How to choose the right welding rod when fusion welding?

The key to selecting welding electrodes lies in considering the base metal, the working conditions, and the construction conditions, combined with the plate thickness and location to determine the diameter.

1. Considering the Base Metal and Working Conditions

For welding of the same type of steel: Choose electrodes of equal strength for ordinary structural steel; for alloy steel, sometimes the composition needs to be similar; for structures with high rigidity and prone to cracking, choose low-strength electrodes; for base metals with high carbon, sulfur, and phosphorus content, choose alkaline low-hydrogen electrodes with good crack resistance.

For welding of dissimilar steels: Generally, choose electrodes that match the lower-strength steel.

For special working conditions: For dynamic loads or impact loads, choose low-hydrogen electrodes with good toughness; for high-temperature, low-temperature, and wear-resistant environments, choose corresponding weather-resistant electrodes.

2. Considering Construction Conditions

For complex, rigid, and easily cracked structures, choose alkaline electrodes with good crack resistance; for structures difficult to clean, choose acidic electrodes that are not sensitive to oil contamination; for structures that cannot be rotated, choose all-position electrodes.

For confined spaces or poor ventilation, choose acidic or low-dust electrodes; for those seeking efficiency, consider high-efficiency electrodes such as iron powder electrodes. 3. Determining the Electrode Diameter

Based on Plate Thickness: Use 2.0-3.2mm for thin plates (<4mm), 3.2-4.0mm for medium-thick plates (4-12mm), and 4.0-5.0mm or thicker for thick plates (>12mm).

Based on Position: For flat welding, thicker electrodes (e.g., 4-5mm) can be used. For vertical and overhead welding, it's best not to exceed 4mm, generally using 3.2mm.

Based on Joint: Use thin electrodes (e.g., 3.2mm) for butt joints as the root pass, and thicker electrodes can be used for the filler layer. T-joints and lap joints, which have good heat dissipation, can use thicker electrodes.

4. Considering Current and Process: The larger the electrode diameter, the higher the required current, which needs to be matched to the equipment's capacity. Manual welding requires consideration of operating habits, while automatic welding is more stable.

5. Considering Economy: While meeting performance requirements, acidic electrodes with good processability can be selected to reduce costs. For large welding volumes, high-efficiency electrodes can be considered. 6. Inspect and Test: Inspect the quality of the welding rods through trial welding. Good welding rods have a stable arc, less spatter, good weld bead formation, and easy slag removal. Weldability tests should be conducted if necessary.

7. Consider Other Factors: If post-weld tempering is required, prevent excessively low weld strength. While meeting performance requirements, choose lower-priced welding rods.