Ni-Cr-Fe Welding Electrode Resisting Ductility Dip Cracking
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Solution Overview
Problem
Existing nickel-chromium-iron welding alloys, particularly those with 30% chromium, are prone to ductility dip cracking (DDC) and root cracking in nuclear power generation applications, despite providing resistance to stress corrosion and hot cracking.
Innovation Solution
A nickel-chromium-iron alloy with a specific composition (27-31% Cr, 6-11% Fe, 0.01-0.04% C, 1.5-4% Mn, 1-3% Nb, 0.01-0.50% Ti, 0.0003-0.02% Zr, 0.0005-0.004% B, and balance nickel) is developed, along with a flux coating that uses a short arc welding technique to produce weld deposits with improved resistance to DDC, root cracking, and stress corrosion cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If 30% chromium content is used in nickel-chromium-iron welding alloy, then stress corrosion cracking resistance is improved, but ductility dip cracking susceptibility increases
Solution Approach 1:
The patent modifies the chemical composition parameters of the welding alloy by adding specific small amounts of boron (0.0005-0.005%) and zirconium (0.001-0.01%), and controlling magnesium content (0.01-0.1%). These parameter changes alter the material's microstructure and properties to achieve both stress corrosion cracking resistance and reduced ductility dip cracking susceptibility in the 30% chromium alloy system.
Solution Approach 2:
The invention creates a composite alloy system by combining nickel, chromium (30%), iron, and trace elements (boron, zirconium, magnesium) to produce a material that exhibits both stress corrosion cracking resistance and resistance to ductility dip cracking. The synergistic interaction of these elements creates a composite material with enhanced dual resistance properties.
2Reliability
If conventional welding alloy composition is used, then stress corrosion cracking resistance is achieved, but root cracking resistance is insufficient
Solution Approach 1:
The patent changes the compositional parameters by incorporating boron (0.0005-0.005%), zirconium (0.001-0.01%), and magnesium (0.01-0.1%) in the 30% chromium nickel-iron alloy. These parameter modifications improve both stress corrosion cracking resistance and root cracking resistance simultaneously.
3Reliability
If short arc welding technique is used, then retention of critical elements (boron, zirconium, magnesium) is improved, but welding process control complexity increases
Solution Approach 1:
The patent changes the welding process parameter from conventional arc length to short arc technique (electrode-to-workpiece distance of 1-5mm). This parameter change ensures better retention of volatile elements like boron, zirconium, and magnesium in the weld metal, achieving the desired compositional control.
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 composition and flux coating combination effectively minimize porosity and cracking, enhancing the weld's strength and corrosion resistance, while the short arc technique ensures retention of critical elements like boron, zirconium, and magnesium, significantly reducing DDC and root cracking occurrences.
Implementation Method 1
a flux coating that uses a short arc welding technique to produce weld deposits
Implementation Method 2
the short arc technique ensures retention of critical elements like boron, zirconium, and magnesium
Data Source
AI summary
A Ni—Cr—Fe alloy in the form of a weld deposit, a welding electrode and flux and a method of welding utilizing the Ni—Cr—Fe alloy. The alloy comprises in % by weight: 27-31 Cr, 6-11 Fe, 0.01-0.04 C, 1.5-4 Mn, 1-3 Nb, up to 3 Ta, 1-3 (Nb+Ta), 0.01-0.50 Ti, 0.0003-0.02 Zr, 0.0005-0.004 B, <0.50 Si, 0.50 max Al, <0.50 Cu, <1.0 W, <1.0 Mo, <0.12 Co, <0.015 S, <0.015 P, 0.01 max Mg, balance Ni plus incidental additions and impurities. The welding method includes welding using a short arc wherein the distance from the electrode tip to the weld deposit is maintained at less than 0.125 inch.