Method and device for inhibiting the reaction between high-aluminum steel slag and steel in continuous casting

Abstract

The present application relates to a kind of methods and devices for inhibiting continuous casting high-aluminum steel slag-steel reaction, the device for inhibiting continuous casting high-aluminum steel slag-steel reaction is connected in the lower surface of the outside of tundish, after continuous casting opening, when molten steel liquid level is stable, disconnect the connection of the device and tundish, the device slowly falls into molten steel surface, and float between molten steel surface and shielding slag;The contact area of the device and the upper surface of molten steel accounts for 20% to 80% of the total area of the upper surface of molten steel.Optimal features are: the barrier slag-steel contact device composed of high thermal conductivity, high-temperature resistant metal and refractory material and other materials can be placed between shielding slag and molten steel, and the specific gravity can be adjusted by the volume of filled corundum.The device for inhibiting continuous casting high-aluminum steel slag-steel reaction can float on the surface of molten steel, block the contact between molten steel and shielding slag, reduce the contact area of molten steel and shielding slag, and inhibit the reaction ability of slag-steel.

Description

Technical Field

[0001] This invention belongs to the field of steelmaking and continuous casting technology, and particularly relates to a method and apparatus for suppressing the reaction between high-alumina steel slag and steel in continuous casting. Background Technology

[0002] Significantly increasing the [Al] content in steel can improve its stacking fault energy, enhance the delayed fracture behavior of TWIP (twin-induced plasticity) steel, reduce its density, and increase its work hardening capacity, thus meeting the high-strength and lightweight requirements of steel products used in automobiles and marine applications. However, because [Al] in molten steel is a reactive element, during the traditional CaO-SiO2-based mold flux casting process, [Al] reacts with components such as SiO2 in the mold flux, causing changes in the composition and properties of the mold flux. This leads to disruptions in the continuous casting process, severely impacting product quality and production efficiency.

[0003] In the prior art, patent publication number CN114130972A discloses a non-reactive protective slag for continuous casting of fluorine-free high-alumina steel. The SiO2, B2O3, and Na2O in this slag still react with [Al] in the molten steel. Patent publication number CN108213365A discloses a non-reactive protective slag for high-alumina steel. This slag is essentially free of components such as SiO2, Na2O, Fe2O3, and B2O3 that react with active elements like [Al] and [Ti] in the molten steel. After use, the composition and properties of the slag remain stable, ensuring the smooth operation of the high-alumina steel continuous casting process. However, this slag has excessively strong crystallization ability, with a crystallization rate reaching 100%; simultaneously, the Li2O content is too high, making the slag expensive. Patent publication number CN106270429A discloses a low-reactivity protective slag and its preparation method. This method limits the silica content in the protective slag to a stable range, reducing the slag-steel reaction characteristics. However, the Na₂O and B₂O₃ in the formulation exhibit strong reactivity with [Al] in the molten steel. Patent publication number CN102764866A discloses a high-Al₂O₃ content continuous casting protective slag for high-alumina steel, which has a good glassy morphology and can significantly reduce the reaction between aluminum in the steel and SiO₂ in the slag. However, the formulation contains Na₂O and B₂O₃, and these components still react with [Al] in the molten steel. The above patents disclose low-reactivity CaO-Al₂O₃-based protective slag formulations, aiming to solve the problem of strong slag-steel reactions during the continuous casting of high-alumina steel. However, CaO-Al2O3-based protective slag still faces two problems: (1) CaO-Al2O3-based protective slag has strong crystallization properties, resulting in low slag consumption in practical applications and unstable surface quality of the produced billets; (2) CaO-Al2O3-based protective slag contains other flux components that are reactive with [Al] in molten steel, such as Na2O and B2O3, which are also reactive with molten steel with high [Al] content, causing changes in the composition and properties of the protective slag and affecting the smooth operation of the continuous casting process.

[0004] Therefore, how to further suppress the slag-steel reaction in continuously cast high-alumina steel, so as to stably obtain good billet quality and ensure the smooth operation of the continuous casting process, is an urgent problem to be solved. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, the purpose of this invention is to provide a method and apparatus for suppressing the slag-steel reaction in continuously cast high-alumina steel. The apparatus is made of metals with high thermal conductivity and high temperature resistance, and refractory materials with high thermal conductivity, high temperature resistance, and oxidation resistance. It floats on the surface of molten steel to reduce the contact area between molten steel and protective slag, thereby suppressing the slag-steel reaction.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for suppressing the slag-steel reaction in continuously cast high-alumina steel involves connecting a device for suppressing the slag-steel reaction to the lower surface of the outer side of the tundish. After continuous casting begins and the molten steel level stabilizes, the device is disconnected from the tundish, and the device slowly falls onto the surface of the molten steel, floating between the molten steel surface and the protective slag. The contact area between the device and the upper surface of the molten steel accounts for 20% to 80% of the total area of ​​the upper surface of the molten steel.

