Welding defects: How to avoid weld failures due to “dissolution” problems?

solderedDefect analysis: How to avoid weld failures due to “dissolution” problems?

When a welded joint fails, often the problem is not in the material itself, but in the microscopic “dissolution” process. Understanding and controlling dissolution is the key to eliminating common welding defects and improving product yields. This article will act as your weld diagnostician, taking you to troubleshoot typical problems caused by improper dissolution.

Common defects I: excessive dissolution
Phenomenon: Welding seam edges appear notch (bite edge), the base material is “gouged”; serious cases even burn through the sheet.

Causal analysis:

Excessive heat input: too high current, too slow welding speed.

Excessive soldering time: In brazing, too much heating time leads to excessive dissolution of the base metal in the brazing material.

Solder/base material mismatch: The selected solder is too aggressive to the base material.

Solution:

Optimisation of welding parameters and use of pulse welding to reduce heat input.

Precise control of brazing holding time.

Re-select the solder with lower activity or more compatible operating temperature.

Common defect II: insufficient dissolution
Phenomenon: The solder can not be spread when brazing, just gathered into a ball; low strength of the weld, easy to peel.

Causal analysis:

Insufficient temperature: Failure to reach the temperature required for the solder to actually melt and dissolve with the base metal.

Poor surface cleanliness: Oxide film, oil and grease prevent the solder from contacting the base metal.

Flux failure: Insufficiently active or deteriorated flux to effectively dissolve the oxide film.

Solution:

Calibrate heating equipment to ensure accurate temperatures.

Strictly enforce pre-weld cleaning procedures (e.g. pickling, mechanical grinding).

Select a high quality, activity-matched flux and pay attention to its effective protection range.

Common defect III: Brittle phase generation
Phenomenon: weldAppearance is good, but brittle fracture occurs when subjected to force.

Causal analysis: When there is excessive dissolution and diffusion between the solder and the base material, hard and brittle intermetallic compounds may be formed at the bonding interface.

Solution:

Strictly control the welding temperature and holding time.

An intermediate layer is added between the base metal and the solder to block the direct interaction of harmful elements.

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