and the raw material proportioning of comparative example 1-2

Set the mass of each example in Table 1-1 as 1kg, and the rest of the data will be changed accordingly as shown in the following table:

Table 1-2 embodiment 2-9 and the raw material ratio of comparative example 1-2

performance test

Viscosity test: According to the standard YB/T185-2017 continuous casting mold flux viscosity test method, the mold flux viscosity test is tested.

Heat transfer efficiency test method: use HF-200 crystallizer slag film heat flow simulator to test the heat flux density of mold flux.

Preparation steps of heat flow tester slag film: at 1300°C, mix 350g of the prepared slag material and put it into a graphite crucible, then add it into a silicon-molybdenum furnace to heat up, melt and stir evenly, and use a stirring rod after the furnace temperature reaches 1400°C Evenly melt the mold slag, make the sensor position in the center of the furnace tube, then start the lifting arm to drive the positioning sensor down to the slag liquid level, when the sensor touches the liquid level, it will automatically rise immediately. The lowering of the lifting arm will drive the copper probe into the slag liquid, and the sensor will start timing. After 80s, the sensor under the slag liquid surface will be taken out to obtain the solid liquid film adhering to the sensor and the inlet and outlet water temperature automatically collected by the computer.

Calculation method of heat flux of slag film: Ф=W·C·△T/(F·1000)

Ф- heat flux density, Mw m ^-2 ; W- cooling water flow rate of heat flux sensor, kg · s ^-1 ; △T- temperature difference between inlet and outlet water of heat flux sensor, ℃; F- effective heat transfer area of heat flux sensor, m ² ; C- Specific heat of water, kg·(kg·℃) ^-1 .

The following table is the viscosity and heat flux of embodiment 2-9 and comparative example 1-2:

The viscosity and heat flux contrast of table 2 embodiment 2-9 and comparative example 1-2

Compared with Example 1, Example 2 increases the content of SiO ₂ , and the data show that the content of SiO ₂ is within a specific range, and the content of SiO ₂ increases, so that the protective slag forms a glass phase, which is beneficial to the lubrication of the slab ;

Compared with Example 1, Example 3 increases the content of CaO. The data show that the content of CaO is within a specific range, the content of CaO is increased, the viscosity of mold flux is significantly reduced, and the ability to absorb inclusions is improved;

Compared with Example ₁ , the _Al2O3 content in Example 4 is constant, and the viscosity has no change;

Compared with Example 1, the content of Fe ₂ O ₃ in Example 5 is reduced, but the viscosity of mold flux does not change, which proves that the content of Fe ₂ O ₃ does not affect the viscosity of mold flux within a specific range;

Compared with Example 1, the MgO content in Example 6 is reduced, and the viscosity of the mold flux is increased. The content of MgO is within a specific range. MgO can reduce the viscosity and freezing point of the mold flux, and increase the fluidity of the mold flux. The chemical stability of mold flux is favorable;

Compared with Example 1, the content of CaF ₂ in Example 6 is reduced, and the viscosity of mold flux is increased. Within a specific content range, increasing the content of CaF ₂ can reduce the viscosity of mold flux;

Example 1 and Examples 7-8 combined with Comparative Examples 1-2 found that the content of ZrO ₂ is within a specific range, the content of ZrO ₂ increases, the viscosity of mold flux increases, and the heat flux of mold flux decreases, proving that The thermal insulation performance of mold slag is enhanced, which reduces the possibility of cracks in the casting slab due to the excessive cooling rate of the casting slab.

Embodiment 10-14 and comparative example 3-4

The difference between Examples 10-14 and Comparative Examples 3-4 and Example 1 is that the raw material ratio is different, and the specific raw material ratio is shown in Table 3-1 and Table 3-2.

