Ni-Based Alloy Tube Composition for Stable Internal Weld Beads
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Solution Overview
Problem
The challenge lies in forming a stable internal bead during butt welding of Ni-based alloy tubes, where excessive reinforcement height leads to corrosive fluid accumulation and corrosion, while reducing heat input results in incomplete melting and weld defects, compromising corrosion resistance.
Innovation Solution
The solution involves optimizing the chemical composition of the Ni-based alloy tubes by controlling the content of elements such as S, O, Si, Mn, and Sn within specific ranges to stabilize the internal bead formation, preventing excessive reinforcement and ensuring stable welding properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the height of internal bead reinforcement is reduced to prevent corrosive fluid accumulation, then corrosion resistance is improved, but the bead becomes unstable and weld defects occur
Solution Approach 1:
The patent applies parameter changes by precisely controlling the chemical composition parameters of the Ni-based alloy, specifically limiting C to 0.001-0.05%, Si to ≤0.50%, Mn to ≤2.0%, P to ≤0.010%, S to ≤0.0050%, and N to 0.050%, while regulating the frequency of twin crystals to ≥70%. These parameter adjustments stabilize the internal bead formation during welding, preventing both excessive reinforcement height and weld defects, thereby simultaneously improving corrosion resistance and weld stability.
2Object-affected harmful factors
If heat input during welding is reduced to decrease reinforcement height, then corrosion resistance is improved, but the butting surface is not completely melted causing weld defects
Solution Approach 1:
The patent employs parameter changes by optimizing the chemical composition of the Ni-based alloy to enable stable internal bead formation at reduced heat input levels. The controlled content of C (0.001-0.05%), Si (≤0.50%), Mn (≤2.0%), P (≤0.010%), S (≤0.0050%), and N (0.050%), along with regulated twin crystal frequency (≥70%), allows the material to achieve complete melting and stable bead formation even with lower heat input, thus improving corrosion resistance while maintaining weld quality.
3Reliability
If the reinforcement height is excessive to ensure stable bead formation, then weld stability is improved, but corrosive fluid accumulates at the toe of weld promoting corrosion
Solution Approach 1:
The patent resolves this contradiction through parameter changes in the alloy composition, specifically controlling C (0.001-0.05%), Si (≤0.50%), Mn (≤2.0%), P (≤0.010%), S (≤0.0050%), and N (0.050%), while regulating twin crystal frequency to ≥70%. These compositional parameters enable the formation of a stable internal bead with appropriate reinforcement height that prevents weld defects while avoiding excessive height that would cause corrosive fluid accumulation, thereby simultaneously achieving weld stability and corrosion resistance.
4Manufacturing precision
If heat input is increased to ensure complete melting of butting surface, then weld quality is improved, but the reinforcement height becomes excessive causing corrosion
Solution Approach 1:
The patent applies parameter changes by optimizing the chemical composition to enable complete melting and high-quality weld formation at moderate heat input levels. The controlled content of C (0.001-0.05%), Si (≤0.50%), Mn (≤2.0%), P (≤0.010%), S (≤0.0050%), and N (0.050%), along with regulated twin crystal frequency (≥70%), allows the material to achieve stable internal bead formation without excessive reinforcement height, thus maintaining weld quality while preventing corrosion.
Data Source
Figure 1
AI summary
A Ni-based alloy tube includes a chemical composition containing, in mass%, C: 0.0010 to 0.0200%, Si: 0.01 to 0.12%, Mn: 0.04 to 0.50%, P: 0.015% or less, S: 0.0001 to 0.0020%, Cu: 0.02 to 0.80%, Co: 0.10 to 2.50%, Cr: 14.0 to 17.0%, Mo: 15.0 to 17.5%, W: 2.8 to 4.8%, Fe: 4.0 to 7.5%, N: 0.0010 to 0.0200%, Al: 0.04 to 0.50%, O: 0.0004 to 0.0100%, Sn: 0 to 0.010% and optionally elements, with the balance: Ni and impurities, and satisfying [0.0010 ≤ S + 2O + 0.2Sn ≤ 0.0170].