Multi-stage synergistic self-repairing type composite enhanced converter slag-stopping sliding plate brick and preparation method thereof

Abstract

The invention discloses a multi-stage synergistic self-repairing type composite enhanced converter slag-stopping sliding plate brick and a preparation method thereof. The material is composed of zirconium system / corundum / spinel multi-scale aggregate, a boron system self-repairing reinforcement phase containing ZrB2, B4C and Al3BC3, a metal Si / Al in-situ hard phase generating agent and functional powder, and is prepared by adopting a normal-pressure sectional drying and high-temperature sintering process. In the service process, cracks are blocked through ZrO2 / B2O3 glass phases, the oxidation resistance, the wear resistance and the thermal shock resistance are improved through Al18B4O33 whisker bridging and SiC / Al4C3 and other in-situ hard phases, the service life of the sliding plate is remarkably prolonged (larger than or equal to 20 heat times), meanwhile, the low-heat-conductivity and low-energy-consumption processes are achieved, and the sliding plate is suitable for the fields of converter slag control and other high-temperature fire-resistant components.

Description

Technical Field

[0001] This invention relates to the field of metallurgical refractory materials and composite materials engineering, and in particular to a multi-level synergistic self-healing composite reinforced converter slag-blocking slide block and its preparation method. Background Technology

[0002] Converter slag-blocking slide block, as a key functional refractory material in converter steelmaking for achieving early slag avoidance and precise slag control in the middle and later stages, is subjected to extreme conditions such as high temperatures ≥1600℃, strong oxidizing slag systems (including FeO, MnO, etc.), high-speed molten steel scouring, and repeated thermal shock. Existing mainstream material systems have the following shortcomings:

[0003] Alumina-carbon sliding plate bricks: low cost and mature technology, but the carbon component oxidizes significantly at ≥520℃, and the strength decays rapidly at room temperature and high temperature; poor thermal shock stability, roughening of the plate surface and slag adhesion are prominent, and the service life is generally 12-15 heats.

[0004] Zirconium / zirconium-carbon sliding bricks: ZrO2 has a high melting point and good slag resistance; however, the raw materials are expensive, densification is difficult, and repeated thermal shock can easily cause through cracks, thus limiting the overall service life.

[0005] Silicon carbide / silicon nitride bonded materials: excellent high-temperature mechanical properties; however, the nitrogen-protected sintering process is complex, energy-intensive and costly, and they are easily oxidized and decomposed in molten iron or vacuum environments, making them unsuitable for repeated opening and closing of slide plates.

[0006] Ternary non-oxide reinforced (such as Al4SiC4): theoretically excellent performance, but requires strict proportioning and synthesis in an inert atmosphere at 1700–1800℃, resulting in high cost and oxidation decomposition starting at about 800℃, leading to insufficient service stability.

[0007] Common problems include: high-temperature oxidation and thermal shock leading to crack propagation and spalling; surface wear and the formation of low-melting-point substances leading to enhanced wetting and adhesion; low lifespan requiring frequent board replacements, affecting cycle time and safety; and high energy consumption and cost, which are not conducive to green manufacturing. Therefore, there is an urgent need for skateboard materials and processes that combine high wear resistance, high oxidation resistance, high thermal shock stability, low thermal conductivity, low cost, and green and replicable processes.

[0008] In summary, existing converter slag baffle brick materials are insufficient to meet the comprehensive requirements of long service life, excellent oxidation / thermal shock resistance, and green, low-cost manufacturing. There is an urgent need to develop a new material system to overcome these shortcomings. Summary of the Invention

[0009] In view of the problems existing in the above-mentioned multi-level synergistic self-healing composite reinforced converter slag-blocking slide block bricks, the present invention is proposed.

