Magnesia-Carbon Sleeve Brick Composition for Crack-Resistant Durability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing sleeve bricks for steelmaking converters suffer from inconsistent durability due to cracking, which is influenced by factors such as thermal shock, stress from molten steel, and external forces, leading to unpredictable and unstable performance.
Innovation Solution
The solution involves optimizing the addition rates of metal powder and graphite based on the thickness of the sleeve brick, with specific ranges for each to enhance durability, including using Al in amounts greater than 3 to 6 mass% for strength and graphite in 5 to 20 mass% for thermal shock resistance, along with controlled particle sizes and organic binders for forming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If metal powder (such as aluminum powder) is added to enhance strength and abrasion resistance, then strength and abrasion resistance are improved, but thermal shock resistance deteriorates
Solution Approach 1:
The invention changes the particle size parameter of the metal powder from conventional fine powder to granular particles with specific size ranges (0.5-2mm for aluminum, 1-3mm for ferrosilicon, 0.5-2mm for ferroboron). This parameter change reduces the total surface area and reaction intensity, thereby improving thermal shock resistance while still providing strength enhancement through carbide and spinel formation.
Solution Approach 2:
The invention creates a composite refractory material combining magnesia, graphite, and granular metal particles. The composite structure allows the metal particles to provide strength enhancement through localized carbide and spinel formation at particle interfaces, while the magnesia-graphite matrix maintains thermal shock resistance. The composite achieves both strength improvement and thermal shock resistance simultaneously.
2Strength
If flake graphite content is reduced to enhance abrasion resistance and oxidation resistance, then abrasion resistance and oxidation resistance are improved, but thermal shock resistance may be affected
Solution Approach 1:
The invention reduces flake graphite content to 10 mass% or less while maintaining thermal shock resistance through the addition of granular metal particles. The metal particles create secondary bonds through carbide formation that compensate for the reduced graphite content, allowing the material to achieve high abrasion resistance without sacrificing thermal shock resistance.
3Strength
If metal powder is added in large amounts to enhance strength, then strength is improved, but thermal shock resistance deteriorates significantly
Solution Approach 1:
The invention changes the particle size parameter from fine powder to granular particles (0.5-3mm), which reduces the total surface area and intensity of reactions. This allows higher metal content (3-10 mass%) to be added while maintaining thermal shock resistance. The granular particles provide strength through localized carbide and spinel formation at particle-matrix interfaces without causing excessive matrix densification that would harm thermal shock resistance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly enhances durability, reducing sudden replacements and stabilizing the production process by extending the service life of the sleeve bricks, particularly in larger sizes.
Implementation Method 1
creation of secondary bonds based on carbide and spinel formation
Implementation Method 2
creation of secondary bonds based on carbide and spinel formation
Implementation Method 3
matrix densification based on volume expansion
Implementation Method 4
the magnesia-carbon based material is excellent in thermal shock resistance
Implementation Method 5
abrasion (erosion) resistance because it is severely exposed to a high-temperature molten steel stream
Implementation Method 6
abrasion (erosion) resistance because it is severely exposed to a high-temperature molten steel stream
Implementation Method 7
subjecting the resulting mixture to kneading, forming and heat treatment
Data Source
Figure 1
AI summary
Disclosed is a magnesia-carbon based sleeve brick for steelmaking converters, which is obtained by adding, to a refractory raw material mix containing 60 to 95 mass% of a magnesia raw material and 5 to 20 mass% of graphite, a metal powder of one or more selected from the group consisting of Al, Si, Mg, Ca, Cr and an alloy thereof, in an amount of greater than 3 to 6 mass%, and an organic binder, in addition to 100 mass% of the refractory raw material mix, and subjecting the resulting mixture to kneading, forming and heat treatment, wherein the sleeve brick is used under a condition that a thickness thereof is set at 70 mm or less. This makes it possible to prevent cracking which would otherwise occur in the sleeve brick itself, to allow the sleeve brick to have enhanced durability. One or more selected from the group consisting of B, B4C, MgB2, CaB6 and CrB may be further added in an amount of 0.1 to 3 mass%, in addition to 100 mass% of the refractory raw material mix, to enhance strength and oxidation resistance and further enhance the durability. The magnesia raw material may comprise a first particle fraction having a particle diameter of greater than 10 to 500 µm and occupying 20 to 50 mass% in the refractory raw material mix, and a second particle fraction having a particle diameter of 10 µm or less and occupying 5 mass% or less in the refractory raw material mix, to additionally enhance corrosion resistance and thermal shock resistance.