Laser Filler-Wire Repair Welding for Low-Distortion Steel Build-Up
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional welding techniques for repairing low-alloy quench and tempered steels, such as those used in submarine pressure hulls, face challenges including high heat input leading to distortion, residual stress, and reduced toughness in the heat-affected zone, as well as limitations in performing high-quality welds in non-flat positions without preheating and post-weld heat treatment.
Innovation Solution
A low power density laser direct energy deposition method using a hot filler wire to deposit weld build-ups on high strength low-alloy steels, which minimizes heat input, eliminates the need for preheating and post-weld heat treatment, and allows for precise control in various welding positions, including vertical uphill, to produce crack-free heat affected zones with optimized microstructure and mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional welding techniques are used to repair low-alloy quench and tempered steels, then the repair weld can be completed, but high heat input leads to distortion and residual stress
Solution Approach 1:
The patent changes the fundamental parameter of heat input by transitioning from conventional arc welding to laser welding. Laser welding provides concentrated, controlled heat input that achieves weld strength while minimizing thermal diffusion that causes distortion. The laser beam's high energy density allows precise heat localization in the weld zone without extensively heating the surrounding base metal.
Solution Approach 2:
The patent replaces the mechanical arc welding system with a laser-based energy delivery system. This substitution enables more precise control over heat input parameters, including power, speed, and focal point, allowing the weld to achieve required strength while the localized heating minimizes thermal distortion of the component geometry.
2Strength
If conventional welding techniques are used, then weld deposition can be achieved, but the heat-affected zone exhibits reduced toughness
Solution Approach 1:
The patent changes the thermal parameters by using laser welding with controlled heat input and faster cooling rates compared to conventional welding. This parameter change produces a refined microstructure in the heat-affected zone with smaller grain sizes, which maintains higher toughness. The rapid cooling inherent in laser welding prevents excessive grain growth that would reduce toughness.
3Reliability
If preheating and post-weld heat treatment are applied, then crack resistance is improved, but process complexity and time increase
Solution Approach 1:
The patent extracts and eliminates the separate preheating and post-weld heat treatment steps from the welding process. By using laser welding with precisely controlled heat input, the process achieves adequate crack resistance through the weld parameters themselves, removing the need for additional heating equipment and process steps.
Solution Approach 2:
The laser welding process itself provides the necessary thermal control to prevent cracking. The concentrated heat input and controlled cooling rate inherent in laser welding create a thermal cycle that minimizes crack susceptibility, making the process self-sufficient without requiring external preheating or post-weld heat treatment operations.
4Adaptability or versatility
If conventional welding is performed in non-flat positions, then welding can be completed, but maintaining weld quality and heat-affected zone refinement becomes difficult
Solution Approach 1:
The patent replaces gravity-dependent arc welding with laser welding, where the laser beam can be precisely directed and maintained perpendicular to the workpiece surface in various positions. This substitution allows consistent heat input and focal point control regardless of welding position, maintaining heat-affected zone refinement in vertical, overhead, and angled positions that are difficult for conventional welding.
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 method reduces distortion and residual stress, enhances the toughness of weld metal and heat-affected zones, and achieves high-quality welds without preheating, meeting mechanical property standards and minimizing the risk of cold cracking, while allowing for efficient on-site repairs in complex geometries.
Implementation Method 1
directing a laser beam onto the substrate to melt a portion of the substrate to form a molten pool
Implementation Method 2
the filler wire is resistance-heated, optionally by a separate energy source
Data Source
AI summary
The present invention discloses build-up welding methods for repair by low power density laser direct energy deposition upon a substrate to be welded, which do not necessarily require preheating of the substrate. The present invention further discloses welded regions formed by such methods, and products comprising such welded regions. Moreover, the present invention relates to laser additive welding methods and processes using a filler wire for various welding positions and orientations.