Ni-Based Nuclear Pipe Composition for Strength Without Remelting
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Solution Overview
Problem
Current Ni-based alloy pipes for nuclear power lack sufficient strength and economic efficiency, with existing methods requiring secondary melting that increases costs and can lead to grain segregation, reducing strength.
Innovation Solution
An Ni-based alloy pipe with a specific chemical composition and processing method that includes cold working to achieve uniform grain diameter and precipitation strengthening using titanium, without secondary melting, resulting in enhanced strength and ductility while maintaining economic efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If secondary melting method is used to increase strength, then strength is improved, but production cost increases and grain segregation occurs
Solution Approach 1:
The invention changes the chemical composition parameters of the Ni-based alloy by precisely controlling the content ranges of C, Si, Mn, P, S, Cu, Ni, Cr, Mo, Co, Al, N, Ti, Zr, and Nb elements. This compositional optimization enables the alloy to achieve high strength through solid-solution strengthening and precipitation hardening without requiring secondary melting, thus reducing production costs while avoiding grain segregation issues
Solution Approach 2:
The invention replaces the expensive secondary melting process with a more economical single-melting approach by optimizing the alloy composition. The carefully controlled chemical composition allows the material to achieve required strength properties through standard manufacturing processes, eliminating the need for costly re-melting operations
2Strength
If secondary melting method is used to increase strength, then strength is improved, but grain segregation occurs decreasing strength uniformity
Solution Approach 1:
The invention optimizes the chemical composition parameters to prevent grain segregation. By controlling the content of alloying elements within specific ranges and satisfying the relational expression involving N, Ti, and grain diameter, the alloy achieves uniform grain structure and consistent strength properties throughout, eliminating the grain segregation problem associated with secondary melting
3Strength
If Ni-based alloy composition is optimized for strength, then strength is improved, but ductility may decrease
Solution Approach 1:
The invention carefully balances the chemical composition parameters to achieve both high strength and good ductility. By optimizing the content ranges of strengthening elements (C, Ti, Nb, N) and ductility-maintaining elements (Ni, Cr, Fe), and by satisfying the relational expression that connects composition to grain diameter, the alloy achieves a favorable combination of strength and ductility that neither extreme composition could provide alone
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 alloy pipe achieves high mechanical properties with improved strength and ductility, suitable for nuclear power applications, and reduces production costs by avoiding secondary melting.
Implementation Method 1
the gist of the present invention is the following Ni-based alloy pipe for nuclear power... satisfying Formula (i) in relation to an average grain diameter, wherein a standard deviation of grain diameters is 20 μm or less, and a hardness of insides of grains is 180 HV or more. (N−Ti×14/48)×d3≥4000
Implementation Method 2
An Ni-based alloy pipe with a specific chemical composition (C: 0.015-0.030%, Si: 0.10-0.50%, Mn: 0.10-0.50%, P: 0.040% or less, S: 0.015% or less, Cu: 0.01-0.20%, Ni: 50.0-65.0%, Cr: 19.0-35.0%, Mo: 0-0.40%, Co: 0.040% or less, Al: 0.30% or less, N: 0.010-0.080%, Ti: 0.020-0.180%, Zr: 0.010% or less, Nb: 0.060% or less) that achieves high strength and ductility through precipitation and solid-solution strengthening
Data Source
AI summary
An Ni-based alloy pipe for nuclear power has a chemical composition consisting of, in mass percent: C: 0.015 to 0.030%, Si: 0.10 to 0.50%, Mn: 0.10 to 0.50%, P: 0.040% or less, S: 0.015% or less, Cu: 0.01 to 0.20%, Ni: 50.0 to 65.0%, Cr: 19.0 to 35.0%, Mo: 0 to 0.40%, Co: 0.040% or less, Al: 0.30% or less, N: 0.010 to 0.080%, Ti: 0.020 to 0.180%, Zr: 0.010% or less, and Nb: 0.060% or less, the balance: Fe and impurities, and satisfying [(N−Ti×14/48)×d3≥4000] in relation to an average grain diameter, wherein a standard deviation of grain diameters is 20 μm or less, and a hardness of insides of grains is 180 HV or more.