• Title/Summary/Keyword: 고장력 강판

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Research for the gavanizability of TRIP steel controlled by surface oxidation (표면 산화물 제어를 통한 TRIP형 고장력강의 도금성 연구)

  • Park, Min-Seo;Kim, Ji-Yeong;Baek, Du-Hyeon;Sim, Yeong-Jun;Lee, Bo-Ryong
    • Proceedings of the Korean Institute of Surface Engineering Conference
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    • 2012.05a
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    • pp.326-326
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    • 2012
  • 현재 자동차 강판 시장은 이산화탄소 저감과 승객의 안전확보를 위하여 고장력강을 요구하고 있는 추세이며, 강도와 성형성을 동시에 확보하기 위하여 DP, TRIP강과 같은 변태강화형 강판을 선호한다. 그러나 강판의 상분율을 제어하기 위해서는 Si, Mn등과 같은 합금원소를 필요로 하게 되며 강판의 생산공정 중 이들 합금원소는 강판의 표면에 산화물로 농화되어 아연도금 특성을 크게 저하시키는 결과를 초래한다. 따라서 본 연구에서는 냉연 아연도금강판의 생산 공정을 모사하고 이들의 산화물 구조를 분석하여 도금특성에 어떠한 영향을 미치는지 고찰하고 Ni-precoating 공정을 이용하여 강판의 도금성 개선의 가능성을 제시하였다.

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A Study on Tool Wear in Drilling of Hot-rolled High Strength Steel (고장력 열연강판의 드릴 가공시 공구마멸에 관한 연구)

  • 신형곤;김성일;김태영
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.10 no.2
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    • pp.10-17
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    • 2001
  • Drilling is one of the most important operations performed in the machining industry. And the material of the workpiece has a profound effect on the tool life, the surface finish produced and the overall economy of the process. Hot-rolled high strength steels have been used for automobile structural material, owing to high hardness and machinability of the material. However, in the drilling of hot-rolled high strength steels, the current knowledge of tool wear and machinability are insuf-ficient. There, it is desirable to monitor drill wear status and hole quality changes during the hole drilling process. Accordingly, this paper deals with the cutting characteristics of the hot-rolled high strength steels using common HSS drill. The performance variables include the drilling thrust, torque and drill wear data obtained from drilling experiments con-ducted on the workpiece. Also drill were is measured by acoustic emission system and computer vision system.

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Improvement of Springback Predictability for Industrial Requirement (현장 적용을 위한 스프링백 예측 정밀도 향상기술)

  • Moon M.S.;Kim S.T.;Kim Y.S.;Chung W.J.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2003.08a
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    • pp.58-66
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    • 2003
  • 세계적으로 자동차의 안전에 관한 규격 강화와 환경 오염에 대한 인식이 확대되면서 차량의 강성 증대 및 경량화를 위하여 고장력 강판의 사용이 증대되면서, 스프링백에 의한 고장력 강판의 치수불량 문제가 크게 대두되었다. 스프링백에 의한 제품의 품질을 개선 시키기 위하여 다양한 해석방법이 연구되었으며, 현재 이들 프로그램들을 현장에 도입하여 사용하고 있다. 본 연구에서는 현장에서 사용하고 있는 판재성형해석 프로그램들의 스프링백 해석 특징을 파악하고 실제 판넬 측정량과 비교하여 해석의 신뢰도를 검증한다.

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An Experimental Study on the Flexural Behavior of RC Beams Strengthened with High-Strength Bars(1) (고장력 인장봉으로 보강된 RC보의 휨거동에 관한 실험적 연구(1))

  • Shin, Kyung-Jae;Kwak, Myong-Keun;Heo, Byung-Wook;Na, Jung-Min;Oh, Young-Suk
    • Journal of the Korea Concrete Institute
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    • v.18 no.4 s.94
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    • pp.527-534
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    • 2006
  • This paper outlines a new strengthening technique for concrete beams using externally unbended high-strength bars. The advantages of proposed method lie in speed and simplicity of construction compared to the alternative strengthening method. Externally unbended reinforcement retains many of the advantages over external unbended prestressed tendons. It eliminates time consuming stressing operations. Clearance requirements around anchorages are reduced as access is not required for prestressing jacks. Test results of eight specimens on reinforced concrete beams using different reinforcement materials such as carbon fiber sheet, steel plate and high-tension bar are reported. The beam strengthened by carbon fiber sheet showed a brittle failure mode due to the separation of fiber. As a result of draped profile of external bar, the maximum strength of the beam were increased by up to 212 percent and the deflections were reduced by up to 65 percent. Test results show that the beams reinforced with high-tension bar are superior to reference specimens, especially for the strength and deformation capacity.

