High-Strength Cryogenic Welding Joint Composition
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Solution Overview
Problem
Current welding materials for cryogenic applications, such as LNG tanks, face challenges with low tensile strength, poor weldability, and high costs due to high nickel and chromium content, while high-manganese steels require improved cryogenic impact toughness and room-temperature yield strength to resist low-temperature impacts.
Innovation Solution
A high-strength welding joint and flux-cored arc welding wire composition optimized with carbon, silicon, manganese, chromium, molybdenum, sulfur, phosphorus, boron, titanium, nitrogen, and optional elements like tungsten, niobium, vanadium, yttrium, and rare earth metals, within specific weight percentages, to maintain austenite stability and prevent high-temperature cracking, ensuring high low-temperature impact toughness and room-temperature yield strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high nickel and chromium content welding materials are used, then room-temperature yield strength is improved, but material cost increases significantly
Solution Approach 1:
The patent changes the chemical composition parameters by reducing nickel content to 1.0-5.0 wt% and chromium content to 1.0-3.0 wt%, while increasing manganese content to 15.0-30.0 wt%. This parameter transformation maintains the required 400 MPa yield strength through optimized high-manganese austenite stabilization, achieving cost reduction without sacrificing mechanical properties
Solution Approach 2:
The patent substitutes expensive nickel and chromium alloying elements with cheaper manganese as the primary austenite stabilizer. By using manganese-rich composition (15-30 wt%) instead of nickel-rich (50 wt% or greater) materials, the invention achieves comparable cryogenic toughness and strength at significantly lower material cost
2Quantity of substance
If high-manganese steel composition is used, then material cost is reduced, but cryogenic impact toughness and room-temperature yield strength are insufficient
Solution Approach 1:
The patent optimizes multiple composition parameters simultaneously: carbon (0.10-0.50 wt%) for strength, manganese (15.0-30.0 wt%) for austenite stabilization, nickel (1.0-5.0 wt%) and chromium (1.0-3.0 wt%) for controlled precipitation hardening, and boron (0.001-0.010 wt%) for grain boundary strengthening. This multi-parameter optimization achieves both high strength (≥400 MPa yield strength) and high cryogenic impact toughness (≥27J at -196°C)
Solution Approach 2:
The patent creates a composite microstructure consisting of retained austenite matrix with dispersed carbide and nitride precipitates. The synergistic combination of multiple alloying elements produces a complex microstructure where high-manganese austenite provides ductility and toughness, while controlled precipitation of carbides (from C and Mn) and nitrides (from N and Ti) provides strength, achieving both high strength and toughness
3Reliability
If thick steel sheets are used to compensate for low welding joint strength, then structural integrity is improved, but weight and manufacturing complexity increase
Solution Approach 1:
The patent changes the welding material composition parameters to achieve superior welding joint strength (≥400 MPa yield strength). By optimizing the chemical composition with high manganese (15-30 wt%) and controlled carbon (0.10-0.50 wt%), nickel (1.0-5.0 wt%), and chromium (1.0-3.0 wt%), the welding joint achieves strength comparable to or exceeding the base metal, eliminating the need for thick sections and enabling weight reduction
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 provides welding joints with enhanced low-temperature impact toughness and room-temperature yield strength, effectively preventing high-temperature cracking and enabling the use in cryogenic environments like LNG tanks, while reducing material costs by minimizing nickel and chromium content.
Implementation Method 1
manganese (Mn) 15.0% to 30.0%, nickel (Ni) 1.0% to 5.0%, chromium (Cr) 1.0% to 3.0%, and molybdenum (Mo) 0.10% to 0.50% to stabilize austenite
Implementation Method 2
to prevent high-temperature cracking and ensure high low-temperature impact toughness
Data Source
AI summary
A high strength welding joint having excellent toughness at low temperature obtained by welding a cryogenic high-strength high-Mn steel, comprising 0.1-0.61 wt % of C, 0.23-1.0 wt % of Si, 14-35 wt % of Mn, 6 wt % or less of Cr, 1.45-3.5 wt % of Mo, 0.02 wt % or less of S, 0.02 wt % or less of P, 0.001-0.01 wt % of B, 0.001-0.2 wt % of Ti, 0.001-0.3 wt % of N, and balance of Fe and inevitable impurities; and a flux-cored arc welding wire comprising 0.15-0.8 wt % of C, 0.2-1.2 wt % of Si, 15-34 wt % of Mn, 6 wt % or less of Cr, 1.5-4 wt % of Mo, 0.02 wt % or less of S, 0.02 wt % or less of P, 0.01 wt % or less of B, 0.1-0.5 wt % of Ti, 0.001-0.3 wt % of N, 4-15 wt % of TiO2, 0.01-9 wt % of at least one of SiO2, ZrO2 and Al2O3, 0.5-1.7 wt % of at least one of alkali elements including K, Na, and Li, 0.2-1.5 wt % of at least one of F and Ca, and balance of Fe and inevitable impurities.