• Journal of Ocean Engineering and Technology
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• v.24 no.6
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• pp.76-80
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• 2010

Oil hydraulic piston pumps are being extensively used around the world, because of their simple design, light weight, effective cost, etc. An oil hydraulic pump is likely to have the serious problems of high leakage, friction, and low energy efficiency after a long period of use. In an oil hydraulic piston pump, the clearance between the valve block and piston plays an important role for volumetric and overall efficiency. In this study, the wear property of the SACM645 material with DLC coating used for a hydraulic piston pump was determined by experimentation with variable heat treatment. To investigate the effect according to the piston surface condition, five different types of specimens were prepared. The maximum tensile strengths of the QT and QT Nitration specimens had similar values of about 800 MPa, but the strains indicated a big difference. In a wear test, the wear characteristic of the DLC coating specimen was shown to be excellent. The QT, QT + IH, QT + Nitration, and matirx specimen showed similar wear characteristics. In the case of a dry condition without oil, the DLC coating specimen had good wear resistance, with no wear shown.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1997.10a
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• pp.219-224
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• 1997

In surface grinding, the contact between the grinding wheel and the workpiece introduces heat and resistance, which restrict the self-dressing of the grits and result in burrs and cracks on the workpiece. Therefore, before or during th grinding wheel for more accurate performance. In order to determine the dressing time monitoring method of grinding wheel in surface grinding, a three-dimensional computer simulation of the grinding operation has been attempted based on the contact mechanism and surface-shaping system between the grinding wheel and the workpiece. The optimal dressing time is determined based on the amount of the grain wear and work surface roughness.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1551-1554
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• 2005

The Titanium has many superior characteristics Which are specific strength, heat resistance, corrosion resistance, organism compatibility, non-magnetic and etc. and their quantity are abundant. this study performed turning operation of Ti-6Al-4V alloy using the TiAlN Coate Tool which treated PVD (Physical Vapor Deposition). Experimental works are also executed to measure cutting force, chip figuration and surface roughness for different cutting conditions. As a result of study. Tool wear was serious at over 100m/min of cutting speed and cutting condition was excellent at 1.0mm of cutting depth.

• Journal of the Korean Society for Heat Treatment
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• v.2 no.4
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• pp.27-39
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• 1989

The effect of gas mixing ratios during gas nitrocarburizing treatment on the formation of compound layer and the mechanical properties has been studied for hot work tool steel by using a combined heat treating technique. The thickness of compound and diffusion layers has been shown to grow as a parabolic relation with increasing the amount of ammonia at a given flow quantity of $CO_2$ gas. The compound layer consists mainly of ${\varepsilon}-Fe_3$(C, N) with small amounts of ${\gamma}^{\prime}-Fe_4N$ and ${\alpha}$-Fe. The combined heat treated hot work tool steel has shown that the thickness of compound layer increases with increasing nitrocarburizing time, but the rate of growth slows down as gas nitrocarburizing time goes more than two hours. Tensile properties have given a remarkable improvement. In particular, the wear resistance of combined heat treated hot work tool steel has exhibited an improvement of about 165% greater than that obtained from conventional quenching and multi-tempering treatments.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.1 s.178
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• pp.185-192
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• 2006

A manufacturing process for a clutch gear which demands high strength and wear resistance, was developed by means of computer simulation. A preform was made by hot forging process and subsequent cold sizing process is applied to complete precise tooth part. Processes to obtain high dimensional accuracy and superior mechanical properties are analyzed and optimal heat treatment cycle to improve cold forgeability is introduced. Prototype was produced and the dimensional accuracy of the prototype was inspected to verify proposed process.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.114-115
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• 2006

[ $FerroTitanit^{(R)}$ ] is an extremely high alloyed PM material containing about 20 to 35 wt.% titanium based carbides. Such materials are designed to achieve a high wear resistance, but the high volume fraction of hard phases causes a comparable low ductility in case of tensile loading. In the present study the mechanical properties of different Ferro-Titanit grades (variations in chemical composition and in heat treatment) were investigated by means of tensile tests. The mechanical properties and the fracture behaviour will be related to the chemical composition, the heat treatment and the microstructure.

• Journal of Korea Foundry Society
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• v.22 no.4
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• pp.174-183
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• 2002

Twin-roll process is a relatively new continuous casting process which can produce high-quality strip products directly, and solidification rate can reach $10^3$ to $10^4$ K/s, leading to fine and uniform microstructures with enhanced mechanical properties. The strip casting condition for producing fine Al-Sn alloy strip was obtained experimentally, and defects appearing on the strip was examined. Crack formation and surface quality of the strip was found to depend mainly on process parameters such as melt temperature, roller gap and rolling speed. Sn structure of network type was observed in Al-20Sn and Al-40Sn alloy strips, and cell spacing of Al-40Sn alloy was smaller than that of Al-20Sn. Banding strength of the heat treated specimens increased with increasing of soaking time and temperature, and bonding strength of Al-20Sn alloy was more superior than that of Al-40Sn alloy. However wear resistance of Al-40Sn alloy contained large amount of soft Sn which possess good anti-friction characteristics was superior than that of Al-20Sn alloy.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2002.11a
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• pp.7-7
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• 2002

It is reported about the recent developments of powder metallurgy technologies in Japan. In this several years, we cannot make no progress in the amount of powder metallurgy parts production. In order to expand the markets, it is necessary to understand the market needs, and promote technical developments to satisfy the needs which include Cost Reduction, Weight Reduction, High Performance and Environmental Friendliness. The key words of developments to meet these needs are as follows, High Productivity Net-shape High Strength High Machinability High Wear-resistance Low Friction High Magnetic Properties High Heat Properties Light Weight. It is reported some examples corresponding with every key words.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.5
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• pp.646-652
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• 2011

Recently, lots of automobile part manufacturers try to increase glass fiber content of their plastic parts to improve strength and impact-resistance. For this reason, injection mold requires high hardness and wear-resistant. Laser surface treatment is used to improve characteristics of wear and to enhance the fatigue resistance for injection mold. In this paper, high carbon steel (HP4MA) for injection mold material was heat-treated to harden surface by using high power diode laser (HPDL). To find the process parameters for laser surface treatment of HP4MA, many experiments are carried out as changing the parameters of surface temperature and travel speed of laser. From the results of the experiments, it has been shown that the maximum average hardness is approximately 711~739 Hv when the temperature and the travel of laser are $1,050^{\circ}C$ and 2 mm/sec.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.4 no.2
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• pp.50-56
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• 2008

The tubes in heat exchanger are typically made of copper alloy, stainless steel, carbon steel, titanium alloy material. Type-439 ferritic stainless steel is ferromagnetic material, and furnish higher heat transfer rates than austenitic stainless steels and higher resistance to corrosion-induced flaws. Ferritic stainless steel can be found in low-pressure(LP) feedwater heaters and moisture separator reheaters(MSRs) in turbine system. LP feedwater heaters generally utilize thin wall Type-439 stainless steel tubing, whereas MSRs typically employ a heavier wall tubing with integral fins. Service-induced damage can occur on the O.D(outside diameter) surface of Type-439 ferritic stainless steel tubing which is employed for MSRs tubing, and the most typical damage mechanism is vibration-induced tube-to-TSP(tube support plate) wear and fatigue cracking. The wear has been reported that occurs mainly on the OD surface. Accordingly, in this study, we have evaluated the flaw sizing capability of magnetic saturation eddy current technique using magnetic saturation probe and flawed specimen.