Thick Steel Plate Weld Joint Layering for Tough Defect-Free Seams
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Solution Overview
Problem
Existing welding methods for thick steel plates, particularly those with a thickness of 50 to 160 mm, struggle to achieve sound welds with high strength and excellent low-temperature toughness, often resulting in defects such as hot cracking and lack of fusion, and are inadequate for cold environments.
Innovation Solution
A welded joint design with specific groove shapes and chemical compositions that include three or more layers of weld metal, each layer having a width between 5.0 mm and 0.4T mm, and a deposition area per layer of 120.0 mm² or less, along with controlled groove angles and chemical elements to ensure high strength and low-temperature toughness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high heat input welding is used to weld thick plates together, then welding efficiency is improved, but the toughness of the weld metal and heat-affected zone cannot be ensured
Solution Approach 1:
The weld is divided into multiple layers (first layer, intermediate layers, and last layer) with different groove angles. Each layer uses optimized welding parameters to control heat input distribution, allowing high efficiency while maintaining toughness through layered construction rather than single-pass welding
Solution Approach 2:
Different groove angles are applied to different layers: the first layer uses a groove angle of 5-15 degrees, intermediate layers use 10-20 degrees, and the last layer uses 15-25 degrees. This local variation in groove geometry optimizes heat distribution and cooling rates in different regions of the weld, ensuring both efficiency and toughness
2Strength
If narrow groove welding is used to reduce heat input, then toughness is improved, but hot cracking and lack of fusion occur
Solution Approach 1:
The welding process is segmented into multiple layers with progressively increasing groove angles. This segmentation allows the weld to build up strength gradually while maintaining proper fusion and avoiding hot cracking through controlled heat distribution across layers
Solution Approach 2:
The groove angle parameter is systematically changed across different layers (5-15° for first layer, 10-20° for intermediate layers, 15-25° for last layer). This parameter progression optimizes both fusion characteristics and crack resistance by adjusting the geometry to match the thermal and mechanical state of each layer
3Reliability
If multi-layer welding is used to ensure sound weld metal, then welding quality is improved, but construction efficiency decreases
Solution Approach 1:
Each layer is assigned a specific groove angle range optimized for its position in the weld structure. This local optimization allows each layer to be welded efficiently while contributing to the overall quality, reducing the total number of passes needed compared to uniform groove angle approaches
Solution Approach 2:
Systematic variation of groove angle parameters across layers enables each layer to be deposited with optimal heat input and cooling rate. This parameter optimization reduces welding time per layer while ensuring sound metallurgical structure, thereby improving overall construction efficiency
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
The solution provides a sound weld metal free of defects, with yield strength of 325 MPa or more, tensile strength of 520 MPa or more, and Charpy impact test energy of 30 J or more at -40°C, enhancing construction efficiency and suitability for offshore structures and wind power generators.
Implementation Method 1
submerged arc welding
Implementation Method 2
submerged arc welding using a flux
Data Source
Figure 1
Figure 2(a)~2(f)
Figure 3(a)~3(f)
AI summary
There are provided a welded joint of steel plates having a plate thickness of 50 to 160 mm or more, the welded joint having sound weld metal free of welding defects, such as hot cracking and lack of fusion, and having both high strength and excellent low-temperature toughness, and a method for manufacturing the welded joint. In the welded joint of the steel plates having a plate thickness T (mm) of 50 to 160 mm, the weld metal includes three or more layers, and the width W (mm) of each layer of the weld metal excluding a first layer and an outermost surface layer is in a range of 5.0 mm or more and 0.4T mm or less.