• International Journal of Fluid Machinery and Systems
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• v.3 no.4
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• pp.309-314
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• 2010

Stainless steel stamping multistage pump has become the mainstream of civil multi-stage pump. Combined with the technological features of stamping and welding pump, the studies of design for hydraulic parts of pump were come out. An $L_{18}$（$3^7$）orthogonal experiment was designed with seven factors and three values including blade inlet angle, impeller outer diameter, guide vane blade number, etc. 18 plans were designed. The two stage of whole flow field on stainless steel stamping multistage pump at design point for design was simulated by CFD. According to the test result and optimization design with experimental research, the trends of main parameters which affect hydraulic performance were got. After being manufactured and tested, the efficiency of the optimal model pump reaches 61.36% and the single head is more than 4.8 m. Compared with the standard efficiency of 53%, the design of the stainless steel stamping pump is successful. The result would be instructive to the design of Stainless steel stamping multistage pump designed by the impeller head maximum approach.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.334-337
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• 2007

Austenitic stainless steel is used as high temperature components such as gas turbine blade and disk because of its good thermal resistance. In the present investigation, tensile and low cycle fatigue(LCF) behavior of stainless steel for turbine disks was studied at wide temperature range $20^{\circ}C\;{\sim}\;750^{\circ}C$. In the tensile tests, it was shown that elastic modulus, yield strength, ultimate tensile strength decreased when temperature increased. The effect on fatigue failure of the parameters such as plastic strain amplitude, stress amplitude and plastic strain energy density was also investigated. Coffin-Manson and Morrow models were used to adjust experimental data and predict the fatigue life behavior at different mean strain values during cyclic loading of high temperature components.

• Journal of the Korean Society for Heat Treatment
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• v.34 no.1
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• pp.1-9
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• 2021

The martensitic stainless steel has excellent corrosion resistance and higher strength by quenching and tempering heat treatment. It has been widely used as blade material due to these properties. The hardness and impact toughness of martensitic stainless steel depended strongly on tempering temperatures. The 12Cr martensite stainless steel (SS 410) tempered about 540℃ showed temper embrittlement. To know cause of temper embrittlement in terms of phase identification, a detailed analysis of electron diffraction patterns during TEM observations has been carried out on the <110>α-Fe and <113>α-Fe zone axes for temper embrittlement specimen. The double electron diffraction spots at 1/3(211) and 2/3(211) positions were observed. The lattice space between individual diffraction spots was about 3.5 Å and this value coincide with three times to α-bcc lattice space (1.17 Å). The area which found double diffraction spots was judged metastable "zone" similar to the omega phase and induced embrittlement of SS410 material.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.11a
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• pp.181-184
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• 2008

Austenitic stainless steel is used as high temperature components such as gas turbine blade and disk because of its good thermal resistance. In the present investigation, tensile and low cycle fatigue behavior of 316 stainless steel was studied at wide temperature range $20^{\circ}C{\sim}750^{\circ}C$. In the tensile tests, it was shown that elastic modulus, yield strength, ultimate tensile strength decreases when temperature increased. The effect on fatigue failure of the parameters such as plastic strain amplitude and plastic strain energy density was also investigated. With the experimental results, a structural analysis of turbine blades of 316 stainless steel were carried out.

• Advances in materials Research
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• v.13 no.3
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• pp.183-194
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• 2024

D3 tools steel and 440C stainless steel (SS) are normally being employed for application such as knife blade and cutting tools. These steels are iron alloys which have high carbon and high chromium content. In this study, lab work focused on the microstructural and corrosion behavior of D3 tools steel and 440C SS after went through heat treatment processes. Heat treatments for both steels were started with normalizing at 1020 ℃, continue with hardening at 1000 ℃followed by oil quenching. Cryogenic treatment was carried out in liquid nitrogen for 24 hours. The addition of cryogenic heat treatment is believed to increase the hardness and corrosion resistance for steels. Both samples were then tempered at two different tempering temperatures, 160 ℃ and 426 ℃. For corrosion test, the samples were immersed in NaCl solution for 30 days to study the corrosion behavior of D3 tool steel and 440C SS after heat treatment. The mechanical properties of these steels have been investigated using Rockwell hardness machine before heat treatment, after heat treatment (before corrosion) and after corrosion test. Microstructure observation of samples was carried out by scanning electron microscopy. The corrosion rate of these steels was calculated after the corrosion test completed. From the results, the highest hardness is observed for D3 tool steel which tempered at 160 ℃(54.1 HRC). In terms of microstructural analysis, primary carbide and pearlite in the as-received samples transform to tempered martensite and cementite after heat treatment process. From this research, for corrosion test, heat treated 440C SS sample tempered with 426 ℃possessed the excellent corrosion resistance with corrosion rate 0.2808 mm/year.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.3 s.174
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• pp.603-612
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• 2000