[0010] Therefore, the purpose of this invention is to provide a multi-level synergistic self-healing composite reinforced converter slag-blocking slide block and its preparation method. The purpose is to significantly improve the oxidation resistance, wear resistance and thermal shock resistance of the slide block under strong oxidation, high-speed scouring and repeated thermal shock conditions, and extend its service life to ≥20–24 heats.

[0011] By optimizing the formula and process, high-density sintering under normal pressure and simplifying the process can be achieved, reducing overall production costs and energy consumption, and meeting the requirements of green manufacturing.

[0012] A scalable composite functional refractory component platform has been developed, adaptable to various scenarios including iron oxide / alkaline slag systems and high-temperature, high-speed fluid scouring.

[0013] To achieve the above objectives, the present invention provides the following technical solution: a multi-level synergistic self-healing composite reinforced converter slag-blocking slide block, comprising:

[0014] Pellet (aggregate):

[0015] Fused zirconia alumina: 3–1 mm, w(Al2O3+ZrO2)≥98%, w(ZrO2)≥40%, 5–12 parts.

[0016] Sintered tabular corundum: 2–1 mm, w(Al2O3)≥99%, ρ≥3.50 g / cm³ 3 15–28 servings.

[0017] Fused zircon-mullite: bigradation of 1–0.5 mm and 0.5–0 mm, w(Al₂O₃) = 40–50%, w(ZrO₂) ≥ 33%, ρ ≈ 3.2 g / cm³ 3 5–20 parts; preferred two-stage ratio of 2:1 to optimize interface sealing and initial glass phase penetration.

[0018] Fused magnesium aluminum spinel particles: 1–0 mm, w(Al2O3)≥70%, w(MgO)≥20%, 8–18 parts.

[0019] Composite powders (reinforced and modified):

[0020] Fused magnesium aluminum spinel powder: 325 mesh, 8–20 parts.

[0021] Self-healing reinforcing phases (at least two types): ZrB2 (200–400 mesh, 2–6 parts), B4C (325 mesh, 0.5–2 parts), Al3BC3 (1–3 μm, 1–4 parts).

[0022] In-situ hard phase generating agent: metallic silicon powder (500 mesh, w(Si)≥99%, 2–5 parts), metallic aluminum powder (1000 mesh, w(Al)≥99%, 2–5 parts).

[0023] Functional powders: α-alumina micro powder (2 μm, w(Al2O3)≥99%, 5–10 parts), carbon black (N330, 25–30 nm, w(C)≥99%, 1–3 parts).

[0024] Additives (combined system):

[0025] High-temperature silicone resin: viscosity (25℃) 3500–4500 CP, addition amount accounts for 1.5–2.5% of the total mass of granules and composite powders.

[0026] Thermosetting phenolic resin: viscosity (25℃) 12000–15000 CP, w (C solid content) ≥50%, addition amount accounts for 3.0–4.0% of the total mass of granules and composite powder.

[0027] Key mechanisms and reaction control

[0028] Primary self-repair and antioxidant barrier:

[0029] ZrB2 oxidation: ZrB2 + O2 → ZrO2 + B2O3; The high melting point ZrO2 particles prevent crack propagation, while the glassy phase of B2O3 flows to seal microcracks and pores, forming a dense composite film that shields oxygen diffusion.

[0030] The atmosphere / temperature profile controls the volatilization rate of B2O3, ensuring that an appropriate amount remains in the service temperature range to continue its self-repairing function.

[0031] Secondary self-healing and toughening:

[0032] Al3BC3 decomposition: Al3BC3 → Al2O3 + B4C (further oxidation → B2O3); B2O3 and Al2O3 form an Al–B–O glass phase, and under suitable molar ratio and local oxygen partial pressure, Al18B4O33 whiskers are generated in situ, achieving bridging and restraint of cracks, crack deflection and energy dissipation.

[0033] In-situ hard phase reinforcement and liquid phase densification:

[0034] Si + C → SiC; Al + C → Al4C3 (controlling phase stability and environment); Al + O2 → Al2O3 protective film; molten Al phase (≥600℃) penetrates and densifies, and works synergistically with the glass phase to seal pores, improving wear resistance and erosion resistance.

