Electromagnetic induction heating tundish steel flow channel refractory material for thin strip cast rolling

Abstract

The invention relates to the technical field of metallurgical refractory materials, and provides an electromagnetic induction heating tundish steel flow channel refractory material for thin strip cast rolling, which is composed of the following components in percentage by mass: 0% < Al2O3 < = 5%, 0% < SiC < = 8%, and the balance of MgO and inevitable impurities. According to the technical scheme, the problems of poor thermal shock resistance, fire resistance and scouring resistance of the refractory material of the steel flowing channel in the related technology are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of metallurgical refractory materials, and in particular to a refractory material for electromagnetic induction heating of a tundish flow steel channel for thin strip casting and rolling. Background Art

[0002] Thin strip casting is a new type of strip steel production technology, representing the cutting-edge of metallurgy and materials research. Its principle involves injecting molten metal between a pair of counter-rotating, water-cooled casting rollers, where it solidifies to form a cast strip. Due to the unique characteristics of the thin strip casting process, the casting superheat of the tundish is approximately 80-100°C, 70°C higher than that of conventional production lines. Furthermore, the production line utilizes electromagnetic induction heating. The skin effect of the current induces currents on the surface of the steel stream within the channel, further increasing the surface temperature of the molten steel. Software simulations have shown that this temperature can reach as high as 1750°C as the induction heating power increases, significantly exceeding the tolerance of traditional refractory materials.

[0003] Furthermore, the flow channels of the electromagnetic induction-heated tundish are difficult to bake during the baking process, resulting in poor baking results. The baking temperature is relatively low, around 600°C, while the casting molten steel temperature is approximately 1660-1680°C. The flow channels are subject to rapid temperature fluctuations in a very short period of time, making them susceptible to thermal shock damage. Furthermore, the skin effect and pinch effect generated by the electromagnetic field can cause localized temperatures in the flow channels to rise above 1750°C, eroding the channels and damaging the refractory materials. Therefore, the flow channels must possess excellent thermal shock resistance, high refractoriness, and erosion resistance. Summary of the Invention

[0004] The present invention provides a refractory material for a steel flow channel of an electromagnetic induction heating tundish for thin strip casting and rolling, which solves the problem of poor thermal shock resistance, fire resistance and erosion resistance of the steel flow channel refractory material in the related art.

[0005] The technical solutions of the present invention are as follows: A refractory material for an electromagnetic induction-heated tundish flow steel channel for thin strip casting and rolling is composed of the following components in percentage by mass: 0% < Al2O3 ≤ 5%, 0% < SiC ≤ 8%, and the remainder being MgO and unavoidable impurities.

[0006] Eliminating Al2O3 will reduce the slag erosion resistance, but adding a large amount will cause volume expansion, resulting in poor thermal shock resistance. Therefore, the addition amount needs to be appropriate. Through experiments, it is determined that it is more appropriate to control the addition amount of Al2O3 to less than 5%. Since MgO+Al2O3→MA spinel, the volume expands by 8%, which greatly reduces the thermal shock resistance. When the addition amount is less than 5%, the expansion is small and the expansion can fill the pores in the material to densify the material structure. The slag is not easy to penetrate, and the material has better slag resistance.

[0007] As a further technical solution, in terms of mass percentage, 5%≤SiC≤8%.

[0008] The electromagnetic induction heating tundish flow steel channel refractory material for thin strip casting and rolling of the present invention undergoes the following reactions during the production process: SiC+MgO+[O]→2MgO•SiO2+CO; The forsterite (2MgO•SiO2) generated by the reaction has a high melting point of about 1890℃, and can adhere to the surface of the flow steel channel to further resist erosion. However, too much forsterite (2MgO•SiO2) will cause a loose structure. Experimental research found that when the addition of SiC is controlled at 5%~8%, the performance of the refractory material is optimal.

[0009] As a further technical solution, MgO is introduced in the form of fused magnesia.

[0010] As a further technical solution, the particle size of the fused magnesia is 1-5 mm.

[0011] As a further technical solution, it is composed of the following components in mass percentage: Al2O3: 3%, SiC: 5%, and the rest are MgO and inevitable impurities.

