simon718, MMA relies on the flux coating burning off in the arc to provide a gas shield for the molten weld pool.This flux then forms the slag which covers the still molten weld and protects it from the atmosphere until it cools.
Now, if you were welding outside in a windy environment using MMA, then it is possible for the gas shield provided by the flux coating to be blown away and you would end up with porosity. It's not nearly as bad as using bare wire MIG or TIG, but the potential is there. For 90% of the time it isn't a problem but for high quality pipework etc. then it is usual to tent in even when using MMA.
Regards
Now, if you were welding outside in a windy environment using MMA, then it is possible for the gas shield provided by the flux coating to be blown away and you would end up with porosity. It's not nearly as bad as using bare wire MIG or TIG, but the potential is there. For 90% of the time it isn't a problem but for high quality pipework etc. then it is usual to tent in even when using MMA.
Regards
