CN114029462B - Rare earth oxide-containing continuous casting mold flux for high-titanium low-aluminum steel and preparation method thereof - Google Patents

Abstract

The invention relates to the technical field of steel continuous casting, in particular to a rare earth oxide-containing continuous casting mold flux for high-titanium low-aluminum steel and a preparation method thereof. The continuous casting covering slag comprises the following components in percentage by mass:CaO 18～23％、SiO ₂ 17～21％、Al ₂ O ₃ 10～15％、MgO 2～5％、Na ₂ O 8～12％、F ^‑ 4～7％、B ₂ O ₃ 1～5％、TiO ₂ 1～4％、Ce ₂ O ₃ 12 to 15 percent and C2 to 5 percent, and the balance of inevitable impurities. According to the invention, through designing the component formula and the proportion of the covering slag, the components in the covering slag have synergistic effect, the CaO content is reduced, and the high melting point CaTiO is inhibited ₃ To reduce SiO ₂ Content, inhibiting the performance deterioration of the casting powder caused by slag steel reaction; simultaneously adding a certain amount of low rare earth oxide Ce ₂ O ₃ And a small amount of TiO ₂ The casting powder has good lubricating property and heat transfer capacity, the continuous casting process is smooth, and the number of continuous casting furnaces and the quality of casting blanks are improved.

Description

A kind of rare earth oxide-containing continuous casting mold flux for high-titanium low-aluminum steel and its preparation method

technical field

The invention relates to the technical field of continuous casting of iron and steel, in particular to a rare earth oxide-containing continuous casting mold flux for high-titanium and low-aluminum steel and a preparation method thereof.

Background technique

Mold slag is a functional material in the continuous casting process. At present, the metallurgical functions in the mold can be summarized into the following five categories: (1) prevent secondary oxidation of molten steel; (2) heat insulation; (3) absorb non- Metal inclusions; (4) Control the lubrication between the mold and the slab; (5) Improve the heat transfer between the mold and the slab. The performance of the mold flux directly determines the quality of the slab, thus affecting the production efficiency.

Adding alloying elements to steel can effectively improve the performance of steel, but at the same time, it also affects the process to varying degrees. Due to the addition of Al and Ti in corrosion-resistant alloy steel, inclusions such as Al ₂ O ₃ , TiO ₂ , and TiN will inevitably be produced during the smelting process, and Al, Ti in steel and SiO ₂ in mold slag during continuous casting Oxidation-reduction reactions that occur:

[Ti]+(SiO ₂ )=(TiO ₂ )+[Si]

4[Al]+3(SiO ₂ )=2(Al ₂ O ₃ )+3[Si]

Therefore, the consumption of _SiO2 in the mold flux will cause a drastic change in the properties of the mold flux. In addition, the inclusions produced during the smelting process will also enter the mold slag. These changes will lead to deterioration of the melting temperature and viscosity of the mold slag, affecting the lubrication and heat transfer of the mold slag. Surface quality problems will cause vicious accidents such as cohesive breakouts in severe cases.

For example, patent CN105642849A discloses mold flux for continuous casting of titanium-containing steel. The composition of mold flux in weight percentage is: CaO 15-35%, SiO ₂ 7-15%, Al ₂ O ₃ 10-30%, F ^- 3 ~15%, _Li2O3 ~10%, BaO5~20%, _{Mn2O3 5} ~20%, _C2 ~12%, MgO≤1.5%, and _Fe2O3≤2 %. The content of SiO ₂ in the mold flux is small, so as to reduce the activity of SiO ₂ and suppress the burning loss of Ti in the steel, but the addition of strong oxidant Mn ₂ O ₃ will also react with Ti in the steel, without Fundamentally solve the burning loss of Ti in steel.

Patent CN111531140A discloses the continuous casting mold flux of high titanium oxide for titanium-containing steel. The components of the mold flux in weight percentage are: (CaO+BaO+MgO+SrO) 31-45%, SiO ₂ 9-13%, Al ₂ O ₃ 18～26%, (NaF+CaF ₂ +BaF ₂ ) 10～16%, Li ₂ O 5～10%, B ₂ O ₃ 2～4%, C5～10% and TiO ₂ 10～20%, the balance unavoidable impurities. The high content of TiO ₂ in the mold slag inhibits the slag-steel reaction, but the high content of TiO ₂ is easy to combine with CaO to form CaTiO ₃ with a high melting point, and the crystallization rate of the mold slag is high, which affects the lubrication between the slab and the mold wall, resulting in The surface quality of the slab deteriorates, which affects the billet repair rate.

