• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.193-197
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• 2002

In this study, the casting/forging process was applied to the Shift-Fork, a manual transmission part of automobiles. In the casting experiments, the effects of additives, Sr, Ti＋B and Mg, on the mechanical properties and the microstructure of a cast preform were investigated. When 0.03% Sr were added into the molten aluminum alloy, the finest silicon-structure was observed in the cast preform and the highest tensile strength and elongation accomplished. And when 0.2% Ti＋B were added into the molten Al-Si alloy, the highest values of tensile strength were obtained. The maximum hardness was in case of 0.2% Mg. In the forging experiment, it was confirmed that the optimal configuration of the cast preform could be predicted by FE analysis. To minimize the cost as the press size, the compact shape of preform was proposed to reduce the volume of flash. The modification of shape in designing preform was performed to attain a satisfactory performance in the areas where the mechanical strength were more required. By using FVM(Finite Volume Method) software, it was verified that a proposed casting design was available. To identify the relationship between effective strain and mechanical properties of the final forged product, the compression test was performed. As the result, the tensile strength and elongation of a cast preform were much higher than before forging. The minimum forging temperature was found 40$0^{\circ}C$ to save heating time.

• 한국해양공학회지
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• 제23권4호
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• pp.52-57
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• 2009

The effect of aging treatment on the microstructure and mechanical properties of super duplex stainless steel with W was investigated. The phase was precipitated mainly at the early stage of aging and a lower aging temperature under $750^{\circ}C$, but the phase was formed after long-term aging treatment between $600^{\circ}C$ and $900^{\circ}C$. The volume fraction of the phase increased with aging temperature up to $750^{\circ}C$ and then decreased up to $900^{\circ}C$. With an increase in the aging time, the volume fraction phase at the early stage of aging increased slightly, and then increased rapidly beyond a certain time. The rapid increase in the tensile strength and hardness and decrease in the elongation and impact toughness were measured with aging temperatures up to $750^{\circ}C$. On the other hand, the tensile strength and hardness decreased slightly, and the elongation and Charpy impact toughness were unchanged with aging temperatures over $750^{\circ}C$. The tensile strength and hardness increased rapidly at the early stage of aging, and then increased slowly beyond a certain time. The elongation and Charpy impact toughness decreased rapidly at the early stage of aging, and then remained unchanged beyond a certain time. The phase that formed at the early stage of aging and the lower aging temperature had a considerable effect on the elongation and Charpy impact toughness of the super duplex stainless steel with W.

• 한국주조공학회지
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• 제21권6호
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• pp.336-342
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• 2001

This study was carried out to examine the effects of adding 0.3at.%Hf in Fe-30at.%Al-5at.%Cr alloy on the variation of microstructures and hot workability. The effect of hot rolling on mechanical properties was estimated by measuring the elongation and tensile strength after rolling at 800 and 1000 respectively. Microstructure of Fe-30at.%Al-5at.%Cr alloy was consisted of large equiaxed grains and it was changed to quasi-equiaxed or columnar structures by adding 0.3at.%Hf to Fe-30at.%Al-5at.%Cr alloy. Every specimens showed a decreased tensile strength after hot rolling compared to that of before rolling. The elongation was increased by hot rolling. Remarkable changes in elongation by hot rollong was observed such as from 1.4% to 4.5% elongation at the specimen of 0.3at.%Hf added to Fe-30at.%Al-5at.%Cr. Fe-30at.%Al-5at.%Cr alloy showed typical cleavage fracture on tensile failure and hot rolling has negligible effects on fracture mode in this alloy. However at the alloy containing Hf fracture mode was changed by hot rolling from intergranular to mixed intergranular and transgranular fracture mode.

• 한국레이저가공학회지
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• 제7권2호
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• pp.19-26
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• 2004

The effect of shield gas on the weldability, mechanical properties and formability of CO2 laser weld joint in 600MPa grade high strength steel was investigated. Bead on plate welds were made under various welding speed and shield gas. Tensile test was carried out under the load of perpendicular and parallel direction to the weld line, Formability of the joint was evaluated by Erichsen test. As the welding speed increases, the porosity fraction decreases. The porosity fraction in the joint used Ar-$50\%He$ mixed gas as a shield gas was lower than that of the joint used Ar gas. Hardness at the weld metal of full penetrated joint was nearly equal to that of water quenched raw metal. In a tensile test under a perpendicular load to the weld axis, strength and elongation of joint produced by optimum condition were nearly equal to those of base metal. However, the strength of joint in a tensile test under a parallel load to weld axis was higher than that of raw metal, but the elongation of joint was lower than that of raw metal. Elongation and formability were further increased by the method of using Ar+He mixed gas as a shield gas as compared with Ar gas. Formabilities of joints were recorded ranging from $58\%\;to\;70\%$ of that of base metal with different shield gases.

• 한국응용과학기술학회지
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• 제39권2호
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• pp.161-168
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• 2022

피마자 기반 수성 폴리우레탄(CPUD)을 얻기 위해 무 변성 피마자유 (CO) 와 투명 필름을 얻기 위해 이소포론 디이소시아네이트(IPDI)를 사용했다. 유연성을 증가시키기 위해 폴리프로필렌글리콜(PPG)의 혼합 효과를 분석하였다. 또한, 사슬연장제로 에틸렌다이아민(EDA)을 사용했다. 각각 피마자유 함유에 따른 변화와 사슬연장제 변화에 따른 인장강도, 연신율 내마모성을 측정했다. 피마자유 함유가 많은 시료의 인장강도가 1.112kgf/㎟, 연신율 88%로 나타났으며, 사슬연장제 함유가 많은 시료의 인장강도가 3.33kgf/㎟, 연신율 99%로 측정되었다. 표면강도는 SEM을 통해 육안으로 확인하였다.

