Duplex Stainless Steel Sheet Inclusion Reduction via AOD Silicon Control
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Solution Overview
Problem
The twin roll strip casting process for duplex stainless steel often results in the formation of fine inclusions due to rapid solidification, which can lead to surface damage, cracks, and reduced corrosion resistance, as non-metallic inclusions are inevitably formed during deoxidizing and ferroalloy processes.
Innovation Solution
A method involving argon oxygen decarburization (AOD) with silicon deoxidation, maintaining silicon content between 0.55 wt% and 0.75 wt%, and controlling slag basicity between 2.2 and 2.5, along with ladle treatment and twin roll strip casting, to minimize inclusions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If rapid solidification is used in twin roll strip casting to achieve high production rate, then productivity is improved, but fine inclusions are formed due to insufficient time for inclusions to grow and combine
Solution Approach 1:
The patent applies preliminary action by performing deoxidation with silicon and controlling slag basicity before the twin roll strip casting process. This preliminary treatment modifies the molten steel composition and slag characteristics in advance, enabling inclusions to be minimized even during rapid solidification. The pre-established chemical conditions ensure that when rapid casting occurs, the already-optimized molten steel produces fewer inclusions despite the short solidification time.
Solution Approach 2:
The patent changes key chemical parameters: silicon content is controlled at 0.55-0.75 wt% and slag basicity (CaO/SiO2) is maintained at 2.2-2.5. These parameter changes fundamentally alter the deoxidation behavior and inclusion formation characteristics. By optimizing these parameters before casting, the process achieves reduced inclusions even under rapid solidification conditions, resolving the contradiction between high productivity and manufacturing precision.
2Stability of the object's composition
If deoxidizing and ferroalloy processes are performed to control molten steel, then chemical composition is improved, but non-metallic inclusions are inevitably formed
Solution Approach 1:
The patent optimizes specific parameter ranges: silicon content at 0.55-0.75 wt% and slag basicity at 2.2-2.5. These parameter changes transform the deoxidation process to produce fewer inclusions. The controlled silicon content ensures adequate deoxidation while the optimized slag basicity promotes inclusion removal, resolving the contradiction between achieving stable chemical composition and minimizing harmful inclusions.
Solution Approach 2:
The patent converts the harmful effect of deoxidation (inclusion formation) into a beneficial process by controlling slag basicity at 2.2-2.5. This optimized basicity condition transforms the deoxidation reaction to favor inclusion removal rather than inclusion formation. The deoxidation process, which normally creates inclusions, is converted into a beneficial treatment that reduces inclusions when combined with the specific silicon content control.
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 approach effectively reduces the number of inclusions in duplex stainless steel sheets, enhancing mechanical properties and corrosion resistance while maintaining cost-effectiveness.
Implementation Method 1
deoxidizing molten steel using silicon (Si) during AOD
Implementation Method 2
rapid solidification of molten steel does not allow for a sufficient time for inclusions to grow and combine with each other
Data Source
AI summary
There is provided a method for manufacturing a duplex stainless steel sheet having reduced inclusions through argon oxygen decarburization (AOD), ladle treatment (LT), and twin roll strip casting. The method includes deoxidizing molten steel using silicon (Si) during the AOD, wherein the molten steel has a silicon (Si) content of 0.55 wt % to 0.75 wt % at the end of the AOD.