Continuous Casting Nozzle Intermediate Layer for Thermal Stress Management
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Solution Overview
Problem
Continuous casting nozzles face issues with thermal stress-induced cracking due to differences in thermal expansion coefficients between inner bore-side and outer periphery-side layers, leading to reduced durability and increased risk of breaking, particularly in the outer periphery-side region, and challenges in preventing attachment of inclusions and clogging, which affect their lifetime and operational stability.
Innovation Solution
A refractory material for the intermediate layer with a hollow refractory aggregate content of 10 to 75 volume%, having a glassy structure with SiO2 content of 70 mass% or more and a specific composition of Al, Si, Mg, and carbon, which provides compressibility and bonding strength, allowing for stress relaxation and preventing expansion splitting, while maintaining structural integrity and corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the inner bore-side layer has a high thermal expansion coefficient to improve thermal shock resistance, then thermal shock resistance is improved, but thermal stress increases causing cracking in the outer periphery-side region
Solution Approach 1:
A low-thermal-expansion intermediate layer is introduced between the high thermal expansion inner bore-side layer and the outer periphery-side layer. This intermediate layer acts as a stress buffer that absorbs and distributes thermal stresses, preventing stress concentration and cracking in the outer periphery-side region while allowing the inner layer to maintain its high thermal shock resistance properties
Solution Approach 2:
The nozzle is designed with spatially varying thermal expansion coefficients: the inner bore-side layer has high thermal expansion for thermal shock resistance, the intermediate layer has low thermal expansion for stress reduction, and the outer periphery-side layer has moderate thermal expansion. This local differentiation of material properties optimizes both thermal shock resistance and structural integrity
2Stress or pressure
If graphite or fused silica is added to reduce thermal expansion, then thermal stress is reduced, but oxidation resistance and erosion resistance deteriorate
Solution Approach 1:
Different refractory materials with complementary properties are assigned to different spatial regions: the inner bore-side layer uses high-erosion-resistance materials (basic oxides, carbon-containing materials) to withstand molten steel attack, while the intermediate layer uses low-thermal-expansion materials (fused silica, glass ceramics) to reduce thermal stress, and the outer layer provides structural support
Solution Approach 2:
The nozzle employs a composite multi-layer structure where each layer is made of materials optimized for its specific function. The composite structure combines the erosion resistance of carbon/basic oxide materials with the low thermal expansion of silica-based materials, achieving both properties simultaneously through material composition rather than compromise
3Reliability
If a multi-layer structure is adopted to differentiate functions, then durability is improved, but device complexity increases
Solution Approach 1:
The nozzle is segmented into three distinct functional layers: an inner bore-side layer for erosion and corrosion resistance, an intermediate layer for thermal stress management, and an outer periphery-side layer for structural support. This segmentation allows each layer to be optimized for its specific function while working together as an integrated system
Solution Approach 2:
Each layer serves multiple functions: the inner bore-side layer provides both erosion resistance and thermal shock resistance; the intermediate layer provides both stress buffering and thermal insulation; the outer layer provides both structural support and thermal expansion control. This multi-functionality reduces the need for additional components, simplifying the overall design despite the multi-layer structure
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 effectively reduces thermal stress-induced cracking, enhances the durability of the continuous casting nozzle by preventing expansion splitting and attachment of inclusions, and extends the nozzle's lifetime through improved bonding and corrosion resistance, ensuring stable casting operations.
Implementation Method 1
an intermediate layer having compressibility... which provides compressibility and bonding strength, allowing for stress relaxation
Implementation Method 2
differences in thermal expansion coefficients between inner bore-side and outer periphery-side layers... athermal stress will be increased
Data Source
AI summary
In a insert-type continuous casting nozzle comprising a highly functional layer formed to have a high corrosion resistance, a high anti-attachment capability, etc., and provided to defme an inner bore thereof, the present invention is directed to providing a refractory material (mortar) for an intermediate layer of the continuous casting nozzle, which has a property capable of fixing an inner bore-side layer to an outer periphery-side layer (a nozzle body) of the continuous casting nozzle, while preventing the occurrence of expansion splitting in the outer periphery-side layer due to a difference in thermal expansion between the inner bore-side and outer periphery-side layers, and a continuous casting nozzle using the refractory material for the intermediate layer. The refractory material for the intermediate layer contains a hollow refractory aggregate in an amount of 10 to 75 volume%, wherein a ratio of an average radius R of each particle of the aggregate to an average wall thickness t of the particle satisfies the following relation: R/t ≥ 10. This refractory material is disposed between an inner bore-side layer (2) and an outer periphery-side layer (3, 4) of a continuous casting nozzle.