Spot Weld Contact Grooves to Limit Hydrogen Penetration
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Solution Overview
Problem
Spot welding of high strength steel sheets often results in delayed fracture due to hydrogen embrittlement cracking, which is exacerbated by the hardness and tensile residual stress at the weld zone, and existing techniques do not adequately address hydrogen penetration during the welding process.
Innovation Solution
Creating line-shaped grooves on the contact surfaces of steel sheets before welding to discharge oil and prevent hydrogen penetration, with specific parameters for the number, width, and surface roughness of the grooves to ensure effective oil discharge and reduce hydrogen embrittlement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If spot welding is performed on high strength steel sheets with oil coating, then the welding process can proceed without additional oil removal steps, but hydrogen penetrates the weld zone causing delayed fracture
Solution Approach 1:
The invention applies preliminary action by forming line-shaped grooves on the steel sheet surface before spot welding occurs. These grooves are created in advance to provide escape paths for oil and hydrogen during the welding process, preventing hydrogen accumulation in the weld zone while maintaining the simplicity of performing spot welding on oiled sheets.
2Reliability
If the steel sheets are cleaned to remove oil before welding, then hydrogen penetration is reduced, but additional processing steps and time are required
Solution Approach 1:
The invention applies the extraction principle by removing the harmful oil coating from specific contact areas through the line-shaped grooves. Instead of removing oil from the entire sheet surface, the grooves extract and channel the oil away from the weld zone during welding, reducing hydrogen penetration without requiring comprehensive surface cleaning operations.
3Reliability
If electrode force is increased during post heat current, then compressive residual stress is introduced to improve hydrogen embrittlement resistance, but the complexity of the welding process increases
Solution Approach 1:
The invention applies preliminary action by pre-forming the line-shaped grooves on the steel sheet surface before welding. This preliminary structural preparation creates passive escape paths for hydrogen that remain effective throughout the welding process, eliminating the need for complex active control of electrode force variations during welding.
Solution Approach 2:
The invention replaces the mechanical approach of varying electrode force during welding with a structural solution - the line-shaped grooves provide passive hydrogen escape paths through their geometry alone. This substitution eliminates the need for complex force control mechanisms while achieving the same hydrogen embrittlement resistance.
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 significantly reduces hydrogen penetration into the weld zone, enhancing the hydrogen embrittlement resistance of the welded joint and improving the overall quality of the spot weld by minimizing the factors contributing to delayed fracture.
Implementation Method 1
a location where the steel sheets contact each other to form a contact part at the time of initial squeezing of the spot welding is worked in advance to form lines of a plurality of line-shaped grooves running through the contact part and connected to the outside of the contact part
Implementation Method 2
spot welding by resistance welding has been used
Implementation Method 3
the weld zone is heated, then immediately quenched, so the spot weld zone of high strength steel sheets becomes martensite structures and the hardness rises
Implementation Method 4
post heat current can be used to anneal the spot weld zone (nugget part and heat affected zone) to lower the hardness of the weld zone
Data Source
AI summary
Art for spot welding able to suppress penetration of hydrogen, one of the factors behind delayed fracture, at the time of spot welding, that is, a spot welding method in which at one or both of the surfaces of the steel sheets becoming the facing surfaces of the overlaid steel sheets, a location where the steel sheets contact each other to form a contact part at the time of initial squeezing of the spot welding is worked in advance to form a plurality of lines running through the contact part and connected to the outside of the contact part and the spot welding is performed at the location of the contact part and also a steel sheet in which the plurality of lines are formed in advance at the location becoming a contact part when steel sheets contact each other at the time of initial squeezing in the spot welding.