PENGARUH PENGELASAN ULANG GAS METAL ARC WELDING (GMAW) PADA PADUAN Al-Mg 5083 TERHADAP KEKUATAN TARIK, STRUKTUR MIKRO DAN CACAT LAS POROSITAS

Abstract

The process of replating or errors in the grafting material welding Al-Mg 5083 often found in the shipping industry it is necessary to repair or re-welding. In this thesis, the process of re-using a welding machine welding GMAW (Gas Metal Arc Welding) with given variations in the depth of the weld metal reduction of 3 mm and 6 mm repair to know how big effect on the value of tensile strength and microstructure and weld defects caused by porosity. From the tensile test results obtained with the highest tensile strength variation reduction of 6 mm depth of the weld metal repair of 78.15 MPa and strain values of 9.66%. We have the largest percentage porosity value at the beginning of the weld material / rejected by the greatest density of 0.467% and repeated variations on the process of welding the weld metal reduction in the depth of 6 mm by 2.5 gram/cm3. The test results obtained radiographic indication of the porosity of the smallest defect in the reduction of the depth variation of the weld metal 6 mm number one with a diameter of 6 mm. In the observation of micro structure, visible amount of magnesium silicate particles (Mg2Si) contained the most variation in weld metal reduction of 6 mm depth of the weld metal. Mg2Al3 presence will also increase the toughness of the material, the content of zirconium (Zr) and some titanium (Ti) role as the resultant refiner details (grain-refiner), increased levels of refinement details with increasing heat input and speed welding.

Key word : Al-Mg 5083, GMAW welding, repair, tensile strength, density, porosity percentage, radiography, microstructure.