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RISS 인기검색어
- 검색키워드
- 주제어 : Stepped austempering (검색결과 5 건)
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Junyu Tian,Wei Wang,Guang Xu,Xiang Wang,Mingxing Zhou,Hatem Zurob 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.5
The microstructure evolution and strain hardening behaviour of a low-carbon carbide-free bainitic steel prepared by eithersingle-step austempering (420 °C or 365 °C), conventional two-step austempering (420 °C then 365 °C) or inverted two-stepaustempering (365 °C then 420 °C) treatments were investigated. The results show that when the total isothermal holdingtime was the same, the inverted two-step austempering treatment (first completing bainitic transformation at low-temperatureand then annealing at high-temperature austempering) led to the highest toughness (30.7 GPa%) due to the finer bainiticmicrostructure and higher fraction of film-like retained austenite. Grain refinement and transformation-induced plasticityallowed the material to achieve high ductility without sacrificing strength. Comparing single-step austempering at 365 °Cwith the inverted two-step austempering process indicates that annealing at a higher temperature after completion of thebainitic transformation resulted in better tensile properties because of a lower dislocation density and more stabler retainedaustenite. In addition, the samples heat-treated by the conventional two-step austempering process exhibited slower bainitetransformation kinetics and the worse tensile properties than the sample which was heat-treated using a single-step austemperingtreatment at 365 °C or the one which was heat-treated using an inverted two-step heat treatment. Through the analysisof the orientation relationships, it is observed that the original austenite and the bainitic plates mainly followed the K-Sorientation relationships regardless of whether the bainite plates were formed in the first or the second heat-treatment step.
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오스템퍼링한 구상흑연주철(ADI)의 드릴 가공시 경도 및 현미경조직변화에 관한 연구
조규재,장우양,심재기,홍성오,김선진 한국공작기계학회 1999 한국생산제조학회지 Vol.8 No.1
This paper was carried out to know the influence of advanced austempered ductile cast iron (ADI) on the tool life and mechanical properties of drilling machinability. For manufactured method of ADI, the spheroidal graphite cast iron were austenized at 900℃ for 1 hour and then austempered for 2 hour at 370℃ in the salt bath. And interrelationship has been investigated between tool life and mechanical characteristics of specimen material on drilling condition when the ordinary and step-feed drilling are carried out to drill holes of specimens. Tensile strength and hardness of ADI decrease and elongation of ADI increases with the increase austempered temperature. It is known that about 2 times of tool life in the case of step-feed decreases compared with ordinary feed due to the high hardness of ADI and hardness ascribed to the fact that retained austenite beame to martensite state due to cutting heat in drilling. Under the constant feed rate 0.1㎜/rev relation between hardness and length of end tip after drilling can be formularized to Hv=788.46L^-0.096 for the cutting speed 6.1m/min.
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ADI 재료의 드릴 가공시 기계적 특성에 관한 실험적 연구
김선진 서강대학 지역발전연구소 1998 지역발전연구 : 서강전문대 Vol.4 No.2
This paper was carried out to know the influence of advanced austempered ductile cast iron (ADI) on the tool life and mechanical properties of drilling machinability. For manufactured method of ADI, the spheroidal graphite cast iron were austenized at 900℃ for 1 hour and then austempered for two hour at 370℃ in the salt bath. And interrelationship has been investigated between tool life and mechanical characteristics of specimen material on drilling condition when the ordinary and step-feed drilling are carried out to drill holes of specimens. The results obtained were as follows ; 1) tensile strength and hardness of ADI decrease and elongation of ADI increases with the increase austempered temperature. 2) It is known that about 2 times of tool life in the case of step-feed decreases compared with ordinary feed due to the high hardness of ADI and hardness ascribed to the fact that retained austenite state became to martensite due to cutting heat in drilling holes. 3) Under the constant feed rate 0.1mm/rev relation between hardness and length of end tip after drilling can be formularized to Hv=788.46L-^(0.096) for the cutting speed 6.1m/min.
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Miftakhur Rohmah,Gusti Umindya Nur Tajalla,Gilang Ramadhan,Yunita Triana,Efendi Mabruri 한국부식방식학회 2024 Corrosion Science and Technology Vol.23 No.1
A Fe-Ni Bainitic steel as a weathering steel application was developed by combining its excellent mechanical properties and corrosion resistance in maritime environments. Nickel concentration (0.4-3 wt%) and inverted austempering multi-step (IAM) process were primary determinants of the microstructure of the Fe-Ni Bainitic steel. The initial austempering steel was performed at 300 o C for 600 seconds to obtain a partly bainitic transformation. The steel was heated again for 1800 s at 450 o C. The microstructure was comprised of ferrite, a blocky martensite/austenite island, and a homogeneous lath-shape bainite structure with widths ranging from 4.67 to 6.89 µm. The maximum strength, 1480 MPa, was obtained with 3 wt% nickel. In this study, corrosion behavior was investigated utilizing potentiodynamic and electrochemical impedance spectroscopy (EIS) tests. A higher nickel content in Fe-Ni Bainitic steel refined the grain size, improved the bainite fraction, lowered the corrosion rate to 0.0257 mmpy, and increased the charge transfer of film resistance to 1369 Ω.
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