CN111590039A

CN111590039A - Continuous casting covering slag for low-carbon high-aluminum steel and preparation method thereof

Info

Publication number: CN111590039A
Application number: CN202010475394.1A
Authority: CN
Inventors: 曾建华; 张敏; 王谦; 周海龙
Original assignee: Pangang Group Panzhihua Iron and Steel Research Institute Co Ltd
Current assignee: Pangang Group Panzhihua Iron and Steel Research Institute Co Ltd
Priority date: 2020-05-29
Filing date: 2020-05-29
Publication date: 2020-08-28

Abstract

The invention belongs to the technical field of molten steel continuous casting, and particularly relates to continuous casting covering slag for low-carbon high-aluminum steel and a preparation method thereof. The invention aims to solve the technical problem of providing the continuous casting mold flux which can ensure the smooth casting of low-carbon high-aluminum steel, realize multi-furnace continuous casting and obtain good casting blank quality. The covering slag comprises the following components in percentage by weight: 15-30% of CaO and SiO₂11～26％，Al₂O₃10～20％，F^－7～13％，C 5～10％，BaO 12～25％，B₂O₃Or Li₂At least one of O, Na₂O，5％≤Na₂O+B₂O₃+Li₂The total content of O is less than or equal to 14 percent, and inevitable impurities. The casting powder ensures the lubricating property of the casting powder to the casting blank, avoids the occurrence of steel leakage, can reduce or prevent the occurrence of surface defects of the casting blank, and ensures the quality of the casting blank.

Description

Continuous casting covering slag for low-carbon high-aluminum steel and preparation method thereof

Technical Field

The invention belongs to the technical field of molten steel continuous casting, and particularly relates to continuous casting covering slag for low-carbon high-aluminum steel and a preparation method thereof.

Background

The low-carbon high-aluminum steel (Al is more than 0.6 percent, and C is less than 0.2 percent) has high Al content and low carbon content, and a large amount of non-metallic inclusions are easily produced in the smelting and continuous casting process, so that the cleanliness of molten steel is low and the continuous casting castability is poor. In particular, Al is an easily-oxidized element, and Al in steel is easily oxidized by SiO in the covering slag in the continuous casting production process₂Oxidation, which causes the alkalinity of the covering slag to rise; simultaneously a large amount of Al₂O₃The casting powder is added into the casting powder, so that the viscosity and the melting point of the casting powder are increased, the consumption of the casting powder is reduced, the lubricating property of the casting powder is reduced due to the change of the properties, the frictional resistance between a casting blank and the wall of a crystallizer is increased, and finally, the occurrence of a steel leakage accident is caused, and the inflow uniformity of the casting powder between the wall of the crystallizer and a blank shell is greatly influenced due to the change of the properties, so that the heat transfer from the casting blank to the wall of the crystallizer is not uniform, and the generation of surface defects of the casting blank is. Therefore, in the continuous casting production of high-aluminum steel, in order to avoid steel leakage, ensure the smooth continuous casting pouring and reduce or prevent the casting blank from avoiding the defects, the research and development of the continuous casting mold flux suitable for the high-aluminum steel is the core technology of the continuous casting production of the high-aluminum steel.

Patent document CN108213365B discloses a non-reactive mold flux for high-aluminum steel, which is composed of the following components in percentage by weight: 26 to 40 percent of CaO and Al₂O₃18％～28％，BaO 14％～28％，Li₂O 2％～10％，F^-6 to 14 percent of MgO, less than or equal to 2 percent of C2 to 8 percent of the total weight of the alloy, and the balance of inevitable impurities, and the balance of the inevitable impurities (Na) in the alloy₂O+K₂O+SiO₂) Less than or equal to 2 percent. The patent is substantially free of SiO₂、Na₂O、Fe₂O₃、B₂O₃Etc. with [ Al ] in molten steel]、[Ti]And the components reacted by active elements and the like, and the components and the performance of the casting powder are still stable after the casting powder is used. However, the network former in the casting powder is low, so that the heat flow density of a crystallizer and the friction force of a casting blank are easy to fluctuate when the casting temperature and the pulling speed fluctuate, and the stable and smooth production is difficult.