• 한국염색가공학회지
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• 제34권2호
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• pp.127-133
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• 2022

With the increasing interest in the expression of individuality and appearance of modern people, it is time to conduct research and development of novel hair coloring from various angles. Therefore, taking into account the order of discoloration of hair pigments, we selected a creative and novel emulsion as a novel material for hair coloring, rather than a cosmetic material such as hot water extract using natural products dealt with in previous studies, commercially available hair manicure, and oxidation hair dye for hair. Thus, the change in tensile strength and elongation of hair samples by color was studied. As a result of the study, hair with green emulsion paint had a significantly higher maximum load, maximum stress, maximum elongation and breaking load, breaking stress, breaking elongation values are shown. Maximum in terms of modulus, green emulsion applied hair and the control group were higher in the 0-15s strain and 15-145s sections, respectively, and the tangential modulus value was much higher in the control group than the experimental group hairs in all the 0-145s sections. This study, which analyzes the dynamic changes of hair samples that extend the daily color gamut, will greatly contribute to the development of innovative hair coloring materials in the research and production of hair beauty works, and it is judged that it will also contribute to the development of the beauty industry.

• 열처리공학회지
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• 제31권5호
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• pp.213-219
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• 2018

This study was carried out to investigate the effect of hot forging ratio and solution treatment temperature on the mechanical properties of incoloy 825 alloy. With an increasing of the hot forging ratio, grain size and range of grain size was decreased. With an increasing of the solution treatment temperature after 90% forging, grain size and range of grain size was increased. Cr carbides and Ti nitrides was precipitated at below $900^{\circ}C$ and volume fraction of precipitate was increased with an decreasing of the solution treatment temperature. With an increasing of the hot forging ratio, hardness, tensile strength and elongation, toughness was increased. With an increasing of the solution treatment temperature after 90% forging, hardness and strength was increased, elongation and toughness was decreased by grain refinement. With an increasing of the forging ratio, effect of solution treatment temperature on the hardness, strength and elongation was small, but on the toughness was large.

• 한국주조공학회지
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• 제31권1호
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• pp.18-25
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• 2011

Effect of Fe and Mn contents on the tensile properties has been studied in Al-9wt%Si-0.3wt%Mg alloy. As Fe content of Al-9wt%Si-0.3wt%Mg-0.5wt%Mn alloy increased from 0.15wt% to 0.45wt%, tensile strength of as-cast alloy decreased from 192 MPa to 174 MPa, and elongation of the alloy also decreased from 4.8% to 4.2%. Decrease of these properties can be explained as the formation of plate shape, ${\beta}-Al_5FeSi$ phase with high Fe/Mn ratio of the alloy. However when Mn content of Al-9wt%Si-0.3wt%Mg-0.45wt%Fe alloy increased from 0.3wt% to 0.5wt%, tensile strength of T6 aged alloy increased from 265 MPa to 275 MPa, and elongation of the alloy increased from 2.3% to 3.6%. These improvements attribute to chinese script, ${\alpha}-Al_{15}(Mn,Fe)_3Si_2$ phase shape-modified from ${\beta}-Al_5FeSi$ phase with low Fe/Mn ratio of the alloy.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.1269-1270
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• 2006

Mg-Zn-RE alloys had a novel lond period stacking ordered (LPO) structure. Their rapidly solidified powder metallurgy (RS P/M) alloys exhibited a combination of high strength and god ductility (tensile yield strength above 550 MPa and elongation above 5%). The LPO Mg-Zn-RE RS P/M alloys had high elevated temperature strength (tensile yield strength above 380 MPa at 473 K) and exhibited a high-strain-rate superplasticity at higher temperatures. In Japan, a national project for developing high strength LPO Mg-Zn-RE RS P/M alloys has started at 2003 for 5 years, which is founded by the Ministry of Economy, Trade and Industry (METI) of Japan. In the national project, project targets in materials performances have been achieved. The developed LPO Mg-Zn-RE RS P/M alloys exhibited higher tensile yield strength, fatigue strength and corrosion resistance than high strength aluminum alloys of extra-super-duralumin (7075-T6).

• 동력기계공학회지
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• 제20권3호
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• pp.11-16
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• 2016

The effect of carbides on the tensile properties in 0.5C-17Cr-0.5Ni martensitic stainless steel was studied. With the increase of austenitizing temperature, the volume fraction of residual carbide was decreased rapidly. In tempered specimens after quenching, the volume fraction of total carbide was decreased with the increase of austenitizing temperature. In tempered specimens after quenching, strength was decrease and elongation was increased with the increase of austenitizing temperature. Tensile strength was increase and elongation was decreased with the increase of volume fraction of residual and total carbides. With the increase of austenitizing temperature, the tensile properties of mod. 0.5C-17Cr-0.5Ni martensitic stainless was affected greatly by residual carbide than tempered carbide.