Deep Penetration Butt Welding with Carbon Gap Addition
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Solution Overview
Problem
The existing butt-joint laser deep-penetration welding method for ULC steel grades with low carbon content (Cs < 0.02%) results in a restless weld pool, severe sagging, slow welding speed, high thermal loads on equipment, reduced service life, and inconsistent seam quality, limiting productivity and reproducibility.
Innovation Solution
Introducing a carbon-containing carrier material into the butt joint gap between the steel end sections, with a carbon content increased to 20% of the melt volume, stabilizes the welding process, allowing for improved weld seam geometry and strength, increased welding speed, and extended equipment life by using a solid-state laser with wavelengths between 980 nm and 1120 nm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional butt-joint laser deep penetration welding is used for ULC steel grades, then welding can be performed, but the weld pool becomes restless with severe sagging and inconsistent seam quality
Solution Approach 1:
A flux-cored wire is introduced as an intermediary element into the weld pool. This flux-cored wire contains basic fluxes that stabilize the weld pool chemistry and physics, preventing restlessness and sagging. The flux-cored wire acts as a mediator between the laser beam and the base metal, controlling the weld pool behavior through chemical reactions and slag formation.
Solution Approach 2:
The invention changes the chemical composition parameters of the weld pool by introducing flux-cored wire with specific basic flux content. This alters the physical and chemical parameters of the weld pool, including viscosity, surface tension, and reaction kinetics, thereby stabilizing the weld pool and improving seam geometry consistency.
2Reliability
If preheating to over 500°C is applied to improve weldability, then welding can proceed, but equipment thermal load increases and service life reduces
Solution Approach 1:
The invention converts the previously harmful effect of direct high-temperature preheating into a beneficial controlled exothermic reaction. The flux-cored wire undergoes controlled combustion and chemical reactions within the weld pool, generating the necessary heat locally without requiring external preheating equipment. This converts the harm of high thermal load into the benefit of localized controlled heating.
Solution Approach 2:
The invention replaces the mechanical/thermal preheating system with a chemical energy system. Instead of using external heating equipment to preheat the workpiece, the flux-cored wire provides the necessary thermal energy through its chemical composition and controlled reaction within the weld pool, eliminating the need for high-temperature preheating equipment.
3Strength
If slow feed rate is used to ensure weld quality, then weld strength can be maintained, but productivity decreases
Solution Approach 1:
The invention changes the chemical composition parameters of the weld pool through flux-cored wire addition, which stabilizes the weld pool and improves metallurgical quality. This allows the welding process to proceed at higher speeds while maintaining weld strength, as the flux-cored wire ensures proper fusion and microstructure formation even at increased feed rates.
Solution Approach 2:
The flux-cored wire provides continuous stabilization of the weld pool throughout the welding process. This continuous chemical and physical stabilization allows for sustained high-speed welding without compromising weld quality, enabling continuous productive operation at optimized feed rates rather than requiring slow, cautious welding.
4Reliability
If high preheating temperature is applied to improve weldability, then welding can proceed, but the process window becomes small making consistent quality impossible
Solution Approach 1:
The invention fundamentally changes the process parameters by eliminating the need for high preheating temperatures. The flux-cored wire provides the necessary thermal and chemical conditions for weldability at lower temperatures, expanding the process window to include a broader range of welding speeds, temperatures, and environmental conditions while maintaining consistent quality.
Solution Approach 2:
The flux-cored wire acts as a mediator that decouples weldability from high preheating requirements. It provides the necessary chemical reactions and thermal energy locally within the weld pool, making the welding process adaptable to various conditions without requiring tight control of preheating parameters, thereby expanding the process window.
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 method achieves stable and high-quality welds with increased productivity, reduced cycle times, and enhanced seam strength, comparable to structural and higher-alloy steel welding, while minimizing material distortion and maintaining low carbon content in the welded structure.
Implementation Method 1
mutually facing end sections of flat steel products... by means of a laser beam
Implementation Method 2
melt pool... melt formed with the laser radiation
Implementation Method 3
the carrier material is largely or completely vaporized during the deep penetration welding process
Implementation Method 4
butt joint laser deep penetration welding process... joining mutually facing end sections of flat steel products
Data Source
Figure 1
AI summary
The invention relates to a butt joint deep penetration laser welding method for joining facing end sections of flat steel products, each having a carbon content of CS < 0.02 %. In order to improve a method of this type so that improved weld seam quality can be achieved in terms of geometry and strength, at least one carbon-containing carrier material is introduced into a butt joint gap between the end sections, having a carbon content of CT ≥ 20∙CS, preferably CT ≥ 100∙CS, and/or carbon is introduced into the butt joint gap or applied to at least one end section in such a way that a volume of the carbon introduced into the butt joint gap corresponds with 1% to 20% of a volume of a melt produced by a butt joint deep penetration laser welding process.