Patent document CN108176831A discloses a continuous casting crystallizer casting powder for high-aluminum steel, which comprises the following chemical components by mass percent: 31 to 39 percent of CaO and SiO₂20％～28％、MgO 3％～7％、Li₂O 2％～4.5％、Al₂O₃5％～10％、Na₂5-10% of O, 2-5% of F, 3-10% of MnO, 4-8% of C and the balance of impurities. The patent covering slag overcomes the defect that the aluminum oxide in the molten steel of the high-aluminum steel enters the slag to deteriorate the slagAnd the obtained casting blank has high qualification rate. The covering slag mainly comprises CaO-SiO₂The casting powder absorbs a small amount of Al₂O₃The performance can be kept stable, but when the number of continuous casting furnaces is higher, SiO in the casting powder₂Is largely reduced by Al in steel, resulting in SiO in the mold flux₂A large reduction of Al₂O₃The melting point and the viscosity of the slag system are greatly changed, and the metallurgical performance of the casting powder is deteriorated.

Patent document CN107498013B discloses a TiO-containing material₂The high-aluminum steel casting powder comprises the following oxides in percentage by mass: 30 to 45 percent of CaO and Al₂O₃16％～24.5％，SiO₂8％～16％，Na₂O 8％～15％，Li₂O 1％～5％，MgO 2％～6％，BaO 3％～7％，F^-6％～10％，TiO₂2.7％～7％，(CaO+BaO)/Al₂O₃Is 1.0 to 2.1. The casting powder has low melting point and viscosity and good crystallization property, and is particularly suitable for continuous casting of high-aluminum steel with the Al content of 1.5-2.5%. When the casting powder is used, the degree of slag steel reaction in the continuous casting process can be effectively weakened, the crystallization property and the lubricating property of the casting powder in the continuous casting process become more stable, and the probability of quality defects such as pits, cracks, inclusions and the like on the surface of a casting blank is greatly reduced. However, TiO in the mold flux₂High-melting-point TiC or TiCN substances are easily generated at the high temperature of the carbon-rich layer, the lubricating property of the covering slag is seriously deteriorated, and the steel leakage risk is greatly increased.

Patent document CN107470576B discloses a low-carbon high-aluminum steel continuous casting mold flux containing ferric oxide and application thereof. The covering slag comprises the following oxide components in percentage by mass: 22-32% of CaO and Al₂O₃19～29％、SiO₂10～16％、MnO 2～8％、Na₂O 6～12％、Li₂O 2～6％、BaO 4％～12％、F^-7％～13％、Fe₂O₃2％～10％、(CaO+BaO)/Al₂O₃1.3 to 2.3, Fe₂O₃/SiO₂0.2 to 0.9. The invention controls the addition of proper amount of Fe₂O₃The casting powder with lower viscosity and good crystallization performance is obtained. The casting powder is applied to the continuous casting production process of low-carbon high-aluminum steel plate blanks, can effectively inhibit slag steel reaction in the continuous casting process, and enables the crystallization property and the lubricating property of the casting powder to be more stable in the continuous casting process. However, Na in the mold flux₂The content of O is too high, and when the liquid level of the crystallizer is active, aluminum in steel is easy to react with Na in slag₂O reacts to form Na₂The O is greatly reduced and the melting point of the mold flux is sharply increased, deteriorating the stable inflow consumption of the mold flux and impairing the normal performance of the lubricating function.

Patent document CN106424622A discloses a continuous casting mold flux for high-aluminum steel and a preparation method thereof, wherein the continuous casting mold flux comprises the following components in percentage by weight: 30 to 45 percent of CaO and Al₂O₃20％～30％、SiO₂≤3％、Li₂O 3％～8％、SrO 1％～3％、Na₂5 to 10 percent of O, 3 to 6 percent of BaO, less than or equal to 3 percent of MgO, 2 to 4 percent of C, less than or equal to 2 percent of F, and the balance of impurities. This patent uses low SiO₂The idea of (1) is to effectively reduce the oxidation of Al, Ti and rare earth elements in steel with strong reducing property and effectively stabilize the content of elements in steel when pouring high-aluminum steel, but because the casting powder has high alkalinity and strong crystallinity, the problems of poor lubricity, poor melting and the like exist in the continuous casting pouring process, and in addition, the Na of the casting powder is Na₂The content of O is high, and the O still reacts with active metals such as aluminum, titanium and the like in the steel, so that elements are burnt.

