Projection Bolt Welding Geometry for Thin Steel Sheet Strength
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Solution Overview
Problem
In the electric resistance welding of projection bolts to thin steel sheets, excessive fusion occurs, leading to insufficient welding strength and increased brittleness, which results in fractures under bending forces due to the formation of a martensite structure and heat-affected zones, especially in high-tensile steel sheets with small thicknesses.
Innovation Solution
A projection bolt welding method that controls the fusion process by adjusting the volume ratio of the initial fusion portion to the steel sheet component and the pressure conditions, ensuring a balanced fusion area to prevent excessive fusion and maintain the integrity of the steel sheet's base material, thereby enhancing welding strength and preventing rust by securing a sufficient clearance for coating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If electric resistance welding is applied to thin high-tensile steel sheets, then welding strength is improved, but excessive fusion occurs leading to martensite structure formation and increased brittleness
Solution Approach 1:
The patent changes the geometric parameters of the welding projection (height, diameter, shape) to control the fusion volume and heat distribution during welding. By optimizing these parameters, the fusion is limited to prevent excessive heating that would create brittle martensite structures in the heat-affected zone, while still achieving sufficient welding strength.
Solution Approach 2:
The welding projection is pre-formed with specific dimensions and geometry before the welding process. This preliminary shaping ensures that during welding, the fusion is concentrated in a controlled manner, preventing excessive heat spread to the surrounding base material that would otherwise create brittle zones.
2Strength
If fusion volume is increased to ensure welding strength, then bonding is improved, but heat-affected zone expands causing brittleness and fracture risk
Solution Approach 1:
The welding projection is designed with non-uniform geometry (varying height and diameter) to create localized fusion zones. The shape is optimized so that fusion occurs primarily in specific regions while minimizing heat exposure to surrounding areas, thereby maintaining base material properties and preventing brittle heat-affected zones.
Solution Approach 2:
By adjusting the welding projection's dimensional parameters (height, diameter, curvature), the patent controls the fusion volume and heat distribution. This ensures sufficient bonding strength is achieved while limiting the expansion of the heat-affected zone that would otherwise cause brittleness.
3Manufacturing precision
If welding projection size is increased to prevent insufficient fusion, then fusion completeness is improved, but excessive fusion occurs causing brittleness
Solution Approach 1:
The patent optimizes the welding projection's dimensional parameters to achieve the precise fusion completeness needed. By carefully selecting height, diameter, and shape parameters, the projection provides just enough fusion volume to ensure complete bonding without creating excessive heat-affected zones that would reduce welding strength.
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 method ensures proper welding strength by controlling the fusion volume and pressure conditions, preventing excessive fusion and maintaining the steel sheet's base material integrity, which reduces the risk of fractures and rust formation, even in thin steel sheets.
Implementation Method 1
welding the projection bolt to a steel sheet component by electric resistance welding
Implementation Method 2
the projection bolt comprising: a shank having an external thread formed therein; a circular enlarged diameter portion being formed integrally with the shank and having a diameter larger than a diameter of the shank; and a circular welding projection arranged at a center of the circular enlarged diameter portion on a side opposite to the shank
Data Source
Figure 1A~2
Figure 3A~3B
Figure 4A~5
AI summary
Provided is a projection bolt welding method, which involves welding a projection bolt to a steel sheet component by electric resistance welding. The projection bolt includes a shank, a circular enlarged diameter portion, and a welding projection including an initial fusion portion with a tapered portion and a main fusion portion. A ratio of a volume of the initial fusion portion to a volume of a portion of the steel sheet component having the same diameter as a diameter of the initial fusion portion is selected, or a ratio of a circular area of the initial fusion portion to a sheet thickness of the steel sheet component is selected.