A lithium-free casting powder for a stainless steel slab continuous casting and application thereof

Abstract

The present application belongs to the technical field of steel metallurgy continuous casting, and particularly relates to a crystallizer non-lithium protecting slag for stainless steel slab continuous casting and application. The non-lithium protecting slag is composed of the following components: calcium oxide 28-40%, silicon oxide 26-38%, aluminum oxide 2-8%, sodium oxide 9-14%, fluoride ion 5-11%, magnesium oxide 1-4%, boron oxide 1-5%, manganese oxide 0.5-3%, total carbon 2-4.5%, and the rest is inevitable impurities and carbonate volatiles; the mass ratio of sodium oxide / magnesium oxide is greater than or equal to 3.5. The hollow particle type protecting slag product designed in the present application can reduce the ton slag cost by 1000-2500 yuan, and has the performance of the conventional lithium-containing austenitic stainless steel slab continuous casting protecting slag, and is beneficial to the smooth running of the austenitic stainless steel high-pulling speed continuous casting process, and reduces the raw material procurement cost of the steel enterprise, so that the market competitiveness of the stainless steel product can be further enhanced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of steel metallurgy continuous casting, and particularly relates to a crystallizer flux for stainless steel slab continuous casting without lithium and application thereof. BACKGROUND

[0002] The high-temperature physical properties of stainless steel have many particularities compared with carbon steel. The chemical composition of 304 austenitic stainless steel mainly consists of C: ≤0.08%, Si: ≤0.08%, Mn: ≤2.00%, P: ≤0.035%, S: ≤0.030%, Cr: 18.0-20.0%, and Ni: 8.00-10.00%. The thermal expansion coefficient of 304 austenitic stainless steel is larger than that of ordinary carbon steel, so the solidification shell in the continuous casting crystallizer may shrink too early, resulting in uneven thickness of the solidification shell. The thermal conductivity of 304 austenitic stainless steel is about 45% lower than that of ordinary carbon steel, so the heat transfer is slow, resulting in large temperature gradient inside and outside the solidification shell. In addition, the solidification interval of stainless steel is large, the solidification speed is small, and the corresponding solidification time is long. Therefore, 304 austenitic stainless steel is very prone to surface depression, cracks and other defects. Compared with carbon steel, uniform weak cooling in the crystallizer is more important.

[0003] The performance of the continuous casting crystallizer flux should be adapted to the steel grade, size and continuous casting process, otherwise not only a large number of surface defects of the cast slab will be caused, but also the continuous casting process will be difficult to proceed. Generally, the continuous casting crystallizer for stainless steel slab adopts a flux with high basicity, high crystallization titanium, low viscosity and uniform heat transfer, so as to ensure that the liquid slag layer has moderate thickness and certain uniform stability. The basicity range is 0.95-1.30, the transition temperature of the flux is about 1200 DEG C, and the melting point of the flux is about 1100 DEG C. In order to make the stainless steel flux have good adaptability, various fluxes are used to ensure that the flux has good stability after absorbing inclusions in the crystallizer. At the same time, CaF2, Na2O, MnO and Li2O are selected as fluxing agents in the austenitic stainless steel crystallizer flux.

[0004] The research of metallurgical workers at home and abroad shows that the addition of Li2O in the crystallizer flux can simultaneously reduce the viscosity and melting temperature of the flux and improve the glass performance of the flux. The reasons for Li2O to improve the glass performance of the flux are as follows: Li2O can form low-melting point phases with most components in the flux; the electrostatic potential of Li+ ion is close to that of the main anion group SiO4 + in the flux; in addition, Li 4- + ion has a small ionic radius, so it can easily enter the crystal lattice of the flux to form a low-melting point phase. +The radius of the ion is small. Therefore, Li2O can play a role in reducing the viscosity of the protective slag and improving its good glassiness, and is one of the key components of the high-speed continuous casting mold protective slag. However, in recent years, the new energy vehicle industry has experienced rapid development, leading to a sharp rise in the price of lithium carbonate. According to relevant reports, since January 2020, the prices of battery-grade lithium carbonate and lithium hydroxide have risen by 1024.2% and 817.6%, respectively. However, as an important fluxing agent for continuous casting mold protective slag, Li2O is mainly added in the form of Li2CO3. If 1% of the effective component of Li2O is added by mass, the required industrial-grade Li2CO3 is sold at 100,000 yuan / ton, and the cost of industrial raw materials per ton of slag needs to increase by about 2,500 yuan. Therefore, seeking lithium-free continuous casting mold protective slag has become an urgent task, and the early development of suitable lithium-free protective slag will effectively reduce the production cost of the steel industry, thereby laying a solid foundation for improving the international competitiveness of China's steel enterprises.

