• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.697-698
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• 2008

This paper deals with finite element characteristic analysis of brushless DC motor according to magnetic property measurement methods. Magnetic property data for non-oriented (NO) electrical steel for electric motors are measured by the Epstein test which is considered as the international standards. Data from Epstein test may result in discrepancy from motor characteristic tests due to innate anisotropic property of NO electrical steel. Finite element analysis were performed for a BLDC motor by various measurement methods such as Epstein test, Ring test and single sheet test (SST), and calculated results were compared with considering anisotropic property conditions.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.175-176
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• 2006

The filling property of the binder treated iron based powder made of atomized iron powder was compared with that of the one made of reduced iron powder. The latter one showed a better filling property than the former one, although the original reduced powder showed a worse flow rate. Changing the particle size distribution of the original atomized powder from wide to narrow like the original reduced iron powder, improved the filling property of the binder treated powder. As a result, the particle size distribution of the original iron powder was found to strongly affect the filling property of the binder treated powder.

• Journal of the Korean Society for Heat Treatment
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• v.16 no.3
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• pp.127-133
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• 2003

The effect of chemical composition on the microstructural change and tensile property in TRIP-assisted steels with different chemical composition was investigated by using SEM, TEM, XRD and UTM. As a result of microscopic observation, the morphology of retained austenite could be identified as two types; a granular type in a steel containing higher Si and a film type in a steel having higher C. For the case of higher C-containing steel with a tensile strength of 860 MPa and a total elongation of 38%, film-typed retained austenite could be observed between lath bainitic ferrite. Actually, metastable retained austenite was a requisite for the good formability, which means that chemical composition plays a significant role in the microstructure and tensile property of TRIP-assisted steels. With respect to tensile property, the steels containing suitable Si and Mn, respectively, showed a typical TRIP effect in stress-strain curve, while a steel containing higher Mn content exhibited the similar behavior shown in dual phase steel.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.3
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• pp.106-113
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• 2007

The effect of chemical composition on the microstructural change and tensile property in TRIP-assisted steels with different chemical composition was investigated by using SEM, TEM, XRD and UTM. As a result of microscopic observation, the morphology of retained austenite could be identified as two types : a granular type in a steel containing higher sillicon and a film type in a steel having higher carbon. For the case of higher carbon-containing steel with a tensile strength of 860 MPa and a total elongation of 38%, film-typed retained austenite could be observed between lath bainitic ferrite. Actually, metastable retained austenite was a requisite for the good formability, which means that chemical composition plays a significant role in the microstructure and tensile property of TRIP-assisted steels. With respect to tensile property, the steels containing suitable silicon and manganese, respectively, showed a typical TRIP effect in stress-strain curve, while a steel containing higher manganese content exhibited the assimilar behavior shown in dual phase steel.

• Corrosion Science and Technology
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• v.17 no.2
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• pp.81-89
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• 2018

In this study, the effect of Nb alloying element on the corrosion fatigue properties of high strength steel is investigated by conducting fatigue experiments under corrosive condition and hydrogen induced condition, potentiodynamic polarization test, tensile test and surface analyses. Nb element is added to enhance the mechanical property of medium carbon steel. This element forms MX-type phases such as carbides and nitrides which are playing an important role in the grain refinement. The grain refinement is one of the effective way to improve mechanical property because both tensile strength and toughness can be improved at the same time. However, MX-type phase precipitates can be a susceptible site to localized corrosion in corrosive environment due to the potential difference between matrix and precipitate. The obtained results showed that Nb-added steel improved corrosion fatigue property by grain refinement. However, it is degraded for hydrogen-induced fatigue property due to Nb, Ti-inclusions acting as a stronger trap.

• Journal of the Korean Society of Industry Convergence
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• v.24 no.4_2
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• pp.435-441
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• 2021

This research was performed to study the effect of the Ni + Mo addition on the fatigue properties in 12Cr steel. After heat treatment of 12Cr steel and 12Cr-Ni-Mo steel, tensile tests, impact tests, hardness tests, and rotary bending fatigue tests were performed, respectively. The fatigue fracture surface was observed and analyzed using SEM and EDS. The fatigue limit of 12Cr steel was 554 MPa, which was 49 MPa higher than 505 MPa of 12Cr-Ni-Mo steel. Striations, which are the shape of the typical fatigue fracture surface, were observed at the fracture surface near the starting point of fatigue fracture in the 12Cr steel and 12Cr-Ni-Mo steel. However, unlike the case of 12Cr steel, 12Cr-Ni-Mo steel also had a mixed fracture surface with the fatigue and the ductile fracture surface. When brittle non-metallic inclusions exist near the starting point of fatigue failure, the crack propagation was further promoted and the fatigue life was drastically reduced.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.144-145
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• 2006

A developed molybdenum hybrid-alloyed steel powder is based on a molybdenum prealloyed steel powder to which molybdenum powder particles are diffusion bonded. The sintered compact made of this powder has a finer pore structure than that of the conventional molybdenum prealloyed steel powder, because the ferritic iron phase $({\alpha}-phase)$ with a high diffusion coefficient is formed in the sintering necks where molybdenum is concentrated resulting in enhanced sintering. The rolling contact fatigue strength of the sintered and carburized compacts made of this powder improved by a factor of 3.6 compared with that of the conventional powder due to the fine pore structures.

• Korean Journal of Materials Research
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• v.13 no.2
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• pp.81-87
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• 2003

Microstructures and mechanical properties of variously heat treated 0.85% carbon steel(eutectoid steel) were evaluated by magnetic property measurements. Microstructural analysis (pearlite interstellar spacing), measurement of mechanical properties(Rockwell hardness, yield stress, fracture stress) and magnetic properties(coercivity, remanence, hysteresis loss, saturation magnetization) were performed to clarify mutual relationships among these parameters. Water quenched specimens with martensite structure showed much higher coercivity and remanence than air cooled or furnace cooled specimens with pearlite structure. The linear dependence of coercivity and remanence on pearlite interlamellar spacing as well as on Rockwell hardness, yield stress and fracture stress was observed in the pearlitic steel. Hysteresis loss and saturation magnetization showed no distinct trend with pearlite interlamellar spacing.

• Journal of Electrochemical Science and Technology
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• v.1 no.2
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• pp.112-116
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• 2010

Fractal property of the passivated steel surface was investigated on the basis of scaling analysis with a special focus on its relationship with corrosion resistance. For this purpose, the surface of stainless steel was intentionally oxidized under a variety of passivation conditions and its scaling property was analyzed by a triangulation method. The morphology of the passivated steel surface was satisfactorily evaluated with fractal dimension. From the chronoamperometry and impedance measurement, it proved that lower fractal dimension leads to more enhanced corrosion resistance. The higher passivity of the steel surface with lower fractal dimension was discussed in terms of active area and structural imperfection.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.89-90
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• 2006

Austenitic stainless steel has been used as a corrosion resistance material. However, austenitic stainless steel has poor wear resistance property due to its low hardness. In this investigation, we apply powder composite process to obtain hard layer of Stainless steel. The composite material was fabricated from planetary ball milled SUS316L stainless steel powder and WC powder and then sintered by Pulsed Current Sintering (PCS) method. We also added TiC powder as a hard particle in WC layer. Evaluations of wear properties were performed by pin-on-disk wear testing machine, and a remarkable improvement in wear resistance property was obtained.