• 비파괴검사학회지
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• 제10권1호
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• pp.24-28
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• 1990

Centrifugally Cast Stainless Steel generally shows similar structure to the weld in austenitic stainless steel in the point of casting. When examining this material ultrasonically, the beam does not generally propagate straightforward but rather deviates from its original direction and this phenomenon called skewing is originally caused by anisotropic material. In order to calculate the beam skewing effect theoretically, work has been performed based on a model approach which has regarded material itself as having been composed of multi-layered columnar dendrite structure and the result was compared with the one from experiment. The result from both theory and experiment showed good correlation and ultrasonic beam showed the least skewing with around 45 degree incident angle.

• 한국표면공학회지
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• 제42권2호
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• pp.79-85
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• 2009

We aimed to develop a Fe-($16{\sim}19$)Cr-($0.1{\sim}0.6$)Ti-($0.1{\sim}0.6$)Nb stainless steel for automotive exhaust parts with high corrosion resistance. The alloys with high Cr content showed high resistance to general corrosion and also localized corrosion. The increase of Ti and Nb contents resulted in a linear increase in the general corrosion resistance, while the pitting potential was improved by addition of these elements up to about 0.4 wt.%. The low-carbon Fe-17Cr-0.4Ti-0.4Nb alloy annealed at $850^{\circ}C$ and air-cooled was considered to be the optimum alloy for our purpose with the critical anodic current density of $247{\mu}A/cm^2$ in 0.05 M $H_2SO_4$ solution and the pitting potential of 310 mVSCE in 0.2 M NaCl solution.

• 한국산학기술학회논문지
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• 제3권2호
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• pp.136-140
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• 2002

정밀하고 복잡한 형상의 금속 부품을 제작하는데 사용되는 정밀주조법은 왁스형을 만드는 과정을 수작업으로 진행하므로 많은 시간과 비용이 소요되었다. 왁스형 제작공정을 개선하기 위해 쾌속조형기를 이용하는 방법을 제안하였다. SLS 형 쾌속조형기를 이용하여 캐스트폼형을 제작하고 여기에 용융된 왁스를 함침시켜 왁스형을 완성한다. 이 방법을 이용하여 스텐레스 스틸 소재의 금속 주분을 제작하였는데, 시간과 비용이 크게 절감되었으며 정밀도도 향상되었다.

• Journal of Welding and Joining
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• 제32권2호
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• pp.29-36
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• 2014

Recently, in order to enhance the function and usefulness of products, cladding of dissimilar materials that maximizes the performance of the material is being widely used in all areas of industry as an important process. Clad steel plate, produced by cladding stainless steel plate, an anticorrosive material, on carbon steel plate, is being used to produce pressure vessels. Stainless steel plate has good corrosion resistance, and carbon steel plate has good rigidity and strength; clad steel can satisfy all of these qualities at once. This study aims to find the ${\delta}$-ferrite behavior, mechanical properties, structure change, integrity and reliability of clad steel weld on hot rolled steel plates. For this purpose, multi-layer welding, repair welding and post weld heat treatment were implemented according to welding procedure specifications (WPS). In order to observe the mechanical properties and toughness of clad steel weld zone, post weld heat treatment was carried out according to ASME Sec. VIII Div.1 UW-40 procedure for post weld heat treatment. With heat treatment at $625^{\circ}C$, the hold time was used as the process variable, increased by intervals that were doubled each time, from 80 to 1,280 min. The structure of weld part was typical cast structure; localized primary austenite areas appeared near central vermicular ferrite and fusion line. The heat affected zone showed rough austenite structure created by the weld heat input. Due to annealing effects of heat treatment, the mechanical properties (tensile strength, hardness, impact value) of the heat affected area tended to decrease. From the results of this study, it is possible to conclude the integrity of clad steel welds is not affected much in field welding, repair welding, multi-layer welding, post weld heat treatment, etc.

• 한국주조공학회지
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• 제6권4호
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• pp.284-289
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• 1986

Decarburization phenomena have been studied by plasma in stainless steel, plain carbon steel and cast iron. It was also investigated the movement of impurity element P,S in the plasma jet metal pool. The plasma jet was obtained by $Ar\;-\;CO_2$ gas mixture with 5 kVA DC power source. It produced enough temperature to dissociate into activated oxygen atom by reaction of $CO_2{\leftrightarrows}CO+O^+$ and it reacted with ${\underline{C}}$ in metal pool. Decarburization rate was increased about 5 times in comparing with the conventional induction melted metal pool by $CO_2$ gas decarburization. Even under the Ar plasma jet, decarburization was obtained by agitation of metal bath by $Ar^+$ bombardment and dilution phenomena of carbon atom under the very high plasma temperature. But heavy element P and S are not much removed because they are too heavy in mass to be activated by $Ar^+$ion bombardment. Desulphurization was achieved by $Ar\;-\;CO_2$ plasma in plain carbon steel and cast iron by the reaction of $SO_2({\underline{S}}+O^+)$. But dephosphorization could not be obtained by $Ar\;-\;CO_2$ plasma, because gaseous reaction of phosphorous oxide (${\underline{P}}+O^+$) was not existed.