Patent document CN103909241A discloses a mold flux for continuous casting of high-aluminum steel, which comprises the following chemical components in percentage by weight: SiO 2₂10～25％，Al₂O₃12～25％，CaO 15～35％，MgO 1～3％，F 6～10％，Na₂O+B₂O₃≤3％，Li₂O 1～4％，Fe₂O₃Less than or equal to 2 percent, 5-10 percent of C, and the balance of impurities. The physical and chemical properties of the continuous casting mold flux are as follows: CaO/SiO₂1.5 to 2.2, a melting point of 1000 to 1100 ℃, and a viscosity of 0.09 to 0.15 pas at 1300 ℃. The covering slag has the advantages of low cost, effective reduction of slag-steel interface reactivity and Al absorption₂O₃High inclusion capacity and energyThe characteristics of lubrication and heat transfer characteristics are effectively coordinated and controlled, the smooth continuous casting process of the high-aluminum steel can be ensured, the high-aluminum steel plate blank with excellent surface quality is cast, and the continuous casting with multiple furnaces can be realized. But with CaO and Al in the slag₂O₃The mainly formed calcium aluminate ore phase has slow growth speed and unstable crystallization property, and the liquid level of the tundish changes between continuous casting furnaces and Al in molten steel₂O₃Under the condition of increasing the content, the heat flux density of the crystallizer is obviously reduced, and the bonding and steel leakage alarming are easily caused.

Disclosure of Invention

The invention aims to solve the technical problem of providing continuous casting mold flux which can ensure the smooth casting of low-carbon high-aluminum steel, realize multi-furnace continuous casting and obtain good casting blank quality and a preparation method thereof.

The invention adopts the technical scheme to solve the technical problems and provides the continuous casting covering slag for the low-carbon high-aluminum steel. The covering slag comprises the following components in percentage by weight: 15-30% of CaO and SiO₂11～26％，Al₂O₃10～20％，F^－7～13％，C 5～10％，BaO 12～25％，B₂O₃Or Li₂At least one of O, Na₂O，5％≤Na₂O+B₂O₃+Li₂The total content of O is less than or equal to 14 percent, and inevitable impurities.

Preferably, the continuous casting mold flux for the low-carbon high-aluminum steel comprises the following components in percentage by weight: 15-30% of CaO and SiO₂11～26％，Al₂O₃10～20％，Na₂O 1～4％，F^－7～13％，C 5～10％，BaO 12～25％，B₂O₃+Li₂O4-12%, and inevitable impurities.

Further, the CaO + BaO is mixed with Al₂O₃+SiO₂The ratio of the contents is 0.6-1.5.

Further, the melting point of the continuous casting mold flux for the low-carbon high-aluminum steel is 1010-1150 ℃; the viscosity at 1300 ℃ is 0.1 to 0.6 Pa.S.

Further, the particle size of the continuous casting mold flux for the low-carbon high-aluminum steel is 0.1-1.0 mm; the covering slag with the granularity of 0.1-1.0 mm accounts for more than or equal to 85 percent.

The invention also provides a preparation method of the continuous casting covering slag for the low-carbon high-aluminum steel, which comprises the following steps: adding carbonaceous material, CaO-containing material and SiO-containing material according to the proportion that the using amount of the pre-molten material of the covering slag is more than or equal to 60wt percent₂Material of Al₂O₃The material, the fluorine-containing material and the barium-containing material are added with sodium salt, and the boron-containing material or the lithium-containing material are added according to the components of the covering slag and prepared according to the conventional process.

Preferably, the raw materials are selected as follows: CaO can be mixed from materials containing CaO, such as the covering slag pre-melting material, wollastonite, cement clinker and the like; SiO 2₂The protective slag can be prepared from SiO-containing materials such as protective slag pre-melting materials, wollastonite, cement clinker, quartz sand, feldspar and the like₂The material is mixed; al (Al)₂O₃Can be prepared from Al-containing casting powder pre-melting material, bauxite, cement clinker, white mud and the like₂O₃The material is mixed; na (Na)₂O may be pre-melted from the mold flux, Na₂CO₃NaF, etc. containing Na₂The material of O is mixed; f^－Can be pre-melted from the mold flux, CaF₂F-containing materials such as fluorite and NaF^－The material is mixed; BaO may be pre-melted from the mold flux, BaCO₃Mixing Ba-containing materials; b is₂O₃The casting powder can be prepared from boron-containing materials such as the pre-melted materials of the casting powder, borax, boric anhydride and the like; li₂O can be prepared from lithium-containing materials such as the covering slag pre-melting material and lithium carbonate; the carbonaceous material may be carbon black, a carburant, coke powder, graphite, or other carbonaceous material.

