High-Mn TIG Weld Metal Composition for Hot Crack Resistance
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Solution Overview
Problem
Hot cracking occurs during TIG welding of high-Mn steel materials, which hinders the formation of welded joints with high strength and excellent cryogenic impact toughness required for cryogenic environments.
Innovation Solution
Introducing 6.0 mass % or more Cr into the weld metal to form Cr phosphide in the liquid phase, thereby suppressing phosphorus segregation and reducing hot cracking, while controlling the chemical composition of high-Mn content steel and weld metal within specific ranges to achieve desired strength and toughness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If TIG welding is performed on high-Mn steel material, then high strength and cryogenic impact toughness can be achieved, but hot cracking occurs during the welding process
Solution Approach 1:
The invention changes the chemical composition parameters of the weld metal by specifying Cr content at 6.0-14.0 mass% and P content at 0.030 mass% or less. This parameter optimization prevents hot cracking while maintaining high strength and cryogenic impact toughness in the welded joint
Solution Approach 2:
Chromium acts as an intermediary element that forms Cr phosphide in the liquid phase during welding. This intermediary compound suppresses phosphorus segregation at grain boundaries, thereby preventing hot cracking while allowing the weld metal to achieve the required mechanical properties
2Reliability
If Cr content is increased to suppress phosphorus segregation, then hot cracking resistance improves, but manufacturing complexity increases
Solution Approach 1:
The invention establishes specific parameter ranges for Cr (6.0-14.0 mass%) and P (0.030 mass% or less) that optimize hot cracking resistance. These defined parameters provide clear manufacturing guidelines, reducing the complexity of composition control while achieving reliable welding results
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 approach significantly reduces hot cracking and achieves high-strength, cryogenically tough TIG welded joints with yield strength of 400 MPa or more and Charpy impact absorbed energy of 28 J or more at -196°C.
Implementation Method 1
introducing 6.0 mass % or more Cr into the weld metal to form Cr phosphide in the liquid phase
Implementation Method 2
a metal is welded by melting a filler metal (a welding rod) in an arc using a non-consumable tungsten electrode rod
Data Source
AI summary
A TIG welded joint in a high-Mn content steel material that can be formed with reduced occurrence of hot cracking during the welding process and has high strength and excellent cryogenic impact toughness. In the TIG welded joint, the high-Mn content steel material has a chemical composition including, by mass %, C: 0.10 to 0.80%, Si: 0.05 to 1.00%, Mn: 18.0 to 30.0%, P: 0.030% or less, S: 0.0070% or less, Al: 0.010 to 0.070%, Cr: 2.5 to 7.0%, N: 0.0050 to 0.0500%, and O: 0.0050% or less, the balance being Fe and incidental impurities, and a weld metal has a chemical composition including C: 0.10 to 0.80%, Si: 0.05 to 1.00%, Mn: 15.0 to 30.0%, P: 0.030% or less, S: 0.030% or less, Al: 0.100% or less, Cr: 6.0 to 14.0%, and N: 0.100% or less, the balance being Fe and incidental impurities.