This research examines the suitability of rice husk waste as an exothermic material for a riser sleeve for use in steel casting production. Exothermic sleeves are used in the steel casting process to compensate for shrinkage of the steel during solidification. Commonly, the exothermic sleeve consists of fuel materials, fillers, and binders. Rice husk waste has potential for use as a fuel material in the exothermic sleeve due to its high calorific value. For this study, rice husk waste was ground to gain a particle size of 60 mesh and then mixed with organic binders of 12wt%, 15wt%, and 18wt%. A H-sleeve was then formed by hand pressing, followed by drying. A series of quantitative tests were carried out to analyze the performance of the rice husk as an exothermic material. These include measurement of modulus extension factor (MEF) and the cooling rate of the steel casting within the liquidus-solidus temperature range. The test results show that the rice husk sleeve mixed with 12wt% of binder extended the solidification time from 273 seconds to up to 511 seconds within the desired temperature range. Furthermore, the best MEF of 1.69 was achieved using the rice husk riser sleeve. This meets the standard MEF value of an exothermic sleeve.
The Pulverizer pipe made of mild steel had erosion failure due to coal dust impacting, thus its service life also reduces. The ceramic coating overlay on the surface of mild steel is one of the appropiate ways to protect the mild steel from erosion. This research is aimed to perform a ceramic coating over the surface of the mild steel using a dipping method to improve its erosion resistance by using the alumina-phosphate ceramic coating. The coating layer is formed by the reaction between monoaluminum phosphate (MAP) as a binder and Al2O3 particles. It transforms into berlinite phase when heated at an elevated temperature. The observation is carried out with the variation of the MAP binder composition Al:P 25:75, 28:72, 30:70 and the Al2O3/MAP slurry is given at 40/60. Scanning electron microscopy is used to characterize the coating morphology. X-ray diffraction is applied to investigate the ceramic coating phases. The gas erosion jet measures erosion resistance of the ceramic coating. From the test result, it can be concluded that the binder composition influenced the erosion behaviour of alumina ceramic coating, the binder with Al:P (30:70) showed the erosion resistance increasing four times compared to the condition without coating.
This research is focused on the application of the Al2O3-phosphate ceramic coating on mild steel surface to protect mild steel from erosion in coal dust environment. Erosion resistance of mild steel could be improved by overlay it with SiC in the Al2O3-phosphate ceramic coating. As a filler, Al2O3 was mixed with 20%, 40%, and 60% SiC by using aluminium phosphate as a binder and heated at 220 °C for 5 hours. X-ray diffraction testing was conducted to observe the phase of Al2O3-SiC phosphate ceramic coating. Meanwhile, surface morphology and adhesion characteristic of Al2O3-SiC phosphate ceramic coating were analyzed by scanning electron microscope. To analyze the erosion resistance quantitatively solid particle impingement test by applying gas jets at the right angle (90°) against a sample surface has been conducted. The results showed that Al2O3-SiC phosphate ceramic coating is strongly bound to the mild steel surface without the presence of any void. The higher the SiC content can increase the ceramic coating density and its erosion resistance. The SiC 60% produces four times higher erosion resistance than uncoated mild steel. The material characterization of Al2O3-SiC phosphate ceramic coating proves that SiC gives a significant impact on the enhancement of erosion resistance of the Al2O3-SiC phosphate ceramic coating.
Hadfield manganese steel is the steel with a composition of 1.0-1.4% C and 10-14% Mn, where the C: Mn ratio is made at 1:10. In as-cast conditions, the steel has a structure of carbide (Fe, Mn) 3C at the grain boundary, formed during slow cooling in the sand mold. The carbide existence can cause brittle properties of the material and needs to be eliminated by a heat treatment process that is homogenization (or solution treatment). In this study, a stepped heat treatment process was carried out by giving preheating at temperatures below the austenitizing temperature of 600 oC and 700 oC. The austenitizing temperature is given lower than the conventional method which usually uses 1050 oC, wherein this study austenitizing heating was given at 980 oC. Rapid quenching is performed using water with agitation or stirring to ensure that the cooling rate is fast enough to generate a 100% austenite structure. The results achieved that the sample with a stepped heat treatment process with a preheating temperature of 600 oC and followed by austenitizing of 980 oC could perform finer austenite grains, with the highest impact value of 255 Joules. A fracture of the impact sample resulting very ductile behavior which can be seen that the impact sample is not completely broken.
Hadfield austenitic manganese steel is made of iron with 1.0–1.4 percentage Carbon and 10–14 percentage Manganese. Hadfield steel was processed to solution heat treatment to eliminate the carbide (Fe, Mn)3C. This study aims to make a smaller grain size of Hadfield steel at once with solution heat treatment. It was expected to improve toughness of Hadfield steel. Solution heat treatment was carried out in stages by implementing pre-isothermal heating at a lower temperature with two variations at 600 degree C and 700 degree C before undergoing high austenitization heating. Pre-isothermal heat at above 450 degree C was promoting pearlite growth. Pearlite growth starting from austenite grain boundary then reformed new grain, which has a smaller size than prior austenite. Second, stage of austenitization heating then was performed at 980 degree C to transform new small grain pearlite to austenite. An agitated water quench was used to ensure a faster cooling rate to achieve 100 percentage austenite structure. Results demonstrate that sample that underwent a stepped heat treatment process at 600 degree C followed by austenitization at 980 degree C produced finer (smaller) austenite grains. That sample had the highest impact value of 329.1 J/Cm2 in comparison to other specimens.
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