High-Ni Steel Weld Joint Composition for Cryogenic Crack Resistance
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Solution Overview
Problem
Weld joints in high Ni steel plates for cryogenic environments face challenges with hot cracking and inadequate low-temperature toughness when using existing welding materials, particularly with high Mn steel wires, which fail to ensure absorbed energy of 27 J or more at -196°C.
Innovation Solution
A weld joint composition with specific chemical compositions for both steel plates and weld metal, along with controlled welding heat input, is used to achieve high strength and low-temperature toughness, where the weld metal contains 13% to 25% Mn and limited Cr content to prevent hot cracking, and the welding heat input is adjusted to 0.5 to 6.0 kJ/mm to ensure fracture propagation through the weld metal rather than the heat-affected zone.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Ni-based alloy welding material containing 50% or more Ni is used, then low-temperature toughness at -196°C equivalent to base metal can be ensured, but welding cost increases significantly
Solution Approach 1:
The invention changes the chemical composition parameters of the welding material by using high Mn content (18-35%) instead of high Ni content (50-65%). This parameter substitution allows achieving similar low-temperature toughness properties through a different compositional approach, thereby reducing material cost while maintaining reliability
Solution Approach 2:
The invention replaces expensive Ni-based alloy welding material with a cheaper high Mn steel welding material. Although Mn-based materials were previously considered insufficient for cryogenic applications, this invention demonstrates that with proper composition control, they can achieve comparable performance at lower cost
2Quantity of substance
If high Mn steel welding material is used, then welding cost is reduced, but hot cracking occurs in the weld joint
Solution Approach 1:
The invention carefully controls the Cr content parameter within a specific range (0.5-5.0%) to prevent hot cracking. By optimizing this compositional parameter along with C content (0.10-0.80%) and Mn content (18-35%), the welding material achieves both cost reduction and hot crack resistance
Solution Approach 2:
The invention creates a composite welding material system combining multiple alloying elements (Mn, Cr, Ni, Mo, C) in specific proportions. This composite approach allows the material to exhibit both cost-effectiveness and resistance to hot cracking through synergistic effects of the elements
3Strength
If Cr content in weld metal is increased to improve strength, then hot cracking resistance decreases
Solution Approach 1:
The invention optimizes the Cr content parameter within a balanced range (0.5-5.0%) rather than maximizing it. This parameter optimization ensures that the weld metal achieves sufficient strength (tensile strength ≥660 MPa) while maintaining hot crack resistance by preventing excessive Cr carbide precipitation at grain boundaries
4Strength
If welding heat input is increased to improve weld metal strength, then fracture propagation shifts to heat-affected zone reducing low-temperature toughness
Solution Approach 1:
The invention establishes a feedback control mechanism for welding heat input based on the desired fracture propagation path. By controlling heat input within 0.5-6.0 kJ/mm, the process ensures that fracture propagates through the weld metal (which has adequate strength) rather than the heat-affected zone, thereby maintaining low-temperature toughness of the weld bond
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 results in a weld joint with high strength and excellent low-temperature toughness without hot cracking, achieving absorbed energy of 27 J or more at -196°C, without the need for expensive Ni-based welding materials.
Implementation Method 1
the components in the flux cored wire are adjusted so as to contain, in the Ni-based alloy outer skin and the flux in total, Mn: 2.0% to 4.5%, Ni: 53% to 65%, Cr: 13% to 19%, Mo: 5% to 14%, Nb: 0.5% to 3.0%... the wire to produce a 9% Ni steel weld joint can yield a weld metal having high strength and excellent toughness
Implementation Method 2
the welding heat input is adjusted to 0.5 to 6.0 kJ/mm to ensure fracture propagation through the weld metal rather than the heat-affected zone
Data Source
AI summary
Provided is a weld joint having high strength and excellent hot crack resistance and low-temperature toughness. High Ni steel plates containing 6.5 mass % to 10.0 mass % of Ni are welded to form a weld metal to obtain a weld joint. The weld metal has a chemical composition containing Mn: 13.0% to 25.0%, Cr: 3.8% or less, Ni: 1.0% to 12.0%, Mo: 0.1% to 5.0%, N: % or less, and O: 0.100% or less, and the strength of the weld metal is adjusted so that the yield strength BYS of each steel plate and the 0.2% proof stress WPS of the weld metal satisfy[WPS]≤[BYS]−100 MPa (1)and the tensile strength BTS of the steel plate and the tensile strength WTS of the weld metal satisfy[WTS]≤[BTS]+100 MPa (2).