Welded Structure Characteristic Stress Determination
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Solution Overview
Problem
Designing welded structures that accurately account for material mechanical properties at the boundary between low-alloy steel or low-carbon steel and austenitic alloy claddings is challenging due to hydrogen embrittlement, which affects stress concentrations and structural integrity.
Innovation Solution
A method involving test piece preparation with austenitic alloy claddings welded to low-alloy steel or low-carbon steel, followed by hydrogen supply and tensile testing to determine characteristic stresses like fracture stress, allowing for design and manufacturing adjustments to mitigate hydrogen embrittlement-induced damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If austenitic alloy welding material is used to weld low-alloy steel or low-carbon steel, then welding compatibility and corrosion resistance are improved, but hydrogen embrittlement occurs at the boundary causing decreased strength
Solution Approach 1:
The patent applies preliminary action by determining the characteristic stress of the welding structure before actual design and manufacturing. Through test pieces that replicate the welding structure, the patent pre-determines the stress values needed for design, allowing engineers to design structures that inherently avoid hydrogen embrittlement damage by ensuring maximum stress remains below the determined characteristic stress.
Solution Approach 2:
The patent employs parameter changes by systematically varying test conditions including hydrogen supply parameters, test piece geometry parameters, and material composition parameters. This allows determination of characteristic stress under different conditions, enabling design adjustments that maintain strength while preserving the benefits of austenitic alloy welding materials.
2Ease of manufacture
If conventional stress testing is performed without hydrogen supply, then testing simplicity is maintained, but hydrogen embrittlement effects are not captured leading to inaccurate characteristic stress values
Solution Approach 1:
The patent applies preliminary action by establishing a standardized hydrogen supply procedure and test methodology before conducting actual stress testing. This preliminary setup includes preparing test pieces with specific geometries, establishing hydrogen supply parameters, and determining testing conditions in advance, which makes the complex hydrogen embrittlement testing systematic and reproducible.
Solution Approach 2:
The patent introduces hydrogen supply as an intermediary element in the testing process. By controlling hydrogen supply to test pieces during stress testing, the patent captures the embrittlement effect that would otherwise be missed, thereby obtaining accurate characteristic stress values that reflect real service conditions without overly complicating the testing procedure.
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
This approach enables the determination of characteristic stresses in welded structures, enabling the design and manufacturing of structures that suppress damage from hydrogen embrittlement by ensuring maximum stress levels are below the fracture stress, thereby enhancing structural integrity.
Implementation Method 1
The hydrogen retained in the austenitic alloy is diffused when an ambient temperature increases. When a member which is a welding target of the welding material is formed of low-alloy steel or low-carbon steel, the hydrogen retained in the austenitic alloy which is the welding material moves to the member side.
Implementation Method 2
When the hydrogen moves to the member side, hydrogen embrittlement occurs in the vicinity of a boundary of low-alloy steel or low-carbon steel. As a result, the strength in the vicinity of the boundary with the welding material in the member decreases.
Data Source
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AI summary
A test piece preparation step of preparing a test piece (50) including a welding structure in which a welding material formed of an austenitic alloy is welded to a member formed of low-alloy steel or low-carbon steel, a hydrogen supply step of supplying hydrogen to the test piece (50), and a characteristic stress acquisition step of applying a load (F) to the test piece (50) to which hydrogen was supplied and acquiring a characteristic stress showing material mechanical properties of the test piece (50) are executed.