[0005] From the literature search, there are currently some studies on stainless steel slab continuous casting mold special protective slag and its application method. The patent with the application publication number CN 112605356A, “Austenitic stainless steel slab continuous casting mold special protective slag and its application method”, proposes a special protective slag for high-strength high-nitrogen (nitrogen content is about 0.25%) austenitic stainless steel slab continuous casting, which can solve the problem of QN1803 and GN1601 series austenitic stainless steel production without special protective slag, which cannot be smoothly produced and produces casting defects. This heat treatment method can solve the use problem, but it is provided with 0.5-2% mass fraction of Li2O, and its viscosity at 1300℃ is 0.35-0.65 Pa·s. Not only is the cost high, but also the viscosity is too large to meet the requirements of lubrication performance under high-speed process, thereby being not conducive to the smooth movement of the initial solidification shell.

[0006] In addition, the patent with the application publication number CN 1285432 C, “Austenitic stainless steel slab mold protective slag”, proposes an austenitic stainless steel slab mold protective slag, which can improve the surface quality of austenitic stainless steel casting, and the stability of the protective slag is good; the high-alkalinity austenitic stainless steel slab mold protective slag is used to produce continuous casting billets, which can reduce the cost of each ton of steel by 5-12 yuan. This method designs the binary basicity (CaO / SiO2) of the protective slag to be between 1.30-1.40. When the continuous casting speed is increased, the proportion of the crystalline layer in the slag film is too large, which inhibits the heat transfer of the steel liquid to the copper mold of the crystallizer, which is not conducive to the downward movement of the shell solidification. Moreover, the method still contains 0.50-0.80% of Li2O, and the cost is still high. SUMMARY

[0007] In order to overcome the shortcomings and deficiencies of the prior art, the purpose of the present application is to provide a method for designing and manufacturing a crystallizer lithium-free casting powder for stainless steel slab casting. The present application is aimed at the technical problem of high-speed continuous casting process of stainless steel slab and the forced increase of production cost of steel enterprises due to the price rise of industrial-grade lithium carbonate. First, the Li2O in the composition of the stainless steel continuous casting crystallizer casting powder is removed, and finally a hollow particle type casting powder process with consistent or even better performance than the existing lithium-containing casting powder is produced by adjusting the components. The present application reduces the procurement cost of raw materials for steel enterprises, and significantly improves the market competitiveness of stainless steel hot-rolled coil products due to the cost reduction.

[0008] The lithium-free austenitic crystallizer casting powder for stainless steel slab casting according to the present application comprises, by mass percentage: calcium oxide 28-40%, silicon oxide 26-38%, aluminum oxide 2-8%, sodium oxide 9-14%, fluoride ions 5-11%, magnesium oxide 1-4%, boron oxide 1-5%, manganese oxide 0.5-3%, total carbon 2-4.5%, and the balance being unavoidable impurities and carbonate volatiles; and the mass ratio of sodium oxide / magnesium oxide is greater than or equal to 3.5.

[0009] In the optimization scheme, the carbon used is composed of carbon black and graphite. As a further preferred scheme, the mass ratio of graphite to carbon black is 4-6:4-6.

[0010] As a preferred embodiment, the lithium-free austenitic crystallizer casting powder for stainless steel slab casting according to the present application comprises, by mass percentage: calcium oxide 33-35%, silicon oxide 31.5-33.5%, aluminum oxide 4.5-5.5%, sodium oxide 10-11.5%, fluoride ions 7-9%, magnesium oxide 1.5-2.5%, boron oxide 2.5-3.5%, manganese oxide 0.8-1.2%, total carbon 3.0-3.5%, and the balance being unavoidable impurities and carbonate volatiles; and the mass ratio of sodium oxide / magnesium oxide is 5-6.

[0011] As a preferred embodiment, the lithium-free austenitic crystallizer casting powder for stainless steel slab casting according to the present application comprises, by mass percentage: calcium oxide 34.5-35%, silicon oxide 32.5-33%, aluminum oxide 4.8-5.2%, sodium oxide 10.5-11.5%, fluoride ions 7-9%, magnesium oxide 1.5-2.5%, boron oxide 2.9-3.1%, manganese oxide 0.8-1.2%, total carbon 3.0-3.5%, and the balance being unavoidable impurities and carbonate volatiles; and the mass ratio of sodium oxide / magnesium oxide is 5-6.

