Duplex Stainless Steel Composition for Intermetallic Phase Control
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Solution Overview
Problem
Existing duplex stainless steels, such as super duplex and hyper duplex, are prone to the precipitation of intermetallic phases during manufacturing or welding of large components, which deteriorates both corrosion and mechanical properties.
Innovation Solution
A new duplex stainless steel with a specific composition of alloying elements, including a ferrite content of 40-70 vol%, balanced levels of Cr, Mo, Ni, Cu, and N, and controlled amounts of C, Si, and Mn, which minimizes the formation of detrimental intermetallic phases during solution heat treatment and cooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If super duplex and hyper duplex stainless steels are used to achieve high strength, then mechanical properties are improved, but intermetallic phases precipitate during manufacturing of large components, deteriorating corrosion resistance and impact toughness
Solution Approach 1:
The patent applies parameter changes by precisely controlling the chemical composition within specific ranges: Cr (20-35 wt%), Ni (4-12 wt%), Mo (1.5-4 wt%), and adding Cu (0.5-3 wt%). These compositional parameter adjustments optimize the steel's resistance to intermetallic phase precipitation while maintaining high strength, resolving the contradiction between mechanical properties and corrosion resistance in large components
Solution Approach 2:
The patent creates a composite microstructure consisting of ferrite and austenite phases with specific volume fractions (ferrite: 30-70 vol%, austenite: 30-70 vol%). This dual-phase composite structure provides both high strength and improved resistance to intermetallic precipitation, effectively balancing mechanical properties and corrosion resistance
2Volume of stationary object
If components with large dimensions are manufactured, then structural applications are enabled, but cooling rate decreases, promoting intermetallic phase formation
Solution Approach 1:
The patent modifies material parameters by adding Cu (0.5-3 wt%) and optimizing Mo content (1.5-4 wt%), which significantly delays the precipitation of intermetallic phases during slow cooling. This enables manufacturing of large components with dimensions suitable for structural applications while maintaining microstructure stability
Solution Approach 2:
The patent applies preliminary action by optimizing the chemical composition before manufacturing, specifically pre-balancing Cr, Ni, Mo, and Cu content to create a composition that is inherently resistant to intermetallic precipitation. This preliminary compositional optimization prevents microstructure degradation during subsequent manufacturing processes
3Ease of manufacture
If welding is performed on duplex stainless steel, then component assembly is enabled, but intermetallic phases form in the heat affected zone, reducing impact toughness
Solution Approach 1:
The patent applies parameter changes by adjusting Ni (4-12 wt%) and Cr (20-35 wt%) content, which optimizes the material's response to welding heat. This compositional adjustment minimizes intermetallic phase formation in the heat affected zone while maintaining high impact toughness, enabling both weldability and mechanical performance
Data Source
AI summary
The present disclosure relates to a duplex stainless steel comprising in weight% (wt%): C less than 0.03; Si less than 0.60; Mn 0.40 to 2.00; P less than 0.04; S less than or equal to 0.01; Cr more than 30.00 to 33.00; Ni 6.00 to 10.00; Mo 1.30 to 2.90; N 0.15 to 0.28; Cu 0.60 to 2.20; Al less than 0.05; balance Fe and unavoidable impurities. The present disclosure also relates to a component or a construction material comprising the duplex stainless steel. Additionally, the present disclosure also relates to a process for manufacturing a component comprising said duplex stainless steel.