Further, the covering slag premelting material comprises the following components in percentage by mass: 15-30% of CaO and SiO₂10～25％，Al₂O₃10～20％，F^－0～13％，BaO 12～22％，2≤Na₂O+B₂O₃₊Li₂The total amount of O is less than or equal to 12 percent, and inevitable impurities.

Furthermore, the melting point of the pre-melted material of the covering slag is 1040-1140 ℃, and the viscosity of the pre-melted material of the covering slag is 0.1-0.8 Pa.S at 1300 ℃.

The invention has the beneficial effects that:

the covering slag for the low-carbon high-aluminum steel adopting the components of the invention reduces SiO in the covering slag₂The invention can oxidize steel Al, and the melting point and viscosity of the casting powder are stable, thereby ensuring the stability of the performance of the casting powder. According to the invention, the lubricating property of the casting blank by the covering slag is ensured by controlling the content of each component in the covering slag, the occurrence of steel leakage is avoided, the occurrence of surface defects of the casting blank can be reduced or prevented, and the quality of the casting blank is ensured. The casting powder for the low-carbon high-aluminum steel can realize continuous casting for more than 240 minutes.

Detailed Description

When continuously casting low-carbon high-aluminum steel (especially Al is more than 0.6 percent and C is less than 0.2 percent), because the content of Al element in the steel is higher and the content of carbon is low, a large amount of non-metallic inclusions are easily produced in the smelting continuous casting process, the cleanliness of molten steel is low and the continuous casting castability is poor. Particularly, Al is very active and is very easy to react with SiO in the covering slag₂Reaction is carried out to lead the alkalinity (CaO/SiO) of the casting powder to₂) Increase of Al in slag₂O₃The content is greatly increased, so that the melting point and the viscosity of the casting powder are increased, and the lubricating property, the fluidity and other related metallurgical properties of the casting powder are deteriorated; when the performance of the mold flux is deteriorated to some extent, a breakout accident and defects on the surface of the cast slab may occur. Aiming at the defects of the prior art, the invention provides the casting powder for the low-carbon high-aluminum steel.

Specifically, the invention provides continuous casting covering slag for low-carbon high-aluminum steel, which comprises the following components in percentage by weight: 15-30% of CaO and SiO₂11～26％，Al₂O₃10～20％，F^－7～13％，C 5～10％，BaO 12～25％，B₂O₃Or Li₂At least one of O, Na₂O，5％≤Na₂O+B₂O₃+Li₂The total content of O is less than or equal to 14 percent, and inevitable impurities.

Preferably, the continuous casting mold flux for the low-carbon high-aluminum steel consists of the following components in percentage by weight: 15-30% of CaO and SiO₂11～26％，Al₂O₃10～20％，Na₂O 1～4％，F^－7～13％，C 5～10％，BaO 12～25％，B₂O₃+Li₂O4-12%, and inevitable impurities.

The invention ensures that the casting powder has low SiO content by controlling the components and the content of the casting powder₂Activity of SiO₂Low reactivity with Al, thereby reducing SiO in the casting powder₂The oxidation to Al ensures the stable performance of the covering slag, and simultaneously, the covering slag has good lubricity, so that the casting blank can be lubricated by the covering slag, and the steel leakage is avoided. The casting powder has stable performance in the casting process, can realize continuous casting for more than 240 minutes, and can reduce or prevent the generation of surface defects of casting blanks.

Further, because of SiO in the mold flux₂The content of the sodium aluminate is too low, so that the casting powder has high alkalinity and strong crystallinity, and the problems of poor lubricity, poor melting and the like exist in the continuous casting process; SiO 2₂Too high a content, which reacts with aluminium in the steel: SiO 2₂+Al→Si+Al₂O₃So that a large amount of aluminum in the high-aluminum steel is burnt, the aluminum enters slag to cause the sharp rise of the melting point and the viscosity of the casting powder, the performance of the casting powder is deteriorated, and the continuous casting is easy to cause breaking of casting, therefore, the invention uses SiO₂The content is controlled to be 11-26%.

