Duplex Stainless Steel Weld Composition for Undercut Suppression
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Solution Overview
Problem
Duplex stainless steel welded joints used in umbilical cables are prone to undercuts at the weld toe, leading to stress concentration and potential fatigue fractures, especially in thinner tubes, which can reduce the cable's lifespan.
Innovation Solution
A duplex stainless steel welded joint with specific chemical compositions for both the base metal and weld metal, including elements like Si, Mn, Cr, Ni, Mo, and N, that satisfy certain ratios and ranges to enhance wettability and reduce viscosity, thereby suppressing undercuts and improving fatigue characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the duplex stainless steel tube thickness is reduced to enhance welding workability and increase welding efficiency, then welding efficiency is improved, but the ratio of defects in the shape of weld metal with respect to the thickness increases, leading to reduced fatigue strength
Solution Approach 1:
The patent applies parameter changes by precisely controlling the chemical composition parameters of the weld metal, specifically limiting Si to 0.05-0.70% and Mn to 0.05-0.85%, and satisfying the relationship Si+3Mn≤3.00. These parameter adjustments optimize the weld metal's properties to suppress undercut formation and improve fatigue strength, resolving the contradiction between using thinner tubes for welding efficiency and maintaining sufficient fatigue strength.
2Ease of manufacture
If the chemical composition of weld metal contains high Si and Mn content, then the weld metal may have improved flowability, but undercuts are more likely to occur at the weld toe, leading to stress concentration and reduced fatigue characteristics
Solution Approach 1:
The patent applies parameter changes by establishing specific compositional parameters for the weld metal: Si content of 0.05-0.70%, Mn content of 0.05-0.85%, and the relationship Si+3Mn≤3.00. These parameter changes optimize the balance between weldability and fatigue characteristics by controlling the flowability and solidification behavior of the weld metal to suppress undercut formation.
Solution Approach 2:
The patent applies composite material principles by creating a weld metal with a specific composite composition that includes multiple alloying elements (Si, Mn, Cr, Ni, Mo, N, etc.) in controlled proportions. This composite composition achieves optimal balance between wettability, flowability, and resistance to undercut formation, thereby improving fatigue characteristics while maintaining ease of manufacture.
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 proposed solution effectively suppresses undercuts and enhances the fatigue characteristics of duplex stainless steel welded joints, ensuring improved durability and longevity of umbilical cables.
Implementation Method 1
specific chemical compositions for both the base metal and weld metal, including elements like Si, Mn, Cr, Ni, Mo, and N, that satisfy certain ratios and ranges to enhance wettability
Implementation Method 2
enhance wettability and reduce viscosity, thereby suppressing undercuts
Data Source
AI summary
A duplex stainless steel welded joint is provided that can suppress undercuts and is excellent in fatigue characteristics. The duplex stainless steel welded joint includes a base metal, and a weld metal consisting of, in mass %, C: 0.001% to 0.030%, Si: 0.05% to 0.70%, Mn: 0.05% to 0.85%, P: 0.030% or less, S: 0.0030% or less, Cr: 21.00% to 28.00%, Ni: 5.00% to 11.00%, Mo: 2.00% to 4.50%, Cu: 0.01 to 4.00%, sol. Al: 0.0010 to 0.0500%, N: 0.080% to 0.400%, and B: 0.0001 to 0.0100%, with the balance being Fe and impurities, and satisfies the content of each element in the base metal and the weld metal, and also satisfies Formula (1) and Formula (2).Si+3Mn≤3.00 (1)0<BH/BW<0.15 (2)