• 한국정밀공학회지
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• 제2권3호
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• pp.41-46
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• 1985

The behavior of the burn-on in sand mold has been investigated by varying the pouring metal, bonding materials, additive materials and molding sand. The results obtained from thease experiments are as follows; 1) The burn-on layer of silica sand decreased in order of carbon steel, gray cast iron and stainless steel, and thease burn layer proceeded mostly by producing FeO. 2) The burning reaction of silica sand mold in carbon steel castings declined with increasingly bentonite content, but water-glass scarcely took part in the burn-on reaction. 3) The addition of feldspar and seacoal to silica sand promoted the inhibiting burn-on. 4) The burn-on layer of sand mold decreased of silica sand, chromite sand and olivine sand.

• 대한치과보철학회지
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• 제20권1호
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• pp.75-81
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• 1982

The purpose of this study was to compare the marginal fitness between Ni-Cr alloy and type III gold alloy, according to two finishing line, chamfer and shoulder. As experimental materials, author selected type III gold alloy and Ni-Cr alloy (Hicrown) which were popularly used in Korea for the full cast crown. Author prepared the wax patterns with milled stainless steel die and ring. The wax patterns were invested, burnouted, and casted. The maginal discrepancy was measured with scanning electron microscope. Author obtained the following results from this study. 1. The maginal fitness of Type III gold alloy was not significantly different from that of Ni-Cr alloy (Hi-crown). 2. There is no significant difference between chamfer and shoulder in case of Type III gold alloy. 3. The maginal fitness of chamfer type is significantly superior to that of shoulder type in the Ni-Cr alloy (Hi-Crown).

• Nuclear Engineering and Technology
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• 제30권6호
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• pp.609-616
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• 1998

Cast duplex stainless steels are extensively used for primary pressure boundary components. These components are, however, embrittled due to the precipitation of $\alpha$' phase by spinodal decomposition and other processes when exposed to reactor operating temperature for a design lifetime or life extension conditions. This report presents a procedure for estimating the current condition and the residual life of safety-related stainless steel components by using ANL database and correlations. The database of Charpy impact energy suggests that CF-8M grade is the most susceptible to thermal aging and CF-3 grade is the least. Thus, the integrity of CF-8M alleys may be degraded seriously and the degree of deterioration may exceed acceptance limit after several years of service in the nuclear reactors.

• Journal of Mechanical Science and Technology
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• 제16권7호
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• pp.902-910
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• 2002

Cast stainless steel may experience embrittlement when it is exposed approximately to 300$\^{C}$ for a long period. In the present investigation, the three classes of the thermally-aged CF8M specimen were prepared using an artificially-accelerated aging method. After the specimens were held for 300, 1800 and 3600hrs. at 430$\^{C}$, respectively, the specimens were quenched in water which is at room temperature. Load versus load line displacement curves and J-R curves were obtained using the unloading compliance method. talc values were obtained using the ASTM E813-87 and ASTM E 813-81 methods. In addition to these methods, talc values were obtained using the SZW (stretch zone width) method described in JSME S 001-1981. The results of the unloading compliance method are J$\_$Q/=543.9kJ/㎡ for virgin materials. The values of J$\_$IC/ for the degraded materials at 300, 1800 and 3600hrs. are obtained 369.25kJ/㎡, 311.02kJ/㎡, 276.7kJ/㎡, respectively. The results obtained by the SZW method are compared with those obtained by the unloading compliance method. Both results are quite similar. Through the elastic-plastic fracture toughness test, it is found that the value of loc is decreased with an increase of the aging time.

• 대한치과보철학회지
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• 제33권3호
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• pp.397-412
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• 1995

The purpose of this study was to analyze the stress distribution in the dentin and post structures by the various post core materials and the amount of remaining coronal tooth structures. The 2-dimensional finite element models of mandibular 2nd premolars was divided into seven types according to the various amount of remaining coronal tooth structures. All types were modeled using equal length, diameter and shape of the post. 2 types of post and core materials were used : 1) cast gold post and core 2) stainless steel post and compsite resin core 10 Newton force was applied as follows 1) vertical force on occlusal fossa 2) $45^{\circ}$ oblique force on buccal surface of buccal cusp tip The results were as follows : 1. There was no apparent difference in the pattern of stress distribution according to the amount of remaining coronal tooth structure. 2. There was no apparent difference in the pattern of stress distribution within the dentin according to the post and core materials. A cast gold post and core generated lower dentin stress than a stainless steel post and resin core. 3. Max. dentinal stress resulting from vertical force was observed in the lingual side of dentin around the crown margin.This stress resulting from oblique force was observed in the lingual root surface of alveolar bone crest level.