• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.05a
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• pp.89-93
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• 2001

This study was carried out to investigate the warm deep drawability of square cups of clad sheet metals, by changing temperatures of die and blankholder and blank materials. Two kinds of clad sheet metals, STS304-A1050-STS304 and STS304-A1050-STS430 were chosen for experiments. The relative drawing depth of STS304-A1050-STS304 clad sheet was increased up to 4.4 at $150^{\circ}C$ that was $29\%$ higher than at room temperature, whereas STS304-A1050-STS430 material was improved to 3.65 at $120^{\circ}C$ which was $16\%$ better than at room temperature. In addition, comparison of wall thickness and hardness of a warm drawn cup with those of room temperature showed more even distributions. Therefore, warm forming technique was confirmed to ive better results in deep drawing of stainless clad sheet metal.

• Journal of Korean Society for Atmospheric Environment
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• v.8 no.1
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• pp.7-12
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• 1992

This study was conducted to determine the effectiveness of silver thiosulfate(STS) in reducing $O_3$ injury to tomato plants(Lycopersicon esculentm Mill. 'Pink Glory'). Two days prior to $O_3$ fumigation, plants were given a foliar spray of STS solution at concentrations of 0, 0.2, 0.4, 0.6 mM contained with 0.05% Tween-20. STS concentrations below 0.6 mM were significantly effective in providing protection aginst $O_3$ exposure(16 h at 0.3 ppm). STS reduced leaf injury rate, defoliation of cotyledons, ethylene production and degree of epinasty induced by $O_3$ injury. STS slightly increased ethylene production in non-$O_3$-fumigated plants, but changes of chlorophyll content and transpiration rate on a whole plant basis were not observed. In $O_3$-fumigated plants, STS treatment reduced chlorophyll destruction but did not affect transpiration rate. STS treatment seemed not to affect peroxidase(POD) and superoxide dismutase (SOD) activity in non-fumigated plants but reduced increasing activity of POD by $O_3$ fumigation. However, such an effect as above was not found in SOD activity. Even though enzymatic protection effects were not confirmed, the fact that reduction of acute injury rate was attained for 16 h fumigation indicates that the phytoprotective effects of STS are not necessarily related to blocking the action of strees-induced-ethylene as an anti-ethylene agent.

• Journal of Welding and Joining
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• v.27 no.2
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• pp.27-31
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• 2009

Ferritic stainless steels have a good heat resistance and economic advantage. They are used for applications such as automotive exhaust systems where resistance to general corrosion is superior to carbon steels. However, there are not enough research for ferritic stainless steels on weldability mainly used as automotive exhaust manifolds. In this study, mechanical and microstructure properties of as-welded STS 429L and STS 444 ferrite stainless steels were confirmed by tensile, bending, hardness test, optical microscopy and scanning electron microscopy. Tensile strength of the STS 444 is higher than the STS 429L when it is a raw material. In contrast to this fact, STS 429L indicated higher tensile strength after butt welded. In addition, the hardness have a increasing tendency as getting down on the bead.

• Transactions of Materials Processing
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• v.10 no.3
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• pp.253-260
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• 2001

This study was performed to investigate the optimized warm forming conditions which gave the maximum drawing depth in square cup drawing of clad sheet metals, by changing the temperatures of die and blankholder and also shapes and materials of blanks. Two kinds of clad sheet metals, STS304-A1050-STS304 and STS304-A1050-STS430 were selected for experiments. The relative drawing depth of STS304-A1050-STS304 clad sheet was increased up to 4.4 at $150^{\circ}C$ that was 29% higher than at room temperature, whereas STS304-A1050-STS430 material was improved to 3.9 at $120^{\circ}C$ which was 15% better than at room temperature. In addition, comparison of wall thickness and hardness of a warm drawn cup with those of room temperature showed more even distributions. No separation between each laminated material after drawing occurred through inspection by microscope as well as application of penetrant test and bond strength test. Therefore, warm forming technique was confirmed to give better results in deep drawing of stainless clad sheet metal.

• Journal of Korean Elementary Science Education
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• v.21 no.2
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• pp.159-170
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• 2002

This study examined the effect on the education of scientific attitude in the process of primary school education by application of STS teaching-learning method with an unit of 6th grade in primary school "environmental pollution and nature conservation". The attitude relating science education, on the other side, is classified into 4 parts; attitude for science, social meaning of science, attitude for science subject and scientific attitude. The study of sexual difference on the above points was examined too. The results was taken as follows. 1. STS Teaching-learning method gives positive effect on the education of scientific attitude more than traditional teaching method, especially on the point of the attitude of science lesson and scientific attitude. 2. STS education has an great influence on the social meaning of the scientific attitude relating science education , investment in science, relation with society, solving social problem, contribution to development of society and technology 3. STS teaching-teaming is thought to be the learning that is more effective for boy than girl. In conclusion The STS Teaching-loaming method is preferable in order to increase the scientific attitude of the Elementary school students. students.