Patent CN108127094A discloses a non-reactive mold flux for high-titanium steel. The composition of the mold flux _{in weight percentage is: CaO9-16%, Al2O3 15-30} %, BaO20-32%, _Li2O5-12 % , MgO≤2%, F ^- 8～15%, TiO ₂ 4～10% and C2～12%, the rest are unavoidable impurities, and keep the impurities (Na ₂ O+K ₂ O+SiO ₂ )≤3 %. The crystallization rate of the mold slag is 80-100%, the lubricating ability of the mold slag is poor, and the phenomenon of cohesive breakout is easy to occur in the continuous casting process, resulting in the termination of continuous casting.

Patent CN110315039A discloses the application of a fluorine-free mold flux in the continuous casting of titanium-containing steel. The components of the mold flux in weight percent are: CaO 30-45%, SiO ₂ 25-40%, Al ₂ O ₃ 2-6%, (MgO+Na ₂ O) 8-15%, Li ₂ O 0-2%, B ₂ O ₃ 4-8%, and (Fe ₂ O ₃ +MnO) 6-10%. The content of (SiO ₂ +B ₂ O ₃ ) in the mold flux is relatively high, and the slag-steel reaction phenomenon is serious. The TiO ₂ formed by the reaction combines with the CaO in the mold flux to form CaTiO ₃ with a high melting point, which affects the lubricating performance of the mold flux. Not suitable for high titanium steel.

Patent CN104399922A discloses a new type of corrosion-resistant alloy steel continuous casting mold flux and its application. The components of the mold flux _in weight percentage are: CaO17-25%, _SiO2 23-31%, _Al2O3 10-15%, MgO1 ~4%, (Na ₂ O+Li ₂ O) 10~14%, B ₂ O ₃ 1~8%, TiO ₂ 1~6%, BaO 4~8%, and F ^- 10~13%. The content of (SiO ₂ + B ₂ O ₃ ) in the _mold flux is relatively high, and the content of B ₂ O ₃ in the mold flux is more than 5% _{. 2} It is easier to react with Ti in the steel, which enhances the slag-steel reaction, and the mold flux is suitable for titanium-containing steel with a low Ti content (0.1-0.3%).

To sum up, the existing designs of these continuous casting mold fluxes all have certain defects: the mold flux has high reactivity, and the burning loss of Ti element in the molten steel is serious; the content of CaO or TiO ₂ in the mold flux is high, and it is easy to form CaTiO ₃ with high melting point affects the lubricating performance of mold flux. Up to now, there has not been a public disclosure of a continuous casting mold flux that can solve the above-mentioned technical problems.

Contents of the invention

(1) Technical problems to be solved

In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a continuous casting mold flux containing rare earth oxides for high-titanium and low-aluminum steel. Synergistic effect, reduce CaO content, inhibit the formation of CaTiO ₃ with high melting point, reduce SiO ₂ content, and inhibit the performance deterioration of mold slag caused by slag-steel reaction; at the same time, add a certain amount of low rare earth oxide Ce ₂ O ₃ and a small amount of TiO ₂ to make the protection The slag has good lubricating performance and heat transfer ability, which makes the continuous casting process go smoothly, and improves the number of continuous casting furnaces and the quality of the slab.

(2) Technical solutions

In order to achieve the above object, the main technical solutions adopted in the present invention include:

In one aspect, the present invention provides a rare earth oxide-containing continuous casting mold flux for high-titanium and low-aluminum steel, which comprises the following components in terms of mass percentage:

CaO18～23%, _SiO2 17～21%, _{Al2O3 10} ～15%, MgO2～5%, _Na2O8 ～12%, F ^- 4～7%, _{B2O3 1} ～5%, TiO ₂ 1-4%, Ce ₂ O ₃ 12-15%, and C2-5%, and the rest are unavoidable impurities.

