Duplex Stainless Steel Flux Cored Wire Corrosion Resistance
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Solution Overview
Problem
Existing flux cored wires for duplex stainless steel face challenges in achieving optimal pitting corrosion resistance, intragranular corrosion resistance, cracking resistance, and high strength while maintaining favorable welding performance, due to limitations in controlling alloy components and high heat input during welding, which also affect productivity and manufacturing costs.
Innovation Solution
A flux cored wire with optimized compositions of chromium (Cr), nickel (Ni), molybdenum (Mo), copper (Cu), nitrogen (N), and oxides such as TiO2, SiO2, ZrO2, Al2O3, Li2O, K2O, Na2O, and metal fluoride, with specific weight percentages and particle size distributions, to enhance mechanical and welding performance, and a method to control the apparent density of the flux to improve productivity and reduce manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the amount of alloy components (Cr, Ni, Mo, N) is increased to improve pitting corrosion resistance and mechanical strength, then corrosion resistance and strength are improved, but manufacturing cost increases and wire drawing becomes difficult
Solution Approach 1:
The patent optimizes the compositional parameters of alloy elements (Cr: 23-30%, Ni: 6-11%, Mo: 1.5-4%, N: 0.08-0.35%) to achieve the desired balance between corrosion resistance and manufacturability. By precisely controlling these parameters, the wire maintains high pitting corrosion resistance while avoiding excessive work hardening during drawing
Solution Approach 2:
The patent creates a composite flux composition containing multiple oxides (TiO2, SiO2, ZrO2, Al2O3, Li2O, K2O, Na2O) and metal fluoride in specific ratios. This composite flux system provides the necessary alloying effects for corrosion resistance while controlling the manufacturing properties of the wire
2Productivity
If high heat input is used during welding to improve welding speed and productivity, then productivity is improved, but control of minute structure change in weld metal becomes difficult, reducing pitting corrosion resistance and toughness
Solution Approach 1:
The patent incorporates nitrogen-containing compounds and specific oxide combinations in the flux before welding. These preliminary additions ensure that nitrogen is available during the welding process to promote austenite formation and stabilize the weld metal structure, even when high heat input is applied
Solution Approach 2:
The patent adjusts the chemical composition parameters of the flux (specific ratios of TiO2, SiO2, ZrO2, Al2O3, Li2O, K2O, Na2O, and metal fluoride) to control the thermal and chemical behavior during welding. This enables maintaining weld metal quality at higher welding speeds
3Reliability
If the amount of flux alloy component is increased to improve corrosion resistance, then corrosion resistance is improved, but work hardening increases, causing wire cutting during drawing and reducing productivity
Solution Approach 1:
The patent optimizes the amount and composition of flux alloy components (controlling TiO2, SiO2, ZrO2, Al2O3, Li2O, K2O, Na2O, and metal fluoride within specific ranges) to achieve the desired corrosion resistance while maintaining wire drawing performance. The balanced composition prevents excessive work hardening
Solution Approach 2:
The patent uses a composite flux system with multiple oxides and metal fluoride in specific proportions. This composite approach provides corrosion resistance through the combined effects of different components while maintaining manufacturability, avoiding the work hardening issues associated with single-component fluxes
Data Source
AI summary
A flux cored wire for duplex stainless steel and a manufacturing method thereof are provided. The flux cored wire can include a sheath and a flux filled into the sheath. The flux cored wire comprises about 24.0-30.0 wt % Cr, about 7.0-10.5 wt % Ni, about 2.0-4.0 wt % Mo, about 0.10-2.50 wt % Cu, about 0.40-1.00 wt % Si, about 1.5-3.0 wt % Mn, about 0.10-0.30 wt % N compound (converted value of N), and the remainder including Fe and inevitable impurities on the basis of the total weight of the wire. The flux comprises about 6.50-12.00 wt % of TiO2+SiO2+ZrO2+Al2O3, about 0.10-0.50 wt % of Li2O+K2O+Na2O, about 0.10-2.00 wt % of the other oxides, and about 0.10-0.50 wt % of metal fluoride (converted value of F) on the basis of the total weight of the wire. The flux can be filled into the sheath at a ratio of about 26-35%.