[0035] Aggregate system synergy:

[0036] ZrO2 phase transformation toughening (t→m) achieves crack passivation and deflection during thermal cycling; spinel's low thermal expansion / high hardness disperses thermal stress and enhances resistance to chemical corrosion; tabular corundum's high-purity stable framework facilitates whisker growth and interfacial bonding.

[0037] Process flow and parameters

[0038] Premixing and mixing:

[0039] Granular material: Weigh and mix according to the mass fraction.

[0040] Composite powder: Dry mix with planetary vibrating high-energy ball mill for 25–35 min to ensure uniform dispersion of fine powder (controlling powder temperature rise and agglomeration).

[0041] High-speed mixing and storage: Mix with binder for 8–10 min until plasticized uniformly, and storage at 25°C and 50–60% relative humidity for 8–10 h to achieve resin impregnation and stress relaxation.

[0042] Molding and segmented drying:

[0043] Hydraulic forming: ≥2000–2500 tons of pressure is used to form blanks with uniform density.

[0044] Segmented drying: After natural cooling for 24 hours, the temperature is increased to 110℃ at a rate of 30℃ / h and held for 20 hours; then increased to 210℃ at a rate of 30℃ / h and held for 24 hours. The segmented platform is used to optimize resin curing and adhesive removal, avoiding internal stress and microcracks.

[0045] Atmospheric pressure sintering and post-treatment:

[0046] Sintering: Hold at 1650–1750℃ for 4–6 h, and adjust the atmosphere / curve to achieve in-situ generation of self-healing film and whiskers, avoiding excessive loss of carbon phase due to over-oxidation.

[0047] Steel hoop: Q235 cold-rolled steel hoop (6 mm thick, 35 mm wide) hot-fitted to suppress crack propagation and edge stress concentration.

[0048] Precision grinding and coating: The working surface is precision ground by CNC grinding machine to a flatness of ≤0.03 mm; a high-temperature resistant coating is applied and dried in infrared to reduce initial wetting and wear.

[0049] Performance metrics:

[0050] Bulk density ≥3.15–3.22 g / cm³ 3 Apparent porosity ≤ 3.5%.

[0051] Compressive strength at 110℃ ≥200–240 MPa; Flexural strength at 1400℃ / 0.5 h ≥40–50 MPa.

[0052] Antioxidant activity (oxidation area after 1400℃×3 h bare calcination) ≤12–16%.

[0053] The flatness of the plate is ≤0.03 mm; the thermal conductivity (1200℃) is ≤5.0 W / (m·K).

[0054] Service life ≥ 20–24 heats (depending on operating conditions).

[0055] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0056] 1. This invention utilizes the oxidation of borides such as ZrB2 and B4C to form a ZrO2 / B2O3 flowing glass phase at high temperature, which can rapidly seal microcracks; simultaneously, Al3BC3 is decomposed in situ to generate Al 18 B4O 33 Whiskers act as bridges, deflects, and pins the crack tips. This multi-level repair mechanism of "glass phase sealing + whisker bridging" effectively inhibits crack propagation and spalling, enabling the service life of the slide block brick to stably reach more than 20 furnace cycles under harsh working conditions, which is more than 1.5 times that of traditional slide blocks.

[0057] 2. By introducing metallic Si / Al powder, high-hardness particles such as SiC and Al4C3 are generated in situ during the sintering process through reaction with carbon. These particles are then combined with aggregates such as zirconium corundum and spinel in the formula, significantly improving the hardness, wear resistance, and resistance to molten steel erosion of the working surface. Simultaneously, the ZrO2 / B2O3 composite film formed by ZrB2 oxidation and the dense Al2O3 layer formed by Al powder oxidation together construct a multi-layered physical barrier, effectively blocking oxygen erosion and exhibiting superior oxidation resistance.