According to a preferred embodiment of the present invention, the physical properties of the continuous casting mold flux satisfy: melting point: 1115-1200° C.; viscosity at 1300° C.: 0.15-0.30 Pa·s; crystallization rate: 20-33%.

According to a preferred embodiment of the present invention, the weight ratio of CaO and SiO ₂ is 1.0-1.1. In this ratio range, the mold flux can obtain proper basicity, and the mold flux has a good ability to absorb inclusions such as Al ₂ O ₃ , TiO ₂ , TiN, etc., and reducing the amount of CaO can inhibit the formation of high melting point CaTiO ₃ ; CaO The weight ratio of SiO ₂ to ≥ 1 reduces the reactivity of SiO ₂ .

According to a preferred embodiment of the present invention, the continuous casting mold flux is used to produce high-titanium low-aluminum steel, the mass fraction of Ti in the high-titanium low-aluminum steel is 0.8-1.2%, and the mass fraction of Al is 0-0.2% %.

The technical principle of the continuous casting mold flux component formula of the present invention is as follows:

The content of CaO is controlled at 18-23%, which is used to provide alkalinity to absorb inclusions. At the same time, the content of CaO is low, which can inhibit the formation of CaTiO ₃ after the mold flux absorbs TiO ₂ and control the performance of the mold flux. The content of SiO ₂ is controlled at 17-21%. As a network former, it plays a key role in the mold flux, providing the glass property of the mold flux, ensuring the smooth flow of the continuous casting process and the quality of the cast slab. Reducing the content of SiO ₂ can reduce the activity of SiO ₂ , reduce the burning loss of Ti, and inhibit the performance deterioration of the mold flux caused by the slag-steel reaction. Adding a small amount of TiO ₂ and 12-15% Ce ₂ O ₃ can, on the one hand, reduce the activity of SiO ₂ , inhibit the reaction between Ti in steel and SiO ₂ in mold slag, reduce the reaction between slag and steel, and reduce the burning loss of Ti; On the other hand, partially replace CaO to provide alkalinity and make up for the problem caused by the reduction of calcium oxide. Na ₂ O in mold flux is beneficial to reduce SiO ₂ activity. A small amount of B ₂ O ₃ is added to the mold flux to reduce the crystallization rate of the mold flux and increase the lubricating ability of the mold flux.

Preferably, the content of B ₂ O ₃ in mold flux is 1.65-4.21%. Preferably, the content of TiO ₂ in the mold flux is 1.55-3.23%. Preferably, the content of Ce ₂ O ₃ in the mold flux is 12.25-14.26%. Preferably, the content of MgO in the mold flux is 2.27-4.30%. Preferably, the content of C in mold flux is 2.78-4.12%. Preferably, the content of F ^- in mold flux is 4.54-6.08%. Preferably, the content of Na ₂ O in the mold flux is 8.63-11.31%. Preferably, the content of SiO ₂ in the mold flux is 17.33-20.63%. Preferably, the content of CaO in mold flux is 18.77-22.51%. Preferably, the content of Al ₂ O ₃ in the mold flux is 10.32-14.43%.

On the other hand, the present invention also provides a method for preparing rare earth oxide-containing continuous casting mold flux for high-titanium and low-aluminum steel, which includes:

S1. Using limestone, quartz sand, bauxite, magnesia, sodium carbonate, fluorite, boric anhydride, titanium dioxide, ceria and carbonaceous materials as raw materials, according to the percentage of components of the mold flux described in the above scheme, Calculate the amount of each raw material, and weigh each raw material according to the amount;

S2, limestone, quartz sand, bauxite, magnesia, sodium carbonate, part of fluorite (15-20% of fluorite total amount), boric anhydride, titanium dioxide and ceria mixed and heated in S1, when When the temperature reaches 1250-1300℃, add the remaining fluorite and keep it warm for 30-40 minutes; after all the raw materials are melted evenly, then cool naturally in the furnace to obtain the glassy premelt;

S3. Crushing and processing the pre-melt material to a particle size of ≤1mm, adding the required amount of carbonaceous material, then adding water and binder to the fine mill, and fine grinding for 30-60 minutes to make a slurry;

S4. Sending the slurry into a spray particle drying tower for drying and granulation to obtain the rare earth-containing continuous casting mold flux for high-titanium and low-aluminum steel.

