Effect of electrode coating thickness

The thickness of the electrode coating (coating) and its chemical composition jointly determine the welding process performance and weld quality. The following is a specific relationship analysis:

1. Relationship between coating composition and welding characteristics
‌Arc stability‌
The chemical composition differences of different coating types (such as titanium type, titanium calcium type, low hydrogen type) significantly affect the arc stability. For example:

Titanium calcium type coating (containing titanium oxide ≥30%) is suitable for AC and DC power supply, the arc is soft and the spatter is small.
Low hydrogen sodium type coating (containing fluorite) requires DC power supply, but has stronger crack resistance and is suitable for high-strength steel.
‌Weld quality impact‌

‌Low hydrogen type coating‌: strictly control the hydrogen content, reduce the risk of pores and cold cracks, and improve the toughness of the weld.
‌Cellulose type coating‌: Contains organic matter, produces a gas-protected molten pool, suitable for vertical welding and overhead welding.
2. Effect of coating thickness on welding process
‌Piercing depth and deposition efficiency‌

Thick coated electrodes can increase the amount of deposited metal, but too thick may reduce the penetration due to the insulation effect, and a larger current is required.
Thin-diameter electrodes (thinner coating) should be used for thin plate welding to avoid burn-through; thin-coated electrodes are also required for the first weld of thick plates to ensure penetration.
‌Operational adaptability‌

The coating thickness affects the melting speed of the electrode: thick-coated electrodes require higher currents, otherwise the electrode is easy to stick (difficult to ignite the arc).

When the space position is limited (such as vertical welding), the coating thickness must match the electrode diameter to ensure the controllability of the molten pool.
3. Defect control and process optimization
‌Prevention of pores and slag inclusions‌

When the coating is damp, hydrogen will be released, resulting in pores, especially low-hydrogen electrodes need to be strictly dried (350–400℃).

Poor coating uniformity may cause incomplete slag wrapping and the formation of slag inclusions.
‌Parameter adjustment points‌

Thick-coated electrodes require higher current to fully melt the coating, but too much current can easily cause undercutting or weld nodules.

Select the power source according to the type of coating: low-hydrogen sodium type only uses DC, and titanium calcium type can use AC.