[0012] As a further preferred, the lithium-free mold flux for a stainless steel slab continuous casting of the present application, the chemical composition of the lithium-free austenite mold flux includes, in percentage by mass: calcium oxide 34.8-34.9%, silicon oxide 32.5-32.6%, aluminum oxide 4.95-5.05%, sodium oxide 10.9-11.1%, fluoride ion 7-9%, magnesium oxide 1.5-2.5%, boron oxide 2.9-3.1%, manganese oxide 0.8-1.2%, total carbon 3.0-3.5%, and the balance being inevitable impurities.

[0013] The protection flux designed and prepared by the present application is a hollow particle type protection flux. The purpose of designing the hollow protection flux is that the hollow particle type protection flux has a certain pressure resistance, avoids or reduces particle breakage, has good fluidity and heat preservation, and can better play the metallurgical function of isolating air, promoting the formation of a three-layer distribution framework of a powder slag layer, a sintered layer and a liquid slag layer when added to the surface of molten steel, and thus is widely used in the spray forming process and produced by the current advanced metallurgical auxiliary material factories.

[0014] The lithium-free mold flux for a stainless steel slab continuous casting of the present application, the industrial raw materials of the lithium-free mold flux include wollastonite, glass powder, soda ash, fluorite, limestone, high-aluminum powder, magnesia, borax pentahydrate, manganese powder, graphite, carbon black and CMC binder.

[0015] In terms of mass parts, the industrial raw material wollastonite is 45-65 parts, the glass powder is 0-15 parts, the soda ash is 10-20 parts, the fluorite is 10-20 parts, the limestone is 10-25 parts, the high-aluminum powder is 3-8 parts, the magnesia is 1-4 parts, the borax pentahydrate is 3-8 parts, the manganese powder is 0.5-3 parts, the graphite is 0.5-2 parts, the carbon black is 0.5-2 parts, and the CMC binder is 1-3 parts.

[0016] The lithium-free mold flux for a stainless steel slab continuous casting of the present application, the binary basicity of the lithium-free mold flux is 0.9-1.10.

[0017] The lithium-free mold flux for a stainless steel slab continuous casting of the present application, the lithium-free mold flux has a starting melting temperature range of 950-1080℃, and a melting time of 25-38 seconds, preferably 35-37.5 seconds.

[0018] The lithium-free mold flux for a stainless steel slab continuous casting of the present application, the lithium-free mold flux has a starting melting temperature range of 950-1080℃, and a melting time of 25-38 seconds, preferably 35-37.5 seconds.

[0019] The lithium-free mold flux for a stainless steel slab continuous casting of the present application,

[0020] The lithium-free mold flux for a stainless steel slab continuous casting of the present application, the lithium-free mold flux has a starting melting temperature range of 950-1080℃, and a melting time of 25-38 seconds, preferably 35-37.5 seconds.

[0021] The crystallization rate of the lithium-free protective slag is 40-60%.

[0022] The finished particle diameter of the lithium-free protective slag is between 0.10-1.00 mm.

[0023] The finished water content of the lithium-free protective slag is not more than 0.35%.

[0024] The present application is a preparation method of a lithium-free protective slag for a crystallizer for stainless steel slab continuous casting, mainly including three steps.

[0025] Step one, formula design - the lithium-free protective slag product is configured from wollastonite, glass powder, soda ash, fluorite, limestone, high-aluminum powder, magnesia, borax pentahydrate, manganese powder, graphite, carbon black, and CMC binder and other industrial raw materials.

[0026] Step two, production - this step mainly includes raw material preparation, weighing and batching, feeding and water adding, slurry ball milling, stirring and storage, and spray granulation.

[0027] Step three, packaging finished product - the protective slag finished product produced in steps one and two needs to be sieved twice first, i.e., the particle protective slag with a particle size greater than 1 mm and a particle size less than 0.1 mm is sieved out and filtered; after sieving, the moisture content of the particle slag is detected, and when the moisture mass percentage is less than 0.35%, it can enter the sealing and packaging link.

