Arc-Welded Laminated Molding for Uniform Ferrite Grain Structure
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Solution Overview
Problem
Additively manufactured objects using arc welding exhibit structural variations due to differences in cooling rates of weld bead layers, leading to non-uniform mechanical strength, making it challenging to achieve consistent tensile strength, fatigue strength, and toughness.
Innovation Solution
The method involves controlling interlayer time and heat input to maintain a surface layer temperature between 200°C to 550°C, ensuring each weld bead layer has an average ferrite grain diameter of 11 µm or less, except for the surface oxide film, resulting in a uniformed structure with consistent mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If arc welding is used for additive manufacturing, then production efficiency is improved, but structural uniformity deteriorates due to varying cooling rates in different layers
Solution Approach 1:
The patent applies preliminary action by pre-heating the substrate and controlling interlayer temperatures before deposition occurs. This prepares the thermal environment in advance to ensure uniform cooling rates across all layers, preventing structural non-uniformity while maintaining high production efficiency through continuous welding processes
Solution Approach 2:
The patent changes thermal parameters (substrate temperature, interlayer temperature, heating rate) to optimize the cooling rate uniformity. By controlling these parameters, the patent achieves consistent microstructural properties across layers while maintaining the productivity benefits of arc welding additive manufacturing
2Speed
If cooling rates vary in weld bead layers, then production speed is improved, but mechanical strength uniformity deteriorates
Solution Approach 1:
The patent changes thermal parameters (substrate temperature, interlayer temperature, heating rate) to optimize the cooling rate uniformity. By controlling these parameters, the patent achieves consistent microstructural properties across layers while maintaining the productivity benefits of arc welding additive manufacturing
Solution Approach 2:
The patent employs feedback control by monitoring temperatures and adjusting heating rates to maintain uniform cooling conditions. This ensures consistent mechanical properties across layers while allowing high production speeds through optimized process control
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 production of additively manufactured objects with substantially uniform strength and excellent mechanical properties, including high Vickers hardness and toughness, by transforming perlite and bainite into fine ferrite phases, while maintaining production efficiency.
Implementation Method 1
an additively manufactured object formed by melting and solidifying a mild steel by use of an arc
Implementation Method 2
melting a metal powder or metal wire by use of a heat source such as laser or arc
Implementation Method 3
melting and solidifying a mild steel by use of an arc
Implementation Method 4
the area ratio of a ferrite phase is 80% or more, the average grain diameter of the ferrite phase is 6 μm or less
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
A laminated molding (11) formed by laminating bead weld layers (61) in which a filler metal W made of mild steel is fused and solidified, wherein at least one bead weld layer (61) has a ferrite phase having an average grain size of 11 µm except for a surface oxide film. Thus, provided are a laminated molding obtained by a laminated molding method using arc welding the texture of which is uniformized to exhibit substantially uniformized strength, and a method for manufacturing the laminated molding.