Ni-Base Alloy Weld Metal Composition for High Heat Input
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Solution Overview
Problem
Existing Ni-base alloy weld metals exhibit unsatisfactory performance in high-heat-input submerged arc welding or electroslag welding, particularly due to ductility-dip reheat cracking, low corrosion resistance, and insufficient tensile strength, primarily attributed to the precipitation of Cr carbide at grain boundaries during high heat input and low cooling rates.
Innovation Solution
A Ni-base alloy weld metal composition is developed with specific ranges of Cr, Fe, Nb, Ta, C, Mn, N, Si, Al, Mo, Cu, B, Zr, Co, P, and S, where Nb and Ta are added to reduce Cr carbide precipitation, and B and Zr are limited to enhance hot cracking resistance, tensile strength, and corrosion resistance, while maintaining solidification cracking resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high heat input welding is used to improve welding efficiency, then productivity increases, but Cr carbide precipitates at grain boundaries causing ductility-dip reheat cracking
Solution Approach 1:
The patent changes the chemical composition parameters of the weld metal by adding specific amounts of Nb (0.01-0.5 mass%) and Ta (0.01-0.5 mass%) to alter the precipitation behavior of carbides. This compositional modification prevents Cr carbide precipitation at grain boundaries during high heat input welding, thereby maintaining hot cracking resistance while enabling high productivity welding processes.
Solution Approach 2:
The patent creates a composite alloy system by combining Ni-base weld metal with multiple alloying elements (Nb, Ta, Cr, Fe, Mn) in specific proportions. This composite composition works synergistically where Nb and Ta form stable carbides that prevent Cr carbide precipitation, while other elements contribute to overall mechanical properties and corrosion resistance, resolving the contradiction between welding efficiency and cracking resistance.
2Reliability
If Nb and Ta are added to reduce Cr carbide precipitation, then hot cracking resistance improves, but manufacturing complexity increases
Solution Approach 1:
The patent optimizes the concentration parameters of Nb and Ta within narrow ranges (0.01-0.5 mass% each) to achieve the desired effect with minimal additions. This precise parameter control prevents excessive alloy complexity while maintaining hot cracking resistance, as the small amounts of Nb and Ta are sufficient to alter carbide precipitation behavior without creating manufacturing handling difficulties.
3Reliability
If B and Zr are limited to enhance solidification cracking resistance, then reliability improves, but tensile strength may be reduced
Solution Approach 1:
The patent adjusts the concentration parameters of B and Zr to optimized ranges (B: 0.003-0.03 mass%, Zr: 0.003-0.03 mass%) that simultaneously achieve solidification cracking resistance and maintain tensile strength. This balanced parameter selection prevents the formation of brittle phases while ensuring sufficient strength, resolving the contradiction between cracking resistance and mechanical strength.
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 optimized composition results in a weld metal with excellent hot cracking resistance, tensile strength, and corrosion resistance, even in high-heat-input welding conditions, by controlling the precipitation of Cr carbide and stabilizing grain boundaries, thereby improving the weld metal's intergranular corrosion and stress corrosion cracking resistance.
Implementation Method 1
Nb and Ta: 1.5% to 2.5% by mass in total... reduce Cr carbide precipitation
Implementation Method 2
stabilizing grain boundaries, thereby improving the weld metal's intergranular corrosion and stress corrosion cracking resistance
Implementation Method 3
submerged arc welding or electroslag welding by means of a strip electrode overlay welding method
Data Source
AI summary
A weld metal contains Cr: 28.0% to 31.5% by mass, Fe: 7.0% to 11.0% by mass, Nb and Ta: 1.5% to 2.5% by mass in total, C: 0.015% to 0.040% by mass, Mn: 0.5% to 4.0% by mass, N: 0.005% to 0.080% by mass, Si: 0.70% by mass or less (and more than 0%), Al: 0.50% by mass or less, Ti: 0.50% by mass or less, Mo: 0.50% by mass or less, Cu: 0.50% by mass or less, B: 0.0010% by mass or less, Zr: 0.0010% by mass or less, Co: 0.10% by mass or less, P: 0.015% by mass or less, and S: 0.015% by mass or less, the remainder being Ni and incidental impurities.