Ni-Based Alloy Welding Wire Hot Cracking and Strength
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Solution Overview
Problem
Ni-30Cr-based wires for welding are prone to hot cracking and have lower tensile strength compared to Ni-15Cr-based or Ni-20Cr-based wires, and post-weld heat treatment can lead to the formation of brittle intermetallic compounds and carburized layers that compromise the bond between the weld metal and base metal.
Innovation Solution
A Ni-based alloy solid wire with a composition of Cr: 27.0 to 31.5 mass %, Ti: 0.80 to 2.40 mass %, Nb: 0.30 to 2.40 mass %, C: 0.020 to 0.040 mass %, and controlled amounts of other elements, which suppresses the precipitation of coarse Cr carbides and reduces carbon diffusion, thereby enhancing tensile strength and corrosion resistance while preventing hot cracking and embrittlement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Ni-30Cr-based wire is used to resist primary water stress corrosion cracking, then corrosion resistance is improved, but hot cracking susceptibility increases and tensile strength decreases
Solution Approach 1:
The patent changes the compositional parameters by precisely controlling Cr content (27.0-31.5 mass%), Ti content (0.80-2.40 mass%), Nb content (0.30-2.40 mass%), and C content (0.020-0.040 mass%), along with their ratios, to achieve both high corrosion resistance and high tensile strength while avoiding hot cracking
Solution Approach 2:
The patent creates a composite alloy system combining Ni, Cr, Ti, Nb, and C elements that work synergistically - Cr provides corrosion resistance, Ti and Nb form fine precipitates for strengthening, and C forms carbides to prevent hot cracking, achieving multiple properties simultaneously
2Reliability
If Ni-30Cr-based wire is used to resist primary water stress corrosion cracking, then corrosion resistance is improved, but hot cracking susceptibility increases
Solution Approach 1:
The patent changes compositional parameters including Cr (27.0-31.5 mass%), Ti (0.80-2.40 mass%), Nb (0.30-2.40 mass%), and C (0.020-0.040 mass%), and their ratios, to suppress hot cracking while maintaining corrosion resistance
Solution Approach 2:
The patent converts the potentially harmful effect of carbon into a beneficial one by controlling C content (0.020-0.040 mass%) to form fine carbide precipitates that strengthen the matrix and suppress hot cracking, rather than allowing carbon to cause coarse Cr carbide formation that would promote cracking
3Stress or pressure
If post weld heat treatment is performed to temper carbon steel, then stress relief is improved, but intermetallic compounds precipitate making weld metal brittle
Solution Approach 1:
The patent performs preliminary action by adding Ti and Nb elements during welding that will precipitate as fine carbides and carbonitrides during subsequent PWHT, thereby preventing the precipitation of coarse Cr carbides and intermetallic compounds that would cause embrittlement
Solution Approach 2:
The patent converts the potentially harmful precipitation of coarse Cr carbides and intermetallic compounds during PWHT into a beneficial fine precipitate structure by having Ti and Nb carbides form first, which suppress further Cr carbide precipitation and maintain ductility while still allowing stress relief
4Stress or pressure
If post weld heat treatment is performed to temper carbon steel, then stress relief is improved, but carbon diffusion generates carburized and decarburized layers making bond brittle
Solution Approach 1:
The patent performs preliminary action by having Ti and Nb carbides form during PWHT before significant carbon diffusion can occur, creating a barrier that suppresses carbon diffusion from base metal to weld metal, thereby preventing carburized and decarburized layer formation that would embrittle the bond
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 results in a Ni-based alloy solid wire and weld metal that are less susceptible to hot cracking, maintain high tensile strength, and resist embrittlement during post-weld heat treatment, offering improved corrosion resistance and welding workability.
Implementation Method 1
precipitation of carbides, and carbonitrides, and/or intermetallic compounds of Ti, Nb, Mo, and W improves the tensile strength of weld metal
Implementation Method 2
precipitation of Ti and Nb carbides suppresses precipitation of coarse Cr carbide at grain boundaries
Implementation Method 3
diffusion of carbon from a base metal toward weld metal in PWHT generates a carburized layer and a decarburized layer
Data Source
AI summary
An Ni-based alloy solid wire for welding has a composition comprising specific amounts of Cr, Ti, Nb, C, S, Mn and Fe, where Mo+W, P, Si, Al, Ca, B, Mg, Zr, Co, O, H, and N are controlled to specific amounts, ([Ti]+[Nb])/[C] is 80 to 150, and the balance is Ni and inevitable impurities. [Ti], [Nb], and [C] represent the contents of Ti, Nb, and C (mass %), respectively.