• 한국환경과학회지
• /
• 제5권4호
• /
• pp.463-471
• /
• 1996

In order to investigate the characteristics of dustfall at eight sites in Pusan, the dustfal1 samples were collected with dust jar method from May to September 1995, and Cr, Mn, Fe, Ni, Cu, Zn, Cd and Pb were analyzed, The main results of this study are summarized as follows; 1) The total mean value of dustfall was 11.30 ton/$^{\circ}C$/month. 2) The maximum and minimum values of dustfall were industrial and resident area respectively, 3) The dustfall showed the general trend in order as May>Jun>September>July. 4) The general trend of the heavymetals in dustfall was in order as Fe>Cu>Zn>Pb>Ni>Cd>Cr>Mn any the concentrations of heavymetals had different tendencies according to sources of Pollutant meterials. 5) The Concentrations of Fe, Cu, Pb, Ni, Cd and Cr in industrial area and Mn, Pb and Zn in traffic area were high. The concentrations of heavymetals in residence area and unpolluted area were generally low. 6) Cr, Cu and Cd were influenced by the steel industry and the metal products plant and Zn was influenced by the automobiles. Mn, Fe and Ni were influenced by the soil as wet as artificial outlet. 7) The correlation between the total amount of dustfall and the concentrations of the heavymetals by month was high and the correlation between the heavymetals of the same origin was high.

• 한국정밀공학회지
• /
• 제22권12호
• /
• pp.93-99
• /
• 2005

In this work, computer-aided process design is carried out to develop an optimal preform of a pressure vessel. Knowledge-based rules are employed to design the preform, and they are formulated using the handbooks of plasticity theories. In the FE-analysis, a commercial finite element code, ABAQUS was employed. Axisymmetric deep drawing of a hemisphere-bottomed cup has been analyzed fur various combinations of die design parameters. The length of the land of die, the clearance between punch and die and the clearance between the blank holder and die are optimized to minimize the forming load. The results of the simulations are verified with the experiments which are scaled down to one tenth of the actual size.

• Journal of Welding and Joining
• /
• 제34권5호
• /
• pp.77-82
• /
• 2016

In this study, Microstructure and hardness of 1st layer with crystallographic orientation were investigated about solidification structure in multipass weld using high Mn-Ni flux cored wire. Microstructure of solidification consisted of austenite matrix and a little ${\varepsilon}-phase$ in grain boundaries. Orientation of grains was usually (001), (101), (111). According to crystallographic orientation, morphology of primary dendrite was different. The depletion of Fe and the segregation of Mn, C, Ni, Si, Cu, Cr, O were found along the grain boundaries. The area of segregation was wide with an order of (001), (101), (111) grains. And hardness of grains with crystallographic orientation increased with an order of (001), (101), (111) grains because of the segregation along dendrite boundary.

• 한국분말야금학회:학술대회논문집
• /
• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
• /
• pp.383-384
• /
• 2006

Fe-4Ni-0.5Mo-1Cu powder was selected as raw material, pressed and sinter-hardened at $1135\;^{\circ}C$ for 30 min with rapid cooling. The density varies in the range of $7.24-7.29\;g/cm^3$. Its fatigue properties have been tested in axial loading of alternating tensile/compressive stress at R=-1 with a servo-pulse pump. The fatigue endurance limit was measured to be 260 MPa. The microstructure showed more homogeneous bainite and martensite. Fractography displayed the fatigue cracks initiated from the pore areas near the surface. A non-typical ductile fatigue striation was found. More dimples occurred on fracture surface due to the plastic deformation, which can prohibit cracking propagation and improve its fatigue properties.

• Nuclear Engineering and Technology
• /
• 제40권2호
• /
• pp.147-154
• /
• 2008

The general corrosion behavior of austenitic and ferritic steels(316L, 304, N controlled 304L, and 410) in supercritical water is investigated in this paper. After exposure to deaerated supercritical water at $480^{\circ}C$/25 MPa for up to 500 h, the four steels studied were characterized using gravimetry, scanning electron microscopy/energy dispersive X-ray spectroscopy(SEM/EDS), X-ray photoelectron spectroscopy(XPS), and X-ray diffraction(XRD). The results show that the 316L steel with a higher Cr and Ni content has the best corrosion-resistance performance among the steels tested. In addition to the oxide layer mixed with $Fe_{3}O_{4}$ and $(Fe,Cr)_{3}O_{4}$ that formed on all the samples, a $Fe_{3}O_{4}$ loose outer layer was observed on the 410 steel. The corrosion mechanism of stainless steels in supercritical water is discussed based on the above results.

