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심리스 튜브 제조용 피어싱 플러그 공구강과 SA210C강의 고온 미끄럼 마모에 미치는 예비산화의 영향
최병영(Byung-Young Choi),구윤식(Yoon-Sik Gu) 한국표면공학회 2013 한국표면공학회지 Vol.46 No.6
Effects of preoxidation on high temperature wear of piercing plug tool steel sliding against SA210C steel used for production of seamless tube have been studied using a pin-on-disc CETR tribometer, under applied normal load of 20 N at 900oC in air. It was found in the preoxidized pin specimens of piercing plug tool steel that the coefficient of friction decreased to about 0.4 at an initial stage followed by showing nearly constant value of about 0.4 during high temperature wear testing. On the other hand, it was also found in the pin specimens without preoxidation that the coefficient of friction increased and fluctuated, ranging from about 0.3 to 0.6 during the tests until the running period of about 800 sec. The compact and continuous Fe-oxide layer was formed on the contact surface of the preoxidized pin specimens after high temperature wear testing followed by penetrating along the grain boundaries of coarse ferrite in the decarburized region beneath the oxide layer due to the lower hardness of the region.
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화력발전용 심리스 튜브 제조에 쓰이는 피어싱 플러그 공구강의 미끄럼 접촉 고온마모거동
최병영 ( Byung Young Choi ),구윤식 ( Yoon Sik Gu ),( Qiang Zhu ),( Hongtao Zhu ),( Kiet Tieu ) 대한금속재료학회(구 대한금속학회) 2015 대한금속·재료학회지 Vol.53 No.12
Sliding wear behaviors of piercing plug tool steels were investigated at 900 ℃ against low Cr ferritic steels containing 2 %Cr and 9 %Cr using a pin-on-disc CETR tribometer under condition of applied normal load of 20N in air. Formation of glaze layers consisting of porous Fe-oxides wear debris with rapid growth on worn surface of piercing plug tool and smooth surface of steels containing 2 % Cr resulted in decreased friction coefficient at an initial period followed by exhibited constant value of about 0.3 during the elevated temperature wear tests. It was found on the cross-section underneath the worn surface of the tool steels against the steels containing 2 %Cr that coarse ferrite with equiaxed grains by phase transformation and dynamic recrystallization was formed showing the decrease in hardness. On the other hand, formation of the glaze layers consisting of compact Cr-rich Fe-oxide wear debris on the worn surface of the tool steels at slow rates of materials transfer from the steels containing 9 %Cr resulted in the fluctuated friction coefficient ranging from about 1.0~1.1 to 0.4 followed by exhibited almost constant value of 0.2~0.3. It was also found on cross-section underneath worn surface of tool steels against the steels containing 9 %Cr that severely deformed microstructures by cyclic applied loading was formed below compact and continuous oxide layers. The results showed that the elevated temperature sliding wear of the piercing plug tool steels was dominated by oxidation, materials transfer and subsurface degradation such as dynamic recrystallization softening or severe deformation.
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강지헌 ( Ji Heon Kang ),김건우 ( Kun Woo Kim ),장진석 ( Jin Seok Jang ),김지욱 ( Ji Wook Kim ),양민석 ( Min Seok Yang ),구윤식 ( Yoon Sik Gu ),안태민 ( Tae Min Ahn ),권순덕 ( Sun Deok Kwon ),이재욱 ( Jae Wook Lee ) 한국복합재료학회 2021 Composites research Vol.34 No.1
본 논문은 차량에 사용되는 B필러의 강화재를 기존의 스틸 소재에서 CFRP(Carbon Fiber Reinforced Plastics)와 GFRP(Glass Fiber Reinforced Plastics)로 대체하여 경량화하는 것이 목표다. 이를 위해서는 무게는 감소시키면서 기존 B필러를 대체할 수 있는 구조안정성을 확보해야 한다. 기존 B필러는 스틸 아우터(outer)를 포함하여 다양한 형상의 스틸 강화재로 구성되며, 이와 같은 스틸 강화재 중 2가지의 스틸 강화재를 복합재로 대체하고자 한다. 이와 같은 스틸 강화재는 강화재 각각을 따로 제작하여 용접을 통해 결합되지만, 복합재 강화재는 패치(patch) 형태의 CFRP와 리브(rib) 구조의 GFRP를 활용하여 압축과 사출 공정을 통해 한번에 제작된다. CFRP는 B필러의 고강도부에 부착되어 측면 하중에 저항하도록 하였으며, GFRP 리브는 위상 최적화(Topology optimization) 기법을 통해 비틀림과 측면 하중을 저항하도록 설계하였다. 구조해석을 통해 기존 스틸 강화재와 비교 분석을 수행하였고, 경량화율을 산출하였다. This paper aims to reduce weight by replacing the reinforcements of the B-pillar used in vehicles with CFRP(Carbon Fiber Reinforced Plastics) and GFRP(Glass Fiber Reinforced Plastics) from the existing steel materials. For this, it is necessary to secure structural stability that can replace the existing B-pillar while reducing the weight. Existing B-pillar are composed of steel reinforcements of various shapes, including a steel outer. Among these steel reinforcements, two steel reinforcements are to be replaced with composite materials. Each steel reinforcement is manufactured separately and bonded to the B-pillar outer by welding. However, the composite reinforcements presented in this paper are manufactured at once through compression and injection processes using patch-type CFRP and rib-structured GFRP. CFRP is attached to the high-strength part of the B-pillar to resist side loads, and the GFRP ribs are designed to resist torsion and side loads through a topology optimization technique. Through structural analysis, the designed composite B-pillar was compared with the existing B-pillar, and the weight reduction ratio was calculated.
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