How to choose welding rods

Choosing the right welding rod requires comprehensive consideration of the characteristics of the parent material, working conditions and process conditions. The following are the key principles and operating guidelines:

1. Based on the matching of the parent material
‌Equal strength principle‌

When welding ordinary structural steel (such as Q235), choose welding rods with a tensile strength of the deposited metal ≥ the parent material, such as J422 (E4303) or J502 (E5003).
If the structure is rigid or easy to crack (such as thick plate butt joint), it is necessary to reduce the strength requirements and select low-hydrogen type welding rods with better crack resistance (such as J427/E4315).
‌Equal composition principle‌

Alloy steel/stainless steel welding requires the weld composition to be similar to the parent material. For example, A132 (E347-16) is selected for welding austenitic stainless steel, and special welding rods containing molybdenum and chromium are selected for heat-resistant steel.
2. Select according to working conditions
‌Load and environment‌

Under dynamic load or impact (such as construction machinery): low hydrogen alkaline welding rods (such as J507/E5015) are preferred to ensure high toughness.
High temperature/corrosive environment: select heat-resistant steel welding rods or stainless steel welding rods (such as A302/E309-16).
‌Structural features‌

Rusted workpieces that are difficult to clean: use acidic welding rods with strong anti-porosity (such as J422).
Limited space (such as inside the pipeline): select low-dust acidic welding rods or small-diameter welding rods (Φ2.5-3.2mm).
3. Adapt to process conditions
‌Welding position and efficiency‌

Flat welding: large diameter welding rods (Φ4.0-5.0mm) can be used to improve efficiency.
Vertical/overhead welding: select all-position welding rods (such as J426/E4316), the diameter should be small (Φ3.2mm), and the current is 10%-20% lower than flat welding.
Pipeline annular seam: special vertical downward electrode (such as E7010) to increase speed.
‌Power supply and operation‌

When only AC power supply: use AC/DC dual-purpose low hydrogen electrode (such as J506/E5016).
Alkaline electrode (such as J507): must be reversed DC, and 350℃ drying is required to prevent pores.
4. Special scene processing
‌Dissimilar steel welding‌: select welding rods according to the low-strength side parent material (such as Q235+16Mn select J427), but the process is formulated according to the high-strength side.
‌Overlay repair‌: select special overlay welding rods (such as CMC-E12HA).
‌Tips for avoiding pits‌: Acidic electrode (J422) has good processability but low toughness, and alkaline electrode (J507) has excellent performance but high requirements for operation, so you need to weigh the needs.