In the complex operating conditions of steel rolling heating furnaces, especially pusher-type heating furnaces with side-discharging, tap channel bricks, as key components, are subjected to multiple challenges, including high temperatures, wear, and chemical corrosion. Their performance directly impacts the efficiency and cost of steel rolling production. Chrome corundum tap channel bricks, due to their superior comprehensive performance, have become one of the preferred materials in the modern steel rolling industry. This article will provide an in-depth analysis of their characteristics, application scenarios, purchasing considerations, and key maintenance points, providing a comprehensive technical reference for relevant practitioners.

I. Performance Advantages of Chrome Corundum Tap Channel Bricks:

1.1 High-Temperature Resistance

Chrome corundum tap channel bricks are primarily composed of α-Al₂O₃, with an appropriate amount of Cr₂O₃ added. They are sintered at high temperatures to form a stable crystal structure. Its refractoriness exceeds 1900°C and it maintains structural stability at long-term operating temperatures of 1650-1700°C, meeting the high-temperature requirements of steel-rolling reheating furnaces during tapping.

1.2 Wear Resistance

The addition of Cr₂O₃ forms an extremely hard Al₂O₃-Cr₂O₃ solid solution, achieving a Mohs hardness of 8.5-9, significantly improving the brick's wear resistance. During the tapping process, the steel billet frequently rubs against the surface of the tapping trough bricks, causing wear to occur easily with ordinary refractory bricks. However, chrome-corundum tapping trough bricks have a significantly lower wear rate. According to actual application data, their wear resistance is 2-3 times that of ordinary corundum bricks, significantly extending the service life of the tapping trough and reducing the frequency of replacement.

1.3 Thermal Shock Resistance

During the production process of steel-rolling reheating furnaces, the tapping trough experiences frequent temperature fluctuations. Thermal shock stress can easily cause cracking and spalling of the bricks. Chrome corundum tap channel bricks have been optimized through formulation and production processes, including the introduction of ZrO₂ microcrack toughening technology, effectively improving their thermal shock resistance. Testing has shown that under 1100°C water-cooled cycling conditions, they exhibit thermal shock stability exceeding 15 times, ensuring stable operation even under drastic temperature fluctuations.

1.4 Corrosion Resistance

Slag formed by iron oxide scale is highly corrosive to tap channel bricks. Chrome corundum tap channel bricks exhibit excellent corrosion resistance against slag containing components such as FeO and CaO. Their apparent porosity is controlled between 6% and 12%, with a high proportion of closed pores, effectively preventing slag penetration and reducing the risk of chemical attack.

II. Application Scenarios and Advantages:

2.1 Tap Channel Lining

The tap channel is a critical passage for billets from the heating furnace into the rolling mill. Chrome corundum tap channel bricks primarily withstand the sliding friction of billets at temperatures between 1100 and 1250°C, as well as the erosion of iron oxide scale and fuel ash. Their excellent wear and corrosion resistance ensures the smoothness of the tap channel surface, reduces scratches on the billet surface, and improves steel quality. Furthermore, their long lifespan reduces downtime and maintenance due to channel wear, thereby improving production efficiency.

2.2 Slide Rail Support Sections

In walking beam reheating furnaces, the slide rail support sections must support the reciprocating motion of hot billets, placing extremely high demands on the bricks for compressive strength and high-temperature resistance. Chrome corundum tap channel bricks, with a compressive strength of ≥150 MPa, provide stable support for the billets and resist deformation at high temperatures, ensuring proper operation of the slide rails and smooth transport of billets within the reheating furnace.

2.3 Taphole Transition Zone

The taphole transition zone is frequently exposed to high-temperature airflow and billet impact, resulting in drastic temperature fluctuations. Chrome corundum taphole bricks' excellent thermal shock resistance makes them suitable for these harsh operating conditions, effectively reducing damage to the bricks caused by thermal shock, ensuring the structural integrity of the taphole and guaranteeing smooth tapping operations.

III. Key Points for Purchasing and Ordering:

3.1 Performance Index Verification

3.1.1 Chemical Composition: Al₂O₃ content should be ≥ 92%, Cr₂O₃ content should be between 3% and 15%, and impurity levels such as Fe₂O₃ ≤ 0.3% and SiO₂ ≤ 1.0% should be strictly controlled to prevent the formation of low-melting-point phases that could affect brick performance. Suppliers should be required to provide chemical composition test reports when purchasing.

3.1.2 Physical Properties: Bulk density ≥ 3.25 g/cm³ to ensure brick compactness; room temperature compressive strength ≥ 180 MPa, high temperature flexural strength (1250°C) ≥ 9.5 MPa to ensure structural strength under high temperature and pressure; refraction under load temperature (0.2 MPa T0.6) ≥ 1680°C to meet high-temperature requirements.

3.2 Dimensional Accuracy

The dimensional accuracy of channel bricks directly impacts masonry quality and performance. Deviations in length, width, and height should be controlled within ±1 mm, and diagonal deviations ≤ 2 mm. For special-shaped bricks, such as curved bricks, radius tolerances must be kept to a minimum to ensure precise alignment with the heating furnace channel. When purchasing, suppliers should be requested to provide detailed dimensional inspection reports and conduct on-site spot checks.

3.3 Production Process Review

Preferably select suppliers that utilize advanced production processes, such as isostatic pressing, which ensures uniform green body density; and high-temperature sintering (≥1750°C), which ensures full dissolution of Cr₂O₃ and improves brick performance. Furthermore, understand the supplier's quality control system to ensure consistent product quality.

3.4 Quality Certification and Testing

Suppliers should provide relevant quality certifications, such as ISO 9001 quality management system certification. Each batch of products should be accompanied by a test report from a third-party testing agency. Test items include key indicators such as apparent porosity and refire line change rate. If necessary, a professional organization may be commissioned to conduct random inspections of products.

IV. Maintenance Key Points:

4.1 Daily Inspection

Perform regular visual inspections of the steel channel bricks to check for cracking, flaking, wear, and other signs of wear. Use infrared thermal imaging to monitor the surface temperature distribution of the bricks to promptly identify abnormal temperature areas caused by localized corrosion, allowing for proactive repair or replacement.

4.2 Surface Cleaning

After each heat cycle, the tap channel bricks are cleaned with high-pressure water (80-100 MPa) to remove attached scale and slag, prevent their accumulation on the brick surface, and reduce the risk of slag erosion. Care should also be taken to avoid damaging the brick surface during the cleaning process.

4.3 Hot Maintenance

During heating furnace operation, the furnace pressure and temperature change rate must be strictly controlled to prevent excessive thermal stress on the tap channel bricks caused by cold air inhalation at the taphole or rapid temperature fluctuations. Minor damage can be repaired hot with a dedicated refractory patching compound to promptly restore brick integrity and extend service life.

Chromium corundum tap channel bricks, with their excellent performance, play an important role in steel rolling heating furnaces. Strictly controlling performance indicators, paying attention to installation quality, and ensuring good maintenance during procurement and use can fully leverage their advantages and provide a strong guarantee for efficient and stable operation of steel rolling production.