[0028] The present application is a method for designing and manufacturing a lithium-free protective slag for a crystallizer for stainless steel slab continuous casting. In step one, the mass ratio of graphite and carbon black is 4-6:4-6, preferably 1:1. The purity of CMC (sodium carboxymethyl cellulose) binder reaches more than 98%, and its 2% aqueous solution viscosity range is 10-1000 mPa·s. In step two, the 325 mesh passing rate of the powder industrial raw material should be greater than 96%, the weighing link is accurate to two decimal places, the feeding link should mix the CMC binder with wollastonite, glass powder and other large raw materials uniformly first and then add water and stir uniformly in the mixing tank, and the stirring time is not less than 30 minutes, and the slurry ball milling time is not less than 30 minutes.

[0029] The lithium-free protective slag is applied to the continuous casting process of austenitic stainless steel slab. When applied, the continuous casting liquid steel pouring temperature is controlled to be 1490-1510℃.

[0030] As a preferred, when used, the crystallizer surface is ensured to be black slag operation, i.e., the liquid steel surface is fully covered with protective slag to prevent secondary oxidation of the liquid steel.

[0031] The austenitic stainless steel includes 304 stainless steel, 304PB type stainless steel, 304L stainless steel, 304H stainless steel, 310S stainless steel, and 316L stainless steel, etc.

[0032] In application, the ton steel slag consumption is 0.23-0.25 kg / t, and the average ton steel slag consumption is only 0.24 kg / t.

[0033] When the austenitic stainless steel is 304PB type stainless steel, under the continuous casting conditions of pouring temperature 1495-1500 DEG C, drawing blank speed 1.35 m / min -1 , crystallizer section four feet 220*1246mm, submerged entry nozzle insertion depth 140mm, the obtained product hot rolling after washing white skin roll product degradation rate is less than 1.5%, far lower than prior art.

[0034] The designed protective slag product not only reaches the performance of lithium-containing austenitic stainless steel slab continuous casting protective slag, but also has lower melting temperature and viscosity, which is beneficial to high-speed continuous casting process, reduces the raw material procurement cost of steel enterprises, and further improves the market competitiveness of products.

[0035] Compared with the prior art, the present application has the following advantages and positive effects:

[0036] 1. The method for designing and manufacturing a crystallizer lithium-free protective slag for stainless steel slab continuous casting according to the present application reduces the ton slag cost of the produced protective slag by about 1000-2500 yuan compared with the ton slag cost of the existing lithium-containing protective slag, improves the profit of the protective slag factory, reduces the material procurement cost of the steel enterprise, and achieves the win-win purpose of both parties.

[0037] 2. The method produces a protective slag with good performance stability, which can meet the production requirements of austenitic stainless steel slab continuous casting process under normal and high-speed conditions.

[0038] 3. The method is simple and easy to implement, can be used for large-scale production of protective slag factories, has a very attractive engineering application value, and the stainless steel hollow particle type protective slag produced by the method will bring good social and economic benefits once put into the market.

[0039] In summary, the present application first replaces the Li2O component in the protective slag with an appropriate amount of B2O3 and Na2O, effectively reduces the ton slag cost of the stainless steel slab continuous casting crystallizer protective slag, controls the ratio of Na2O to MgO, and finally produces a hollow particle type protective slag process with the same or even better performance than the existing lithium-containing protective slag under the synergistic effect of other components. The present application is simple and easy to implement, can provide reliable and stable theoretical and technical support for academic research and actual production, can be used for batch production in industry, is suitable for the demand of large-scale production, has very high engineering application value, and will produce significant social and economic benefits once put into the market. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 A process flow chart for manufacturing the crystallizer lithium-free mold powder for stainless steel slab continuous casting according to the present application is shown in Figure 1.

[0041] Figure 2 Figure 2 is a microstructure characterization diagram of the hollow particle type mold powder obtained in Example 2. DETAILED DESCRIPTION

[0042] The composition design and manufacturing method of the crystallizer lithium-free mold powder for stainless steel slab continuous casting according to the present application will be further explained in connection with specific Examples 1-3 and Comparative Examples 1-7, however, the explanation and description will not constitute undue limitations on the technical solutions of the present application.

