AC Welding Waveform for Cryogenic Stainless Steel Toughness
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Solution Overview
Problem
Current submerged arc welding methods for stainless steel result in welds with lower toughness at cryogenic temperatures, requiring expensive controlled ferrite number electrodes and strict welding procedures, which are costly and inefficient.
Innovation Solution
A submerged arc welding system using a modified AC welding waveform with a negative effect, controlled by a welding power source and controller, allows for the use of higher ferrite number electrodes to achieve welds with toughness greater than 40 foot-pounds at -320°F, similar to those produced with more expensive controlled ferrite number electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional DC welding is used with standard 316 L electrodes, then welding process is simple and cost-effective, but weld toughness at cryogenic temperatures is insufficient
Solution Approach 1:
The patent applies parameter changes by modifying the welding waveform parameters (introducing AC waveform with specific negative effect values, adjusting pulse duration and amplitude) to transform the welding process from conventional DC to a controlled AC waveform. This parameter modification enables standard 316 L electrodes to produce welds with toughness exceeding 40 foot-pounds at -320°F, resolving the contradiction between maintaining process simplicity and achieving superior cryogenic toughness.
2Strength
If controlled ferrite number electrodes (316 LCF) are used, then weld toughness at cryogenic temperatures is improved, but electrode cost increases significantly
Solution Approach 1:
The patent employs the principle of using cheaper consumables (standard 316 L electrodes instead of expensive 316 LCF controlled ferrite electrodes) by compensating through waveform control. The modified AC waveform with negative effect values creates conditions that enable inexpensive electrodes to produce high-toughness welds, eliminating the need for costly specialized electrodes while achieving the same or superior performance.
Solution Approach 2:
By changing the welding waveform parameters to AC with controlled negative effect, the patent transforms the performance characteristics of standard electrodes, enabling them to achieve cryogenic toughness levels previously only attainable with expensive controlled ferrite electrodes. This parameter transformation resolves the cost-performance contradiction.
3Strength
If strict welding procedure control is implemented, then adequate toughness level is achieved, but fabrication complexity and time increase
Solution Approach 1:
The patent implements parameter changes by establishing specific AC waveform parameters (negative effect values, pulse characteristics) that inherently produce consistent high-toughness welds. This standardized parameter approach simplifies operator control compared to strict procedural constraints, as the waveform parameters automatically guide the process toward optimal results, reducing the burden on fabricators while ensuring adequate toughness.
4Productivity
If conventional welding waveforms are used, then deposition rate is limited, but with modified AC waveform higher deposition rates are achieved
Solution Approach 1:
The patent applies parameter changes by transitioning from conventional DC or simple AC waveforms to a specifically engineered AC waveform with negative effect values and pulse characteristics. This parameter optimization increases deposition rate while the waveform is controlled through standard welding power sources with programmable parameters, managing the complexity through standardized control interfaces.
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 system provides improved mechanical properties and increased deposition rates, achieving superior toughness and cost-effectiveness by utilizing a 316 L or 308 L electrode with a ferrite number of 10 or less, while maintaining high wire feed speed and reducing labor and electricity costs.
Implementation Method 1
a welding power source which generates a welding output for performing a welding process on stainless steel, the welding output having at least one of a welding output current or welding output voltage in accordance with an AC welding waveform
Data Source
AI summary
Specific AC welding waveforms are utilized to increase the toughness level of austenitic stainless steel above what is achieved using the same welding consumables using standard DC welding waveforms.