Laser Overlay Welding on Small-Diameter Inner Surfaces
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Overlay welding on small-diameter inner surfaces is challenging due to high welding heat input, leading to reduced hardness and increased difficulty in preventing defects like porosity, blowholes, and cracks, making it difficult to secure the required hardness and prevent welding defects.
Innovation Solution
The method involves forming a bottomed depression on the base material, feeding filler material to its bottom face, and irradiating a laser beam to melt the filler material, which indirectly heats the surface to be overlaid, reducing base material melting and dilution, and performing overlay welding in a layered manner to prevent cracks and ensure hardness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high welding heat input is applied to perform overlay welding on small-diameter inner surfaces, then the welding process can be completed, but the hardness of the overlaid portion decreases due to base material dilution
Solution Approach 1:
A bottomed depression is formed in advance on the inner surface of the workpiece before overlay welding. This depression confines the filler material and limits the molten pool formation, preventing excessive base material melting and dilution. The preliminary structural preparation enables controlled welding with reduced heat input requirements.
Solution Approach 2:
The depression creates a localized confined space where the welding process occurs. By concentrating the welding operation within this specific geometric constraint, the heat input is localized and controlled, preventing excessive thermal diffusion to the surrounding base material while maintaining adequate melting of the filler material for proper overlay formation.
2Productivity
If continuous heat input is applied to the filler material to ensure complete overlay, then the welding process is efficient, but crystal grains grow largely and the required hardness cannot be secured
Solution Approach 1:
The laser beam irradiation is performed in a periodic or pulsed manner rather than continuous heating. This allows intermittent heat input that melts the filler material sufficiently for overlay formation while providing cooling intervals that prevent excessive crystal grain growth. The periodic heating cycle controls the thermal history of the filler material to achieve desired microstructure and hardness.
3Productivity
If high welding heat input is used to complete the overlay welding process, then the welding can be finished, but welding defects such as porosity, blowholes, and cracks increase
Solution Approach 1:
The bottomed depression is prepared in advance to confine the welding process. This preliminary structural preparation creates a controlled environment that guides molten metal flow and gas evacuation, preventing trap formation that leads to porosity and blowholes. The depression geometry also reduces thermal stress concentration that could cause cracking.
4Adaptability or versatility
If overlay welding is performed on small-diameter inner surfaces using conventional methods, then the process can be attempted, but the operation has high degree of difficulty and stable working method is demanded
Solution Approach 1:
The bottomed depression is formed as a preliminary preparation step that transforms the difficult small-diameter inner surface geometry into a more manageable configuration. This pre-processed geometry provides a natural containment structure that facilitates filler material delivery and laser beam focusing, significantly reducing the operational difficulty of the subsequent welding process.
Solution Approach 2:
The depression creates a localized working zone with optimized geometry for the welding operation. By concentrating the welding activity within this confined space, the process becomes more controllable and less sensitive to positioning errors, improving ease of operation on small-diameter surfaces.
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 facilitates overlay welding by reducing heat input to the base material, increasing the hardness of the overlaid portion, preventing defects, and allowing for easier automation, while ensuring the required hardness and stability of the overlaid portion.
Implementation Method 1
a laser beam as a heat source is irradiated on the bottom face of the depression
Implementation Method 2
the melted filler material comes in contact with the surface to be overlaid, the surface to be overlaid melts due to heat of the filler material
Implementation Method 3
a laser beam as a heat source is irradiated on the bottom face of the depression to which the filler material is fed, thereby forming an overlaid portion
Data Source
Figure 1~2
Figure 3(a)~3(c)
Figure 4(a)~4(d)
AI summary
To facilitate overlay welding while securing a certain hardness of an overlaid portion and preventing welding defects, an overlay welding method for performing overlay welding on a surface P to be overlaid of a base material 50 includes a preparing step of forming a bottomed depression 51, with the surface P to be overlaid being a circumferential surface 51a thereof, and an overlaying step at which a filler material is fed toward a bottom face 51b of the depression 51, and a laser beam as a heat source is irradiated on the bottom face 51b of the depression 51 to which the filler material is fed, thereby forming an overlaid portion W reaching the surface P to be overlaid, while filling the bottom face 51b of the depression 51 with a melted filler material.