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Process Optimization for Black Seam & Heavy Spatter in Galvanized Steel Welding with Medium Frequency Seam Welders
Jul 09,2026
Galvanized steel sheets are widely used in mass production for their lightweight and excellent corrosion resistance. Medium frequency seam welders can form continuous welds efficiently. However, blackened weld beads and severe spatter frequently occur during actual production, which mar appearance, raise manufacturing costs, reduce joint strength and corrosion resistance, and restrict production efficiency and product quality. HaiFei Intelligent’s medium frequency seam welder enables welding of galvanized steel without prior zinc layer removal.
1. Analysis of Root Causes
(1) Causes of Black Weld Beads
1.Excessive heat input: Overhigh welding current or low travel speed creates excessive temperature on weld and surrounding areas. Steel oxidizes to form black oxide layers, while vaporized zinc powder adheres and darkens seams further.
2.Residual oxidation & contaminants: Unremoved surface oil, dust and oxide films before welding mix into the molten pool or carbonize under high heat, darkening welds.
3.Abnormal roller electrode condition: Oxidation, abrasion or contaminant buildup on rollers plus poor heat dissipation raise electrode temperature and accelerate weld oxidation.
4.Adverse working environment: Humidity, poor ventilation, dust and corrosive gas intensify weld oxidation and blackening.
(2) Causes of Severe Welding Spatter
1.Rapid zinc vaporization: Zinc has far lower boiling point than steel. Zinc layer vaporizes instantly during welding; trapped vapor bursts through molten metal to form spatter.
2.Mismatched welding parameters: Excessive current, insufficient roller pressure, or mismatched speed and current aggravate spatter.
3.Unstable contact resistance: High conductivity of zinc creates uneven resistance distribution, concentrating current locally and triggering overheating & spatter alongside cold joints.
4.Roller & lap gap issues: Worn rollers, misalignment or improper lap clearance lead to uneven current and localized overheating, generating spatter.
2. Process Optimization Solutions
1.Rational parameter control: Limit current to avoid excessive heat input; boost roller pressure to squeeze out liquid zinc and zinc vapor; raise travel speed to shorten high-temperature residence time; adjust medium frequency and adopt segmented pulse welding to reduce oxidation and spatter.
2.Standard pre-weld surface treatment: Clear surface oxides, oil and dust; weld immediately after cleaning to prevent secondary oxidation.
3.Optimized roller maintenance: Select matched roller electrodes, grind and clean regularly to guarantee good heat dissipation.
4.Regular equipment maintenance: Calibrate welder precision periodically; verify constant pressure & constant temperature functions; maintain cooling systems to stabilize parameters.
5.Controlled welding environment: Keep welding zones dry, ventilated and dust-free, away from corrosive fumes.
6.Standard post-weld treatment: Clear weld slag and spatter promptly; apply simple anti-corrosion protection to boost corrosion resistance and surface finish.
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Wuxi HAIFEI Intelligent Equipment Co., Ltd.
Wuxi HAIFEI Welding Equipment Co., Ltd.
Add: 28 Shuiyun Road, Yuecheng, Jiangyin, Jiangsu Province, China. (Postal Code: 214404)
Mobile: +86 18915302352
Email: wushijie@jshaifei.com