Classification and selection of welding electrodes

I. Classification of Welding Electrodes: A Multi-Dimensional "Identity Card"

Welding electrodes are like tools with different characteristics, each possessing unique features from various perspectives:

Classified by Application (Most intuitive)

Structural steel electrodes: For welding ordinary carbon steel and low-alloy steel, such as in construction and bridges.
Heat-resistant steel electrodes: For welding components that operate at high temperatures, such as boilers and engines.
Stainless steel electrodes: For welding stainless steel, ensuring corrosion resistance.
Hardfacing electrodes: For depositing wear-resistant and corrosion-resistant layers on the surface of parts.
Low-temperature steel electrodes: For welding structures that operate in low-temperature environments.
Cast iron electrodes: Specifically for repairing or welding cast iron parts.
Nickel and nickel alloy electrodes, copper and copper alloy electrodes, aluminum and aluminum alloy electrodes: For welding corresponding non-ferrous metals.
Special purpose electrodes: Such as underwater welding electrodes, iron-manganese-aluminum welding electrodes, etc.

Classified by Coating Composition and Slag Characteristics (Technical core)

Acidic electrodes: The coating contains a large amount of acidic oxides (such as SiO₂, TiO₂), and the slag is acidic. Advantages: Insensitive to oil and rust, suitable for both AC and DC power, stable arc. Disadvantages: Poor weld plasticity and toughness. Typical representative: E4303 (titanium-calcium type).
Basic electrodes: The coating contains alkaline oxides (such as CaO, MgO), and the slag is alkaline. Advantages: Good weld mechanical properties (high strength, plasticity, and toughness), strong crack resistance. Disadvantages: Sensitive to oil, rust, and water, requires DC power, poor processability. Typical representative: E5015 (low-hydrogen sodium type).
Classified by Electrode Characteristics
High-efficiency iron powder electrodes: High efficiency.
Moisture-resistant electrodes: Good moisture resistance.
Underwater electrodes, gravity welding electrodes, vertical downward welding electrodes, root pass electrodes, etc.: For specific positions or environments. II. Electrode Selection: A "Selection Guide" for the Right Solution

Choosing the right welding electrode is like matching the right medicine to the "illness," and the key is to consider the workpiece and the requirements:

Based on the chemical composition and mechanical properties of the workpiece:

Welding of the same type of steel: The weld metal strength is usually equal to or slightly higher than that of the base metal. For rigid joints that are prone to cracking, electrodes with slightly lower strength can be selected.
Welding of dissimilar steels: The weld strength should not be lower than the minimum strength of the weaker base metal, while ensuring plasticity and toughness.
High-carbon steel and alloy structural steel: High carbon, sulfur, and phosphorus content makes them prone to cracking, so alkaline low-hydrogen electrodes with good crack resistance should be selected.

Based on the working conditions of the workpiece:

Dynamic load and impact load: Requires high impact toughness and plasticity of the weld, so alkaline low-hydrogen electrodes should be selected.
High temperature, low temperature, wear resistance, and other special conditions: Select corresponding heat-resistant steel, low-temperature steel, surfacing electrodes, etc.

Based on the shape, rigidity, and welding position of the workpiece:

Thick and rigid structures: High welding stress and prone to cracking, so alkaline low-hydrogen electrodes should be selected.
Welding position: For flat welding, use E4303; for all-position welding (vertical, overhead, horizontal), all-position electrodes (such as E4315, E5015) are required.

Based on welding construction conditions:

Site conditions: If there is no DC power supply, low-hydrogen AC/DC dual-purpose electrodes are needed; if ventilation is poor, acidic electrodes or low-dust electrodes should be selected.
Efficiency and economy: For mass production, high-efficiency electrodes such as iron powder electrodes and gravity welding electrodes can be selected.