[0043] Preparation process of Examples 1-3 and Comparative Examples 1-7:

[0044] 1) The industrial raw materials such as limestone, glass slag, wollastonite, high-aluminum powder, magnesia, fluorite, soda ash, borax pentahydrate, manganese powder, lithium carbonate, graphite, carbon black and CMC binder (sodium carboxymethyl cellulose) are accurately weighed after the error is not more than 0.05% according to the chemical composition content of the mold powder shown in Table 1; then each industrial raw material is mechanically stirred for 10 minutes to fully mix the components;

[0045] 2) The mixed mold powder samples in Examples and Comparative Examples are poured into graphite crucibles and heated to 1500°C in a medium-frequency induction furnace to melt, and each sample is kept for 10 minutes to remove volatile components and evenly melt the slag components;

[0046] 3) The molten liquid slag is poured into a cold quenching furnace, and the glass state mold powder sample obtained after rapid cooling is placed in a 120°C oven for drying for 6 hours;

[0047] 4) After the glass state mold powder sample is ground, the required amount of carbonaceous material (graphite 1%, carbon black 1%) and CMC binder (2%) are added to prepare a thick slurry with a solid-liquid ratio of 1:1.

[0048] 5) The obtained slurry is sent to a spray granulation drying tower for drying and granulation, and the product requires moisture less than 0.35%, particle size in the range of 0.10-1.00mm, and is sealed in bags for use.

[0049] The effective components (wt.%) and main physicochemical properties of Examples 1-3 and Comparative Examples 1-7 are shown in Table 1 and Table 2, respectively:

[0050] Table 1 Comparison of effective chemical components of Examples and Comparative Examples

[0051]

[0052]

[0053] Note: R2 in Table 1 is binary basicity, i.e. the ratio of CaO / SiO2 in the mold powder.

[0054] Table 2 Example and Comparative Example Performance Test Statistics

[0055]

[0056] From the performance comparison results of Examples 1-3 and Comparative Examples 1-7, it can be seen that the initial melting temperature range of Examples 1-3 is 974.3-1003.7℃, and the melting time is 35.8-37.2s, both of which are lower than those of Comparative Examples 1-3. Secondly, in terms of viscosity at 1300℃, the viscosity value of Examples 1-3 at 1300℃ is in the range of 0.168-0.185 Pa·s, which is lower than the viscosity range of Comparative Examples 1-7 at 1300℃, which is 0.183-0.197 Pa·s. Because the performance of the mold powder in the example series has a lower melting temperature and viscosity, a thicker liquid slag layer can be produced during continuous casting process, thereby improving the lubricating effect of the mold powder, which will be more conducive to high-speed continuous casting process. Finally, in terms of the cost of lithium-containing samples in Examples 1-3 and Comparative Examples 1-3, the Li2O content of Examples 1-3 is less than that of Comparative Examples 1-3 by 0.5%-1.5% respectively. According to the current price of 20 yuan per ton of industrial-grade lithium carbonate, the cost of producing one ton of industrial mold powder can be saved by 1000-3000 yuan, which shows that the raw material cost of the examples in the invention can be significantly lower than that of the lithium-containing mold powder in the comparative examples.

[0057] Taking the products obtained in Examples 1-3 as experimental objects, a pilot experiment (2-furnace steel liquid continuous casting test) was carried out, and the steel grade treated was 304 stainless steel, and the continuous casting temperature was between 1485-1505℃; the withdrawal speed was 1.30 m·min -1 Other continuous casting conditions were: mold cross-sectional size of four feet (220x1246mm), and immersion nozzle insertion depth of 140mm. It was found that when the product obtained in Example 2 was used for stainless steel continuous casting, the heat transfer curve was relatively smooth, the continuous casting process was smooth, and the surface quality of the cast blank was good, showing excellent performance; therefore, taking the product obtained in Example 2 as the object, and taking 304PB type stainless steel as the treatment object, the continuous casting conditions were: pouring temperature 1495-1500℃, withdrawal speed 1.35 m·min -1, the four-meter section of the crystallizer (220x1246mm), and the immersion type water inlet insertion depth of 140mm, a large test (one entire pouring, i.e. 20 furnace liquid pouring test) was conducted, and it was found that the product of the present application can not only replace the existing Li-containing protective slag, but also in the continuous casting test, the heat flow curve during the casting process is stable, the ton steel slag consumption is only 0.24kg / t, which is lower than the ton steel slag consumption of the original lithium-containing slag 0.27kg / t, further reducing the auxiliary material procurement cost for the enterprise. And the degradation rate of the obtained hot-rolled and offline washed white skin coil product is only 1.49%, which is far lower than the degradation rate of 6.25% of the current lithium-containing protective slag product. This not only reduces the production cost, but also improves the surface quality of the stainless steel hot-rolled coil, bringing significant economic benefits to the steel enterprises.

[0058] In summary, the above examples and comparative examples show that the composition design and manufacturing method of the lithium-free protective slag for the crystallizer for stainless steel slab continuous casting proposed in the present scheme are feasible, and have certain practical value and industrial application potential.

