Pengaruh Short Immersing Time Dan Laju Pendinginan Proses Copperizing Terhadap Perubahan Mikrostruktur Dan Perilaku Tembaga Pada Dead Mild Steel

Pada dead mild steel dengan maksimal 0,15%C tidak banyak memberikan efek penguatan. Dengan penambahan paduan tembaga dapat mencapai keseimbangan kekuatan dan keuletan dengan penghalusan butir, solid solution, atau presipitasi Cu. Penelitian ini bertujuan untuk menganalisis perubahan mikrostruktur dan perilaku tembaga pada baja AISI 1006 meliputi fase yang terbentuk, komposisi, dan persebaran Cu. Metode penambahan tembaga yang digunakan dengan mencelupkan baja ke dalam tembaga cair atau yang disebut metode copperizing menggunakan prinsip difusi. Spesimen dipotong dengan dimensi 6x3x0,3cm. Kemudian dilakukan pemanasan awal pada temperatur 900oC dan proses peleburan tembaga pada temperatur 1100oC. Dilanjutkan proses pencelupan spesimen ke tembaga cair dengan waktu immerse 5 dan 7 menit, dan variasi laju pendinginan menggunakan annealing, normalizing, dan quenching. Setelah itu dilakukan pengujian struktur mikro, SEM EDX untuk analisis topografi dan persebaran Cu, OES untuk mengetahui komposisi kimia, dan XRD untuk identifikasi fase dan microstrain. Hasil pengujian menunjukkan semakin lama waktu celup dan laju pendinginan, semakin banyak kadar Cu yang berdifusi yang menyebabkan luas ukuran butir mengecil yaitu dengan kadar Cu tertinggi yang berdifusi sebesar 0.277% pada baja AISI 1006 copperizing 7 menit pendinginan annealing yang menyebabkan luas ukuran butir mengecil hingga sebesar 11114.6622 μm2. Pada spesimen dengan pendinginan anil memperlihatkan fase ferit dan pada pendinginan normal memperlihatkan fase poligonal ferit, sedangkan pada pendinginan quench memperlihat fase granular bainit. Pada spesimen copperizing dengan pendinginan normal dan quench menunjukkan bahwa Cu larut seluruhnya didalam kristal Fe membentuk solid solution. ===================================================================================== In dead mild steel with a maximum of 0.15%C won’t contribute many effects to its strengthening. By adding copper as an alloying element, a balance between strength and ductility through grain refinement and solid solution, or Cu precipitation could be obtained. This research aimed to analyze microstructures changes and copper behavior in AISI 1006 including phases formed, composition, and Cu distribution. Method of copper addition used in this research was called copperizing, which is done by immersing steel into molten copper and taken advantage of diffusion principle. Specimens were cut into 6x3x0.3cm smaller pieces. Then, preheated the specimens to 900oC and melting the copper simultaneously at 1100oC in different heat-processing. Next, immersion process of the specimens into molten copper was done with different immersion times, which were 5 and 7 minutes. Subsequently, the specimens were also cooled down in three different ways, which were annealed, normalized, and quenched. Tests were ready to be conducted to these specimens. The tests conducted were microstructural analysis, SEM-EDX test to observe topography and Cu distribution, OES to determine the chemical composition of the specimens, and lastly XRD to identify the phases and microstrain. The results show that the longer the immersion time and cooling, the higher the Cu diffusion. These results in smaller grain area with the highest level of Cu successfully diffused in a specimen were 0.277%. These phenomenons refer to the AISI 1006 copperized for 7 minutes and then annealed which reduce its grain area up to 11114.6622 μm2. The structural analysis for the annealed specimens show that they are mainly composed of ferrites and for the normalized ones, they were composed of polygonal ferrites and the quenched ones show the presence of granular bainites. In the normalized-copperized and the quenched-copperized specimens, it can be seen that Cu was dissolved into Fe crystals to form a solid solution