Electroslag Welding Wire Composition for Cryogenic Toughness
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Solution Overview
Problem
Electroslag welding of 5.0%-10.0% Ni steel for cryogenic applications faces challenges in achieving high efficiency with heat input of 10 kJ/mm or more, resulting in weld metal with compromised cryogenic toughness due to excessive heat input and cooling rates, leading to coarsened structures and reduced absorbed energy.
Innovation Solution
A solid wire for electroslag welding with specific chemical composition limits for elements like Si, Mn, Ni, REM, and others, along with optional additions of Ca, Mg, Cu, Cr, Mo, W, Nb, V, and B, to refine the weld metal structure and enhance cryogenic toughness, while maintaining high efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If electroslag welding is used to achieve high efficiency with heat input of 10 kJ/mm or more, then welding productivity is improved, but the weld metal structure becomes coarsened and cryogenic toughness deteriorates
Solution Approach 1:
The invention changes the chemical composition parameters of the solid wire, specifically controlling Si content at 0.01-0.10%, Mn at 0.05-0.25%, Ni at 10.5-14.0%, and adding REM at 0.002-0.080%. These parameter changes enable the weld metal to maintain fine structure and excellent cryogenic toughness even under high heat input electroslag welding conditions, resolving the contradiction between welding efficiency and cryogenic toughness
Solution Approach 2:
The invention creates a composite chemical composition system in the solid wire that combines multiple alloying elements (Si, Mn, Ni, REM, Al, Ti, Nb, V, B) in specific proportions. This composite composition works synergistically to control weld metal solidification, refine grain structure, and prevent coarsening under high heat input, thereby maintaining both high welding efficiency and excellent cryogenic toughness
2Speed
If high heat input is applied during electroslag welding, then welding speed is improved, but the weld metal is held at high temperature for long hours causing structure coarsening
Solution Approach 1:
The invention modifies the chemical composition parameters to control solidification behavior. By limiting Si to 0.01-0.10% and Mn to 0.05-0.25%, and adding REM (0.002-0.080%), the weld metal achieves faster solidification rate and finer grain structure even when held at high temperature for extended periods, thus maintaining structure fineness while enabling high welding speed
Solution Approach 2:
The invention performs preliminary action by pre-configuring the optimal chemical composition in the solid wire before welding. The controlled alloy content and REM addition are prepared in advance to ensure that during the high heat input welding process, the weld metal solidifies into a fine-grained structure, preventing coarsening before it can occur
3Quantity of substance
If Ni content is reduced in steel for cryogenic service, then material cost is reduced, but the strength and cryogenic toughness of the base metal decrease
Solution Approach 1:
The invention changes the composition parameters by using a solid wire with 10.5-14.0% Ni content that produces weld metal with 10.0-13.0% Ni. This optimized Ni range, combined with controlled Si (0.01-0.10%) and Mn (0.05-0.25%), maintains both strength and cryogenic toughness in the weld metal, enabling the use of lower Ni base metals (5.0-10.0%) while achieving excellent weld joint properties
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 the production of weld joints with excellent strength and cryogenic toughness, suitable for high heat input conditions, by controlling the chemical composition and microstructure of the weld metal, thereby improving the efficiency and performance of the welding process.
Implementation Method 1
the base metal and the welding wire are molten and welded mainly using Joule heat of the molten slag as a heat source
Implementation Method 2
a cooling rate in the vicinity of the water-cooled copper backing plate during the welding is conspicuously large, and the strength of the weld metal in such a region locally increases
Data Source
AI summary
A solid wire for electroslag welding, including Fe and, by mass % based on a total mass of the wire: C: more than 0% and 0.03% or less; Si: more than 0% and 0.10% or less; Mn: more than 0% and 0.25% or less; Ni: 10.5%-14.0%; S: more than 0% and 0.010% or less; Al: more than 0% and 0.250% or less; REM: 0.002%-0.080%; and O: more than 0% and 0.0090% or less.