1.What is the core reason for the negative impact?
Zinc has a low boiling point (907℃) ◦ Zinc vaporizes rapidly at high welding temperatures (＞1500℃), generating high-pressure vapor, which leads to:
→ Increased spatter: Zinc vapor breaks through the molten metal, forming spark spatter;
→ Porosity defects: Vapor is trapped in the weld to form pores (especially laser welding);
→ Unstable welding: Arc/resistance welding process fluctuates.
Difference in zinc layer conductivity ◦ The resistance of the galvanized layer is lower than that of the steel substrate. During resistance welding, the current is split, and a higher current is required to form an effective nugget.
Electrode contamination ◦ Zinc reacts with copper electrodes to form brass alloy (Zn-Cu), leading to:
→ Electrode adhesion: The zinc layer adheres to the electrode surface;
→ Shortened electrode life: The life of traditional electrodes is reduced to 1/3~1/5 of that of zinc-free steel.
2.How can I choose the type of galvanizing to optimize weldability?
Prioritize electrogalvanizing (EG): Thin zinc layer (5~10μm) greatly reduces spatter and electrode loss, suitable for high-beat body production lines.
Typical applications: exterior covers such as doors and hoods.
Galvanizing (GA) is a balanced choice ◦ The zinc-iron alloy layer has a high melting point (640℃→1200℃), the amount of steam is reduced by more than 50%, and the electrode life is increased to 1.5 times that of EG.
Typical applications: parts such as body frames and floors that require both corrosion resistance and welding.
Avoid thick hot-dip galvanizing (HDG) for precision welding
It is only recommended for non-appearance structural parts (such as chassis parts), and strict process control is required during welding.
3.What is the "four-step method" for optimizing galvanized sheet welding?
Material selection and matching: EG for appearance parts/precision welding, GA for structural parts, avoid using HDG in high-precision welding areas;
Equipment upgrade: zinc-resistant electrode + dynamic parameter control system;
Process adaptation: increase pressure/current, double pulse welding, reserve exhaust gap;
Local treatment: laser cleaning of welding spot area (higher cost but significant effect).
4.What are the special challenges and countermeasures for new energy vehicles?
Battery pack welding:
Problem: Dissimilar metal welding of galvanized steel and aluminum shell (prone to produce brittle Zn-Al alloy); Solution: Use friction stir welding (FSW) or ultrasonic welding to avoid molten zinc participating in the reaction. Lightweight materials: Ultra-high strength steel galvanized sheet (such as DP1000+EG): Need to increase welding pressure + pulse current to prevent cracking.
5.What are the industry's best practices and innovative solutions?
Electrode technology innovation: Dispersion-strengthened copper electrode (such as Cu-Cr-Zr): life is 3 times longer than that of traditional electrodes; Composite coating electrode: surface plating with molybdenum (Mo) or nickel (Ni) to prevent zinc diffusion.
Intelligent adaptation of welding parameters: Dynamic resistance monitoring: real-time adjustment of current to compensate for the shunt effect of the zinc layer; Adaptive pressure control: dynamic increase of electrode pressure according to the thickness of the zinc layer (such as EG: 250kgf → HDG: 400kgf).
Material pretreatment ◦ Laser cleaning: partial removal of the zinc layer before welding (accuracy ±0.5mm); Conductive coating: spray conductive paste on the solder joint area to reduce shunt.