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Energy Efficiency and Conservation Technologies
Published in Swapan Kumar Dutta, Jitendra Saxena, Binoy Krishna Choudhury, Energy Efficiency and Conservation in Metal Industries, 2023
Jitendra Saxena, Binoy Krishna Choudhury
It consists of the following processes: Reduction: iron oxide, as oxide pellets or lump ore, contains about 30% oxygen by weight. In direct reduction, the oxygen in iron oxide reacts with CO and H2 at elevated temperatures to form metallic iron, CO2 and H2O (vapor). The CO and H2 reduce iron oxide and are known as reductants. The CO2 and H2O oxide iron are known as oxidants.Reforming: the reducing gas is produced from the recirculation of the gas taken from the top of the reduction furnace. This gas is first cleaned by the top gas scrubber. It is then compressed, mixed with natural gas and passed through catalyst-filled tubes. These tubes are heated in a refractory line furnace called a reformer.Carburization: carburizing is the process by which carbon content of the material is increased. This carbon in the reduced product is essential to the most efficient use of the reduced product in iron or steel making.
Additives and Mechanism of Effectiveness
Published in Wilfried J. Bartz, Engine Oils and Automotive Lubrication, 2019
The borates have been used as extreme pressure (EP) additive in lubricants since the 1960s. Especially, the derivatives of organo-borates were used as friction modifiers in the 1980s. Their excellent performances such as EP property, friction reducing ability, oxidation stability, and anticorrosion function motivates to study their action mechanism. As a result, the adsorption film, friction polymer and the permeating layer of boron and carbon reduce the friction and wear of rubbing pairs. The carburization and boronization during friction processes using organoborate additive have similar effects to chemical heat treatment of machine elements to modify their surface with carbonic and boric compounds. Seven kinds of alkoxy aluminium were synthesized and their antiwear properties evaluated on the four-ball machine. The carburization of machine elements' surfaces may enhance their antiwear property. Through tests, the assumption that aluminium, possessing similar properties to boron, can be used to synthesize EP agents has been proved.
Heat Treatment Defects and Their Determination
Published in Bankim Chandra Ray, Rajesh Kumar Prusty, Deepak Nayak, Phase Transformations and Heat Treatments of Steels, 2020
Bankim Chandra Ray, Rajesh Kumar Prusty, Deepak Nayak
Decarburization involves the removal of carbon from the steel surface when it is heated at elevated temperatures (around 650°C). Carbon reacts with oxygen or hydrogen at this temperature, and this depth of carburization is a function of time, temperature, and furnace atmosphere. As shown in Figure 15.3, there is a variation in ferrite content on the surface of as-rolled eutectoid steel. This phenomenon gravely reduces the quenched hardness, wear resistance, and fatigue strength. Decarburization involves the following reactions: C+O2=CO2Fe3C+O2=3Fe+CO2C+CO2=2COFe3C+CO2=3Fe+2COFe3C+H2O=3Fe+H2+CO
Detrimental effects of low-rank coal utilization to the operational condition of large capacity updraft moving-bed gasifier
Published in International Journal of Coal Preparation and Utilization, 2022
Phiciato Phiciato, Miftahul Huda
The main purpose of the metallurgical analysis is to analyze the effect of heat exposure to rotating grate. We recall that steam to carbon ratio dropped significantly at 270 h which promoted very low carbon conversion and thus the large quantity of char in the ashtray. Simultaneously, the rotating grate was exposed to high temperature due to the absence of ash zone. The initial suspect is that the presence of char and high-temperature operation has provoked carburization process of the grate. Carburization is a common process for surface hardening of steel, where carbon diffuses into the surface and creates lattice distortion of the crystal structure. The carburization process of Top sample is analogous to conventional pack carburizing in which the steel part is encased in a bed of charcoal, heated between 850°C and 950°C and held for several hours. As a consequence, the hardness and brittleness of steel surface rise with the increase of carbon content. However, it is not desirable to have maximum carbon content at the surface exceeding 0.8% as the surface tends to fail in a brittle manner (Lucas and Vander Voort 2009). Excessive carburization at the surface can result in premature fatigue failures because of the high gradient of carbon concentration between the surface (carbon rich) and the inner (carbon poor) part. The carbon-rich surface can create high residual tensile stress that results in increased distortion and dramatically reduce fatigue strength (Mackenzie and Scott 2008). In this case, a large quantity of char promotes the embrittlement of grate and fatigue crack as a result of excessive carburizing.
Sliding wear of electro-carburized mild steel with different microstructures
Published in Tribology - Materials, Surfaces & Interfaces, 2021
Jester L. J. Ling, Willey Y. H. Liew, Nancy J. Siambun, Jedol Dayou, Yee Yan Lim, Zhong-Tao Jiang
Carburization processes are conventional methods used to improve the wear resistance of mild steel. During carburization, carbon is diffused into the steel at a high temperature in order to form a reasonably thick carburized layer. The type of microstructure formed in the carburized layer has a significant effect on the steel’s wear resistance. If the steel is subjected to rapid cooling, the microstructure of the carburized layer is dominated by hard martensite which has been found to have superior abrasive resistance [1,2]. Suchánek and Kuklík [3] reported that carburized low carbon steel exhibited abrasive wear resistance similar to high-carbon structural and tool steels.
Evaluation of electrical conductivity and magnetic permeability variations with depth from surface voltage measurements
Published in Inverse Problems in Science and Engineering, 2021
John Bowler, Nguyen Trung Thành, Paul Sacks
We first analyse the performance of the proposed algorithm by testing it against simulated data. The coefficients in Examples 5.1 and 5.2 were chosen as decreasing functions of z, i.e. increasing with depth, to mimic the conductivity and magnetic permeability of case-hardened metals used in our experiments. In case-hardening of metals using carburization, carbon particles migrate into the surface of the metals making it harder than the substrate. This makes the electric conductivity and magnetic permeability of the surface layer smaller than those in the substrate layer. The values of these parameters are also in practical ranges.