[0012] In the electromagnetic induction heating tundish flow steel channel refractory material for thin strip casting and rolling of the present invention, magnesium oxide is introduced in the form of fused magnesia. In addition to magnesium oxide, the fused magnesia also contains other inevitable impurities such as calcium oxide, silicon dioxide, and ferric oxide.

[0013] As a further technical solution, the product is made by gel casting or pouring molding.

[0014] As a further technical solution, the linear change rate of the refractory material at 1500°C×3h is ≤0.50%.

[0015] As a further technical solution, the bulk density of the refractory material is ≥2.80 g / cm 3 .

[0016] As a further technical solution, the compressive strength of the refractory material at 110°C×24h is ≥72.4MPa.

[0017] As a further technical solution, the 110°C×24h flexural strength of the refractory material is ≥12.53MPa.

[0018] The working principle and beneficial effects of the present invention are: The present invention utilizes magnesia refractory materials for the steel flow channel, offering advantages such as high refractoriness, excellent resistance to alkaline slag corrosion, and abundant raw material resources. Furthermore, by optimizing the refractory composition to 0% by mass <5% Al₂O₃ and 0% by mass <8% SiC, with the remainder consisting of MgO and unavoidable impurities, its thermal shock resistance is enhanced, thereby increasing the tundish's service life, saving production costs, and improving casting continuity (the continuous casting time for the tundish steel flow channel is increased from 4-5 hours to 12 hours), thereby increasing production efficiency and yield. Silicon carbide (SiC) has a high melting point (above 2600°C) and excellent high-temperature resistance, making it stable in high-temperature environments. Its low coefficient of thermal expansion makes SiC less susceptible to cracking due to thermal stress at high temperatures. SiC also acts as a binder to enhance the refractory's cohesiveness. Furthermore, its high thermal conductivity facilitates rapid heat dissipation, reducing heat accumulation and temperature gradients, thereby enhancing the material's thermal shock resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] Figure 1 It is the ternary phase diagram of MgO-SiO2-Al2O3; Figure 2 This is a graph showing cracks and steel leakage in the flow channel after the refractory material is applied in Comparative Example 2; Figure 3 This is the flow steel channel diagram; Figure 4 This is a diagram of the steel flow channel after the refractory material is applied in Example 1. DETAILED DESCRIPTION

[0021] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0022] Depend on Figure 1 It can be seen from the MgO-SiO2-Al2O3 ternary phase diagram that magnesia refractory materials can withstand high temperatures of up to 2000°C, aluminum refractory materials can withstand high temperatures up to 2000°C, and silicon refractory materials can withstand high temperatures up to 1900°C. Therefore, the present invention uses magnesia refractory materials.

[0023] In the following examples and comparative examples: MgO is introduced in the form of fused magnesia; The particle size of fused magnesia is 1-3 mm, including MgO: 96.5 wt%, CaO: 1.8 wt%, SiO2: 0.65 wt%, lgL: 0.1 wt%, Fe2O3: 0.75 wt%, Al2O3: 0.2 wt%, purchased from Haicheng Yushan Import and Export Trading Co., Ltd. Al2O3 is introduced in the form of alumina, and the purity of alumina is 99.99%; SiC is introduced in the form of silicon carbide with a purity of 99.9%.

[0024] Example 1 The electromagnetic induction heating tundish flow steel channel refractory material is composed of the following components in percentage by mass: Al2O3: 3%, SiC: 6.68%, and the rest is MgO and inevitable impurities; Preparation method: According to the above target composition, fused magnesia, alumina and silicon carbide are mixed, cast into shape, and baked at 400°C for 48 hours to obtain the product.

[0025] Example 2 The electromagnetic induction heating tundish flow steel channel refractory material is composed of the following components in mass percentage: Al2O3: 1%, SiC: 8%, and the rest is MgO and inevitable impurities; Preparation method: According to the above target composition, fused magnesia, alumina and silicon carbide are mixed, cast into shape, and baked at 400°C for 48 hours to obtain the product.

