ANALISIS DISTORSI DAN SIFAT-SIFAT MEKANIK LAS MIG 2-LAYER BAHAN AA5083-H116 DAN AA5052

MUDJIJANA, Prof. Ir.Mochammad Noer Ilman, S.T., M.Sc., Ph.D., IPM.

2020 | Disertasi | DOKTOR TEKNIK MESIN

Indonesia merupakan negara maritim sehingga banyak diperlukan kapal untuk menghubungkan pulau-pulau yang ada di wilayah Negara Kesatuan Republik Indonesia. Bahan kapal dapat dibuat dari baja A36, komposit, dan aluminium paduan AA5xxx. Pembuatan kapal dari bahan logam dilakukan dengan pengelasan. Pengelasan aluminium paduan menggunakan las TIG (tungsten inert gas) dan MIG (metal inert gas). Pengelasan aluminium paduan sulit dilakukan karena adanya oksida pada permukaan pelat dan sangat sulit terhindar dari porositas. Parameter penting hasil dari pengelasan adalah distorsi dan sifat-sifat mekanik. Tujuan penelitian ini melakukan analisis distorsi dan sifat-sifat mekanik pada bahan AA5083-H116 dan AA5052 yang dilas MIG 1-layer dan 2-layer menggunakan elektroda 5356. Bahan AA5083-H116 dan AA5052 dibuat spesimen berukuran 300 × 75 × 3 mm dan 400 × 75 × 5 mm. Sepasang spesimen dilas menggunakan MIG 200S Tenjima dengan elektroda ER5356. Pengelasan dilakukan 1-layer dan 2-layer menggunakan 5 metode. Pengelasan 1-layer (S-MIG), 2-layer multi-run, dan konvensional menggunakan variabel bebas kecepatan las, sedangkan variabel kontrol tegangan dan arus. Pengelasan tandem mendatar (1G) dan harisontal (2G) menggunakan variabel bebas jarak elektroda, sedangkan variabel kontrol tegangan, arus, dan kecepatan las. Variabel terikat adalah distorsi, strukturmikro, kekerasan, kekuatan tarik, kekuatan bending, ketangguhan impak Charpy, dan laju perambatan fatik.Selama pengelasan berlangsung siklus termal diukur menggunakan NI USB-9162 dan ADAM-4561+ dengan sensor kawat termokopel tipe-K. Hasil las di inspeksi visual dan radiografi, selanjutnya bila dinyatakan baik dilakukan pengukuran distorsi menggunakan dial indikator. Selanjutnya, spesimens untuk strukturmakro dan mikro disiapkan dan dietsa menggunakan etsa 10% NaOH atau Keller agents. Sifat-sifat mekanik dianalisis berdasarkan standar ASTM E-92, E-8, D-790, E-23, and E-647.Sebagian spesimen dikarakterisasi menggunakan SEM dan EDS. Hasil penelitian menunjukkan las MIG 2-layer tandem dapat meningkatkan laju produksi sekitar 37% dibandingkan dengan las MIG 1-layer. Kecepatan las lebih rendah menghasilkan temperatur puncak dan distorsi lebih tinggi. Las MIG 1-layer menggunakan jig puli bertingkat menghasilkan kekuatan tarik maksimum pada kecepatan las 10 mm/s, sedangkan las MIG 1-layer menggunakan alat pengatur kecepatan CNC menghasilkan kekuatan tarik maksimum pada kecepatan las 8 mm/s. Distorsi las MIG 2-layer multi-run lebih kecil daripada las MIG 2-layer tandem dan konvesional untuk bahan AA5052. Sifat mekanik tertinggi pada las MIG 2-layer tandem pada jarak elektroda 18 mm untuk bahan AA5083-H116 dan AA5052. Pengamatan dengan SEM menemukan retak mikro baik di bagian butir atau di batas butir strukturmikro. Analisis EDS di daerah weld metal (WM) menunjukkan kandungan unsur Mg sesuai yang terdapat pada bahan standar AA5083-H116 dan AA5052. Las MIG 2-sisi kampuh-X (2G) menggunakan penjepit pelat memanjang spesimen menghasilkan kekuatan tarik lebih tinggi dibandingkan dengan las MIG 2-layer mendatar (1G) dengan 6 bidang penjepit. Las MIG 2-sisi kampuh-X (2G) dengan jarak elektroda 27 mm menghasilkan distorsi paling kecil dan kekuatan tarik lebih besar dibandingkan dengan las MIG 2-layer mendatar (1G).

