The characteristics of the Fe-10.5Mn-1.3Mo-2.5Ni steel alloy results of casting were further investigated after a heat treatment process was carried out through 2 stages, namely heating from room temperature to 700 ° C with a holding time of 3 hours, then raising it again to a temperature of 1000 ° C. with variations in holding time for 1 hour, 2 hours, and 3 hours followed by quenchant in water and 1.5% NaCl  solution. The results showed that heat treatment followed by water quenching has produced higher hardness up to 2 hours holding time and subsequently decreased at longer holding time.. Meanwhile, the hardness value gradually increased with a longer holding time in 1.5% NaCl solution cooling process. The highest hardness value reached 235 BHN at the 2 hours holding time followed by water cooling. The results of the impact value of water and NaCl 1.5% varied. In water, the holding time of 1 hour increased at the holding time of 2 hours and decreased at the holding time of 3 hours. Meanwhile, in 1.5% NaCl, the highest value of holding time is 1 hour, then it decreases at 2 hours holding time and increases in 3 hours holding time. The highest impact value of 101 Joule was resulted in heat treatment with 1 hour holding time followed by 1.5 NaCl solution rapid cooling. The microstructure showed that undissolved carbides which dispersed at the grain boundaries and within the grains affecting on high hardness value.

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The study focused on the effect of forging load and heat treatment on the corrosion behavior of A588-1%Ni weathered steel. The samples used were hot forged steel (A588%-1%Ni) with a load of 50 tons and 75 tons at a temperature of 800-850 °C. The test sample was reheated at an intercritical temperature between A3–A1, around 780 °C, held for 1 hour, and then cooled to room temperature. The cooling media used are water, oil, and open air. Forging loads and heat treatment variation affect the microstructure and corrosion rate of A588-1%Ni. Based on the metallographic test and after the hot forging process, A588-1%Ni laterite steel has a microstructure as ferrite-perlite. Then, after heat treatment as ferrite and cementite-containing phase, pearlite, bainite, or martensite may very well. Cooling water delivers a uniformly distributed lath martensite with an acicular ferrite phase. In addition, the oil media creates bainite with an acicular ferrite phase coarser size. The open-air media produces a pearlite + ferrite phase. Corrosion behavior of laterite steel subjected to hot forging process and followed by heat treatment was evaluated in 3% NaCl solution. Oil cooling with bainite-ferrite microstructure has the lowest corrosion rate, which is 11.96x10-3 mmpy.

Kebutuhan material baja dengan berbagai kombinasi sifat mekanik menjadi isu yang sangat penting dalam perkembangan teknologi pada berbagai bidang. Kombinasi sifat mekanik tersebut dapat diwujudkan antara lain melalui mekanisme modifikasi fasa atau struktur mikro dalam suatu material. Berbagai teknik untuk memodifikasi fasa telah banyak dikembangkan, salah satu diantaranya melalui proses perlakuan panas.  Penelitian ini membahas  pengaruh variasi penggunaan media pendingin terhadap struktur mikro dan nilai kekerasan baja Fe-Ni. Sampel baja yang digunakan merupakan baja hasil proses tempa panas dengan pembebanan 100 ton pada suhu 1000°C. Sampel baja hasil tempa dipanaskan kembali pada suhu diantara Ac1 dan Ac3 yaitu 780 °C selama 1 jam. Kemudian masing-masing sampel dilanjutkan dengan proses pendinginan menggunakan beberapa media pendingin diantaranya udara, oli dan air. Berdasarkan analisis yang telah dilakukan, sampel baja as-cast dan baja pendinginan udara memiliki struktur mikro berupa ferit-perlit. Fasa ganda ferit-martensit terbentuk pada sampel dengan pendingin oli dan air dengan morfologi dan fraksi area yang berbeda. Bentuk fasa martensit yang dihasilkan media pendingin air cenderung berbentuk lath halus, sedangkan media pendingin oli menghasilkan fasa martensit berbentuk blok. Selanjutnya, fraksi area fasa ferit-martensit yang terbentuk juga dipengaruhi oleh kecepatan pendinginan. Fraksi area martensit memiliki kecenderungan meningkat seiring dengan peningkatan kecepatan pendinginan. Kondisi tersebut berpengaruh terhadap nilai kekerasan; sampel baja hasil pendinginan dengan media air memiliki nilai kekerasan tertinggi yaitu 520 HV.

