Electroslag Welding Wire Composition for 9% Ni Cryogenic Joints
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Solution Overview
Problem
Current welding methods for 9% Ni steel, used in cryogenic applications, result in weld metals with lower strength and cryogenic toughness compared to the base metal, necessitating increased plate thickness and inefficient heat input during gas shielded arc welding.
Innovation Solution
Development of an electroslag welding wire and flux combination with specific chemical compositions, including 6.0-15.0% Ni, C, Si, Mn, and Fe, and optional elements like Cu, Cr, Mo, W, Nb, V, and B, which satisfy certain relationships to achieve high heat input welding with improved mechanical and cryogenic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If gas shielded arc welding is used for 9% Ni steel, then welding efficiency is improved with heat input of 1.4 to 2.2 kJ/mm, but the weld metal strength is lower than the base metal requiring increased plate thickness
Solution Approach 1:
The invention changes the chemical composition parameters of the weld material by specifying precise ranges for C (0.03-0.09%), Si (0.10-0.50%), Mn (0.50-1.50%), Ni (6.0-15.0%), and other alloying elements, along with satisfying specific relationship equations, to achieve both high strength and excellent cryogenic toughness in the weld metal
Solution Approach 2:
The invention uses a composite wire structure combining steel core with multiple alloying elements and flux coating, creating a composite material system that provides both structural strength and desirable welding characteristics for achieving high-strength welds with improved efficiency
2Reliability
If Ni-based weld material is used to achieve excellent cryogenic toughness, then cryogenic properties are improved, but strength is lower than base metal and plate thickness must be increased
Solution Approach 1:
The invention optimizes the Ni content to 6.0-15.0% and precisely controls the interactions between Ni, C, Si, Mn, and other elements through specified relationship equations, achieving a balanced microstructure that simultaneously delivers exceptional cryogenic toughness and high strength properties
3Productivity
If electroslag welding is used with high heat input of 10 kJ/mm or more, then welding efficiency is improved, but maintaining mechanical properties becomes difficult
Solution Approach 1:
The invention specifies precise chemical composition ranges and relationship equations that account for high heat input conditions, controlling the transformation of alloying elements during electroslag welding to maintain excellent mechanical properties including tensile strength ≥620 MPa and elongation ≥20% even at heat inputs of 10 kJ/mm or more
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 enables weld joints with enhanced strength and cryogenic toughness, even at high heat inputs of 10 kJ/mm or more, improving working conditions and mechanical performance while reducing atmospheric contamination and spatter.
Implementation Method 1
electroslag welding wire containing, by mass %... C: more than 0% and 0.07% or less; Si: more than 0% and 0.50% or less; Mn: more than 0% and 1.0% or less; Ni: 6.0 to 15.0%; and Fe: 79% or more
Implementation Method 2
a weld joint obtained using these weld materials... wherein a weld metal in the weld joint contains, by mass %: C: more than 0% and 0.07% or less; Si: more than 0% and 0.50% or less; Mn: more than 0% and 1.0% or less; Ni: 6.0 to 15.0%
Data Source
AI summary
Disclosed herein is an electroslag welding wire containing, by mass % based on total mass of the wire: C: more than 0% and 0.07% or less; Si: more than 0% and 0.50% or less; Mn: more than 0% and 1.0% or less; Ni: 6.0 to 15.0%; and Fe: 79% or more. The electroslag welding wire satisfies the following relationship (1): 0.150≤C+Si/30+Mn/20+Ni/60≤0.300 (1).