High-Mn Steel Weld Metal Composition for Hot-Crack-Resistant SAW Joints
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Solution Overview
Problem
Hot cracking occurs during submerged arc welding of high-Mn steel materials, which compromises the strength and cryogenic impact toughness of the welded joints, necessitating a solution to enhance both properties simultaneously.
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 optimizing the chemical composition of both the high-Mn steel and weld metal to achieve high strength and excellent cryogenic impact toughness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional welding methods are used on high-Mn steel, then welding can be performed, but hot cracking occurs during the welding process
Solution Approach 1:
The patent changes the chemical composition parameters of the weld metal by introducing 6.0 mass% or more Cr to form Cr phosphide in the liquid phase, thereby suppressing phosphorus segregation and preventing hot cracking during submerged arc welding of high-Mn steel
Solution Approach 2:
Cr phosphide acts as an intermediary substance that forms in the liquid phase during welding to suppress phosphorus segregation at grain boundaries, thereby preventing hot cracking without requiring changes to the base high-Mn steel composition
2Strength
If high-Mn steel is used to achieve high strength and cryogenic toughness, then material performance is improved, but hot cracking occurs during welding
Solution Approach 1:
The patent maintains the high-Mn steel base material composition for achieving high strength and cryogenic toughness while changing the weld metal composition by adding 6.0 mass% or more Cr to prevent hot cracking, thereby resolving the contradiction between material performance and welding quality
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, high-cryogenic-impact-toughness submerged arc welded joints with yield strengths 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
Data Source
AI summary
A submerged arc 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 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.