Triyoga, Dimas (2015) Analisa Pengaruh Pengelasan Multiple Repair Baja Karbon Rendah Terhadap Sifat Mekanik, Struktur Mikro Dan Tegangan Sisa. Masters thesis, Institut Teknologi Sepuluh Nopember.
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Abstract
Kemungkinan terjadi kesalahan dalam proses pengelasan tidak dapat dihindari dan berakibat fatal bagi komponen. Untuk mengatasinya diperlukan repair, apabila kesalahan dalam proses pengelasan dilakukan berulang kali maka perlu dilakukan multiple repair welding pada sambungan las tersebut. Akibat dari multiple repair welding yang dilakukan akan berpengaruh besar terhadap sifat mekanik dan struktur mikronya. Dalam penelitian ini melakukan investigasi mengenai pengelasan multiple repair dengan metode las SMAW dan metode repair gouging pada pelat baja ASTM A36 dengan dimensi 400 x 300 x 9 mm yang diasumsikan terjadi cacat las pada sambungan lasnya dengan variasi 1x, 2x dan 3x serta lokasi repair pada daerah mahkota las hingga ke bagian tengah logam las (filler) pada setiap variasi pengelasan repair. Elektroda las yang digunakan adalah E7016 dan elektroda untuk proses repair adalah elektroda karbon. Berdasarkan hasil analisa hasil uji mekanik yaitu dimulai dari pengujian tarik ditemukan bahwa nilai rata-rata tarik berturut-turut dimulai dari tanpa repair hingga repair 3x yaitu sebesar 430.32 MPa, 456.93 MPa, 479.26 MPa dan 511.17 MPa. Sedangkan persentase nilai rata-rata kekerasan menunjukkan kenaikan yaitu sebesar 0.9% (base metal), 1.14% (HAZ) dan 9.3% (weld metal) pada masing-masing variabel dimana nilai rata-rata kekerasan tertinggi ditunjukkan pada spesimen repair 3x di area weld metal sebesar 215 HVN. Melalui analisa pengamatan tampilan makro didapatkan persentase lebar HAZ pada spesimen repair 1x, 2x dan 3x dibandingkan dengan tanpa repair, yaitu sebesar 7.4 %, 10.44% dan 13.51% serta hasil analisa tegangan sisa memiliki nilai rata-rata yang lebih tinggi seiring dengan bertambahnya jumlah repair yaitu sebesar 91.94 MPa (base metal), 89.91 MPa (HAZ) dan 137.552 MPa (weld metal). Hasil analisa pengamatan melalui struktur mikro menghasilkan perbandingan yang berbanding lurus dengan hasil pengujian mekanik yang menampilkan gambar dengan ditandai adanya perubahan persentase pertumbuhan butir pada HAZ yaitu sebesar 9%, 9.56% dan 10.13%. Semua hasil analisa didapatkan bahwa semakin banyaknya jumlah repair maka akan merubah ukuran butir dan menghasilkan tegangan sisa yang akan mempengaruhi sifat mekaniknya, melalui hasil analisa tegangan sisa juga dapat disimpulkan untuk banyaknya repair sebaiknya dilakukan sebanyak 2x dikarenakan nilai tegangan sisa yang terlalu tinggi bila lebih.
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The possibility of error in the welding process can’t be avoided and could be fatal to the structure itself. In term to overcome this situation a treatment is necessary to repair it, if the errors in the welding process is then repeated to perform multiple weld repair at the joint. Then result of multiple repairs will carried out affect greatly to the mechanical properties and microstructures. This research was investigating about multiple repair welding where weld defect assumed accour into ASTM A36 steel plate weld joints, 400 x 300 x 9 mm for its dimension. Using SMAW for the weld method and gouging method as the repair weldment. The repair variations are 1x, 2x and 3x along with the repair locations at weld bead to middle of weld metal, respectively. Using E7016 as the weld electrode and carbon electrode for its repair. Through the all analysis results of mechanical tests, first from tensile tests have found increasing, as the tensile values into repaired 3x compared to non repaired are 430.32 MPa, 456.93 MPa, 479.26 and 511.17 MPa, respectively. Hardness average values have been found increased also at all area along with percentage values are 0.9% (base metal), 1.14% (HAZ) and 9.3% (weld metal), in each variable. The highest hardness have been reached by 3x repaired with 215 HVN at weld metal area. HAZ macro structure analysis have found that width increasingly in each variable, as the average values are 7.4%, 10.44% and 13.51%. Residual stress also found another increasing average values as the same as the repair gouging has been added in number at each variables, as the values showed 91.94 MPa (base metal), 89.91 (HAZ) and 137.552 MPa (weld metal). Microstructure analysis found a straight line comparison along with mechanical tests which by the pictures showed many developments of the HAZ grain size in each variables, those are 9 %, 9.56% and 10.13%. All the result analysis concluded that by the time repair welding has been added in number will increase the size of grain and produce residual stress which will be changing the mechanical properties along with the residual value and it can be concluded that the number of repair welding not to be allowed in 2x for the purpose material, since it was produced bigger values when it was added.
| Item Type: | Thesis (Masters) |
|---|---|
| Additional Information: | RTMt 671.52 Tri a |
| Uncontrolled Keywords: | Baja ASTM A36, Variasi multiple repair, Lokasi repair, Uji mekanik, Analisa tegangan sisa dengan XRD, Struktur makro dan mikro. |
| Subjects: | T Technology > TS Manufactures > TS227 Welding. |
| Divisions: | Faculty of Industrial Technology > Material & Metallurgical Engineering > 27101-(S2) Master Thesis |
| Depositing User: | Yeni Anita Gonti |
| Date Deposited: | 26 Mar 2020 04:55 |
| Last Modified: | 26 Mar 2020 04:55 |
| URI: | http://repository.its.ac.id/id/eprint/75559 |
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