Analisis Flow Rate Gas Back Purging Ar pada Pengelasan Stainless Steel dengan Proses GTAW terhadap Struktur Mikro dan Laju Korosi dengan Media Decalcium
Austenitice stainless steel 316 and 316L type is one of common grades used in piping system for petrochemical, pharmateucal and food and beverages industries. It has non-magnetic, good mechanical properties, good weldability and good corrosion resistance compare with 304 and 304L.Gas back purging method in welding stainless steel pipe is needed to avoid surface oxidation on root pass. In this research there will be flow rate variation of 6 ℓ/min, 10 ℓ/min, 14 ℓ/min and 18 ℓ/min to determine suitable flow rate. The main object to get lowest corrosion rate between gas back purging variations on welding stainless steel. There will be immersion corrosion test and microstructure. The result of microstructure, form of delta ferrite in welding 316L with gas flow 6 ℓ/min is 33,379%. Welding 304L with same gas flow rate has 26277%. But, the number of delta ferrite reduce by enchanching gas flow rate of 10 ℓ/min. The highest corrosion rates occur in 304L with 6 ℓ/min gas flow rate, 0.261 mm/y, and the lowest corrosion rates occur in 316L by 18 ℓ/min gas flow rate, 0.041 mm/y. This reveals by enchancing flow rate is inadequate to protect root surface against oxydation during welding.