• 열처리공학회지
• /
• 제15권4호
• /
• pp.166-171
• /
• 2002

The effects of Ni and N addition to 304 stainless steel on mechanical properties and microstructure were investigated within temperature ranged from $-196^{\circ}C$ to $25^{\circ}C$. The addition of nickel and nitrogen induced the stability against the formation of provide significantly enhanced ductility at $-196^{\circ}C$ and reduce the Md temperature. Fe-18Cr-10Ni-0.2N alloy showed the ${\gamma}$ phase in deformed structure which it was beneficial to enhance the tensile strength and elongation at $25^{\circ}C$ and $-196^{\circ}C$.

• 한국레이저가공학회지
• /
• 제3권1호
• /
• pp.38-45
• /
• 2000

A 4㎾ RS840 CO2 laser with a powder auto-feeding apparatus has been used to deposit multiple overlapping tracks of Ni-base superalloy on to low carbon steel. It was found that the surface roughness(turbulence) of an overlapped cladding layer decreased with the increase of the overlapping ratio in an oscillating manner. When the overlapping ratio had values of 0.62, the surface turbulence was lowest. Overlapping ratio offer significant potential for improvement of materials surface properties such as corrosion performance and wear resistance. This paper reports that the overlapping ratio shows best corrosion resistance. The tensile residual stresses generated at the higher overlapping ratio( ＞ 0.45) and the element concentration of Fe increased in the surface layer at the lower overlapping ratio( ＜ 0.45) may lead to worse corrosion resistance.

• Corrosion Science and Technology
• /
• 제20권3호
• /
• pp.158-168
• /
• 2021

Austenitic 316 stainless steel was irradiated with protons accelerated by an energy of 2 MeV at 360 ℃, the various defects induced by this proton irradiation were characterized with microscopic equipment. In our observations irradiation defects such as dislocations and micro-voids were clearly revealed. The typical irradiation defects observed differed according to depth, indicating the evolution of irradiation defects follows the characteristics of radiation damage profiles that depend on depth. Surface oxidation tests were conducted under the simulated primary water conditions of a pressurized water reactor (PWR) to understand the role irradiation defects play in surface oxidation behavior and also to investigate the resultant irradiation assisted stress corrosion cracking (IASCC) susceptibility that occurs after exposure to PWR primary water. We found that Cr and Fe became depleted while Ni was enriched at the grain boundary beneath the surface oxidation layer both in the non-irradiated and proton-irradiated specimens. However, the degree of Cr/Fe depletion and Ni enrichment was much higher in the proton-irradiated sample than in the non-irradiated one owing to radiation-induced segregation and the irradiation defects. The microstructural and microchemical changes induced by proton irradiation all appear to significantly increase the susceptibility of austenitic 316 stainless steel to IASCC.

• 한국표면공학회지
• /
• 제24권3호
• /
• pp.144-150
• /
• 1991

The stainless steel 304 oxidized at $70^{\circ}C$ in 2.5M CrO3/5.0M H2SO4 solution and at $200^{\circ}C$ , $300^{\circ}C$, and $400^{\circ}C$ in the air are analyzed with X-ray Photoelectron Spectroscopy (XPS) to obtain depth composition profile of the surface region. It is confirmed that the surface region has a quite different composition from that of the bulk. This is due to a difference in the outward diffusion rates of the oxidized species in the surface region. The order of diffusion rates is Fe > Cr > Ni in the experimental temperature range. In spite of the inferior rate of diffusion, Cr is enriched in the surface when it is oxidized in the CrO3/H2SO4 solution. This is due to preferential dissolution of oxidized Fe.

• Bulletin of the Korean Chemical Society
• /
• 제23권11호
• /
• pp.1541-1544
• /
• 2002

The concentration of B in steels is important due to its influence on mechanical properties of steel such as hardenability, hot workability, and creep resistance. An analytical method has been developed to determine B in steel samples by high-resolution inductively coupled plasma mass spectrometry (HR-ICP-MS). National Institute of Standard and Technology Standard Reference Material (NIST SRM) 348a was analyzed to validate the analytical method. The steel sample was digested in a centrifuge bottle with addition of aqua regia and $^{10}B$ spike isotope. Sample pH was then adjusted to higher than 10 to precipitate most matrix elements such as Fe, Cr, and Ni. After centrifugation, the supernatant solution was passed through a cation exchange column to enhance the matrix separation efficiency. B recovery efficiency was about 37%, while matrix removal efficiency was higher than 99.9% for major matrix elements. The isotope dilution method was used for quantification and the determined B concentration was in good agreement with the certified value.