• Journal of Powder Materials
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• v.6 no.1
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• pp.111-118
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• 1999

Ni(Fe)Al powders containing a homogeneous distribution of the in-situ formed AIN and $Al_2O_3$ dispersoids have been produced by mechanical alloying process in a controlled atmosphere using high energy attrition mill. The powders have been successfully consolidated by hot extrusion process. The phase information investigated by TEM and XRD analysis reveals that Fe can be soluble up to 20% to the NiAl phase ($\beta$) at room temperature after MA process. Subsequent thermomechanical treatment under specific condition has been tried to induce secondary recrystallization (SRx) to improve high temperature properties, however, the clear evidence of SRx was not obtained in this material. Mechanical properties in term of strength at room temperature as well as at high temperatures have been improved by the addition pf AIN, and the room temperature ductility has been shown to be improved after heat treatment, presumably due to the precipitation of second phase of $\alpha$ in this material.

• Journal of Powder Materials
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• v.7 no.3
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• pp.131-136
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• 2000

The effect of tempering temperature on the three point bending fatigue behavior of a P/M high speed steel JYPS-23 (1.28% C, 4.20% Cr, 6.40% W, 5.00% Mo, 3.10% V, bal. Fe) was investigated. The number of cycles to failure of the specimen austenitized at $1175^{\circ}C$ drastically increased with increasing tempering temperature. As tempering temperature increased from 500 to $620^{\circ}C$, the volume fraction and average size of carbides (MC or M6C) did not significantly changed, while hardness decreased drastically. The reduced hardness is due to the softening of matrix, which increased the resistance of the fatigue crack propagation. For a practical application, powder compacting test were also conducted with the P/M high speed steel punches tempered at 500, 580, and $620^{\circ}C$. The number of compacting cycles to failure of the punches also increased with increasing tempering temperature.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.53 no.3
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• pp.129-134
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• 2004

To analyze the performance of the gas circuit breaker(GCB), the flow field variables such as temperature, pressure and density should be evaluated accurately In the puffer chamber of puffer type GCB, the pressure rise may Exceed 20 bar and in this range of high pressure, $SF_6$ gas deviates the ideal gas property. Therefore, the real gas property of $SF_6$ should be taken into consideration for the accurate analysis of flow field. This paper presents the analysis technique of cold gas flow in GCB employing the real gas state equation of SF6. The FVFLIC method is Employed to solve the axisymmetric Euler equation. To reduce the computational effort of real gas state equation, the relationship between density and pressure is approximated by the polynomial at the temperature of 300K. The proposed method is applied to the test GCB model and simulation results show good agreement with the experimental ones.

• Journal of the Korean Society for Heat Treatment
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• v.22 no.3
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• pp.162-168
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• 2009

A horizontal tube furnace with a wide uniform-temperature zone was developed using isothermal characteristics of a heat pipe. The heat pipe heating system consists of a concentric annular shaped stainless-steel container, sodium as a working fluid and a screen mesh wick structure. The performance test of the heat pipe revealed that temperature changes along seven consecutive positions of the heat pipe outer wall were less than${\pm}0.1^{\circ}C$, thereby ensuring the high isothermal property. The isothermal property of the heat pipe-adapted tube fumace was investigated and compared to a conventional non-heat pipe type tube furnace. The temperature distribution measurement showed that the uniform temperature zone, in which temperature change is less than${\pm}$1$^{\circ}$C, of the heat pipe employed tube furnace system was about three times longer compared to the conventional tube furnace system.

• Textile Coloration and Finishing
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• v.25 no.3
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• pp.206-214
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• 2013

There has been an increasing demand for high performance and energy-saving of blind. In order to develop the eco-friendly blind textiles, heat treatment process has been utilized for LM(Low Melting) polyester fabrics and the changes of the physical properties of the treated fabrics were examined according to temperature of heat treatment. Morphology, surface reflectance, contact angle, luster, thermal property and mechanical property of heat treated LM polyester fabrics were investigated. As results, morphology analysis of thermal treated fabrics confirmed that degree of fusion of LM polyester yarns improved with increase of temperature. Surface reflectance of thermal treated fabrics decreased with increase of temperature. Luster and contact angle of a water droplet on thermal treated fabrics increased slightly with increase of temperature. The mechanical properties of the fabrics by KES-FB system were found to be temperature-dependent and especially, bending and shear properties among them were highly related to temperature.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.379-380
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• 2002

Steam generators (S/G) of pressurized water reactors are large heat exchangers that use the heat from the primary reactor coolant to make steam in the secondary side for driving turbine generators. Reciprocating sliding wear experiments have been performed to examine the wear properties of Incoloy 800 and Inconel 690 steam generator tubes in high temperature water. In present study, the test rig was designed to examine the reciprocating and rolling wear properties in high temperature (room temperature - $300^{\circ}C$) water. The test was performed at constant applied load and sliding distance to investigate the effect of test temperature on wear properties of steam generator tube materials. To investigate the wear mechanism of material, the worn surfaces were observed using scanning electron microscopy. At $290^{\circ}C$, wear rate of Inconel 690 was higher than that of Incoloy 800. It was assumed to be resulted from the oxide layer property difference due to the a\loy composition difference. Between 25 and $150^{\circ}C$ the wear loss increased with increasing temperature. Beyond $150^{\circ}C$, the wear loss decreased with increasing temperature. The wear loss change with temperature were due to the formation of wear protective oxide layer. From the worn surface observation, texture patterns and wear particle layers were found. As test temperature increased, the proportion of particle layer increased.