[0058] 3. This invention employs an atmospheric pressure sintering process, replacing some of the nitrogen protection or hot-pressing sintering required for high-performance materials, significantly simplifying equipment requirements and reducing energy consumption. The innovative segmented drying and sintering curve design optimizes resin curing, binder removal, and internal reaction processes, shortening the production cycle, improving yield and performance consistency, and effectively controlling overall manufacturing costs while enhancing product performance.

[0059] 4. The material of this invention has a thermal conductivity as low as 5.0 W / (m·K) at 1200℃, which reduces heat loss, decreases the temperature gradient and thermal stress inside the brick, and thus improves thermal shock resistance. The low thermal conductivity and smooth anti-oxidation layer together reduce the wettability of steel slag, reduce slag adhesion and abnormal hole enlargement in the working hole, and ensure the accuracy and stability of slag blocking operation. Detailed Implementation

[0060] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0061] The ratios of ZrB2, B4C, and Si / Al are finely adjusted based on the slag system (FeO, MnO, CaO / SiO2 ratio, viscosity) to balance the self-healing glass phase, whisker formation, and hard phase content. ZrB2 and B4C are stored in sealed containers with low humidity; metal powder is protected from prolonged air exposure; ball milling controls the filling rate and ball-to-material ratio to prevent over-milling and agglomeration. Sintering employs a three-stage heating / isothermal platform to regulate the formation and penetration depth of the glass phase, and to balance whisker growth and surface / internal densification.

[0062] Example 1

[0063] This embodiment aims to provide a standard composite system for sliding tile bricks, the formulation and process of which are as follows:

[0064] Granular material (parts): fused zirconia alumina 7; tabular alumina 22; zirconia mullite 1–0.5mm 12; zirconia mullite 0.5–0mm 6; spinel particles 14.

[0065] Composite powder (parts): spinel powder 14; ZrB2=4; Al3BC3=2; B4C=1; metallic silicon 3; metallic aluminum 3; α-Al2O3 7; carbon black 2.

[0066] Additives (%): Organosilicon 2.0%; Phenolic resin 3.5%.

[0067] Process: Premixed ball milling for 30 min → mixing for 9 min → acclimation for 9 h → molding with a 2500-ton hydraulic press → segmented drying (110℃×20 h; 210℃×24 h) → sintering at 1700℃×5 h → steel hoop heat fitting → CNC precision grinding and anti-oxidation coating.

[0068] Performance: ρ = 3.18 g / cm³ 3 P o =3.0%, σc=225MPa, σb=44MPa, oxidation area=12%, λ(1200℃)=4.6W / (m·K), lifespan=21 furnace cycles.

[0069] Usage morphology: The casting hole is uniformly enlarged, the plate surface is slightly oxidized, the sliding surface is smooth with little roughness and no obvious peeling.

[0070] Example 2

[0071] This embodiment aims to provide a skateboard brick with enhanced antioxidant properties, whose formula and process are adjusted based on Example 1 as follows:

[0072] Adjustments: ZrB2=5, Al3BC3=3, B4C=1.5, spinel powder=12, metallic silicon=2, metallic aluminum=2.

[0073] Sintering: 1680℃×6h, with a moderate increase in oxygen partial pressure to guide the formation of a continuous ZrO2 / B2O3 film and a suitable amount of residue.

[0074] Performance: ρ = 3.19 g / cm³ 3 P O =2.9%, σc=238MPa, σb=48MPa, oxidation area=11%, λ(1200℃)=4.4W / (m·K), lifespan=22 furnace cycles.

[0075] Microstructure: The surface is continuously covered by a glass film and an oxide film; Al is visible at the interface. 18 B4O 33 Whisker distribution and bridging.