Preferably, each raw material meets the following requirements: limestone: CaCO ₃ >95%; quartz sand: SiO ₂ >95%; bauxite: Al ₂ O ₃ >75%, SiO ₂ <4%; magnesia: MgO >85% %, SiO ₂ <6%, Al ₂ O ₃ <2%; Sodium Carbonate: Na ₂ CO ₃ >95%; Fluorite: CaF ₂ 88-90%, SiO ₂ <6.0%, S<0.05%; Boric Anhydride : B ₂ O ₃ >95%; titanium dioxide: TiO ₂ >98%; ceria: Ce ₂ O ₃ >99%; carbonaceous material: C >95%.

Preferably, in S4, dry and granulate in a spray particle drying tower to obtain a moisture content of ≤0.5% and a particle size of 0.1-1.2mm (≥80%) to obtain the rare earth-containing continuous casting mold flux for high-titanium and low-aluminum steel.

(3) Beneficial effects

The rare earth oxide-containing mold flux for continuous casting of high-titanium and low-aluminum steel provided by the invention can effectively control the slag-steel reaction and absorb inclusions such as Al ₂ O ₃ , TiO ₂ , and TiN. In the continuous casting process, the mold slag has good fluidity and normal slag consumption, greatly reduces defects such as longitudinal cracks and slag inclusions in the slab, and significantly improves the quality of the slab and production efficiency.

Detailed ways

In order to better explain the present invention and facilitate understanding, the present invention will be described in detail below in conjunction with specific embodiments.

The invention provides a component composition of rare earth oxide-containing continuous casting mold flux for high-titanium and low-aluminum steel: CaO 18-23%, SiO ₂ 17-21%, Al ₂ O ₃ 10-15%, MgO 2-5 %, Na ₂ O 8～12%, F ^- 4～7%, B ₂ O ₃ 1～5%, TiO ₂ 1～4%, Ce ₂ O ₃ 12～15%, and C2～5%, the rest are unavoidable of impurities.

The preparation method of the above-mentioned rare earth-containing continuous casting mold flux comprises the following steps:

(1) Using limestone, quartz sand, bauxite, magnesia, sodium carbonate, fluorite, boric anhydride, titanium dioxide, ceria and carbonaceous materials as raw materials, according to the weight percentage of the mold powder, calculate the The amount of raw materials, and weigh each raw material according to the calculated amount, and select the raw materials whose weight percentage meets the following requirements:

Limestone: CaCO ₃ >95%; Quartz sand: SiO ₂ >95%; Bauxite: Al ₂ O ₃ >75%, SiO ₂ <4%; Magnesia: MgO >85%, SiO ₂ <6%, Al ₂ O ₃ <2%; Sodium carbonate: Na ₂ CO ₃ >95%; Fluorite: CaF ₂ 88-90%, SiO ₂ <6.0%, S <0.05%; Boric anhydride: B ₂ O ₃ >95%; Titanium dioxide: TiO ₂ >98%; ceria: Ce ₂ O ₃ >99%; carbonaceous material: C >95%.

(2) Limestone, quartz sand, bauxite, magnesite, sodium carbonate, fluorite (15-20% of fluorite total amount), boric anhydride, titanium dioxide and ceria mixed in the step (1) , Put it into the submerged arc furnace for heating, when the temperature reaches 1250-1300°C, add the rest of fluorite, and finally keep it in the submerged arc furnace for 30-40 minutes. After each raw material is melted evenly, the furnace is then naturally cooled to obtain a glassy premelt.

(3) Crushing and processing the pre-melted material to a particle size of ≤1mm, adding the required amount of carbonaceous material, then adding water and binder into the fine mill, and fine grinding for 30-60 minutes to make a slurry.

(4) Sending the slurry into a spray particle drying tower to dry and granulate to obtain a moisture content of ≤0.5% and a particle size of 0.1-1.2 mm (≥80%) to obtain the rare-earth-containing continuous casting mold flux for high-titanium and low-aluminum steel.

According to the above preparation method, the continuous casting mold fluxes of the following Examples 1-4 were respectively obtained.