Na₂O can reduce the surface tension of the covering slag, is not beneficial to slag-steel separation and increases the risk of slag entrapment of the crystallizer, but the proper addition is beneficial to reducing the melting point and the viscosity of the covering slag, so the Na of the invention₂The content of O is controlled to be 1-4%.

Al of the invention₂O₃The content of (A) is controlled to 10 to 20% in order to ensure good lubricity and reduce inclusions. If Al is present₂O₃Has high content of Al in the steel absorbed by the covering slag₂O₃The inclusion capacity is weak, the viscosity and melting point of the slag system are raised too low, and the good lubricity is not realized.

Further, CaO + BaO and Al in the casting powder for the low-carbon high-aluminum steel₂O₃+SiO₂The ratio of the contents is 0.6-1.5. The lubricating property of the casting blank by the covering slag is ensured,the production of the breakout condition is avoided, the production of defects of casting blanks can be reduced or prevented, and continuous pouring can be realized. CaO + BaO and Al₂O₃+SiO₂The proportion of the content is too high, the alkalinity of the covering slag is high, the crystallinity is strong, and the problems of poor lubricity, poor melting and the like exist in the continuous casting process; the ratio is too low, the alkalinity is low, and when the number of continuous casting furnaces is high, SiO in the casting powder₂Is largely reduced by Al in steel, resulting in SiO in the mold flux₂A large reduction of Al₂O₃The melting point and the viscosity of the slag system are greatly changed, and the metallurgical performance of the casting powder is deteriorated. If Al is present₂O₃The casting powder has high crystallinity due to high content, and has the problems of poor lubricating property and the like in the continuous casting process.

The melting point of the continuous casting covering slag for the low-carbon high-aluminum steel is 1010-1150 ℃, and the viscosity of the continuous casting covering slag for the low-carbon high-aluminum steel is 0.1-0.6 Pa.S at 1300 ℃ so as to ensure smooth pouring.

The present invention will be further illustrated by the following specific examples.

The inventive example was verified in a slab continuous casting crystallizer and the chemical composition (% by weight) of the cast high aluminum steel is shown in table 1. The casting machine has a casting speed of 0.8-1.3 m/min.

TABLE 1 cast high-Al steel chemistry

C	Si	Mn	P	S	Al
						0.15～0.20	≤0.03	1.4～1.6	0.01～0.02	≤0.01	1.5～1.75

The covering slag premelting material adopted by the embodiment of the invention comprises the following components in percentage by mass: 15-30% of CaO and SiO₂10～25％，Al₂O₃10～20％，F^－0～13％，BaO 12～22％，2≤Na₂O+B₂O₃₊Li₂The total amount of O is less than or equal to 12 percent, and inevitable impurities. The melting point is 1040-1140 ℃, and the viscosity is 0.1-0.8 Pa.S at 1300 ℃.

Example 1

The continuous casting covering slag for the low-carbon high-aluminum steel comprises the following components in percentage by mass: CaO: 15% of SiO₂：18％，Al₂O₃：20％，Na₂O：1％，F^－：7％，C：10％，BaO：20％，B₂O₃：3％Li₂O: 4%, and inevitable impurities. The melting point of the casting powder is 1030 ℃ and the viscosity is 0.17Pa.S at 1300 ℃.

The preparation method of the continuous casting covering slag for the low-carbon high-aluminum steel comprises the following steps: adding carbonaceous material, CaO-containing material and SiO-containing material according to the proportion that the using amount of the pre-molten material of the covering slag is more than or equal to 60wt percent₂Material of Al₂O₃The material, the fluorine-containing material and the barium-containing material are added with sodium salt and the boron-containing material and the lithium-containing material according to the components of the covering slag, and the material is prepared according to the conventional process.

The high aluminum steel is cast using methods well known to those skilled in the art.

Example 2

The continuous casting covering slag for the low-carbon high-aluminum steel comprises the following components in percentage by mass: CaO: 28% of SiO₂：17％，Al₂O₃：15％，Na₂O：4％，F^－：13％，C：5％，BaO：12％，B₂O₃：1％，Li₂O: 3%, and inevitable impurities. The melting point of the mold flux is 1100 ℃, and the viscosity is 0.42Pa.S at 1300 ℃.

