MgO Refractory Nozzle with Void Layer for Thermal Shock Resistance
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Solution Overview
Problem
Conventional refractory materials for continuous casting equipment face challenges in achieving both excellent erosion/corrosion resistance and thermal shock resistance, as high-expansion materials like MgO-containing magnesia lead to increased risk of crack formation due to thermal expansion, and techniques to improve thermal shock resistance often compromise erosion/corrosion resistance.
Innovation Solution
A refractory material is developed with an approximately continuous void layer formed around MgO-containing particles, which absorbs thermal expansion without relying on the additivity rule, allowing for a high MgO content while maintaining low thermal expansion and erosion/corrosion resistance, achieved by forming a void layer free of solids like carbon and controlling its thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If MgO-containing magnesia is used to improve erosion/corrosion resistance, then erosion/corrosion resistance is enhanced, but thermal expansion increases causing crack formation
Solution Approach 1:
The patent introduces a porous structure with voids distributed throughout the refractory material matrix. These voids act as expansion compensation spaces that absorb thermal expansion stress, preventing crack formation while allowing high MgO content (40-90 wt%) to maintain erosion/corrosion resistance. The porosity is controlled at 5-30% to balance expansion resistance with structural integrity.
Solution Approach 2:
The patent creates a composite refractory material combining MgO-containing magnesia particles with a binder system that forms a matrix containing distributed voids. This composite structure allows the MgO particles to provide erosion/corrosion resistance while the void-containing matrix absorbs thermal expansion, resolving the contradiction between these two properties.
2Reliability
If carbon content is reduced to prevent microstructural degradation, then decarburization resistance improves, but thermal shock resistance deteriorates
Solution Approach 1:
The patent uses a controlled porous structure with voids that absorb thermal expansion stress during heating and cooling cycles. This porous architecture provides thermal shock resistance by reducing thermal stress concentration, while the refractory material maintains low carbon content (0.1-5 wt%) to resist decarburization by molten steel.
3Stability of the object's composition
If SiO2 amount is reduced to prevent melting point lowering, then melting point stability improves, but thermal shock resistance worsens due to increased thermal expansion
Solution Approach 1:
The patent introduces a porous structure with voids that compensate for thermal expansion in SiO2-reduced compositions. By providing expansion compensation spaces, the porous structure allows the use of low-SiO2 refractory materials (maintaining high melting point stability) without suffering from increased thermal expansion and crack formation.
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 refractory material significantly improves thermal shock resistance while maintaining excellent erosion/corrosion resistance, enabling its use in various applications, including continuous casting nozzles, by effectively managing thermal expansion and preventing crack formation.
Implementation Method 1
an approximately continuous void layer which surrounds a surface of each of the plurality of MgO-containing particles and absorbs thermal expansion
Data Source
Figure 1(a)~1(b)
Figure 2(a)~2(d)
Figure 3~4
AI summary
Provided is a refractory material having both excellent erosion/corrosion resistance and thermal shock resistance, which has hardly been obtainable by conventional techniques, and a casting nozzle using the refractory material. The refractory material of the present invention contains: MgO in an amount of 40 mass% or more; a free carbon component in an amount of 4 to 30 mass%; and one or more selected from the group consisting of B2O3, P2O5, SiO2 and TiO2, in a total amount of 0.3 to 3 mass%, with the remainder being at least one other type of additional refractory component, wherein a void layer exists in an interface between a carbon-containing matrix microstructure residing at least on opposite sides of a maximum-size one of a plurality of MgO-containing particles in the refractory material, and the maximum-size MgO-containing particle, wherein a sum of respective thicknesses of the void layer at two positions on the opposite sides is 0.2 to 3.0% in terms of a ratio with respect to a particle size of the maximum-size MgO-containing particle, and wherein an inorganic compound comprised of MgO and the one or more selected from the group consisting of B2O3, P2O5, SiO2 and TiO2 exists in an entirety or a part of a surface of each of the plurality of MgO-containing particles.