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As a professional in the field of welding, I'm curious to know if a gas is necessary when welding with flux core. Flux core welding, also known as self-shielded arc welding, utilizes a wire electrode that contains a flux material within its core. This flux produces the necessary shielding gas as it melts, but does this mean external gas is still required? Could you elaborate on the advantages and disadvantages of using gas versus not using gas when performing flux core welding? Additionally, are there any specific applications or materials where the use of gas is particularly beneficial?