Why do indentations and pores appear on the surface of flux-cored wire welds?

The main cause of indentations and pores on the surface of flux-cored wire welds is that the structure of the flux-cored wire allows moisture from the air to penetrate the flux core through gaps, preventing the flux from drying. This prevents hydrogen from escaping during welding, leading to pores.

Specific Causes

Structural Characteristics

Flux-cored wire is a thin steel strip rolled into a tube. It is a seamed wire, allowing moisture from the air to penetrate through the gaps into the flux core.

Moisture Decomposition

When the flux becomes damp, it decomposes at high temperatures to produce hydrogen. If this hydrogen is not released promptly, it becomes trapped within the weld during solidification, forming pores.

Influencing Factors

Improper welding parameters: Excessive current or voltage overheats the weld pool, hindering the escape of decomposition gases from the flux core.

Poor contact with the contact tip: Arc instability, uneven droplet transfer, and entrainment of gases into the weld pool.

Base metal contamination: Impurities such as oil and rust release gases during welding that remain in the weld. Preventive Measures
Drying: Ensure the flux-cored wire is stored in a dry environment to avoid moisture.

Parameter Adjustment: Optimize current, voltage, and other parameters to prevent overheating of the weld pool.

Equipment Inspection: Regularly maintain the contact tip and wire feed mechanism to ensure good contact.