Pengaruh Variasi Arus Listrik terhadap Struktur Kristal dan Sifat Mekanik pada Baja Karbon Sedang dengan Las Laser untuk Perbaikan Mold = The Effects of Electric Current Variation on Crystal Structure and Mechanical Properties and on Medium Carbon Steel with Laser Welding for Mold Reparation

Budiarto, Budiarto and Nainggolan, Cherie Yolanda (2023) Pengaruh Variasi Arus Listrik terhadap Struktur Kristal dan Sifat Mekanik pada Baja Karbon Sedang dengan Las Laser untuk Perbaikan Mold = The Effects of Electric Current Variation on Crystal Structure and Mechanical Properties and on Medium Carbon Steel with Laser Welding for Mold Reparation. JOURNAL OF MECHANICAL ENGINEERING, MANUFACTURES, MATERIALS AND ENERGY, 7 (1). pp. 64-78. ISSN 2549 6239

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Abstract

Penelitian ini bertujuan untuk mengetahui perngaruh variasi kuat arus pada las laser terhadap ukuran krstalit, kerapatan dislokasi, regangan kisi dan sifat mekanis pda baja karbon sedang serta kawat filler SKD 61. Peralatan las laser yang digunakan adalah mold laser welding machine “JAL” model JAL-UK-MW400. Kondisi proses pengelasan laser frekuensi 10 Hz, pulse 5,.5, 6.5, dan 7.5 ms, dan kuat arus pengelasan 60, 70, dan 80 A. Kemudian, dilakukan proses PWHT-Tempering pada temperatur 700°C selama 2 jam. Hasil uji XRD menunjukkan bahwa ukuran kristal meningkat dengan peningkatan kuat arus dengan ukuran kristal tertinggi terdapat pada spesimen dengan kuat arus pengelasan 80 A sebesar 12.8428 nm dan ukuran kristal terkecil terdapat pada spesimen matriks sebesar 8.7155 nm. Akan tetapi, untuk nilai kerapatan dislokasi dan regangan kisi mengalami penurunan seiring dengan peningkatan kuat arus pengelasan. Hasil uji sifat mekanik kekerasan dan kuat tarik menunjukkan bahwa setelah melalui proses PWHT terlihat bahwa nilai kekerasan dan kuat tarik mengalami penurunan, dimana sebelum proses PWHT nilai kekerasan dan kuat tarik tertinggi terdapat pada spesimen dengan kuat arus pengelasan 80 A di daerah pusat las, sebesar 388.46 HB dan 1340.187 MPa. Setelah melalui proses PWHT, nilai kekerasan dan kuat tarik tertinggi terdapat pada spesimen dengan kuat arus pengelasan 80 A di daerah pusat las, sebesar 232.07 HB dan 1011.09 MPa. Kata Kunci: Baja Karbon Sedang M300; Kekerasan, Kuat Tarik, Las laser; Struktur Kristal. / This study aims to determine the effect of variations in current strength in laser welding on crystallite size, dislocation density, lattice strain, and mechanical properties of medium carbon steel and SKD 61 filler wire. The laser welding equipment used is the "JAL" mold laser welding machine model JAL- UK-MW400. The condition of the laser welding process is 10 Hz, pulse 5,.5, 6.5, and 7.5 ms, and the welding current is 60, 70, and 80 A. Then, the PWHT-Tempering process is carried out at a temperature of 700°C for 2 hours. XRD test results showed that the crystal size increased with increasing current strength, with the highest crystal size found in specimens with a welding current of 80 A of 12.8428 nm, and the smallest crystal size was found in matrix specimens of 8.7155 nm. However, the value of dislocation density and lattice strain decreased along with the increase in the strength of the welding current. The results of the mechanical strength and tensile strength test showed that after going through the PWHT process, it was seen that the hardness and tensile strength values decreased, whereas, before the PWHT process, the highest hardness and tensile strength values were found in specimens with a welding current of 80 A in the weld center area, amounting to 388.46 HB and 1340.187 MPa. After going through the PWHT process, the highest hardness and tensile strength values were found in specimens with a welding current of 60 A in the metal parent region, amounting to 292.96 HB and 952.028 MPa. Keywords: Crystal Structure; Hardness; Laser Welding; M300 Carbon Steel; Tensile Strength.

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