[0008] The device for suppressing the slag-steel reaction in continuously cast high-alumina steel is heated to 600–1400°C and then connected to the tundish.

[0009] The device for suppressing the slag-steel reaction in continuously cast high-alumina steel is a geometric plate-like structure with a thickness ≤10mm.

[0010] The device includes an outer frame and a covering layer. The outer frame is covered by the covering layer, and the outer frame has through holes with the diameter of the through holes matching the outer diameter of the immersion nozzle.

[0011] The outer frame is connected to the lower surface of the outer side of the intermediate package by steel wire.

[0012] The outer frame is composed of a hollow thin plate and corundum filled inside the thin plate.

[0013] The thin plate is an SM2050 high-temperature alloy plate, and the volume ratio of the SM2050 high-temperature alloy plate to corundum in the outer frame is (1-3):1.

[0014] The thin plate is a titanium plate, and the volume ratio of the titanium plate to corundum in the outer frame is (1-5):2.

[0015] The method for preparing the coating includes the following steps:

[0016] 1) Take a -200 mesh high thermal conductivity refractory material and grind it at a high speed of 4000-5000 r / min for 10-20 min to make fine powder;

[0017] 2) The fine powder prepared in step 1) is sprayed onto the surface of the outer skeleton using plasma spraying or laser cladding.

[0018] The high thermal conductivity refractory material is one or more of molybdenum disilicide, hexagonal boron nitride, and titanium diboride.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] This invention employs a slag-steel contact barrier constructed from various materials including highly thermally conductive and high-temperature resistant metals and refractory materials. It can be placed between the protective slag and molten steel, and its specific gravity can be adjusted by the volume of corundum used for filling. This device, which inhibits the slag-steel reaction in continuously cast high-alumina steel, floats on the surface of the molten steel, blocking contact between the molten steel and the protective slag, reducing the contact area between them, and suppressing the slag-steel reaction. The device possesses high thermal conductivity, high-temperature resistance, and oxidation resistance, without altering the composition and physicochemical properties of the protective slag, ensuring that the protective slag fulfills its metallurgical function. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of a device for suppressing the slag-steel reaction in continuously cast high-alumina steel inside the crystallizer.

[0022] Figure 2 This is a schematic diagram of the device for suppressing the slag-steel reaction in continuously cast high-alumina steel.

[0023] Figure 3 This is a schematic diagram of the internal structure of a device for suppressing the slag-steel reaction in continuously cast high-alumina steel.

[0024] In the diagram: 1-External skeleton 2-Clad layer 3-Corundum 4-Thin plate 5-Through hole 6-Protective slag 7-Crystallizer copper plate 8-Molten steel 9-Solidified billet shell 10-Submerged entry nozzle. Detailed Implementation

[0025] The present invention will now be described in detail with reference to the accompanying drawings, but it should be noted that the implementation of the present invention is not limited to the following embodiments.

[0026] Example 1:

[0027] See Figure 2 , Figure 3 Using a twin-strand slab continuous casting machine as the carrier, the crystallizer has a cross-section of 1100mm × 230mm, and the protective slag uses one of CaO-SiO2, CaO-Al2O3, or CaO-SiO2-Al2O3 as the slag-based component. The device for inhibiting the slag-steel reaction in continuously cast high-alumina steel adopts a rectangular, polygonal, or circular sheet structure. This embodiment uses an easily machinable rectangular structure with dimensions of 750mm × 170mm × 8mm, with a central opening... The device's position on the molten steel surface is determined by the through-hole through which the submerged entry nozzle passes through the frame. This placement near the entry nozzle, away from the crystallizer's copper plate, prevents interference with the flow of protective slag at the meniscus. Since the molten steel temperature is higher near the entry nozzle and lower around the crystallizer, this placement also prevents poor heat transfer, which could affect the melting of the protective slag. The device's position on the molten steel surface can also be restricted by the crystallizer wall. The contact area between the device and the upper surface of the molten steel is 50% of the total upper surface area of ​​the molten steel.

