ABSTRAK
Pengaruh arus listrik dan jenis gas pelindung terhadap sifat fisik mekanik sambungan las titik logam tak sejenis antara baja SS400 dan aluminium paduan AA5083, telah diteliti pada studi ini. Metode pengelasan yang digunakan adalah spot TIG welding dengan parameter holding time dan laju aliran gas konstan. Variasi arus listrik yang digunakan adalah 70 A; 80 A; 90 A; dan 100 A. Variasi gas pelindung yang digunakan adalah gas argon; 95% Ar-5% CO2 dan 90% Ar-10% CO2. Pengujian struktur makro dan mikro dilakukan untuk mengetahui sifat fisik sambungan las.Pengujian tarik-geser dan kekerasan mikro vikers dilakukan untuk mengetahui sifat mekanik sambungan las.
Hasil penelitian menunjukkan bahwa semakin besar arus listrik dan kandungan CO2 pada gas pelindung mengakibatkan kapasitas dukung beban geser meningkat dan nilai kekerasan menurun.Variasi arus listrik 100 A dan gas pelindung 90% Ar-10% CO2 menghasilkan sambungan las dengan kapasitas dukung beban geser tertinggi.Ukuran nugget meningkat seiring dengan meningkatnya arus listrik dan kandungan CO2 pada gas pelindung. Nilai kekerasan menurun seiring dengan meningkatnya arus listrik dan kandungan CO2 pada gas pelindung, karena meningkatnya heat input menyebabkan pendinginan semakin lambat dan ukuran butir semakin besar.
Kata kunci: las spot TIG, gas pelindung, gas CO2, gas argon, baja SS400, aluminium paduan AA5083
ABSTRACT
The effect of electric current and the type of shielding gas to the mechanical-physical properties of dissimilar spot TIG welded joints between SS400 steel and AA5083 aluminum alloy has been investigated in this study. Welding method used is spot TIG welding with holding time and gas flow rateparameterswere constantly maintained. The variations of electric current being used are 70 A, 80 A, 90 A, and 100 A. Whilst the variations of shielding gas being used is argon; 95% Ar-5% CO2, and 90% Ar-10% CO2. Macro and micro structural testing was conducted to determine the physical properties of the welded joint. Tensile-shear testing and micro hardness Vikers were conducted to determine the mechanical properties of welded joints.
The results showed that the greater the electric current and the CO2 content in the shielding gas made shear load-bearing capacity increase and hardness values decrease. The variations of electric current of 100 A and a shielding gas 90% Ar-10% CO2 produced welded joints with the highest shear load-bearing capacity. The nugget size increased as the increasing of electric current and the CO2 content in the shielding gas. Hardness value decreased as the increasing of the electric current and CO2 content in the shielding gas. This happened due to the increasing of heat input caused the cooling got slower and the grain size got bigger.
Keywords: TIG spot welding, shielding gas, CO2 gas, argon gas, SS400 steel, aluminum alloy AA5083