As core equipment in steelmaking, the quality of the converter lining construction directly determines its service life and production efficiency. This solution, drawing on advanced domestic and international experience, constructs a systematic solution from three perspectives: material selection, process optimization, and quality control. Focusing on addressing the varying working conditions in different locations, it proposes a comprehensive technical system encompassing zoning material selection, precise construction, and dynamic maintenance.
01 Material System and Performance Compatibility
(I) Working Layer Material Selection
Magnesia Carbon refractory Bricks System
Slag Line Area: MT18A magnesia carbon bricks (MgO ≥ 88%, C ≥ 14%) are used. Their slag erosion resistance index is 35% higher than that of ordinary magnesia carbon bricks, making them suitable for areas with slag erosion rates exceeding 2mm/cycle.
Charging Side: Anti-oxidation magnesia carbon bricks with 0.5% metallic aluminum powder are used. After a 1600°C × 3h thermal shock test, the residual strength retention rate reaches 82%. The taphole is equipped with integrally cast magnesium-carbon casing bricks, with an inner diameter tolerance controlled within ±0.5mm. High-alumina ramming material is used to ensure leak-free operation over 2,000 thermal cycles.
Amorphous Material Application
The annular area of the furnace cap utilizes Al₂O₃-MgO self-flowing castable material, with a construction fluidity ≥220mm and a bulk density of 2.95g/cm³ after drying at 110°C for 24 hours.
The permeable bricks are surrounded by a corundum quick-drying anti-seepage material, with a penetration depth of ≤1mm/24 hours, effectively blocking the permeation path of molten steel.
(II) Permanent Layer Material Optimization
The fired magnesia bricks utilize fused magnesia aggregate (MgO ≥97%), with an apparent porosity of ≤16% and a linear change rate of only -0.12% after firing at 1550°C for 3 hours.
A 5mm-thick Helu ceramic fiber paper expansion joint is installed between the permanent layer and the working layer, with a compensation coefficient of 0.8%/1000°C to prevent thermal stress concentration.
02 Standardized Construction Process
(I) Construction Preparation
Environmental Control
A temperature and humidity monitoring system is installed in the masonry area. Construction can only begin when the ambient temperature is >5°C and the relative humidity is <70%. Refractory bricks must be preheated at 200°C for 24 hours, with a moisture content of ≤0.3%.
Equipment Calibration
A laser rangefinder is used to locate the furnace center, with an accuracy of ≤±1mm. The vibration amplitude of the vibrating rod is controlled at 0.5±0.05mm, with a frequency of 12,000 times/min, to ensure a ramming material density of ≥2.8g/cm³.
(II) Sectional Masonry Technology
Furnace Bottom Construction
The permanent layer is laid using the "cross-cut" method, with the upper and lower layers of magnesia bricks staggered at 90°, and the mortar joint thickness ≤1mm.
A laser alignment system is used during the installation of air-permeable bricks, achieving a positioning accuracy of ±0.2mm. Silicon carbide sealing material is used around the tail pipe. Furnace Shaft Construction
The working layer utilizes the "spiral ascending method," with each ring of door bricks offset by ≥3 pieces. Expansion joints are arranged in a "three horizontal, four vertical" pattern, with spacing controlled at 1.2-1.5m.
Prestressed anchoring technology is used at the trunnion, with dovetail grooves cut into the surface of the refractory bricks and 8mm diameter 310S stainless steel anchors inserted.
Furnace Cap Construction
Adjustable curved formwork is used to ensure the roundness error of the tapered portion is ≤3mm/m.
The furnace mouth press bricks are magnesia dry vibrating material, rammed in three layers, with a compaction coefficient of ≥0.95 for each layer.
(III) Key Node Control
Transition Zone Treatment
Customized special-shaped bricks are used for the arc transition between the melt pool and the furnace bottom, with a curvature radius deviation of ≤±2mm.
A 2mm thick phosphate binder is applied between the permanent layer and the working layer to form a transition bonding layer. Furnace Curve Optimization
A three-stage heating method is used:
Low-temperature section (room temperature - 300°C): heating rate ≤ 15°C/h, hold constant for 8 hours to remove free water;
Medium-temperature section (300-800°C): heating rate ≤ 25°C/h, hold constant for 12 hours to decompose crystalline water;
High-temperature section (800-1200°C): heating rate ≤ 35°C/h, hold constant for 24 hours to achieve sintering and densification.
03 Quality Control System
(I) Process Monitoring
Infrared Thermal Imaging Inspection
Surface temperature scans are conducted after each layer of masonry is completed. Areas with a temperature difference greater than 15°C require partial rework.
The furnace shell temperature is monitored in real time during the baking process, and the emergency cooling system is activated when a local hot spot exceeds 250°C.
Ultrasonic Testing
Spot checks are conducted on key areas (ventilation refractory bricks and tapholes). Defects with an equivalent diameter greater than φ3mm are considered unqualified. (II) Acceptance Criteria
Dimensional Accuracy
Furnace body verticality deviation ≤ 5mm/m, total height deviation ≤ 15mm.
Expansion joint width deviation ≤ ±1mm, straightness deviation ≤ 2mm/m.
Physical and Chemical Specifications
Working layer apparent porosity ≤ 18%, compressive strength ≥ 80MPa (1400°C x 3h).
Permanent layer refractoriness under load ≥ 1650°C (0.2MPa).
04 Innovative Technology Applications
3D Printed Prefabricated Parts
For complex structures (such as the base of breathable bricks), Al₂O₃-ZrO₂-C printed parts are used, achieving a dimensional accuracy of ±0.1mm and improving installation efficiency by 40%.
Intelligent Temperature Control System
Embedded fiber optic sensors monitor temperature gradients in real time and automatically adjust heating power when ΔT > 50°C/h. Nano-modification Technology
Adding 0.3% nano-SiO₂ to the castable increases the thermal shock parameter (TSP) from 250 to 400 times (water-cooled at 1100°C).
05 Converter Drying Solution
After placing firewood and coke into the converter, heat it for 5-8 hours. When the temperature reaches 1200-1300°C, molten iron can be added for a trial burn. The first heat of steel must be filled entirely with molten iron; no scrap is allowed.
06 Furnace Optimization
Based on CFD simulation, the lining thickness distribution was adjusted, increasing the slag line thickness by 15% and reducing the trunnion area by 10% compared to the conventional design.
Through collaborative innovation in materials, processes, and maintenance, the converter lining life has been extended to over 8,000 heats, refractory consumption has been reduced to 0.8 kg/ton of steel, and overall maintenance costs have been reduced by 35%. In actual applications, dynamic adjustments need to be made based on specific furnace parameters. It is recommended to conduct laser scanning inspections every 50 furnaces and establish a three-dimensional digital twin model to guide precise maintenance.