[0028] Processing procedure for a device to suppress the slag-steel reaction in continuously cast high-alumina steel:

[0029] 1) Machining SM2050 high-temperature alloy into a hollow thin shell (with a core) The material has a through-hole (thickness ≤ 8mm) and is filled with corundum. The volume ratio of SM2050 high-temperature alloy to corundum is 3:1. The corundum can be in granular or small-piece form. The density of the finished material is 7.0 g / cm³. 3 This allows it to float on the surface of molten steel. The shell wall is as thin as possible, ensuring good thermal conductivity while meeting the impact strength requirements of the molten steel. The shell (plate) material has a high density, while corundum has a low density; mixing the two can adjust the density of the outer skeleton. In addition, the outer skeleton material combines high temperature resistance, a certain strength, and high thermal conductivity, while also considering fire resistance and thermal conductivity.

[0030] 2) Coating: Molybdenum disilicide (MoSi2) is crushed, passed through a 200-mesh sieve, and ground at 4500 r / min for 20 min to make fine powder.

[0031] 3) The fine powder prepared in step 2) is sprayed onto the surface of the thin shell in step 1) using plasma spraying. The surface material is then modified to obtain the finished product. The resulting coating is a high-temperature resistant coating with high thermal conductivity. The surface of the outer skeleton is modified to meet the working conditions of heat transfer and long-term immersion in molten steel.

[0032] See Figure 1 The device for inhibiting the slag-steel reaction in continuous casting is heated to 1100℃ and then fixed to the lower outer surface of the tundish with a steel wire. The through hole is aligned with the submerged entry nozzle, and the submerged entry nozzle passes through the through hole. After continuous casting begins and the molten steel level stabilizes, the fixing steel wire is cut, and the device is slowly lowered into the molten steel surface. After stabilization, it floats on the molten steel surface.

[0033] Comparative Example 1 uses a conventional casting method.

[0034] After the casting of a single tank of high-alumina steel with an Al content of 4.0 wt%, the modification of the protective slag in Comparative Example 1 and Example 1 is shown in Table 1.

[0035] Table 1. Changes (wt%) in the chemical composition of the protective slag before and after the slag-steel reaction in Comparative Example 1 and Example 1.

[0036] CaO <![CDATA[Al2O3]]> <![CDATA[SiO2]]> <![CDATA[R2O]]> <![CDATA[Li2O]]> F <![CDATA[B2O3]]> MnO Comparative Example 1 +3.5 +17.4 -6.2 -7.1 +1.3 -4.9 -4.3 -3.2 Example 1 +2.4 +8.4 -2.9 -2.8 +1.2 -4.1 -3.7 -2.5

[0037] Example 2:

[0038] See Figure 2 , Figure 3 Using a twin-strand slab continuous casting machine as the carrier, the crystallizer has a cross-section of 1100mm × 230mm. The protective slag uses one of CaO-SiO2, CaO-Al2O3, or CaO-SiO2-Al2O3 as the slag-based component. The device for inhibiting the slag-steel reaction in continuous casting of high-alumina steel adopts a rectangular plate structure with dimensions of 900mm × 170mm × 6mm, with an opening in the middle. The device has a through-hole through which the submersible nozzle can pass, thus positioning the device on the molten steel surface. The position of the device on the molten steel surface can also be restricted by the crystallizer wall. The contact area between the device for inhibiting the high-alumina steel slag-steel reaction in continuous casting and the upper surface of the molten steel accounts for 60% of the total upper surface area of ​​the molten steel.

[0039] The processing of a device for suppressing the slag-steel reaction in continuously cast high-alumina steel includes the following steps:

[0040] 1) Machining a titanium plate into a hollow, thin shell (with a core) (Through-hole), thickness ≤6mm, filled with corundum, the volume ratio of titanium plate to corundum is 4:1, and the density of the finished material is 4.4g / cm³. 3 .

[0041] 2) Coating: Hexagonal boron nitride (HBN) is crushed, passed through a 200-mesh sieve, and ground at 5000 r / min for 15 min to make fine powder.

[0042] 3) The fine powder prepared in step 2) is sprayed onto the surface of the thin shell in step 1) using laser cladding method to modify the surface material, thus obtaining the finished product.

[0043] See Figure 1 The device for inhibiting the slag-steel reaction in continuous casting is heated to 1200℃ and then fixed to the lower outer surface of the tundish with a steel wire. The through hole is aligned with the submerged entry nozzle, and the submerged entry nozzle passes through the through hole. After continuous casting begins and the molten steel level stabilizes, the fixing steel wire is cut, and the device is slowly lowered into the molten steel surface. After stabilization, it floats on the molten steel surface.