As a maritime country, Indonesia needs a large number of ships for connecting among islands within the Indonesia archipelago. The ships can be made of A36 steel, composite materials or AA5xxx aluminum alloy. Ship can be manufactured by meanss of welding. Aluminium alloy alloys can be welded using TIG and MIG welding. Due to the presence of oxide on the surface of the alloy, porosity within the weld metals of such alloy become more difficult to avoid. Important parameters of welding include distortion and mechanical properties. The aim of this dissertation is to analysisthe distortion and mechanical properties of AA5083-H116 and AA5052 materials being welded using 1-layer and 2-layer MIG welding technique and 5356 electrode. Specimens of 300 ï‚´ 75 ï‚´ 3 mm and 400 ï‚´ 75 ï‚´ 5 mm sizes made from AA5083-H116 and AA5052 materials. A pair of specimens was welded using MIG 200S Tenjima machine and ER5356 electrode. The welding was carried out in 1-layer and 2-layer using 5 different techniques. 1-layer welding (S-MIG), 2-layer multi-run, and conventional technique employing welding speed as independent variable whereas voltage and current were kept constant as controlled variables, For the horizontal 1G and 2G, the independent variable is electrode distance, while voltage, current and welding speed were kept contant. The dependent variables are distortion, microstructure, hardness, bending strength, tensile strength, Charpy impact toughness, and fatigue crack growth rate. During the welding, thermal cycle was measured and recorded using NI USB-9162 and ADAM-4561+ as well as K-type thermocouple. Weld beads were visually observed and also investigated using radiography, and, when they were pass, further distortion was measured using a dial indicator. Next, specimens for micro- and macrostructure evaluation were prepared by etching using 10% of NaOH or Keller agents, whereas the mechanical properties were evaluated according to the ASTM E-92, E-8, D-790, E-23, and E-647. Selected specimens were also evaluated using SEM and EDS. The result shows that (a) the tandem of 2-layer MIG welding technique can increase production rate by approximately 37% compared to 1-layer MIG.) Lower welding speed resulted in higher peak temperature and distortion. 1-layer MIG welding using a multistage pulley jig produced the highest tensile strength at welding speed of 10 mm/s, whereas 1- layer MIG welding where welding speed was controlled using a CNC machine produced the highest tensile strength at welding speed of 8 mm/s. Welding distortion of 2-layer multi-run MIG welding was found being smaller than that of the tandem 2-layer MIG welding as well as than that of conventional welding for AA5052 material. The highest mechanical properties of the tandem 2-layer MIG welding was found at electrode distance of 18 mm for both the AA5083-H116 and AA5052 materials. SEM evaluation showed that microcrack was observed at the grain and grain boundary. EDS analysis showed that Mg content of the weld metal was in good agreement with those of standard AA5083-H116 and AA5052 materials. Double-sided X-groove MIG welding (2G) using longitudinal specimen clamping produced higher tensile strength in comparison with that 2-layer horizontal MIG (1G) using 6 clamps. X-grove double sided MIG welding (2G) at electrode distance of 27 mm produced the smallest distortion and the highest tensile strength in comparison with the horizontal 2-layer MIG welding did.

Kata Kunci : AA5083-H116, AA5052, ER5356, distortion, MIG welding, multi-run, tandem