Shielded metal arc welding
Shielded Metal Arc Welding is an arc welding process where fusion is done by an electric arc struck between a work piece and the flux covered electrode.
There is no need any other shielding source in this process because its electrodes are itself covered by flux which is melt during welding and covered hole weld pool by producing slag.it is used without the application of pressure, and with filler metal from the electrode.
In 1888, manual metal arc welding (MMA) was first invented in Russia with a bare wire welding with no flux for Shielding.
Flux covered electrodes were discovered in Sweden in 1900 by Kjellberg. Till then welding was done through bare wire