Steel filler metal structural characterization, welding in stainless steel aisi 304, for the construction of equipment in the food industry

Abstract

 The equipment used for processing, preserving and storing food is made of stainless steel and the most common way to assemble it is by welding. Welding intended to be in direct contact with food or in environments for processing food requires a special methodology for its realization, and must be developed for certain service conditions; this type of welding is called sanitary welding. The present work aims to structurally characterize AISI 304 stainless steel welds, for the construction of equipment in the food industry. Three different types of arc welding were performed: TIG, MIG and Coated Electrode in sheets of 4.7 mm thickness, in order to compare their main characteristics. The welds were characterized macro and micro structurally by Optical Microscopy (OM), Scanning Electron Microscopy (SEM) and EDS, determining phases, chemical composition of the phases, micro constituents and defects present in the welds. In addition, hardness tests were carried out on the welded sheets, from the base material, through the ZAC to the center of the welds, by means of the Vickers hardness test. It was determined that the joints welded with the TIG process presented the best characteristics for this application, without ruling out that an improvement in the manufacture of the bevels and an increase in the energy of the process could improve the penetration and characteristics of the MIG welds.