자동차용 강판의 온도에 따른 기계적 특성

  • Hyeon, Ju-Sik;Lee, Bo-Ryong;Mun, Man-Bin
    • Proceedings of the Materials Research Society of Korea Conference
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    • 2010.05a
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    • pp.39.1-39.1
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    • 2010
  • 겨울철 혹한지방에서의 차량운행 또는 여름철 혹서지방에서의 장시간 차량 운행시 차체를 구성하고 있는 강판에는 약 $-50^{\circ}C{\sim}150^{\circ}C$의 온도환경에 처하게 된다. 따라서 이러한 저온 고온 환경하에서 차체 충돌상품성 예측 및 충돌안전 설계를 위해 온도에 따른 차체 강판의 기계적 물성평가가 요구된다. 이를 위해 본 연구에서는 자동차용 충돌부재에 주로 쓰이는 HS440MPa, HS590MPa급 냉연 고장력 강판에 대해 $-60^{\circ}C{\sim}200^{\circ}C$의 온도범위로 저온 고온 인장시험을 수행 하였다. 각각의 인장시험 결과로부터 온도 별 항복강도, 인장강도, 연신율, 가공경화지수 등 기계적 물성 변화를 평가하였다. 저온 고온 인장시험은 ZWICK Z250 만능재료시험기를 사용하였고 KS5호 규격의 인장시편을 사용하였으며, 시편에 충분한 온도를 가하기 위하여 목표온도 도달 후 20분간 유지한 뒤 인장시험을 수행하였다. 인장시험결과 HS440MPa, HS590MPa급 두 강종 모두 온도가 낮아질수록 강도 및 연신율 등이 증가하였고, 온도가 증가할수록 강도 및 연신율 등 기계적 물성이 저하 되었다. 즉, 우리가 주로 평가해왔던 상온($25^{\circ}C$)에 비해 저온 고온 환경하에서는 강판의 기계적 물성 변화가 큰 것을 알 수 있다. 따라서 혹한 또는 혹서 지방 등 온도차이가 큰 운행환경하에서의 차체 강도 및 충돌안전성 확보를 위해 온도에 따른 강판의 정확한 물성평가가 필요하고 차체 설계시 온도에 따른 강도변화를 충분히 고려하여야 한다.

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Characteristic of Mechanical Clinching for Al5052 to High-Strength Steels (Al5052 합금소재와 고장력강판의 이종재료 클린칭 접합특성)

  • Lee, Chan-Joo;Lee, Sang-Kon;Lee, Seon-Bong;Kim, Byung-Min
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.34 no.8
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    • pp.997-1006
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    • 2010
  • For manufacturing modern cars, so-called multi-materials, such as aluminum alloy with high-strength steels, are used. For obtaining such materials, a new joining method is required to achieve the multi-material design. Mechanical clinching is one of joining methods used to join the dissimilar materials. The objective of this study is to investigate the characteristics of mechanical clinching of Al5052 alloy to high-strength steels (SPFC440, 590, 780). Using FE-analysis and clinching experiment, the joinability of Al5052 alloy to high-strength steel is evaluated by geometrical shape of mechanical clinched joint, such as neck-thickness and undercut. Further, the joint strength is evaluated by performing a single-lap shear test. The upper high-strength steel SPFC780 was not clinched because of the necking of the upper sheet. The joint strength increased with increasing strength of the upper sheet. For the lower high-strength steel sheet, the joinability and joint strength decreased with increasing strength of the lower sheet.

A Statistical Quality Evaluation Using Indentation Geometry and Dynamic Resistance Of Inverter DC Resistance Spot Welding (DP 590 GA 강재의 압흔형상과 동저항을 이용한 인버터 DC 용접기의 통계적 품질평가)

  • An, Ju-Seon;Kim, Jae-Seong;Lee, Bo-Young;Eun, Jung-Mok;Kim, Dong-Cheol
    • Proceedings of the KWS Conference
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    • 2009.11a
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    • pp.68-68
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    • 2009
  • Recently, resistance spot welding using Inverter DC is applied to improve the weldability of high strength steel for the auto-body fabrication. In this study, inverter DC spot welding machine, which is developed in the domestic, was evaluated weldability of the galvanized and cold rolled dual-phase steel(tensile strength : 590MPa). The welding conditions (welding time, current and force) were decided by tensile-shear test, and welding strength and nugget size were analyzed by statistical analysis methods which involved dynamic resistance and indentation. The results of the statistical analysis was utilized for real-time estimation of the invisible nugget size and tensile strength. Moreover, it can be achieved without the conventional destructive testing of welds.

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Weldability and Optimum Welding Conditions on the 4 Lap Spot Welded Joint of High Strength Steel Sheets in Automobile (고장력 강판 적용에 따른 자동차용 4겹 다층 점용접물의 용접성 및 적정 용접조건)

  • Kwon Il-Hyun;Kim Hoi-Hyun;Baek Seung-Se;Yang Seong-Mo;Yu Hyo-Sun
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.30 no.5 s.248
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    • pp.481-487
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    • 2006
  • Spot-welding is a widely used manufacturing method for thin-sheet components, especially in mass-production industries such as the car industry. Automobiles are often constructed by multi-lap spot welding to secure the passenger from the accident, where optimisation of the welding conditions is a major economic consideration. This research is conducted to investigate weldability characteristics with various welding conditions on the 4-lap spot welded joint of structural steel sheets in automobile. The relationship between the tensile-shear strength and the indentation depth has been investigated to propose the optimum welding conditions. The welding current and the welding time have a greater effect on the welding characteristics than the electrode force. It was found that the electrode force has a relatively close relationship with the expulsion occurrence. The design curves for optimum welding are proposed for the 4-lap spot welded joint.