Table 1 Composition and main physical and chemical properties of continuous casting mold flux in Examples 1-4

It can be seen from Table 1 above that the melting point, viscosity and crystallization rate of the mold flux of the present invention are reasonable, which can make the mold flux have a good lubricating effect in the mold.

Apply the mold flux of Example 1 in the above table 1 to the steel type of Ti=0.99%, Al=0.08%, apply the mold flux of Example 2 to the steel type of Ti=0.98%, Al=0.12%, and implement The mold flux in Example 3 is applied to the steel grade with Ti=1.13%, Al=0.16%, and the mold flux in Example 4 is applied to the steel grade with Ti=0.94%, Al=0.10%. The pouring temperature is 1425~1440℃, and the casting speed is 0.50.4~0.6m/min.

The results show that the mold slag and steel slag interfaces of Examples 1 to 4 have very little solid condensation, the surface quality of the slab is good, no large amount of slag inclusions are found, the surface quality and subcutaneous quality of the slab are good, and the entire continuous casting goes smoothly and continuous casting The number of furnaces is more than 3 furnaces, and the original qualified rate of casting slabs is above 90%. Among them, the average grinding amount of the slab in Example 1 is 8.7%, the average grinding amount of the slab in Example 2 is 9.6%, the average grinding amount of the slab in Example 3 is 8.6%, and the slab in Example 4 The average grinding amount is 9.0%, and the average grinding amount of the slab is reduced by more than 83% compared with the existing mold slag. The composition of Ti and Al in the slab is qualified, which is in line with the element content of the steel grade. The burning loss rate of Ti is 12.50%, 15.29%, 14.14% and 14.63% respectively; the burning loss rate of Al is 14.29%, 9.09%, 6.67% respectively. % and 11.11%.

Table 2 below shows the contents and physical and chemical properties of each component of the mold flux of Comparative Examples 1-4. Wherein Comparative Examples 1 and 2 do not contain Ce ₂ O ₃ , and in Comparative Examples 3 and 4 Ce ₂ O ₃ accounts for 23.12% and 22.30% of the mold flux.

Table 2 Composition and main physical and chemical properties of continuous casting mold flux in comparative examples 1 to 4

It can be seen from Table 2 above that the melting point, viscosity and crystallization rate of the mold fluxes of Comparative Examples 1 and 2 are reasonable, which can make the mold fluxes have a good lubricating effect in the mold. In order to verify the performance of the mold flux of the comparative example, the mold flux of the comparative example 1 was further applied to the steel type with Ti=0.95%, Al=0.08%, and the mold flux of the comparative example 2 was applied to the steel with Ti=1.00%, Al=0.09 % of the steel grades, the mold flux of Comparative Example 3 was applied to the steel grades of Ti=1.08% and Al=0.17%, and the mold flux of Comparative Example 4 was applied to the steel grades of Ti=1.08% and Al=0.18%. The pouring temperature is 1425-1440°C, and the casting speed is 0.4-0.6m/min.

The results show that the mold slags of Comparative Examples 1 and 2 have good surface quality during the casting process, and no large amount of slag inclusions are found. furnace. The average grinding amount of the slab in Comparative Example 1 was 6.2%, and the average grinding amount of the slab in Comparative Example 2 was 8.6%. However, the content of Ti in the slab is unqualified, and the burning loss rate is 35.71% and 35.14%, respectively. In addition, according to the test, when the content of Ce ₂ O ₃ in the mold flux is lower than 12%, the burning loss rate of Ti in the slab is still high, which cannot be controlled to an ideal level suitable for practical application.

During the casting process of the mold slags of Comparative Examples 3 and 4, large slag rings appeared, and the liquid level of the crystallizer fluctuated greatly, so continuous casting was not possible. Longitudinal cracks appear on the surface of the slab, and there is a certain phenomenon of slag inclusion. The slab average grinding amount of comparative example 3 is 25.3%, the slab average grinding amount of example 4 is 21.5%,

It can be seen that when there is a lack of Ce ₂ O ₃ in the mold slag, if the amount of CaO and SiO ₂ in the slag system is simply lowered, there will be serious burning loss of elements, and the composition of the slab is unqualified and cannot be accepted. However, when the content of Ce ₂ O ₃ in the mold flux is too high, there are problems of poor surface quality of cast slab and high amount of grinding, which increases the production cost.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than limiting them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: It is still possible to modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the technical solutions of the various embodiments of the present invention. scope.

