Ni-Based Alloy Solid Wire for Welding Cracking Resistance
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Solution Overview
Problem
Existing Ni base high Cr alloys for welding suffer from ductility dip cracking and poor weldability, with previous solutions failing to adequately prevent cracking and achieving tensile strength comparable to the base material.
Innovation Solution
A Ni base alloy solid wire with a composition of Cr: 27.0 to 31.5 mass%, Ti: 0.50 to 0.90 mass%, Nb: 0.40 to 0.70 mass%, Ta: 0.10 to 0.30 mass%, and controlled amounts of other elements, which forms microscopic complex carbides at grain boundaries to enhance cracking resistance and tensile strength, while optimizing weldability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Ni-30Cr based filler metal is used for overlay welding or joint welding, then corrosion resistance comparable to base material is achieved, but cracks are likely to be caused in the weld metal
Solution Approach 1:
The patent applies parameter changes by precisely controlling the composition parameters of the filler metal, specifically limiting Cr to 27-31.5 mass%, C to 0.010-0.030 mass%, and adding specific amounts of Ti (0.50-0.90 mass%), Nb (0.40-0.70 mass%), and Ta (0.10-0.30 mass%). This compositional parameter optimization prevents excessive Cr carbide precipitation while maintaining corrosion resistance, thereby resolving the contradiction between corrosion resistance and crack resistance
Solution Approach 2:
The patent creates a composite microstructure by combining multiple carbide-forming elements (Ti, Nb, Ta) with Cr in the filler metal composition. This composite approach at the microstructural level produces a complex carbide system that refines grain structure and prevents coarse Cr carbide precipitation at grain boundaries, thereby improving crack resistance while maintaining the corrosion resistance provided by the high Cr content
2Strength
If Al and Ti are added at 0.5 to 3.0 mass% to improve tensile strength, then tensile strength increases, but a large amount of slag is caused during welding
Solution Approach 1:
The patent applies parameter changes by optimizing the content of Al to 0.10 mass% or less and Ti to 0.50-0.90 mass%, rather than using the broader 0.5-3.0 mass% range. This precise parameter control achieves the necessary tensile strength through controlled carbide precipitation and solid solution strengthening while minimizing oxide formation and slag generation during welding
Solution Approach 2:
The patent applies local quality by distributing multiple strengthening elements (Ti, Nb, Ta) in specific controlled amounts throughout the filler metal composition. This creates localized strengthening effects through fine carbide precipitation at grain boundaries and solid solution strengthening in the matrix, achieving high tensile strength without the excessive Al addition that would cause slag formation
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 solution effectively suppresses ductility dip cracking and increases the tensile strength of weld metal to match or exceed that of the base material, while maintaining excellent weldability by controlling the precipitation of carbides and minimizing slag formation.
Implementation Method 1
forms microscopic complex carbides at grain boundaries to enhance cracking resistance and tensile strength
Data Source
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Figure 3
AI summary
An object of the present invention is to provide a Ni base alloy solid wire for welding, which has excellent cracking resistance to ductility dip cracking in weld metal, can increase the tensile strength of the weld metal to not less than the tensile strength of the base material, and has excellent weldability. The present invention provides a solid wire which has a composition containing Cr: 27.0 to 31.5 mass%, Ti: 0.50 to 0.90 mass%, Nb: 0.40 to 0.70 mass%, Ta: 0.10 to 0.30 mass%, C: 0.010 to 0.030 mass%, and Fe: 5.0 to 11.0 mass%, and is regulated to Al: 0.10 mass% or less, N: 0.020 mass% or less, Zr 0.005 mass% or less, P:0.010 mass% or less, S: 0.0050 mass% or less, Si: 0.50 mass% or less, and Mn: 1.00 mass% or less, with the balance including Ni and inevitable impurities.