Ni-Based Welding Wire Composition for Hot-Crack-Resistant LNG Joints
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Solution Overview
Problem
Current submerged arc welding methods for high-strength steels used in LNG storage tanks face challenges in achieving high tensile strength, toughness, and hot-cracking resistance while maintaining low-temperature properties, with existing technologies failing to sufficiently suppress hot-cracking and ensuring adequate ductility.
Innovation Solution
A Ni-based alloy wire with specific chemical composition, including Ta and REM, is developed to enhance tensile strength and hot-cracking resistance through precipitation strengthening and carbonitride formation, allowing for high-strength, high-toughness welds with reduced hot-cracking, suitable for flat, horizontal fillet, and lateral posture welding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high-strength steels (yield strength: 620 MPa or more, tensile strength: 750 MPa to 880 MPa) are used to increase strength, then tensile strength is improved, but toughness and hot-cracking resistance properties are degraded
Solution Approach 1:
The invention changes the chemical composition parameters of the welding wire by precisely controlling the content ranges of alloying elements (Ni: 65-82.4%, Mo: 15-25%, W: 2.5-10%, Ta: 0.002-0.1%, and other elements within specified ranges) to achieve a balance between high tensile strength (720 MPa or more) and improved toughness with hot-cracking resistance, resolving the trade-off between strength and reliability
Solution Approach 2:
The invention creates a composite alloy system combining multiple elements (Ni-Mo-W-Ta-based) where each element contributes specific properties: Ni provides base strength and ductility, Mo and W enhance strength through solid solution strengthening, and Ta forms precipitates for strengthening while improving hot-cracking resistance. This composite material approach achieves both high tensile strength and reliability
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 Ni-based alloy wire achieves high tensile strength, excellent ductility, and suppressed hot-cracking, enabling the production of high-quality welding joints with improved mechanical properties for LNG storage tank applications.
Implementation Method 1
a high-quality welding joint capable of being applied to flat welding, horizontal fillet welding, and lateral posture welding, having high tensile strength and toughness
Data Source
AI summary
A Ni-based alloy wire for submerged arc welding according to an aspect of the present invention includes, as a chemical composition, by mass %, C: 0.001% to 0.060%, Si: 0.01% to 3.00%, Mn: 0.01% to 6.00%, Mo: 15.0% to 25.0%, W: 2.5% to 10.0%, Ta: 0.002% to 0.100%, Ni: 65.0% to 82.4%, Al: 0% to 2.00%, Ti: 0% to 2.00%, Cu: 0% to 1.0%, P: 0% to 0.0200%, S: 0% to 0.0200%, N: 0% to 0.1000%, O: 0% to 0.0100%, Fe: 0% to 10.0000%, Co: 0% to 0.1000%, Cr: 0% to 1.0000%, V: 0% to 0.1000%, Nb: 0% to 0.1000%, B: 0% to 0.0100%, Bi: 0% to 0.0100%, Ca: 0% to 0.0200%, REM: 0% to 0.0300%, Zr: 0% to 0.1000%, and a remainder: impurities; in which a value X is 0.010% to 0.180%.