[0026] Example 3 The electromagnetic induction heating tundish flow steel channel refractory material is composed of the following components in mass percentage: Al2O3: 5%, SiC: 1%, and the rest is MgO and inevitable impurities; Preparation method: According to the above target composition, fused magnesia, alumina and silicon carbide are mixed, cast into shape, and baked at 400°C for 48 hours to obtain the product.

[0027] Example 4 The only difference from Example 1 is that it is composed of the following components in mass percentage: Al2O3: 3%, SiC: 8%, and the rest is MgO and inevitable impurities.

[0028] Example 5 The only difference from Example 1 is that it is composed of the following components in mass percentage: Al2O3: 3%, SiC: 5%, and the rest is MgO and inevitable impurities.

[0029] Example 6 The only difference from Example 1 is that it is composed of the following components in mass percentage: Al2O3: 3%, SiC: 3%, and the rest is MgO and inevitable impurities.

[0030] Comparative Example 1 The only difference from Example 1 is that it is composed of the following components in mass percentage: Al2O3: 3%, SiC: 9%, and the rest is MgO and inevitable impurities.

[0031] Comparative Example 2 The electromagnetic induction heating tundish flow steel channel refractory material is composed of the following components in percentage by mass: Al2O3: 5%, SiO2: 1%, C: 3%, and the rest is MgO and inevitable impurities; Preparation method: According to the above target composition, fused magnesia, alumina, silica and phenolic resin are mixed, cast into shape, and baked at 400°C for 48 hours to obtain the product.

[0032] Comparative Example 3 The electromagnetic induction heating tundish flow steel channel refractory material is composed of the following components in mass percentage: SiO2: 6%, C: 3%, and the rest is MgO and inevitable impurities; Preparation method: According to the above target composition, fused magnesia, silicon dioxide and phenolic resin are mixed, cast into shape, and baked at 400°C for 48 hours to obtain the product.

[0033] The refractory materials obtained in Examples 1 to 6 and Comparative Examples 1 to 3 were subjected to the following performance tests: (1) Thermal shock resistance: Refer to GB / T 5988-2022 "Test method for permanent linear change of refractory materials upon heating" and test the permanent linear change upon heating (1500℃×3h); (2) Bulk density: Refer to GB / T 2999-2016 “Test method for bulk density of refractory particles”, in which method 2 is selected for the determination of sample volume; (3) Compressive strength (110℃×24h): Refer to GB / T 5072-2023 "Test method for compressive strength of refractory materials at room temperature"; (4) Flexural strength (110°C × 24h): Refer to GB / T 3001-2017 “Test method for flexural strength of refractory materials at room temperature”; The test results are recorded in Table 1.

[0034] Table 1 Test results of various properties of refractory materials

[0035] As can be seen from Table 1, the linear change rate of the refractory materials obtained in Examples 1 to 6 is lower than that in Comparative Examples 1 to 3, and the bulk density, compressive strength and flexural strength are higher than those in Comparative Examples 1 to 3, indicating that the present invention improves the thermal shock resistance, compressive strength and flexural strength by optimizing the composition of the refractory material to 0% < Al2O3 ≤ 5%, 0% < SiC ≤ 8% by mass, with the remainder being MgO and unavoidable impurities.

[0036] According to Comparative Example 2, it can be seen that although Al2O3 can improve the slag corrosion resistance, the reaction of Al2O3 with MgO (Al2O3+MgO=MgO•Al2O3) to generate magnesium aluminum spinel will cause an 8% volume expansion, resulting in poor thermal shock resistance and easy fracture of the flow steel channel. Therefore, Al2O3 is eliminated, and the optimized flow steel channel refractory material is shown in Comparative Example 3. After multiple experiments, the optimized flow steel channel still has poor thermal shock resistance and worse corrosion resistance than before. This is mainly because although SiO2 can improve the compressive strength, excessive SiO2 addition will react with MgO to generate forsterite (2MgO•SiO2), causing a loose structure, which is not conducive to the sintering densification of the material, but instead causes a decrease in compressive strength.

[0037] In addition, compared with magnesia refractories, although Al2O3 corundum refractories with a purity of 95% have good thermal shock resistance, due to the particularity of the steel grade, there are silica inclusions in the steel grade. The corundum refractory material will react with the molten steel to form aluminum silicate, which has a melting point of about 1550°C. The local temperature of the tundish is about 1750°C, which will cause severe erosion.

