Submerged Arc Welding Heat Input and Bevel Angle Control
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Solution Overview
Problem
Submerged arc welding methods struggle to consistently achieve high toughness in the welded heat affected zone during steel plate butt welding, leading to variations in toughness due to the development of a local brittle zone caused by reheating during the welding process.
Innovation Solution
A submerged arc welding method that controls the welding heat input and inclination angles of the weld metal borderline and the unmelted steel plate borderline, ensuring θ1 ≥ 15°, θ2 ≥ 15°, and Q ≤ 1.3 × t (kJ/cm) for steel plates with 20mm to 40mm thickness, with the top side welding heat input being larger than the bottom side and using 3 electrodes or more for each pass.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If large current and voltage are applied to increase depth of fusion and eliminate unmelted portions, then welding efficiency and fusion depth are improved, but welding heat input increases causing deterioration in toughness of the welded heat affected zone
Solution Approach 1:
The invention applies parameter changes by precisely controlling welding current, voltage, and speed to maintain welding heat input within a specific range (Q ≤ 1.3 × t1.37). This resolves the contradiction by optimizing the balance between fusion depth and heat input, preventing toughness deterioration while ensuring adequate welding efficiency.
Solution Approach 2:
The invention employs dynamic adjustment of welding parameters during the welding process. By making welding conditions adaptable and variable rather than fixed, the system can optimize both fusion depth and heat input control in real-time, resolving the contradiction between productivity and reliability.
2Manufacturing precision
If welding conditions are adjusted to form a wide bead for controlling surface defects, then surface quality is improved, but welding heat input increases causing toughness deterioration
Solution Approach 1:
The invention uses parameter changes by adjusting voltage and welding speed to control bead width while maintaining heat input within acceptable limits. This allows achieving good surface quality without excessive heat input that would deteriorate toughness.
3Productivity
If multiple electrodes are used for single pass welding of bottom side and top side, then welding efficiency is improved, but the welded heat affected zone is reheated causing development of local brittle zone with varied toughness
Solution Approach 1:
The invention applies dynamics by making welding parameters adaptable and variable during the process. By dynamically adjusting current, voltage, and speed for each electrode pass, the system prevents excessive reheating and maintains uniform toughness throughout the welded heat affected zone, resolving the contradiction between efficiency and toughness uniformity.
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 method stabilizes the toughness of the welded heat affected zone, improving industrial outcomes by reducing the area susceptible to toughness deterioration and enhancing crack propagation energy, regardless of groove shape, current, voltage, speed, or electrode arrangement.
Implementation Method 1
Submerged arc welding is a highly efficient welding technique widely used when welding steel plates
Implementation Method 2
supply of a large current to increase the depth of fusion
Data Source
Figure 1
Figure 2~3
AI summary
In a method for butt welding a steel plate with submerged arc welding by welding a top side of the steel plate after welding a bottom side thereof, an angle θ1 between a top side borderline and a line perpendicular to a first parallel line is 15° or more, the top side borderline connecting a junction and a first intersection point, the junction being an intersection between a melting borderline of bottom side weld metal and a melting borderline of top side weld metal, the first intersection point being an intersection between a first parallel line and the melting borderline of the top side weld metal, the first parallel line traversing a position 5 mm from the junction in a direction of an upper surface of the steel plate and being parallel to the upper surface. An angle θ2 between a bottom side borderline and a line perpendicular to a second parallel line is 15° or more, the bottom side borderline connecting the junction and a second intersection point, the second intersection point being an intersection between a second parallel line and the melting borderline of the bottom side weld metal, the second parallel line traversing a position 5 mm from the junction in a direction of a lower surface of the steel plate and being parallel to the lower surface. A total heat input Q (kJ/cm) of a bottom side welding heat input and a top side welding heat input of the steel plate and a wall thickness t (mm) of the steel plate satisfy the relationship Q ≤ 1.3 × t1.37. A high-toughness welded heat affected zone is thus stably obtained.