[0059] The above examples are only for illustrating the present application, and are not a limitation of the present application. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present application. Therefore, all equivalent technical solutions should belong to the scope of the present application, which should be limited by the claims.

Claims

1. A crystallizer flux for stainless steel slab continuous casting without lithium, characterized by: The chemical composition of the lithium-free protective slag includes, in percentage by mass, calcium oxide 28-40%, silicon oxide 26-38%, aluminum oxide 2-8%, sodium oxide 9-14%, fluoride ion 5-11%, magnesium oxide 1-4%, boron oxide 1-5%, manganese oxide 0.5-3%, total carbon 2-4.5%, and the balance being inevitable impurities and carbonate volatiles; the mass ratio of sodium oxide / magnesium oxide is greater than or equal to 3.5; The lithium-free protective slag is a hollow particle type protective slag. The industrial raw materials of the lithium-free protective slag include wollastonite, glass powder, soda ash, fluorite, limestone, high-aluminum powder, magnesia, borax pentahydrate, manganese powder, graphite, carbon black and CMC binder. The wollastonite is 45-65 parts, the glass powder is 0-15 parts, the soda ash is 10-20 parts, the fluorite is 10-20 parts, the limestone is 10-25 parts, the high-aluminum powder is 3-8 parts, the magnesia is 1-4 parts, the borax pentahydrate is 3-8 parts, the manganese powder is 0.5-3 parts, the graphite is 0.5-2 parts, the carbon black is 0.5-2 parts and the CMC binder is 1-3 parts.

2. The lithium-free mold powder for continuous casting of stainless steel slabs according to claim 1, characterized in that: The chemical composition of the lithium-free protective slag includes, in percentage by mass, calcium oxide 33-35%, silicon oxide 31.5-33.5%, aluminum oxide 4.5-5.5%, sodium oxide 10-11.5%, fluoride ion 7-9%, magnesium oxide 1.5-2.5%, boron oxide 2.5-3.5%, manganese oxide 0.8-1.2%, total carbon 3.0-3.5%, and the balance being inevitable impurities and carbonate volatiles; the mass ratio of sodium oxide / magnesium oxide is 5-6.

3. The lithium-free mold powder for a stainless steel slab continuous casting according to claim 2, characterized by: The chemical composition of the lithium-free protective slag includes, in percentage by mass, calcium oxide 34.5-35%, silicon oxide 32.5-33%, aluminum oxide 4.8-5.2%, sodium oxide 10.5-11.5%, fluoride ion 7-9%, magnesium oxide 1.5-2.5%, boron oxide 2.9-3.1%, manganese oxide 0.8-1.2%, total carbon 3.0-3.5%, and the balance being inevitable impurities and carbonate volatiles; the mass ratio of sodium oxide / magnesium oxide is 5-6.

4. The lithium-free mold powder for a stainless steel slab continuous casting according to claim 3, characterized by: The chemical composition of the lithium-free protective slag includes, in percentage by mass, calcium oxide 34.8-34.9%, silicon oxide 32.5-32.6%, aluminum oxide 4.95-5.05%, sodium oxide 10.9-11.1%, fluoride ion 7-9%, magnesium oxide 1.5-2.5%, boron oxide 2.9-3.1%, manganese oxide 0.8-1.2%, total carbon 3.0-3.5%.

5. The lithium-free mold powder for continuous casting of stainless steel slabs according to claim 1, characterized in that: The binary basicity of the lithium-free protective slag is 0.9-1.

10.

6. The mold powder for continuous casting of stainless steel slabs according to claim 1, characterized by: The starting melting temperature range of the lithium-free protective slag is 950-1080℃, and the melting time is 25-38 seconds.

7. The lithium-free mold powder for a stainless steel slab continuous casting according to claim 6, characterized by: The melting time is 35-37.5 seconds.

8. The lithium-free mold powder for a stainless steel slab continuous casting according to claim 6, characterized by: The starting melting temperature of the lithium-free protective slag is 970-1005℃. The viscosity of the lithium-free protective slag at 1300℃ is 0.08-0.25 Pa·s.

9. Use of a lithium-free mould flux for a continuous casting of a steel slab according to any one of claims 1 to 8, characterized in that: The lithium-free protective slag is applied to the continuous casting process of the austenitic stainless steel slab; when applied, the continuous casting liquid steel pouring temperature is controlled to be 1490-1510 ℃.

Images