[0076] Example 3

[0077] This embodiment aims to provide a wear-resistant and erosion-resistant sliding plate brick, the formula and process of which are adjusted based on Example 1 as follows:

[0078] Adjustments: Silicon metal = 4, Aluminum metal = 4 (in-situ hard phase reinforcement), ZrB2 = 3, B4C = 1; Spinel powder = 10; α-Al2O3 = 8.

[0079] Sintering: 1720℃×4.5h, to control the in-situ growth and distribution of the surface hard phase.

[0080] Performance: ρ = 3.17 g / cm³ 3 P O =2.7%, σc=223MPa, σb=42MPa, oxidation area=12%, λ(1200℃)=4.8W / (m·K), lifespan=24 furnaces.

[0081] Mechanism: In-situ formation of SiC / Al4C3 improves the hardness and erosion resistance of the plate surface, while reducing the coefficient of friction and wettability.

[0082] Example 4

[0083] This embodiment aims to provide a thermally shock-resistant, stable sliding block, whose formula and process are adjusted based on Example 1 as follows:

[0084] Adjustments: Zircon mullite only 1–0.5mm=10, no 0.5–0mm; ZrB2=3, Al3BC3=2, B4C=1.

[0085] Performance: ρ = 3.16 g / cm³ 3 P O =3.6%, σc=228MPa, σb=45MPa, oxidation area=12%, λ(1200℃)=4.7W / (m·K), lifespan=19–20 heats.

[0086] Evaluation: The absence of small-sized zircon mullite reduces interfacial blocking and initial glass phase penetration, and slightly decreases thermal shock resistance; it is recommended to retain the two-stage gradation to improve overall performance.

[0087] Comparative Example 1 (without Si / Al metal)

[0088] Differences: Remove metallic silicon and metallic aluminum; otherwise, it is the same as in Example 1.

[0089] Result: ρ = 2.97 g / cm³ 3 P O =10%, σc=146 MPa, σb=23 MPa, oxidation area=30%, λ(1200℃)=6.2 W / (m·K), lifespan=12–14 furnaces.

[0090] Cause: The absence of in-situ hard phase and oxide film results in poor density and a significant decrease in wear resistance and oxidation resistance.

[0091] Comparative Example 2 (without B4C / Al3BC3, TiC / metallic Ti was used instead)

[0092] Differences: B4C and Al3BC3 were removed, and TiC=2 and metallic Ti=3 were added.

[0093] Result: ρ = 3.18 g / cm³ 3 P O =3.1%, σc=221 MPa, σb=36 MPa, oxidation area=13%, λ(1200℃)=5.3 W / (m·K), lifespan=15–18 heats.

[0094] Reasons: TiC easily forms an oxidized and decarburized layer in oxidizing molten steel, resulting in a loose structure, cracks, and spalling; the lack of boron-based self-healing means that cracks cannot be effectively sealed and bridged.

[0095] Example Preparation Index Parameters

[0096]

[0097] Overall, the performance of the examples was better than that of the comparative samples:

[0098] Density and porosity: The bulk density of the examples was maintained at 3.16–3.19 g / cm³. 3 The apparent porosity of the sample was ≤3.6%; the apparent porosity of the comparative sample could be increased to about 10%, indicating insufficient densification.

[0099] Mechanical properties: The high-temperature flexural strength of the example sample can reach 42–48 MPa; the comparative sample drops to 23–36 MPa, and the high-temperature load-bearing capacity is significantly reduced.

[0100] Antioxidant properties: In the example, the oxidation area during bare firing (1400℃×3h) was ≤11–12%; the oxidation area of ​​the comparative sample increased to 13–30%, with obvious problems of surface peeling and slag adhesion.

[0101] Thermal conductivity: The thermal conductivity of the examples (1200°C) was controlled at approximately 4.4–4.8 W / (m·K), which is beneficial for reducing temperature gradient and thermal stress; the thermal conductivity of the comparative samples increased to approximately 5.3–6.2 W / (m·K). Service life: The examples achieved a service life of 21–24 heats under industrial / simulated conditions; the comparative samples only achieved a service life of 12–18 heats.