Example 3

The continuous casting covering slag for the low-carbon high-aluminum steel comprises the following components in percentage by mass: CaO: 15% of SiO₂：19％，Al₂O₃：19％，Na₂O：2％，F^－：7％，C：10％，BaO：19％，B₂O₃：5％，Li₂O: 2%, and inevitable impurities. The melting point of the casting powder is 1134 ℃, and the viscosity of the casting powder is 0.18Pa.S at 1300 ℃.

Comparative example

The comparative example mold flux comprises the following components: CaO: 30% of SiO₂：31％，Al₂O₃：4％，Na₂O+K₂O：11％，MgO：3％，F^－：10％，C：5％，Li₂O：1％，Fe₂O₃: 1% and the balance impurities. The melting point of the casting powder is 983 ℃, and the viscosity is 0.1 Pa.S.

The preparation method of the comparative example covering slag adopts a conventional process for preparation.

The results of the examples and comparative examples are shown in Table 2.

TABLE 2 effects of application of examples and comparative examples

	Peeling defect (%)	Surface depressions (%)	Pouring time (min)
				Example 1	0	1.5	220
Example 2	0	1	240
				Example 3	0	1.2	230
Comparative example	2	10	80

As can be seen from Table 2, the comparative example had 10% dishing and about 2% subcutaneous defects; the higher surface depression makes the casting blank have to be taken off-line for cleaning, which increases the production process and metal consumption. Only the embodiment eliminates the defect of delamination, reduces the defect of surface depression of the casting blank and effectively solves the defects of the surface and the subcutaneous of the casting blank. Also, the casting time for the examples was much greater than the comparative examples.

Claims

1. The continuous casting covering slag for the low-carbon high-aluminum steel is characterized by comprising the following steps: the paint consists of the following components in percentage by weight: 15-30% of CaO and SiO₂11～26％，Al₂O₃10～20％，F^－7～13％，C 5～10％，BaO 12～25％，B₂O₃Or Li₂At least one of O, Na₂O，5％≤Na₂O+B₂O₃+Li₂The total content of O is less than or equal to 14 percent, and inevitable impurities.

2. The continuous casting mold flux for low-carbon high-aluminum steel according to claim 1, characterized in that: the paint consists of the following components in percentage by weight: 15-30% of CaO and SiO₂11～26％，Al₂O₃10～20％，Na₂O 1～4％，F^－7～13％，C 5～10％，BaO 12～25％，B₂O₃+Li₂O4-12%, and inevitable impurities.

3. The continuous casting mold flux for low-carbon high-aluminum steel according to claim 1 or 2, characterized in that: CaO + BaO and Al₂O₃+SiO₂The ratio of the contents is 0.6-1.5.

4. The continuous casting mold flux for low-carbon high-aluminum steel according to any one of claims 1 to 3, characterized in that: the melting point of the continuous casting covering slag for the low-carbon high-aluminum steel is 1010-1150 ℃; the viscosity at 1300 ℃ is 0.1 to 0.6 Pa.S.

5. The continuous casting mold flux for low-carbon high-aluminum steel according to any one of claims 1 to 4, characterized in that: the particle size of the continuous casting covering slag for the low-carbon high-aluminum steel is 0.1-1.0 mm; the covering slag with the granularity of 0.1-1.0 mm accounts for more than or equal to 85 percent.

6. The method for preparing the continuous casting mold flux for the low-carbon high-aluminum steel as claimed in any one of claims 1 to 5, characterized in that: adding carbonaceous material, CaO-containing material and SiO-containing material according to the proportion that the using amount of the pre-molten material of the covering slag is more than or equal to 60wt percent₂Material of Al₂O₃The material, the fluorine-containing material and the barium-containing material are added with sodium salt, the boron-containing material or the lithium-containing material according to the components of the covering slag to prepare the coating.

7. The method for preparing the continuous casting mold flux for the low-carbon high-aluminum steel according to claim 6, characterized by comprising the following steps: the covering slag premelting material comprises the following components in percentage by mass: 15-30% of CaO and SiO₂10～25％，Al₂O₃10～20％，F^－0～13％，BaO 12～22％，2≤Na₂O+B₂O₃₊Li₂The total amount of O is less than or equal to 12 percent, and inevitable impurities.

8. The method for preparing the continuous casting mold flux for the low-carbon high-aluminum steel according to claim 6 or 7, characterized in that: the melting point of the covering slag pre-melting material is 1040-1140 ℃, and the viscosity is 0.1-0.8 Pa.S at 1300 ℃.