Baja mangan austenitik merupakan baja yang digunakan secara luas pada industri tambang dan mineral karena memiliki ketahanan aus dan ketangguhan yang tinggi. Secara umum, baja mangan austenitik yang dibuat melalui proses pengecoran memiliki kecenderungan getas dengan ketangguhan yang rendah karena terbentuknya formasi karbida. Proses solution treatment diikuti dengan pendinginan cepat menjadi hal penting untuk melarutkan karbida sehingga menjamin terbentuknya  struktur full austenit pada temperatur kamar. Penelitian ini bertujuan untuk mengetahui pengaruh variasi holding time dan media pendingin pada proses solution treatment terhadap kekerasan dan ketangguhan paduan baja Fe12Mn1.5Mo. Pada penelitian ini, karakteristik baja Fe12Mn1.5Mo hasil cor diinvestigasi lebih lanjut setelah dilakukan proses solution treatment dalam dua tahap, yaitu memanaskan dari temperatur ruang sampai 700oC dengan holding time 3 jam, kemudian dinaikkan sampai temperatur 1000 oC dengan variasi holding time selama 1 jam, 2 jam dan 3 jam diikuti dengan quenching menggunakan 3 media pendingin berbeda (air, larutan garam 1.5% dan 3%). Pada pendinginan menggunakan larutan garam 1.5% dan 3% menunjukkan bahwa semakin lama holding time, maka nilai kekerasan dan nilai impak juga semakin meningkat. Sementara itu, spesimen yang didinginkan menggunakan air menghasilkan nilai yang berfluktuasi untuk kedua sifat mekanik. Nilai kekerasan tertinggi sebesar 344 BHN pada variasi holding time 2 jam diikuti dengan pendinginan air, sementara nilai impak tertinggi sebesar 73.7 J/cm2 dihasilkan pada variasi holding time 1 jam dengan pendinginan air.  Nilai impak terendah sebesar 48.8 J/cm2 dihasilkan pada variasi holding time 1 jam dengan pendinginan larutan garam 3%. Hasil metalografi menunjukkan bahwa struktur mikro matriks austenit yang mengakibatkan nilai kekerasan yang rendah sedangkan karbida tak terlarut yang terdispersi di batas butir dan di dalam butir yang mengakibatkan nilai kekerasan yang tinggi. Di sisi lain, Proses solution treatment yang berlangsung kurang sempurna berakibat pada menurunnya ketangguhan karena terbentuknya presipitasi karbida.

Lateritic ore is one of the raw materials for the steel industry. Lateritic ore processed into laterite steel has more advantages than steel in the market. It has better tensile strength, hardness, corrosion resistance, and welding properties. Lateritic steel is made by performing a casting process. This research aims to investigate the effect of reduction percentage on mechanical properties and microstructure of the lateritic steel after the hot rolling process. The specimens were heated to austenitization temperature at 1000 0 C for 1 hour before the rolling process. The reduction percentage varies by 10%, 15%, and 20%. Hardness and impact test was conducted using a Rockwell Hardness and Charpy method. The microstructure was observed using an optical microscope. The results showed the optimum hardness of 58 HRC in a hot rolling sample with 20% reduction. The highest impact strength of 46 Joule and ductile fracture took place in this sample. The microstructure of this sample showed a bainitic phase causing lower hardness.

Conventional gasoline engines suffer from low performance and NOx emissions.  Controlled auto-ignition (CAI), sometimes referred to as homogeneous charge compression ignition (HCCI), is a promising concept to solve such problems. CAI has the potential to improve spark ignition (SI) engine fuel economy while at the same time solving the trade-off of NOx-soot emissions found in compression ignition (CI) engines. The CAI engine can reach a fuel economy comparable to that of a conventional diesel engine with ultra-low NOx and negligible soot emissions. However, controlling auto-ignition remains the biggest difficulty that hinders the implementation of CAI as a commercial engine. Research towards a cleaner and more efficient engine is driven by the progressively stringent emission regulation imposed worldwide. Therefore, the CAI was developed to meet the emissions target while maintaining engine performance. CAI works on the principle of lean mixture and auto-ignition. To obtain CAI combustion, the temperatures in the cylinder must be sufficient to initiate auto-ignition. Without the use of a spark plug or injector, the CAI suffers from a direct control mechanism to start the combustion. The most practical approach to controlling the initiation of auto-ignition in CAI is diluting the intake charge by either trapping the residual gas or recirculating the exhaust gas. Both approaches enable the engine to achieve CAI combustion without requiring significant modifications to control the onset of CAI combustion phase.

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