The paper presents the analysis and experimental research that is performed to correlate the welding procedure with hardness in HAZ (Heat Affected Zone) and toughness of welded joints of austenitic stainless steel X6CrNiTi18-10, used to build cryogenic tanks to liquid nitrogen storage. For this were welded a sample by MIG welding process.In a first step it was estimated the hardness of HAZ with a soft computer, and then it was made a testing to its experimental verification welding procedure. The results showed that the welding procedures developed and implemented resulted in obtaining the HAZ hardness almost equal to those of basic material. This shows that the HAZ properties are unaffected and a good weldabillity of austenitic stainless steel. In a second step the toughness were measured at room temperature and work temperature, -196°C.