Corrosion characteristics on the 12Cr alloy steel of turbine blade was electro-chemically investigated in 3.5wt% NaCI and 12.7wt% Na2S04 solution, respectively. Electro-chemical polarization test, Huey test and Oxalic acid etching test were previously conducted to estimate corrosion susceptibility of the material. And, using the horizontal corrosion fatigue tester, corrosion fatigue characteristics of 12Cr alloy steel in distilled water, 3.5wt% NaCI solution, and 12.7wt%(1M) Na2S04 solution were also fracture-mechanically estimated and compared their results. Parameter considered was room temperature, 60'C and 90'C. Corrosion fatigue crack length was measured by DC potential difference method.Obtained results are as follows,1) 12Cr alloy steel showed high corrosion rate in 3.5wt% NaCI solution and Na2S04 solution at high tempratue.2) Intergranular corrosion sensitivity of 12 Cr alloy was smaller than austenitic stainless steel.3) Corrosion fatigue crack growth rate in 3.5wt% NaCI and 12.7wt%(IM) Na2S04 solution is entirely higher than in the distilled water, and also increased with the temperature increase.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.1
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• pp.135-140
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• 2022

Most machines are made of several types of . In particular, the shaft system of the ship consists of the brass of the propeller blade and the stainless steel of the shaft. When dissimilar the electrolyte solution of seawater, a voltaic cell and a shaft electromotive force is generated. This electromotive force causes electrical corrosion of the bearing and shaft supporting the shaft system. prevent this corrosion, a shaft grounding system is installed in ships. As for the experimental method, various information acquired by designing a program to periodically measure the electromotive force of the controllable pitchpropeller) system using an A/D converter of NI. This study analyzed the generation and characteristics of accumulator electromotive force for CPP and considered the installation location of the grounding system to remove the accumulator electromotive force.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.5
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• pp.63-68
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• 2017

This study determines the selection of an appropriate jig material for the blade edge of the medical sapphire knife. The physical properties of the jig material affects the edge shape and chipping phenomenon in machining of the medical sapphire knife. If a grinding wheel is used, brittle workpieces such as sapphire are easily damaged by the propagation of cracks because the grinding force significantly increases. It is important to constantly maintain the grinding force in the grinding process of the brittle materials. The grinding force can be kept constantly by inducing the elastic deformation of the Jig material because the elastic deformation of brittle work-piece is negligibly low. The chipping phenomenon may be reduced by selecting the proper Jig material. Aluminum, copper, stainless steels and carbon steel were used as Jig materials. The experiment was conducted using a cast iron grinding wheel, which was installed on a conventional grinding machine with the ELID grinding system. The thickness and width of the chipping area were measured using an optical microscope and FE-SEM to analyze the shape of the blade edge. According to the experiment result, the chipping phenomenon decreased, and the sharp edge was formed when the jig materials with low elastic modulus were used.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.4
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• pp.423-428
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• 2016

The last stage blades of a low pressure (LP) turbine get frequently fractured because of stress corrosion cracking. This is because they operate in a severe corrosive environment that is caused by the impurities dissolved in condensed steam and high stress due to high speed rotation. To improve the reliability of the blades under severe conditions, 12% Cr martensitic stainless steel, having excellent corrosion resistance and higher strength, is widely used as the blade material. This paper shows the result of root cause analysis on a blade which got fractured suddenly during normal operation. Testing of mechanical properties and microstructure examination were performed on the fractured blade and on a blade in sound condition. The results of testing of mechanical properties of the fractured blade showed that the hardness were higher but impact energy were lower, and were not meeting the criteria as per the material certificate specification. This result showed that the fractured blade became embrittled. The branch-type crack was found to have propagated through the grain boundary and components of chloride and sulfur were detected on the fractured surface. Based on these results, the root cause of fracture was confirmed to be stress corrosion cracking.