Weld Pool Pre-Melting for Uniform Arc Weld Initiation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional arc welding techniques face challenges in achieving uniform weld quality, particularly at the initiation point, leading to potential discontinuities that affect the strength and fatigue performance of joints, and require additional grinding steps that slow down the welding process.
Innovation Solution
A method involving a secondary melting device to form a molten weld pool, followed by deactivation and activation of a primary welding device to initiate and complete the weld, with the secondary device remaining deactivated throughout, using a shielding atmosphere and a movable barrier to protect it from thermal radiation, and employing a common support structure for both devices during relative movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional arc welding is used to create a weld pool in cold solid metal, then the welding process can be initiated, but the weld pool becomes non-uniform with metallic phases and gas bubbles, requiring additional grinding operations that reduce productivity
Solution Approach 1:
The invention applies preliminary action by pre-heating the workpiece surface at the weld initiation point using a heating device (such as a laser, induction heater, or resistance heater) before initiating the arc welding process. This pre-heating creates a localized molten pool in advance, ensuring that when the arc is struck, the welding occurs in uniformly molten metal rather than cold solid metal, thereby eliminating non-uniformities, metallic phases, and gas bubbles that would otherwise require grinding removal
Solution Approach 2:
The invention changes the temperature parameter of the workpiece surface by applying concentrated heat to raise the local temperature above the melting point before welding begins. This parameter change transforms the workpiece surface from cold solid state to molten state, creating optimal conditions for uniform weld pool formation and eliminating the need for subsequent grinding operations
2Reliability
If the weld pool is created in cold solid metal, then the welding process can start, but discontinuities appear in the weld that adversely impact strength and fatigue performance
Solution Approach 1:
The heating device performs preliminary action by creating a uniform molten pool before welding begins, ensuring that the welding process occurs entirely in molten metal without interruptions from cold solid metal. This preliminary molten pool creation eliminates discontinuities such as metallic phases and gas bubbles, resulting in welds with improved homogeneity, strength, and fatigue performance
3Extent of automation
If a welding torch moves along a rail to perform circumferential welding, then automatic welding can be achieved, but the weld initiation point creates a local bead that must be ground off, adding time and reducing productivity
Solution Approach 1:
The heating device performs preliminary action at the weld initiation point by creating a localized molten pool before the welding torch arrives. This ensures that when welding begins, the process occurs in uniformly molten metal without creating a local bead at the initiation point, thereby eliminating the need for grinding operations and reducing the overall welding cycle time while maintaining automatic welding capability
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 enhances weld pool homogeneity and quality by initiating the weld in hot liquid metal rather than cold solid metal, reducing discontinuities and eliminating the need for grinding, thus improving the efficiency and reliability of the welding process.
Implementation Method 1
activating a secondary melting device to form a molten weld pool in a workpiece
Implementation Method 2
using a shielding atmosphere and a movable barrier to protect it from thermal radiation
Implementation Method 3
the secondary device remaining deactivated throughout, using a shielding atmosphere and a movable barrier to protect it from thermal radiation
Data Source
Figure 1a~1b
Figure 1c~1d
Figure 1e~2
AI summary
A weld is formed in a workpiece such as a pipeline by firstly activating a melting device, such as a laser, to form a molten weld pool in the workpiece and then activating a welding device, such as a GMAW torch, to initiate a weld in the weld pool. The weld therefore incorporates the weld pool homogeneously. Relative movement between the activated welding device and the workpiece continues and completes the weld while the melting device remains deactivated.