Graphite-Free Magnesia Carbon Brick Spalling Resistance
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Solution Overview
Problem
Magnesia carbon bricks without flake graphite face challenges in spalling resistance and corrosion resistance, particularly in oxidative atmospheres, leading to heat loss and carbon pickup, and insufficient durability in furnaces.
Innovation Solution
Incorporating specific ranges of pitch, carbon black, aluminum, and aluminum alloy into the refractory raw material mixture, along with controlled particle size distributions of magnesia, to achieve excellent spalling and corrosion resistance without graphite, through a process involving kneading, molding, and heat-treating at 150 to 400°C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If flake graphite is included in magnesia carbon brick, then thermal conductivity is improved, but heat loss and carbon pickup occur
Solution Approach 1:
The patent removes flake graphite from the brick composition entirely, extracting the harmful element while maintaining necessary carbon functions through alternative means (carbon black and pitch binders), thereby eliminating heat loss and carbon pickup problems
Solution Approach 2:
The patent changes the carbon source from flake graphite to carbon black and pitch binders, fundamentally altering the carbon component parameters to achieve low thermal conductivity while maintaining structural integrity and spalling resistance
2Strength
If flake graphite is included in magnesia carbon brick, then spalling resistance is improved, but corrosion resistance deteriorates in oxidative atmosphere
Solution Approach 1:
The patent extracts flake graphite from the composition, eliminating the source of corrosion in oxidative atmospheres while maintaining spalling resistance through optimized magnesia particle distribution and binder system
Solution Approach 2:
The patent creates a composite material system combining magnesia with carbon black and pitch binders, where the composite structure provides both spalling resistance and corrosion resistance without relying on flake graphite
3Loss of energy
If flake graphite is excluded from magnesia carbon brick, then heat loss and carbon pickup are reduced, but spalling resistance decreases
Solution Approach 1:
The patent applies local quality by using carbon black and pitch binders specifically at the micro-level to maintain binding and spalling resistance, while the bulk material remains graphite-free to minimize heat loss
Solution Approach 2:
The patent changes the carbon component parameters from flake graphite to carbon black with pitch binder, achieving spalling resistance through the binder system rather than through bulk graphite inclusion
4Reliability
If magnesia carbon brick uses dense structure to improve corrosion resistance, then elastic modulus increases excessively, but spalling resistance deteriorates
Solution Approach 1:
The patent changes the density and elastic modulus parameters to optimal ranges (elastic modulus 70-90 GPa) through controlled sintering and binder selection, achieving both corrosion resistance and spalling resistance simultaneously
Solution Approach 2:
The patent uses composite material formulation with magnesia, carbon black, and pitch binder to achieve a balanced microstructure that provides both corrosion resistance and appropriate elasticity for spalling 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
The solution provides magnesia carbon bricks with enhanced spalling and corrosion resistance, reducing heat loss and carbon pickup, and improving furnace durability, as demonstrated by low apparent porosity and elastic modulus after heat-treatment.
Implementation Method 1
adding an organic binder to a refractory raw material mixture followed by kneading, molding, and heat-treating
Implementation Method 2
a pitch and/or a carbon black is used with a total amount of 0.1% or more by mass and 2.0% or less by mass
Data Source
Figure 1
AI summary
Provided are a magnesia carbon brick which does not include graphite yet has excellent spalling and corrosion resistances, and a method for producing thereof. The brick is obtained by adding an organic binder to a refractory raw material mixture followed by kneading, molding, and heat-treating, wherein the mixture includes total 0.1 to 2.0 mass% of pitch and/or carbon black, total 0.1 to 1.0 mass% of aluminum and/or aluminum alloy, 3.0 to 10.0 mass% of magnesia having particle diameter of less than 0.075 mm, and 87.0 to 96.0 mass% of magnesia having particle diameter of 0.075 to 5 mm; and a mass ratio of magnesia having particle diameter of 1 to 5 mm to that of 0.075 to 1 mm is 1.66 to 2.34; graphite is not included therein; and an apparent porosity thereof after heat-treatment under reductive atmosphere at 1400°C for 3 hours is 8.0% or less.