Claims (6)

1. The rare earth oxide-containing continuous casting mold flux for the high-titanium low-aluminum steel is characterized by comprising the following components in percentage by mass:

CaO 18～23％、SiO ₂ 17～21％、Al ₂ O ₃ 10～15％、MgO 2～5％、Na ₂ O 8～12％、F ^- 4～7％、B ₂ O ₃ 1～5％、TiO ₂ 1～4％、Ce ₂ O ₃ 12-15% and C2-5%, the rest is inevitable impurities; among them, caO and SiO ₂ The weight ratio is 1.0-1.1;

the continuous casting mold flux is used for producing high-titanium low-aluminum steel, wherein the mass fraction of Ti in the high-titanium low-aluminum steel is 0.8-1.2%, and the mass fraction of Al in the high-titanium low-aluminum steel is 0-0.2%.

2. The continuous casting mold flux according to claim 1, wherein physical properties of the continuous casting mold flux satisfy: melting point: 1115 to 1200 ℃; viscosity at 1300 ℃: 0.15-0.30 Pa · S; the crystallization rate is as follows: 20 to 33 percent.

3. The continuous casting mold flux according to claim 1, wherein B is B ₂ O ₃ The content of the casting powder is 1.65 to 4.21 percent; tiO 2 ₂ The content of the casting powder is 1.55 to 3.23 percent; ce ₂ O ₃ The content of the casting powder is 12.25 to 14.26 percent; siO 2 ₂ The content of the casting powder is 17.33-20.63%; the content of CaO in the casting powder is 18.77-22.51%.

4. A preparation method of rare earth oxide-containing continuous casting mold flux for high-titanium low-aluminum steel is characterized by comprising the following steps:

s1, taking limestone, quartz sand, bauxite, magnesia, sodium carbonate, fluorite, boric anhydride, titanium dioxide, ceria and carbonaceous materials as raw materials, calculating the use amount of each raw material according to the component percentage content of the continuous casting protective slag in claim 1, and weighing each raw material according to the use amount;

s2, mixing and heating the limestone, the quartz sand, the bauxite, the magnesia, the sodium carbonate, part of fluorite, boric anhydride, the titanium dioxide and the ceria weighed in the S1, adding the rest fluorite when the temperature reaches 1250-1300 ℃, and preserving the heat for 30-40 min; after the raw materials are melted uniformly, naturally cooling the raw materials in a furnace to obtain a glass state pre-melted material;

s3, crushing the pre-melted material to the particle size of less than or equal to 1mm, adding a required amount of carbonaceous material, then adding water and a binder into a refiner, and finely grinding for 30-60 min to prepare slurry;

and S4, feeding the slurry into a spray particle drying tower for drying and granulating to obtain the continuous casting mold flux containing the rare earth oxide for the high-titanium low-aluminum steel.

5. The method according to claim 4, wherein each raw material satisfies the following requirements: limestone: caCO ₃ More than 95 percent; quartz sand: siO 2 ₂ More than 95 percent; bauxite: al (Al) ₂ O ₃ ＞75％，SiO ₂ Less than 4 percent; magnesia: mgO > 85%, siO ₂ ＜6％，Al ₂ O ₃ Less than 2 percent; sodium carbonate: na (Na) ₂ CO ₃ More than 95 percent; fluorite: caF ₂ 88～90％，SiO ₂ Less than 6.0 percent and S less than 0.05 percent; boric anhydride: b ₂ O ₃ More than 95 percent; titanium dioxide: tiO 2 ₂ More than 98 percent; ceria: ce ₂ O ₃ More than 99 percent; carbonaceous material: c is more than 95 percent.

6. The preparation method according to claim 4, wherein in S4, the continuous casting mold flux containing the rare earth oxide for the high titanium low aluminum steel is obtained by drying and granulating in a spray granule drying tower to obtain granules with the water content of less than or equal to 0.5% and the mass ratio of the granules with the granularity of 0.1-1.2 mm of more than 80%.