[0102] Conclusion: Examples 1-3 are significantly superior to the comparative samples in key indicators such as bulk density, porosity, high-temperature strength, oxidation resistance, thermal conductivity and actual furnace life, especially in terms of service life (≥21 furnaces) and oxidation resistance (≤12% of bare calcined oxidation area). Among them, Comparative Example 1 (without Si / Al) performed the worst due to insufficient densification. Although Comparative Example 2 (with boron-based self-healing phase replacement) can achieve a high density, its oxidation resistance and self-healing function are insufficient, and its overall service life is moderate to low.

[0103] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A multi-level synergistic self-healing composite reinforced converter slag-blocking slide block, characterized in that, Its raw materials, by weight, include: Granular material; Composite powders; and Additives; The composite powder comprises: (a) A self-healing reinforcing phase selected from at least two of zirconium diboride (ZrB2), boron carbide (B4C), and boron trialuminum tricarbide (Al3BC3); and (b) In-situ hard phase generating agents, including metallic silicon powder and metallic aluminum powder.

2. The multi-level synergistic self-healing composite reinforced converter slag-blocking slide block according to claim 1, characterized in that, The granular material comprises: 5-12 parts of fused zirconium corundum, 15-28 parts of sintered tabular corundum, 5-20 parts of fused zirconium mullite, and 8-18 parts of fused magnesium aluminum spinel particles.

3. The multi-level synergistic self-healing composite reinforced converter slag-blocking slide block according to claim 1 or 2, characterized in that, The composite powder also includes: 8-20 parts of fused magnesium aluminum spinel powder, 5-10 parts of α-alumina micro powder, and 1-3 parts of carbon black.

4. The multi-level synergistic self-healing composite reinforced converter slag-blocking slide block according to claim 1, characterized in that, The self-healing reinforcing phase comprises: 2-6 parts of zirconium diboride (ZrB2), 0.5-2 parts of boron carbide (B4C), and 1-4 parts of boron trialuminum tricarbide (Al3BC3).

5. The multi-level synergistic self-healing composite reinforced converter slag-blocking slide block according to claim 1, characterized in that, The in-situ hard phase generating agent comprises: 2-5 parts of metallic silicon powder and 2-5 parts of metallic aluminum powder.

6. The multi-level synergistic self-healing composite reinforced converter slag-blocking slide block according to claim 1, characterized in that, The additives include high-temperature silicone resin and thermosetting phenolic resin; wherein the amount of high-temperature silicone resin added accounts for 1.5-2.5% of the total mass of the granules and composite powder, and the amount of thermosetting phenolic resin added accounts for 3.0-4.0% of the total mass of the granules and composite powder.

7. The multi-level synergistic self-healing composite reinforced converter slag-blocking slide block according to claim 2, characterized in that, The fused zircon mullite is produced using bi-graded particles of 1-0.5 mm and 0.5-0 mm.

8. The multi-level synergistic self-healing composite reinforced converter slag-blocking slide block according to claim 1, characterized in that, The bulk density of the sintered product is not less than 3.15 g / cm³. 3 The apparent porosity is not higher than 3.5%.

9. The multi-level synergistic self-healing composite reinforced converter slag-blocking slide block according to claim 1, characterized in that, Its high-temperature flexural strength after being kept at 1400℃ for 0.5 hours is not less than 40 MPa.

10. The preparation method of the multi-level synergistic self-healing composite reinforced converter slag-blocking slide block according to any one of claims 1-9, characterized in that, Includes the following steps: S1. Mix the granular material, composite powder and additives evenly, and then allow the mixture to settle. S2. Press the trapped material into a blank using a press. S3. The blank is dried in stages, which includes holding at 110°C and then holding at 210°C. S4. The dried blank is sintered at atmospheric pressure at a temperature of 1650-1750℃.

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