Clean Steel Preparation via Segmented Desulfurization and Self-Service Slag
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Solution Overview
Problem
Conventional methods for producing clean steel are inefficient in achieving high cleanliness standards, leading to increased production costs and insufficient cleanliness in the final product, as they struggle to effectively remove harmful elements like S, P, and inclusions, and control their distribution.
Innovation Solution
A method involving the use of desulfurizing, dephosphorizing, and purifying balls composed of specific slag and oxide materials, which are added at various stages of the steelmaking process to control sulfur, phosphorus, and oxygen content, and inclusion size, utilizing a reaction-induced microheterogeneous charging method to create ultra-fine bubbles for uniform composition and inclusion removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional refining methods are used to remove harmful elements, then some cleanliness is achieved, but the final steel cleanliness is insufficient (S≦0.035%, P≦0.035%, inclusions 1.0-0.5 degree)
Solution Approach 1:
The patent divides the desulfurization process into multiple stages: preliminary desulfurization in the blast furnace (reducing S to 0.01%), pre-desulfurization in the iron folding room (reducing S to 0.0015%), and final desulfurization in the converter (reducing S to 0.004%). This segmented approach allows each stage to achieve partial cleanup, culminating in the required cleanliness standard of S 5-20 ppm that conventional single-stage methods cannot achieve.
Solution Approach 2:
The patent performs preliminary desulfurization and dephosphorization actions before the main steelmaking process. By reducing sulfur to 0.0015% before converter charging and phosphorus to 0.014% during converter tapping, the system prepares the molten metal in advance, making the final steel meet cleanliness requirements (S 5-20 ppm, P 20-60 ppm) that would be difficult to achieve through converter operations alone.
2Manufacturing precision
If stricter requirements for ferroalloy and auxiliary materials are imposed to improve cleanliness, then steel quality improves, but production cost increases
Solution Approach 1:
The patent utilizes the blast furnace slag and iron folding room slag as self-contained desulfurization agents. The slag naturally contains CaO and other basic oxides that react with sulfur in the molten iron. This self-service approach eliminates the need for expensive external desulfurizing agents while achieving the required cleanliness (S 5-20 ppm) and reduces production costs by 0.8-1.6 USD per ton.
Solution Approach 2:
Instead of discarding the blast furnace slag and iron folding room slag as waste, the patent recovers their desulfurization value. The slag is deliberately added back to the molten iron to remove sulfur, transforming a waste product into a useful reagent. This recovery approach achieves cleanliness standards (S 5-20 ppm) while avoiding the cost of purchasing expensive ferroalloys and auxiliary materials.
3Manufacturing precision
If more refining operations are performed to reduce inclusions, then cleanliness improves, but process complexity and cost increase
Solution Approach 1:
The patent merges the desulfurization function into existing process stages (blast furnace tapping and iron folding) rather than adding separate refining operations. The same slag that is produced as a byproduct is reused for desulfurization, combining waste disposal and purification functions. This merging achieves inclusion control (equivalent diameter 0.5-10 μm) without increasing process complexity or requiring additional refining equipment.
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
This method significantly reduces sulfur and phosphorus content, controls inclusion size and distribution, and lowers production costs by achieving the desired cleanliness standards of S 5–20 ppm, P 20–60 ppm, oxygen 3–15 ppm, and inclusion equivalent diameter 0.5–10 μm, while reducing the cost per ton of steel by 0.8–1.6 USD.
Implementation Method 1
preliminarily desulfurizing in an iron melt channel during blast furnace tapping and during iron folding in an iron folding room, adding a desulfurizing ball into the iron melt during the blast furnace tapping or the iron folding, in such a manner that S≦0.01% by weight in the iron melt after preliminarily desulfurizing
Implementation Method 2
adding a purifying ball at a late stage of the RH refining when a vacuum degree is at 66.7-500 Pa; achieving the desired cleanliness standards of S 5-20 ppm, P 20-60 ppm, oxygen 3-15 ppm
Implementation Method 3
dephosphorizing and controlling sulfur during converter steelmaking, in such a manner that P≦0.014% and S≦0.004% during tapping
Implementation Method 4
utilizing a reaction-induced microheterogeneous charging method to create ultra-fine bubbles for uniform composition and inclusion removal
Implementation Method 5
finely desulfurizing the iron melt by dusting desulfurization, and filtering out desulfurized slags by a slag filter
Implementation Method 6
controls inclusion size and distribution, and lowers production costs by achieving the desired cleanliness standards of inclusion equivalent diameter 0.5-10 μm
Data Source
AI summary
A method for preparing low-cost clean steel includes steps of: preliminarily desulfurizing iron melt: preliminarily desulfurizing in an iron melt channel during blast furnace tapping and during iron folding in an iron folding room, adding a desulfurizing ball into the iron melt during the blast furnace tapping or the iron folding; dephosphorizing and controlling sulfur: dephosphorizing and controlling sulfur during converter steelmaking, in such a manner that P≦0.014% and S≦0.004% during tapping; rapidly dephosphorizing by slag-forming: rapidly dephosphorizing by slag-forming during converter tapping, at a converter end point, controlling a C content at 0.02˜0.10%, adding a dephosphorizing ball through an alloy chute during the converter tapping, blowing argon and stirring at the same time; purifying steel melt during RH refining: adding a purifying ball at a late stage of the RH refining when a vacuum degree is at 66.7˜500 Pa; and continuously casting with whole-process protection.