Selecting the diameter of the electrode for welding

Electrode diameter is a key parameter in manual arc welding. It is determined solely by the diameter of the metal rod, without regard to the coating thickness. What determines the choice of electrode diameter? The primary factor for selecting the diameter is the thickness of the metal being welded, but the type of weld joint, the shape of the edges being prepared for welding, the spatial position of the joint, and the chemical composition of the metal being welded must also be taken into account. The quality of the weld joint depends on the correct selection of electrodes.

For butt welds in the down position, the electrode diameter is selected based on the thickness of the metal, using the following table:

Metal thickness, mm / Electrode diameter, mm

• 1-2 mm / 1.6-2
• 3-5 mm / 2.5-3
• 6-11 mm / 4-5
• 12-24 mm / 5-6
• 25 mm or more / 6 mm or more

It should be noted that the use of electrodes larger than 6 mm in diameter is limited due to their large mass. Furthermore, proper root welding is difficult with such electrodes.

When welding metal up to 4 mm thick, the edges are usually not chamfered, and the weld is performed in a single layer. If the metal being welded is thicker, the edges are chamfered to ensure a high-quality joint, and the weld is multilayered. In multilayer butt joints, the first layer is made with an electrode 2-3 mm in diameter, or less commonly, a 4 mm electrode, and subsequent layers are made with larger diameter electrodes.

For welded T-, corner and lap joints, the following rule applies when selecting the electrode diameter:

For connections made in one pass, electrodes with a diameter of 2-6 mm are used, depending on the thickness of the metal (see the list above).

For multi-layer joints, the first layer is made with 2-3 mm electrodes. The more critical the structure, the smaller the electrode diameter used, which promotes a good root pass, reduces heating of the base metal, and therefore reduces welding stress and deformation.

Some experts recommend taking into account the required weld size when making T-joints and corner joints. For a 3-5 mm shank, use a 3-4 mm electrode, and for a 6-8 mm shank, use a 4-5 mm electrode.

Vertical welding is performed with electrodes no larger than 5 mm in diameter. Overhead welds are performed with electrodes no larger than 4 mm in diameter.

At the same time, every welder should be aware that metal thickness is not always the only criterion when selecting electrode diameter. Experienced welders know that the choice of electrode diameter depends on the type of joint, position, and other factors. Correct selection of electrode diameter helps to achieve high-quality welds.