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How can a manual metal arc electrode have an electrode efficiency greater than 100%?

 

Frequently Asked Questions

The method used to determine the efficiency of manual metal arc electrodes is defined in ISO 2401:1972 (BS EN 22401:1994) 'Covered electrodes - Determination of the efficiency, metal recovery and deposition coefficient'.

The electrode efficiency is calculated by dividing the mass of weld metal deposited by the mass of core wire consumed. The mass of core wire is less than the total mass of electrode consumed i.e. core wire + flux covering.

An electrode efficiency greater than 100% is possible when constituents of the flux covering on the electrode enter the weld pool and contribute to the mass of weld metal deposited.

The composition of the weld metal is often controlled by adding alloying elements to the flux covering. Electrodes are produced more economically by modifying the flux composition to match different parent metal compositions than by changing the composition of the core wire. Furthermore, iron powder may be added to the flux coating to improve the metal deposition rate.

During welding, the flux covering breaks down to supply material to the weld pool and protect the molten metal from atmospheric contamination. Therefore, both the flux and the core wire contribute to the mass of weld metal deposited, but only the mass of core wire consumed is used to determine the electrode efficiency.

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