Argon arc welding protects gas purity by 4 to 9 and 5 to 9

Members, what are the effects of 4 and 5 of the gas purity of argon arc welding on the quality of the weld?: 9 If the process is assessed with 5 9, can be used for 4 of the 9 welding. The execution criteria are RCCM, but the standards are not described in detail. Who knows, trouble tell, thanks