• Journal of the Korean earth science society
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• v.18 no.6
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• pp.473-479
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• 1997

The purpose of this study is to analyze the effects of STS program in Earth Science instruction on science-related attitude and scientific achievement of high school students. The students were divided into an experimental group and a control group. The experimental group was taught by the STS program and the control group was taught by the conventional lecture. The science-related attitudes have been improved in the experimental group more positively than in the control group. The experimental group showed a higher improvement in scientific achievements than the control group.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.390-395
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• 2003

This study examined the effects of the testing temperature on the mechanical properties of the stainless steels (STS301CSP-3/4H and STS301CSP-H) for flat spring. Hardness test and fatigue test were performed at room temperature (2$0^{\circ}C$ Tensile testandcreeptestwere performed attemperature range 2$0^{\circ}C$~10$0^{\circ}C$. The micro-victors hardness values of STS301CSP-3/4H and STS301CSP-H were HV=443 and HV=488. respectively. The Elastic modulus, tensile strength, yield strength and strain of these materials were decreased with increasing testing temperature. respectively. The maximum creep strain for 100hr atcreep temperature (10$0^{\circ}C$~20$0^{\circ}C$ and creep stress (Tensile strength$\times$50%) of these materials were 0.53％~0.58%. The fatigue limit of STS301CSP-3/4H and STS301CSP-H were 64.5Kgf/mm$^2$ and 67.4Kgf/mm$^2$, respectively.

• Journal of Power System Engineering
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• v.19 no.6
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• pp.12-18
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• 2015

Austenitic stainless steels generally experience the occurrence of chromium-depleted zones at the boundaries, known as sensitization, caused by the carbide precipitation that takes place due to a welding process or heat treatment. Normally, the depleted zones become the focus of the intense corrosion. In this study, the Cr-free organic/inorganic hybrid solution was developed, and the artificially degraded STS316S and STS347H with the solution-coating investigated the corrosion resistance by salt spray test. Both the OIBD-1 and OIBD-2 solutions improved the corrosion resistance of STS310S and STS347H. The corrosion resistance with the OIBD-1 solution was better than that of OIBD-2 solution. Additionally, Both solutions have been proven excellence in adhesion ability, boiling water resistance and flexibility. However, a problem of rubbing after the boiling was found out to be overcome.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.138-138
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• 2016

의료용 공구로 사용되는 합금은 마르텐사이트계 스테인리스강의 대표 강종인 420스테인리스강이 사용되며, 이 합금은 고온의 오스테나이트 상태에서 ?칭하면 마르텐사이트 조직으로 변태하여 현저하게 경화하는 특징을 가지고 있으며, 오스테나이트화 후 템퍼링시 우수한 기계적 성질이 얻어진다. 그러나 템퍼링 온도의 영향으로 석출탄화물이 형성되어 기계적 성질이나 내식성이 저하되는 단점이 있다. 본 연구에서는 STS 420스테인리스강의 템퍼링 온도에 의한 내식성 문제점을 개선시키기 위해 STS630 합금을 사용하여 다양한 석출 열처리 조건 및 플라즈마 질화공정을 연구하였다. 구입한 소재의 균일한 성분 조정을 통한 미세 편석 및 물성부여를 위한 균질화 조건 도출 열처리를 실시하였으며, STS630의 고용화열처리는 오스테나이트 균일조직이 되는 온도영역으로 가열하여 급냉하는 것으로 마르텐사이트 변태시키는 열처리를 진행하였으며, 열처리온도는 $1020{\sim}1060^{\circ}C$로 설정하였다. 석출경화 열처리는 $460{\sim}480^{\circ}C$와 $500{\sim}520^{\circ}C$의 온도에서 실시, 제품에 따른 인성을 부여하였으며, 질화공정은 플라즈마 장비를 이용하여 플라즈마 가열 ${\rightarrow}$플라즈마 이온질화를 통하여 가장 최적의 공정을 도출하였다.- 질화가 마무리 된 시료는 내식성 및 물성 평가를 통해 제품으로서의 특성을 평가하였다. 석출경화 열처리에 의해 STS420합금에 버금가는 인장강도 및 경도값이 나타났으며, 플라즈마 질화에 따라 물성 값의 향상이 나타났다. 용출실험결과 STS420합금의 경우 Fe, Cr원소의 용출이 나타나며 변색이 형성되었으나 STS630합금의 경우 그 현상이 미미하였다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.843-848
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• 2017

Metal exposed to high temperature/high pressure/oxidizer-rich environment may cause rapid oxidation(ignition and combustion). In this study, a DC power supply test system that controls the temperature of specimen by supplying power to the specimen was constructed and after simulating the high temperature/stagnation/oxidizer-rich environment, the metal oxidation and ignition of STS series metal materials were evaluated. As a result, we was confirmed that the deformation (discoloration) of the selected material, the change in the surface roughness and the peeling of the metal surface were observed, and that the weight and the specimen thickness were changed. The most oxidized specimen was STS 304 and the less oxidized specimen was XM-19.