Plate Brick Nitriding Process for Oxidation Resistance
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Solution Overview
Problem
Conventional plate bricks with aluminum nitride bonds face issues with oxidation resistance, leading to surface roughening and reduced durability due to hydration and reaction with gases during burning and reuse.
Innovation Solution
A method of producing plate bricks involves adding an organic binder to a refractory raw material mixture containing aluminum, kneading, and burning in a nitrogen gas atmosphere with controlled oxygen and carbon monoxide concentrations to enhance aluminum nitride formation, thereby improving oxidation resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a plate brick is burned within carbon in a reducing atmosphere to form aluminum carbide or aluminum nitride bonds, then mechanical strength and corrosion resistance are improved, but hydration resistance deteriorates due to aluminum carbide reacting with water vapor
Solution Approach 1:
The patent applies inert atmosphere by conducting the burning process in a nitrogen gas environment instead of a carbon-based reducing atmosphere. This prevents the formation of aluminum carbide while still enabling aluminum nitride bond formation through controlled nitrogen exposure, thereby eliminating the hydration resistance problem while maintaining strength improvements
Solution Approach 2:
The patent changes the atmospheric parameters during burning by controlling oxygen partial pressure (10^-15 to 10^-20 atm) and nitrogen exposure conditions. This parameter control allows selective formation of aluminum nitride bonds without aluminum carbide, resolving the contradiction between strength improvement and hydration resistance
2Strength
If silicon carbide is used to improve oxidation and abrasion resistance, then strength and surface durability are enhanced, but corrosion resistance deteriorates when silicon carbide oxidizes to SiO2 which reacts with FeO or CaO to form low melting-point materials
Solution Approach 1:
The patent changes the chemical environment parameters during burning by controlling oxygen partial pressure to extremely low levels (10^-15 to 10^-20 atm). This prevents oxidation of silicon carbide to SiO2, thereby maintaining corrosion resistance while preserving the abrasion resistance benefits of silicon carbide
Solution Approach 2:
The patent converts the potential harm of silicon carbide oxidation into a benefit by controlling the atmosphere to prevent oxidation entirely. The silicon carbide remains in its stable, resistant form, providing both abrasion and corrosion resistance simultaneously
3Manufacturing precision
If the sliding surface is polished to improve sliding abrasion resistance, then surface smoothness and initial durability are enhanced, but the surface becomes more susceptible to microstructure loosening due to thermal shock and chemical reactions
Solution Approach 1:
The patent creates a composite bonding microstructure containing both aluminum nitride bonds and retained silicon carbide particles within an alumina matrix. This composite structure provides both surface smoothness from the dense microstructure and thermal shock resistance from the aluminum nitride bonds, resolving the contradiction between polish accuracy and 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
The method results in plate bricks with improved oxidation resistance and surface-roughening resistance, extending their usable life and durability by suppressing microstructural degradation and hydration reactions.
Implementation Method 1
burning the shaped body in a nitrogen gas atmosphere at a temperature of 1000 to 1400° C. wherein: at least when a temperature of a furnace atmosphere is 300° C. or more, the atmosphere is set to a nitrogen gas atmosphere
Implementation Method 2
when the temperature of the furnace atmosphere is 1000° C. or more, an oxygen gas concentration in the atmosphere is maintained at 100 volume ppm or less, and a sum of a carbon monoxide gas concentration and a carbon dioxide gas concentration is maintained at 1.0 volume % or less
Data Source
AI summary
Disclosed is a method of producing a plate brick, which comprises: adding an organic binder to a refractory raw material mixture containing aluminum and/or an aluminum alloy; kneading them; forming the kneaded mixture into a shaped body; and burning the shaped body in a nitrogen gas atmosphere at a temperature of 1000 to 1400° C., wherein: when a temperature of a furnace atmosphere is 300° C. or more, the atmosphere is set to a nitrogen gas atmosphere; and when the temperature of the furnace atmosphere is 1000° C. or more, an oxygen gas concentration in the atmosphere is maintained at 100 volume ppm or less, and a sum of a carbon monoxide gas concentration and a carbon dioxide gas concentration is maintained at 1.0 volume % or less. This makes it possible to form a large amount of fine and uniform aluminum nitride in a plate brick to prevent microstructural degradation due to hydration caused by formation of aluminum carbide and suppress oxidation of a carbon bond so as to improve surface-roughening resistance.