Duplex Stainless Clad Steel Composition to Suppress Sigma Phase
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional duplex stainless clad steel plates exhibit insufficient corrosion resistance due to the precipitation of sigma phase, carbides, and nitrides, which depletes corrosion-resistant elements and affects the mechanical properties of the cladding metal, and there is a need for improved strength and toughness, especially in low-temperature environments.
Innovation Solution
A duplex stainless clad steel plate is produced with specific chemical compositions for the cladding and base metals, including controlled Ceq and Nb/N ratios, and a microstructure with a ferrite phase area fraction of 35-65%, along with controlled cooling and tempering processes to prevent the precipitation of sigma phase and carbides, enhancing corrosion resistance and mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional duplex stainless steel composition and processing is used, then manufacturing cost is reduced, but corrosion resistance is insufficient due to sigma phase, carbide, and nitride precipitation
Solution Approach 1:
The invention changes the chemical composition parameters by strictly controlling Ceq (0.35-0.45) and Nb/N ratio (≥3.0), and controls processing parameters including cooling rates (cladding metal: 0.3-10°C/s, base metal: 1.0-5.0°C/s) and tempering temperature (≤700°C) to prevent harmful precipitation while maintaining cost-effectiveness
Solution Approach 2:
The invention uses a composite structure with duplex stainless steel cladding metal bonded to base metal, where the duplex stainless steel layer contains controlled amounts of alloying elements (Cr: 18-26%, Ni: 4-10%, Mo: 2-4%) to achieve superior corrosion resistance while the base metal provides structural support, optimizing overall cost-performance
2Reliability
If alloying element content is increased to improve corrosion resistance, then pitting corrosion resistance is improved, but manufacturing cost increases
Solution Approach 1:
The invention optimizes alloying element content within specific ranges (Cr: 18-26%, Ni: 4-10%, Mo: 2-4%) and controls the Pitting Resistance Equivalent (PREN) to achieve maximum corrosion resistance while avoiding excessive alloying that would increase cost, using controlled cooling rates to prevent element depletion
3Strength
If conventional cooling and processing methods are used, then processing speed is maintained, but mechanical properties and toughness are insufficient
Solution Approach 1:
The invention uses a multi-stage periodic processing approach: controlled cooling at 0.3-10°C/s to room temperature, followed by tempering at 700°C or lower, which sequentially achieves microstructure refinement and property optimization without excessive processing time
Solution Approach 2:
The invention changes processing parameters by controlling cooling rates (0.3-10°C/s for cladding metal, 1.0-5.0°C/s for base metal) and tempering temperature (≤700°C) to achieve optimal mechanical properties and toughness while maintaining reasonable processing speed
4Reliability
If duplex stainless steel is used as solid metal to ensure corrosion resistance, then corrosion resistance is achieved, but cost advantage is lost
Solution Approach 1:
The invention creates a composite clad steel structure where a duplex stainless steel cladding layer (providing corrosion resistance with controlled Cr: 18-26%, Ni: 4-10%, Mo: 2-4%) is bonded to a base metal layer (providing structural support), achieving superior corrosion resistance at lower overall cost compared to solid duplex stainless steel
Solution Approach 2:
The invention applies local quality by concentrating expensive alloying elements (Cr, Ni, Mo) only in the cladding layer where corrosion resistance is needed, while the base metal uses cheaper materials, optimizing overall material cost while maintaining superior corrosion resistance at critical surfaces
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 solution results in a duplex stainless clad steel plate with improved corrosion resistance and mechanical properties, specifically pitting corrosion resistance, strength, and toughness, while maintaining cost-effectiveness by optimizing the use of alloying elements.
Implementation Method 1
A clad steel plate is a steel plate where two or more steel plates having different properties are bonded or joined together
Implementation Method 2
allowing the rolled clad body to naturally cool; then reheating the rolled clad body to 950° C. to 1100° C.; then cooling the rolled clad body such that the duplex stainless steel plate is cooled at a cooling rate of 0.3° C./s or higher
Data Source
AI summary
Disclosed is a duplex stainless clad steel plate in which a duplex stainless steel plate as a cladding metal is bonded or joined to one or both surfaces of a base steel plate, in which the base steel plate comprises a predetermined chemical composition such that Nb/N is 3.0 or more and Ceq is 0.35 to 0.45, and the duplex stainless steel plate comprises: a predetermined chemical composition such that PI is 33.0 to 38.0; and a microstructure containing a ferrite phase in an area fraction of 35% to 65%, and in the microstructure, an amount of precipitated Cr is 1.00% or less and an amount of precipitated Mo is 0.50% or less.