Stiffened Plate Laser-Arc Welding Root Penetration
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Solution Overview
Problem
Existing methods for welding stiffening materials onto steel plates, such as arc welding, often result in thermal shrinkage leading to tensile residual stress, melt-through, and unmelted parts, which degrade the welding quality and fatigue strength of stiffened plates, especially in closed sectional structures.
Innovation Solution
The method involves forming single-bevel or single-J grooves on stiffening materials, where the root portions are subjected to laser beam welding and the splay portions to arc welding, preventing melt-through and unmelted parts, and using a refraction-type laser welding apparatus to apply laser beam welding from the directions of the splay portions, ensuring complete melting and reducing tensile residual stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If arc welding is applied to single-bevel or single-J grooves in closed sectional structures, then welding can be performed from the outside only, but melt-through occurs and unmelted parts remain in the root portion
Solution Approach 1:
The welding process is divided into two distinct stages: first laser beam welding to achieve complete penetration and eliminate unmelted parts in the root portion, then arc welding to fill the groove and complete the joint. This segmentation allows each welding method to perform its optimal function without the drawbacks of using either method alone.
Solution Approach 2:
Laser beam welding is performed first as a preliminary action to create a sound, fully penetrated root portion before arc welding is applied. This preliminary welding action ensures that the critical root area is free of defects before the filler metal is added in the subsequent arc welding step.
2Ease of manufacture
If arc welding is used to weld stiffening material onto steel plate, then welding can be completed, but tensile residual stress is created due to thermal shrinkage
Solution Approach 1:
The arc welding process is replaced with laser beam welding for the root portion. Laser beam welding produces less thermal shrinkage and consequently generates lower tensile residual stress compared to arc welding, thereby improving the fatigue strength of the welded joint while still achieving complete welding.
3Manufacturing precision
If laser beam welding is applied to root portion from reverse side, then complete melting is achieved without unmelted parts, but the apparatus complexity increases
Solution Approach 1:
Instead of attempting to weld the root portion from the outside where melt-through and incomplete penetration occur, the laser beam welding approach inverts the strategy by welding from the reverse side (inside) of the closed sectional structure. This allows the laser beam to directly melt and penetrate the root portion completely without the problems of over-melting or unmelted areas.
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 improves welding quality and fatigue strength by preventing gaps and cracks, while maintaining the rigidity of the stiffened plate through controlled thermal shrinkage and stress distribution.
Implementation Method 1
the root portion of the single-bevel or single-J groove is subjected to laser beam welding
Implementation Method 2
the splay portion is subjected to arc welding and filled with weld metal
Implementation Method 3
weld metal is thermally shrunk when the temperature of the weld metal is decreased after welding
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A stiffened plate obtained by welding one or a plurality of stiffening materials (20) onto the surface of a steel plate (10), the stiffened plate in which a single-bevel or single-J groove (24) is formed in an end (22) of the stiffening material, which contacts the steel plate; and a root portion (26) of the single-bevel or single-J groove is subjected to laser beam welding, and a splay portion (28) to arc welding.