Pengaruh Variasi Shielding Gas Pada Pengelasan Pipa Duplex Stainless Steel Terhadap Hardness , Struktur Mikro, dan Ferrite Content

Abstract

Duplex Stainless Steel (DSS) is a type of stainless steel with a combination of 2 (two)
phases in a balanced proportion, namely ferritic and austenitic. Duplex Stainless Steel has a
balanced amount of ferritic and austenitic phases. However, unlike its parent metal, the solidification
microstructure of the weld-melt zone does not have nearly equal amounts of ferritic and austenitic
phases. The mechanical properties of duplex welding may decrease due to the selection of shielding
gas. So, the analysis of 3 types of shielding gas variations namely Shielding Gas Pure Ar 99.999%,
Shielding Trimix Gas Ar 87.5% + He11% + H2 1.5% and, Shielding Mixed Gas Ar 98% + N2 2%
against duplex pipes needs to be done by testing hardness, microstructure and ferrite content. The
results of these 3 tests were obtained for hardness values, trimix gas shielding variation of 288 HVN,
shielding pure Ar 277 HVN, shielding mixed gas 276 HVN. In microstructure testing, it was found
that shielding trimix gas got the most ferrite value, and shielding mixed gas got the most austenite
value. Meanwhile, ferrite content testing obtained a shielding trimix gas value of 34.3%, shielding
pure Ar of 33.2%, shielding mixed gas 32.4%. This is due to each microstructure element, such as
nitrogen gas as (austenite forming) and helium gas as (ferrite forming). The higher the austenite, the
lower the hardness.