Liquid Steel Purification for A-Shaped Segregation Control
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Solution Overview
Problem
A-shaped segregation in steel ingots, characterized by the accumulation of inclusions such as Al2O3 and MnS, significantly affects the mechanical properties and quality of forged pieces, and existing methods are either impractical or inapplicable for large steel ingots, leading to abandoned products.
Innovation Solution
A method involving controlled phosphorus and sulfur content, vacuum carbon deoxidation, deep desulfurization, and vacuum degasification to purify liquid steel, preventing the entry of steel slag and reducing inclusions, thereby eliminating A-shaped segregation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If external cooling or foreign cooling matter is introduced to fast solidify the steel ingot, then A-shaped segregation is eliminated or decreased, but the method is difficult to operate and inapplicable to large steel ingots
Solution Approach 1:
The patent applies preliminary action by purifying the liquid steel before casting to remove inclusions that would otherwise cause A-shaped segregation. The steel is treated with purifying agents and subjected to vacuum degasification prior to solidification, preventing inclusion accumulation in the segregation zone rather than attempting to correct the problem after solidification begins
Solution Approach 2:
The patent extracts harmful inclusions from the liquid steel through multiple mechanisms: slag removal to eliminate oxide inclusions, vacuum degasification to remove gas bubbles, and chemical treatment to precipitate and remove sulfide inclusions. This extraction of harmful elements prevents them from accumulating in the A-shaped segregation region
2Manufacturing precision
If external cooling or foreign cooling matter is introduced to fast solidify the steel ingot, then A-shaped segregation is eliminated or decreased, but large inclusions may be introduced resulting in abandonment of the steel ingot
Solution Approach 1:
The patent converts the harmful effect of rapid cooling (which can trap inclusions) into a benefit by using controlled solidification conditions combined with pre-purification. The slow solidification rate allowed by the purification method actually helps float remaining inclusions to the surface where they can be removed, while still achieving good segregation control through the pre-removed inclusion content
Solution Approach 2:
The patent performs preliminary purification actions including slag removal, vacuum degasification, and chemical treatment to eliminate inclusions before the casting process begins. This preliminary cleanup prevents inclusion introduction during solidification rather than attempting to manage inclusions during the solidification process itself
3Manufacturing precision
If traditional methods are used to solve A-shaped segregation, then segregation is reduced, but productivity decreases due to abandoned products
Solution Approach 1:
The patent applies preliminary action by implementing comprehensive purification measures during steelmaking and before casting. By removing inclusions, controlling composition, and degassing the liquid steel beforehand, the method prevents A-shaped segregation formation, eliminating the need for post-casting rejection and reworking, thus maintaining high productivity while achieving excellent segregation control
Solution Approach 2:
The patent converts the traditionally harmful slow solidification requirement (which reduces productivity) into a benefit by showing that with pre-purification, controlled solidification rates can be used without causing inclusion trapping. The pre-removed inclusions mean that slower solidification actually improves quality without the usual productivity penalty, as no abandonment is needed
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 effectively reduces harmful elements and inclusions, improving the purity of steel ingots and preventing A-shaped segregation, making it suitable for large steel ingots and continuous casting blanks, enhancing their internal quality.
Implementation Method 1
pre-deoxidizing the liquid metal using a vacuum carbon deoxidation process
Implementation Method 2
vacuum carbon deoxidation process for reducing the amount of inclusions
Implementation Method 3
performing vacuum degasification in a vacuum degassing furnace for purifying the liquid metal
Data Source
AI summary
A method for controlling A-shaped segregation of steel ingot. The method includes: 1) controlling a content of phosphorus in liquid steel at less than or equal to 0.005 wt. % upon tapping from an electric furnace, preventing steel slag from entering a ladle, controlling content of harmful elements at less than or equal to 100 ppm; and adding between 3 and 15 kg of calcium oxide and less than or equal to 0.5 kg of aluminum to each ton of the liquid steel; 2) pre-deoxidizing the liquid metal using vacuum carbon deoxidation; 3) de-sulfurizing, controlling content of oxygen, and controlling the content of sulfur in the liquid steel at less than or equal to 0.005 wt. %; and 4) performing vacuum degasification, controlling the total oxygen content at less than or equal to 15 ppm; and casting the steel in the presence of inert gas or in vacuum.