Why do welding rods need to be dried strictly before welding?

The core purpose of rigorously drying welding rods before welding is to remove moisture from the flux coating to avoid welding defects and ensure weld quality. Specific benefits include:

1. Preventing Porosity and Cracks

Water decomposes into hydrogen and oxygen at high temperatures. Hydrogen dissolves in the molten pool, easily forming pores. This can cause cold cracking during cooling (particularly significant in low-alloy steels). After drying, the diffusible hydrogen content can be controlled below 5ml/100g, while the porosity should not exceed 3%.

2. Optimizing Welding Process Performance

Drying the flux coating restores insulation, stabilizes arc combustion, reduces spatter and arc interruption, and improves slag fluidity, reducing the risk of slag inclusions.

3. Improving the Mechanical Properties of the Weld

By reducing the hydrogen content, the impact toughness and tensile strength of the weld metal can be increased by 15%-30%. Furthermore, dried welding rods can be stored longer in a humidity environment ≤60%.

Drying Process Requirements

Acidic welding rods (such as structural steel welding rods): Typically require drying at 150-250°C for 1-2 hours. Basic low-hydrogen welding rods: Dry at 350-450°C for 1 hour and store in a heat-insulated container at 100-150°C. Excessively high temperatures can cause the coating to decompose, while excessively low temperatures can result in incomplete moisture removal.

Drying must strictly follow the welding rod instructions; different brands of welding rods should not be mixed.