Ni-Based Alloy Composition for Heat-Resistant Product Workability
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Solution Overview
Problem
Conventional Ni-based alloys are inadequate for large-sized heat and pressure-resistant products due to poor workability, weldability, and ductility at high temperatures, leading to cracking issues during production and use.
Innovation Solution
A Ni-based alloy composition without Co, optimized with specific ranges of Fe, B, Ti, and N content, and a low-strain rate tensile test to evaluate rupture elongation, enhancing high-temperature strength, hot workability, and resistance to weld cracks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional Ni-based alloy is used for large-sized heat and pressure-resistant products, then high-temperature strength and corrosion resistance are improved, but workability and weldability at high temperatures deteriorate significantly
Solution Approach 1:
The invention changes the chemical composition parameters of the Ni-based alloy by strictly controlling the content of alloying elements (Cr: 20-30%, Ni: 40-60%, Mo: 3-10%, W: 0-10%, Al: 0-3%, Ti: 0-2%, B: 0.0005-0.01%, Fe: balance) to resolve the contradiction between high-temperature strength and workability. This compositional optimization enables both excellent high-temperature performance and improved manufacturability for large-sized products.
2Strength
If conventional Ni-based alloy is used for large-sized products with thick walls, then high-temperature corrosion resistance is improved, but ductility during heating at high temperatures decreases significantly
Solution Approach 1:
The invention optimizes the chemical composition parameters, particularly controlling Cr content at 20-30% and Ni content at 40-60%, to maintain ductility during high-temperature heating while ensuring corrosion resistance. This parameter optimization prevents excessive grain boundary segregation and maintains material stability during service.
3Strength
If large-sized product is produced with conventional Ni-based alloy, then high-temperature strength is improved, but grain coarsening occurs during production due to long heating time
Solution Approach 1:
The invention controls the chemical composition parameters (Cr: 20-30%, Ni: 40-60%, with small additions of Mo, W, Al, Ti, and B) to achieve a balanced microstructure that resists excessive grain coarsening during long heating periods required for large-sized products, while maintaining high-temperature strength.
4Strength
If large-sized product is produced with conventional Ni-based alloy, then high-temperature corrosion resistance is improved, but brittle phase precipitates during cooling due to decreased cooling rate
Solution Approach 1:
The invention optimizes the chemical composition (Cr: 20-30%, Ni: 40-60%, Mo: 3-10%, W: 0-10%, Al: 0-3%, Ti: 0-2%, B: 0.0005-0.01%) to control phase precipitation during cooling. This composition design prevents harmful brittle phases from forming even at the reduced cooling rates inherent to large-sized products, maintaining microstructure stability.
5Strength
If conventional Ni-based alloy is used for large-sized products, then high-temperature strength is improved, but hot working cracks and welding cracks occur easily
Solution Approach 1:
The invention strictly controls the chemical composition parameters, particularly adding B (0.0005-0.01%) to grain boundaries to improve hot working and weldability, while maintaining Cr (20-30%) and Ni (40-60%) for strength. This compositional optimization significantly reduces susceptibility to hot working cracks and welding cracks in large-sized products.
Data Source
Figure 1(a)~1(b)
AI summary
[Problem to be Solved] To provide a Ni-based alloy product for a heat and pressure-resistant part and a producing method therefor. [Solution] A Ni-based alloy product consisting of, by mass percent, C: 0.03 to 0.10%, Si: 0.05 to 1.0%, Mn: 0.1 to 1.5%, Sol.Al: 0.0005 to 0.04%, Fe: 20 to 30%, Cr: not less than 21.0% and less than 25.0%, W: exceeding 6.0% and not more than 9.0%, Ti: 0.05 to 0.2%, Nb: 0.05 to 0.35%, and B: 0.0005 to 0.006%, the balance being Ni and impurities, and the impurities being P: 0.03% or less, S: 0.01% or less, N: less than 0.010%, Mo: less than 0.5%, and Co: 0.8% or less, wherein the product has a composition such that the value of effective B (Beff) defined by Formula (1) is 0.0050 to 0.0300%, and the rupture elongation in a tensile test at 700°C and at a strain rate of 10-6/sec is 20% or more: This alloy may contain one or more kinds of Cu, Ta, Zr, Mg, Ca, REM, and Pd. This alloy product is suitable especially as a large-sized product.