Penerapan active flux pada proses las TIG atau A-TIG bertujuan untuk menaikkan penetrasi las sehingga produktifitasnya meningkat. Pengelasan pada bahan tebal penetrasinya meningkat, lapisan lasan berkurang sehingga mengurangi efek cost to cast pada pengelasan multi layer. Dalam penelitian ini dilakukan pengelasan pada bahan AISI 316L dengan 3 jenis serbuk oksida active fluxyaitu: Fe2O3, TiO2, dan Cr2O3, dan sebagai pembanding dilakukan proses las SMAW dengan elektroda AWS A5.4 (E308-16) dan proses las TIG konvensional. Hasil penelitian menunjukkan bahwa penetrasi meningkat dibandingkan terhadap proses pengelasan  konvensional hingga mencapai 22 s.d 50 % dan terhadap proses pengelasan SMAW (49 s.d 83)%. Distorsi proses las A-TIG cenderung menurun dibandingkan  terhadap proses las TIG konvensional dan SMAW. Nilai kekerasan di HAZ dan WM pada semua proses A-TIG terutama proses las A-TIG flux Cr2O3 meningkat secara signifikan. Komposisi δ-ferit di WM semua jenis proses las meningkat, terutama pada proses las SMAW, fraksi volume δ-ferit meningkat secara signifikan.Kata Kunci : TIG, A-TIG, active flux, δ-ferit, SMAW

The success of Dissimilar Metal Welding (DMW) occurred in optimal Heat-input (HI) parameters. The quality of welding joints was affected by dilution, hardness value, and intermetallic microstructure. DMW quality research was carried out on stainless steel SA SS312-TP304 and SA 53GrB carbon steel using the GTAW (Gas Tungsten Arc Welding) process with Heat-input of 1866.6 to 2362.2 J/mm. Visual observation on weld joints was not found weld defects. The optimal dilution area in the Schaeffler Diagram was obtained 35.35% austenitic area and without ferrite content. The lowest hardness value on carbon steel was 145 HV. The highest hardness value of 197 HV occurred in filler-metal dilution on carbon steel, so the difference in the value of hardness was high. The hardness value on stainless steel was 184 HV and in filler-metal stainless steel dilution was 172– 90 HV, so the difference in hardness value was low. Microstructure filler-metal dilution on stainless steel was austenite-dendritic, filler-metal dilution on carbon steel was fine-grained dendritic, and on allweld metal coarse-grained dendritic metal. HAZ stainless steel austenite microstructure and ferrite-pearlite carbon steel with an indication of a ferrite net. Observation of dilution, hardness value, and microstructure in DMW did not have a significant effect. This welded joint could be used as a reference in the DMW fabrication process for stainless steel and carbon steel pipe connections.