Nozzle Sand Formulation for Ladle Steel Free Opening
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Solution Overview
Problem
Current nozzle sands used in steelmaking processes face issues with non-free opening due to increased permeation of molten steel into the sand bed over time, leading to wear and high costs associated with zircon and chromite sands, which are subject to supply and pricing fluctuations.
Innovation Solution
A nozzle sand formulation comprising 50-60 wt % raw dolomitic lime, 20-30 wt % synthetic forsterite, 15-20 wt % tabular alumina, and 3-8 wt % metallurgical grade coke, designed to break down at high temperatures, creating a low-density compressible layer that limits permeability and heat soak, facilitating easy opening and reducing corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If zircon sand is used to improve free opening, then the nozzle can open freely, but the sand adheres to refractories causing wear and requiring mechanical removal
Solution Approach 1:
The patent removes zircon sand from the sand blend entirely, extracting the problematic component that causes adhesion and wear while maintaining free opening capability through alternative materials like chromite sand and limestone
Solution Approach 2:
The patent uses a composite sand blend comprising chromite sand, limestone, and silica sand in specific proportions, creating a material composition that provides both free opening and reduced adhesion properties through the synergistic effects of its components
2Ease of manufacture
If chromite sand is used as a lower cost alternative, then cost is reduced, but it is still subject to commercial fluctuations and has similar adhesion issues
Solution Approach 1:
The patent introduces limestone as an intermediary material that modifies the interaction between the sand bed and molten steel, reducing adhesion of chromite sand to refractories while maintaining the cost-effectiveness of chromite as the base material
Solution Approach 2:
The patent changes the chemical composition parameters of the sand blend by adding limestone (calcium carbonate) which reacts with chromite sand to form a less adhesive composite material, thereby reducing adhesion while maintaining cost advantages
3Duration of action of moving object
If the hold time of molten steel increases, then more alloying can occur, but permeation into the sand bed increases causing non-free open
Solution Approach 1:
The patent changes the physical and chemical parameters of the sand bed by using finer particle size distribution and adding limestone filler, which reduces permeability and allows the sand bed to maintain its integrity during extended hold times up to 300 minutes
Solution Approach 2:
The patent creates a composite sand structure with chromite sand, limestone, and silica sand that provides enhanced resistance to steel permeation over time, maintaining free opening capability even after extended hold periods
4Reliability
If fine carbon is added to limit permeation, then permeation is reduced, but it increases the complexity of the sand formulation
Solution Approach 1:
The patent replaces expensive and complex carbon-based permeation barriers with a simpler, more economical approach using limestone and properly graded sand particles that provide permeation resistance through physical structure rather than chemical additives
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 new sand formulation allows for easier expulsion of the sand bed under ferrostatic pressure, reducing nozzle wear and operational costs while maintaining refractoriness at high temperatures, ensuring efficient steel flow and minimizing corrosion.
Implementation Method 1
raw dolomite as it will be further referred, is a mixture of calcium carbonate and magnesium carbonate that breaks down at temperatures above about 1391° F. forming calcium oxide, magnesium oxide, and carbon dioxide
Implementation Method 2
this low density grain will act as a compressible layer under the ferrostatic load of a full steel ladle. The coarse grains will compress into ultra-fine particles which will limit permeability of the molten steel into the sand bed
Implementation Method 3
The low density grains that aren't compressed will act as an insulating layer to reduce heat soak from the melt into the sand bed, further limiting permeation of the steel into the sand bed
Implementation Method 4
The molten steel contacts the sand bed and forms a composite sand-steel 'interfacial zone.'When the slide gate is opened, the loose sand flows out and the ferrostatic head pressure of the steel breaks through the interfacial zone and into the receiving tundish
Data Source
AI summary
A nozzle sand and method of use and operation, utilizes as a constituent component a granulated material that will break down to lose structural integrity and strength when subjected to temperatures and weight of molten ferrous materials, to compact to form at least a partial barrier to penetration of the molten ferrous material while remaining at least substantially in a granulated state. When the nozzle is opened, the loose nozzle sand will freely flow from the nozzle and the barrier will break under the weight of the ferrous material, such that the ferrous material will flow from the vessel through the nozzle. As a representative formulation, the nozzle sand can include between about 50 percent and about 60 percent by weight raw dolomitic lime; between about 20 percent and about 30 percent by weight forsterite; and between about 15 percent and about 20 percent by weight tabular alumina.