[0044] Comparative Example 2 uses a conventional casting method.

[0045] After the casting of a single high-alumina steel tank with an Al content of 4.0 wt%, the modification of the protective slag in Comparative Example 2 and Example 2 is shown in Table 2.

[0046] Table 2 shows the changes (wt%) in the chemical composition of the protective slag before and after the slag-steel reaction in Comparative Example 2 and Example 2.

[0047] CaO <![CDATA[Al2O3]]> <![CDATA[SiO2]]> <![CDATA[R2O]]> <![CDATA[Li2O]]> F <![CDATA[B2O3]]> MnO Comparative Example 2 +3.4 +16.4 -5.6 -6.9 +1.2 -4.7 -4.5 -3.1 Example 2 +2.1 +7.2 -2.1 -2.6 +0.9 -3.8 -3.1 -2.3

[0048] The comparison shows that the degree of deformation of the protective slag in the embodiment employing the device for suppressing the slag-steel reaction in continuous casting of high-alumina steel is much smaller than that in the comparative example. Furthermore, this invention is also applicable to cases where the protective slag is a liquid protective slag.

[0049] This invention adds a highly thermally conductive barrier device to the slag-steel contact surface. While maintaining thermal conductivity, it weakens the slag-steel reactivity by reducing the slag-steel contact area (especially for special steels that are reactive with the protective slag). The density of the device for suppressing the slag-steel reaction in continuous casting of high-alumina steel can be adjusted by adding or removing corundum. The density and barrier area ratio of the device are designed according to the density and reactivity of different protective slags, effectively reducing the reactivity between slag and steel during the continuous casting of high-alumina steel. The invention is simple to operate, has significant effects, and can meet the requirements of the high-alumina steel continuous casting process.

Claims

1. A method for suppressing the slag-steel reaction in continuously cast high-alumina steel, characterized in that, The device for suppressing the slag-steel reaction in continuous casting is connected to the lower surface of the outside of the tundish. After continuous casting begins and the molten steel level stabilizes, the device is disconnected from the tundish. The device slowly falls onto the surface of the molten steel and floats between the molten steel surface and the protective slag. The contact area between the device and the upper surface of the molten steel accounts for 20% to 80% of the total area of ​​the upper surface of the molten steel. The device for suppressing the slag-steel reaction in continuous casting is heated to 600 to 1400°C and then connected to the tundish. The device for suppressing the slag-steel reaction in continuously cast high-alumina steel includes an outer frame and a covering layer. The outer frame is covered by the covering layer, and the outer frame has through holes with the diameter of the through holes matching the outer diameter of the submersible nozzle. The outer frame is composed of a hollow thin plate and corundum filled inside the thin plate.

2. The method for suppressing the slag-steel reaction in continuously cast high-alumina steel according to claim 1, characterized in that, The device for suppressing the slag-steel reaction in continuously cast high-alumina steel is a geometric plate-like structure with a thickness ≤10mm.

3. The method for suppressing the slag-steel reaction in continuously cast high-alumina steel according to claim 1, characterized in that, The outer frame is connected to the lower surface of the outer side of the intermediate package by steel wire.

4. The method for suppressing the slag-steel reaction in continuously cast high-alumina steel according to claim 1, characterized in that, The thin plate is an SM2050 high-temperature alloy plate, and the volume ratio of the SM2050 high-temperature alloy plate to the corundum in the outer frame is (1~3):

1.

5. The method for suppressing the slag-steel reaction in continuously cast high-alumina steel according to claim 1, characterized in that, The thin plate is a titanium plate, and the volume ratio of the titanium plate to the corundum in the outer frame is (1~5):

2.

6. The method for suppressing the slag-steel reaction in continuously cast high-alumina steel according to claim 1, characterized in that, The method for preparing the coating includes the following steps: 1) Take a -200 mesh high thermal conductivity refractory material and grind it at a high speed of 4000~5000 r / min for 10~20 min to make fine powder; 2) The fine powder prepared in step 1) is sprayed onto the surface of the exoskeleton using plasma spraying or laser cladding.

7. The method for suppressing the slag-steel reaction in continuously cast high-alumina steel according to claim 6, characterized in that, The high thermal conductivity refractory material is one or more of molybdenum disilicide, hexagonal boron nitride, and titanium diboride.

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