[0038] Application examples: The refractory materials obtained in each embodiment and each comparative example were respectively applied to thin strip casting and rolling: the thin strip casting and rolling process is as follows: the tundish is baked to 900-1100°C before pouring, the steel flow channel (such as Figure 3 The temperature (as shown) is approximately 400-600°C, and the upper steel temperature of the ladle is 1660-1680°C. After the ladle begins pouring, molten steel enters the tundish casting chamber through the ladle's long nozzle. Two channels for electromagnetic induction heating are symmetrically embedded in the tundish's bottom, connecting the tundish's casting chamber and distribution chamber. The distribution chamber and casting chamber are separated by a refractory wall. An iron core is positioned outside the channels, with coils wound around one side of the core. Molten steel flows from the casting chamber through two flow channels into the distribution chamber, then through the tundish outlet into the distribution ladle. Within the flow channels, the molten steel is heated by electromagnetic induction heaters. When the molten steel temperature in the tundish falls below 1615°C, electromagnetic induction heating is activated to heat or maintain the molten steel.

[0039] In the electromagnetic induction heating tundish, the temperature rise of the unit volume of molten steel in the channel per unit time can be expressed by the formula MC pΔT=PΔt Where: M is the mass of the heated molten steel in the channel, kg; C p is the heat capacity of molten steel, J / (kg•℃); P is the input power of electromagnetic induction heating, W; Δt is the heating time, s; ΔT is the change of molten steel temperature, ℃. In addition, under the skin effect of the electromagnetic field of electromagnetic induction heating, the local temperature of the downstream steel channel is as high as 1750℃.

[0040] After application, it was found that the flow channel of the tundish in Comparative Examples 1 to 3 (the flow channel of Comparative Example 2 is shown in FIG. Figure 2 As shown in the figure, after about 4 to 5 hours of casting, the pouring was stopped and cracks, leakage, and peeling appeared in the steel flow channel. Figure 4 It can continuously cast for 12 hours, which increases the service life of the tundish, saves production costs, and improves casting continuity, production efficiency and yield rate.

[0041] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A refractory material for electromagnetic induction heating of tundish flow steel channel for thin strip casting, characterized in that: It is composed of the following components in mass percentage: 0%<Al2O3≤5%, 0%<SiC≤8%, and the rest are MgO and inevitable impurities.

2. The electromagnetic induction heating tundish flow steel channel refractory material for thin strip casting and rolling according to claim 1, characterized in that: In terms of mass percentage, 5%≤SiC≤8%.

3. The electromagnetic induction heating tundish flow steel channel refractory material for thin strip casting and rolling according to claim 1, characterized in that: MgO is introduced in the form of fused magnesia.

4. The electromagnetic induction heating tundish flow steel channel refractory material for thin strip casting and rolling according to claim 3, characterized in that: The particle size of the fused magnesia is 1-5 mm.

5. The electromagnetic induction heating tundish flow steel channel refractory material for thin strip casting and rolling according to claim 3 or 4, characterized in that: It is composed of the following components in mass percentage: Al2O3: 3%, SiC: 5%, and the rest are MgO and inevitable impurities.

6. The electromagnetic induction heating tundish flow steel channel refractory material for thin strip casting and rolling according to claim 1, characterized in that: It is made by gel casting or pouring molding.

7. The electromagnetic induction heating tundish flow steel channel refractory material for thin strip casting and rolling according to claim 1, characterized in that: 1500℃×3h linear change rate ≤0.50%.

8. The electromagnetic induction heating tundish flow steel channel refractory material for thin strip casting and rolling according to claim 1, characterized in that: Bulk density ≥2.80g / cm 3 .

9. The electromagnetic induction heating tundish flow steel channel refractory material for thin strip casting and rolling according to claim 1, characterized in that: 110℃×24h compressive strength ≥72.4MPa.

10. The electromagnetic induction heating tundish flow steel channel refractory material for thin strip casting and rolling according to claim 1, characterized in that: 110℃×24h flexural strength ≥12.53MPa.

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