• Journal of Power System Engineering
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• v.14 no.1
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• pp.59-64
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• 2010

Ferritic stainless steel is currently increasingly used for automotive exhaust material. The material for exhaust manifold is used in the temperature range of 500∼$850^{\circ}C$. Therefore, high temperature characteristic is an important one that affects it's life span. It has been investigated the effect of alloying elements of Cr, Mo, Nb, Ti in the ferritic stainless steel for exhaust manifold on the high temperature tensile strength. There was a few difference in the tensile strength at $600^{\circ}C$ with the exception of low Cr steel, but the steels containing higher Cr, Mo or Nb elements showed significantly higher tensile strength at the temperature of $800^{\circ}C$. The precipitates of the specimens after heat treating at the test temperature were electrolytic extracted, and quantitatively analysed using by SEM-EDS and TEM. The alloying elements of Cr and Mo increased the tensile strength as a solid solution strengthener, and on the other hand Nb element enhanced the strength by forming the fine intermetallic compounds such as NbC or $Fe_2Nb$.

• Corrosion Science and Technology
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• v.23 no.4
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• pp.278-282
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• 2024

Recently, hot rolled galvanized steel is widely used in automotive parts. As the paradigm of the automotive market has changed from fossil fuel vehicle to electric vehicle, the automotive industry needs more high-strength steels to reduce weights of automobiles. However, because high-strength steel contains high solute carbon, it is expected to have a risk of stretcher-strain on the surface due to dislocation trapping by solute [C] and [N]. Generally, galvanized steel is supposed to pass through a furnace around the temperature of Zinc pot to increase material temperature. Otherwise, the inhibition layer could not be formed. However, solute carbon and nitrogen are volatile enough to move around the furnace temperature. Moreover, the ratio of ferrite phase and precipitated Fe3C can be variable, resulting in yield point elongation related to the stretcher strain. Furthermore, the quality of the galvanized surface can be affected by a high temperature of the furnace. Although a relatively hot rolled galvanizing line furnace has a lower temperature than an annealing line furnace, it can affect various quality aspects. In other words, this paper aims to determine how these phenomena appear concerning furnace temperature.

• Journal of Welding and Joining
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• v.18 no.3
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• pp.106-113
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• 2000

Single crystallization behavior ad high temperature tensile properties of TLP bonded joints of Ni-base single crystal superalloy, CMSX-2 were investigated using MBF-80 and F-24 insert metals. CMSX-2 was bonded at 1523~1548K for 1.5~1.8ks in vacuum. The (100) orientation of bonded specimen was aligned perpendicular to the joint interface. Crystallographic orientation analyzed points over the bonded region possessed the almost same orientation across the joint interface and misorientation $\Delta^{\theta}$ was negligibly small in as-bonded and post-bond heat-treated situations. It was confirmed that single crystallization could be readily achieved during TLP bonding. The tensile strengths of all joints at elevated temperatures were equal to or greater than those of base metal the range of testing temperature between 923K and 1173K. The elongation and reduction of area in values were almost the same as those of base metal. SEM observation of the fracture surfaces of joints after tensile test revealed that the fracture surface indicated the similar morphologies each other, and that the fracture of joints occurred in the base metal in any cases.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.56.2-56.2
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• 2012

Clinically-favored materials for bone regeneration are mainly based on bioceramics due to their chemical similarity to the mineral phase of bone. A successful scaffold in bone regeneration should have a 3D interconnected pore structure with the proper biodegradability, biocompatibility, bioactivity, and mechanical property. The pore architecture and mechanical properties mainly dependent on the fabrication process. Bioceramics scaffolds are fabricated by polymer sponge method, freeze drying, and melt molding process in general. However, these typical processes have some shortcomings in both the structure and interconnectivity of pores and in controlling the mechanical stability. To overcome this limitation, the rapid prototyping (RP) technique have newly proposed. Researchers have suggested RP system in fabricating bioceramics scaffolds for bone tissue regeneration using selective laser sintering, powder printing with an organic binder to form green bodies prior to sintering. Meanwhile, sintering process in high temperature leads to bad cost performance, unexpected crystallization, unstable mechanical property, and low bio-functional performance. The development of RP process without high thermal treatment is especially important to enhance biofunctional performance of scaffold. The purpose of this study is development of new process to fabricate ceramic scaffold at room temperature. The structural properties of the scaffolds were analyzed by XRD, FE-SEM and TEM studies. The biological performance of the scaffolds was also evaluated by monitoring the cellular activity.