1. Risk of airtightness
Excessive penetration can lead to over-melting of the effective sealing area between the top cover and the aluminum shell, potentially damaging the sealing structure, reducing pressure resistance (standard requirement >1.1 MPa), and increasing the risk of helium leakage (requirement <9.9×10 Pa·m³/s).
2. Hot cracks and porosity defects
When the penetration depth is too large, hot cracks are easily generated at the joint surface (due to the increased temperature gradient). At the same time, the decrease in keyhole stability will lead to an increase in process porosity. These defects will significantly reduce the tensile strength of the weld.
3. Appearance defects and spatter
Excessive melt depth, accompanied by violent fluctuations in the keyhole, can easily lead to melt pool collapse, resulting in large spatter and pit defects.
4. Deterioration of material properties
Excessive penetration depth can lead to an expansion of the heat-affected zone, and intensified evaporation of low-boiling-point elements (such as Mg and Zn) in aluminum alloys, which may alter the material composition and reduce the fatigue strength and corrosion resistance of the weld.
5. Assembly interference
Excessive melting may cause heat damage to the top cover or internal structure of the housing (such as explosion-proof valves and insulating membranes).
In summary, excessive penetration depth can negatively impact welding quality in many ways, including sealing performance, mechanical strength, appearance quality, and material properties. Therefore, it is necessary to optimize process parameters to ensure that the penetration depth is within the standard range.