Table 3-1 embodiment 10-14 and the raw material proportioning of comparative example 3-4

Set the mass of each example in Table 3-1 as 1kg, and the rest of the data changes accordingly as shown in the following table:

Table 3-2 embodiment 10-14 and the raw material proportioning of comparative example 3-4

Example 10 Example 11 Example 12 Example 13 Example 14 Comparative example 3 Comparative example 4 SiO₂/kg 0.30 0.29 0.30 0.33 0.29 0.32 0.29 CaO/kg 0.32 0.31 0.33 0.31 0.33 0.34 0.32 Al₂O₃/kg 0.07 0.06 0.07 0.07 0.07 0.07 0.07 Fe₂O₃/kg 0.04 0.04 0.04 0.04 0.04 0.04 0.04 MgO/kg 0.04 0.04 0.04 0.04 0.04 0.04 0.04 CaF₂/kg 0.04 0.04 0.04 0.04 0.04 0.05 0.04 ZrO₂/kg 0.06 0.05 0.06 0.05 0.06 0.06 0.06 Y₂O₃/kg 0.06 0.04 0.04 0.04 0.04 0.00 0.07 Na₂O and Li₂O/kg 0.08 0.13 0.08 0.08 0.08 0.09 0.08 Na₂O/Li₂0 1 1 2 1 1 1 1 CaO/SiO₂ 1.08 1.08 1.08 0.95 1.15 1.08 1.08

The following table is the viscosity and heat flux of embodiment 10-14 and comparative example 3-4:

The viscosity and heat flux contrast of table 4 embodiment 10-14 and comparative example 3-4

Compared with Example 1, Example 10 increases the content of Y ₂ O ₃ , within a specific content range, increases the content of Y ₂ O ₃ , reduces the viscosity of mold flux, and reduces the heat flux of mold flux ;

In Example 1 and Example 10 combined with Comparative Examples 3-4, it is found that within a specific content range, the higher the content of Y ₂ O ₃ , the lower the viscosity of mold flux, and it cooperates with ZrO ₂ to reduce the heat flow of mold flux Density, that synergistically increases the thermal insulation properties of the mold flux.

Compared with Example 1, Example 11 increases the content of Na ₂ O and Li ₂ 0. Na ₂ O and Li ₂ 0 in mold flux can destroy the network structure of silicate, and can reduce the protection within a specific content range. The viscosity of the slag.

Compared with Example 1, Example 12 has increased Na ₂ O/Li ₂ 0. Within a specific content range, the Na ₂ O content increases, the crystallization tendency increases, and nepheline is easy to precipitate, which is not conducive to lubrication.

Compared with Example 1, Examples 13-14 show that within a certain content range, the ratio of CaO/ _SiO2 increases, that is, the basicity increases, which improves crystallization and reduces heat transfer.

This specific embodiment is only an explanation of this application, and it is not a limitation of this application. Those skilled in the art can make modifications to this embodiment without creative contribution according to needs after reading this specification, but as long as the rights of this application All claims are protected by patent law.

Claims (6)

1. The covering slag for the continuous casting crystallizer is characterized by comprising the following components of SiO ₂ 24.00-31.00 parts of CaO26.00-33.00 parts of Al ₂ O ₃ 5.40-5.70 parts of Fe ₂ O ₃ Not more than 3.00 parts of MgO not more than 3.00 parts of Na ₂ O and Li ₂ 6.50-10.50 parts of O and CaF ₂ 3.50-7.50 parts of ZrO ₂ 4.5-5.5 parts of Y ₂ O ₃ 3.5-4.5 parts;

the Na is ₂ O and Li ₂ The weight ratio of 0 is 1:1-2:1;

the CaO and SiO ₂ In a weight ratio of 0.95:1-1.08:1.

2. A method for producing the mold flux for a continuous casting crystallizer claimed in claim 1, wherein: mixing SiO ₂ 24.00-31.00 parts of CaO26.00-33.00 parts of Al ₂ O ₃ 5.40-5.70 parts of Fe ₂ O ₃ Not more than 3.00 parts of MgO not more than 3.00 parts of Na ₂ O and Li ₂ 6.50 to 10.50 portions of O and CaF ₂ 3.50-7.50 parts of ZrO ₂ 4.5-5.5 parts of Y ₂ O ₃ 3.5 to 4.5 portions of the powder slag of the finished product of the covering slag are obtained after uniform mixing and grinding.

3. The method for preparing the mold flux for the continuous casting mold as defined in claim 2, wherein: and drying the finished product of the covering slag powder slag.

4. The method for preparing the mold flux for the continuous casting mold according to claim 2, characterized in that: the milling process uses a ball mill.

5. The method for preparing the mold flux for the continuous casting mold as defined in claim 2, wherein: the particle size of the finished product of the covering slag powder is 100-200 meshes.

6. The method for preparing the mold flux for the continuous casting mold as defined in claim 2, wherein: and storing the finished product of the casting powder in a dry environment.