• 제목/요약/키워드: Fine Grained Steel

검색결과 50건 처리시간 0.037초

DEVELOPMENT OF HYPER INTERFACIAL BONDING TECHNIQUE FOR ULTRA-FONE GRAINED STEELS

  • Kazutoshi Nishimoto;Kazuyoshi Saida;Jeong, Bo-young;Kohriyama, Shin-ichi
    • 대한용접접합학회:학술대회논문집
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    • 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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    • pp.776-780
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    • 2002
  • This paper describes the concept and the characteristics of hyper interfacial bonding developed as a new concept joining process for UFG (ultra-fine grained) steel. Hyper interfacial bonding process is characterized by instantaneous surface melting bonding which involves a series of steps, namely, surface heating by high frequency induction, the rapid removing of heating coil and joining by pressing specimens. UFG steels used in this study have the average grain size of 1.25 ${\mu}{\textrm}{m}$. The surface of specimen can be rapidly heated up and melted within 0.2s. Temperature gradient near heated surface is relatively steep, and peak temperature drastically fell down to about 1100K at the depth of 2~3mm away from the heated surface of specimen. Bainite is observed near bond interface, and also M-A (martensite-austenite) islands are observed in HAZ. Grain size increases with increasing heating power, however, the grain size in bonded zone can be restrained under 11 ${\mu}{\textrm}{m}$. Hardened zone is limited to near bond interface, and the maximum hardness is Hv350~Hv390.

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국산 플럭스 코어드 와이어 용접에서 입열량이 용접부의 미세조직과 인성에 미치는 영향 (A Study on the Effect of Heat Input on the Microstructure and Toughness of Weldments Made by Domestic Flux Cored Wires.)

  • 고진현;국정한
    • Journal of Welding and Joining
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    • 제11권4호
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    • pp.57-69
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    • 1993
  • In the present study, the microstructure and Charpy V notch toughness of multipass $CO_2$ FCA weldment in three different heat inputs(1-3KJ/mm)were investigated. The weldments using two different domestic FCAW wires(AWS E71T-1 and E71T-5 equivalent) in C-Mn steel were chemically analysed. The following conclusions can be inferred. 1. T-1 wire Showed a stable arc transfer, less spatter and harsh, a better bead spreading and easy slag removal, whereas T-5 wire suffered from the arc stability, which tended to increase spatter and produce a more convex bead. 2.The microsturctures of the top beads of the weldments in three different heat inputs consisted of coarse-grained boundary ferrite and Widmanstatten ferrite side plate with increasing heat inputs. The modest fraction of acicular ferrite in the two wire weldments was observed in the 2KJ/mm heat input. 3.The fine-grained reheated zones of both welds consisted of a duplex microstructure of polygonal ferrite and second phases. 4. The basic flux weldment of T-5wires showed a higher Charpy impact property than that of T-1 wires because of a higher fraction of acicular ferrite in the weld microstructure.

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대입열 EH36-TM강의 Tandem EGW 용접부 미세조직 및 기계적 성질 (Mechanical Properties and Microstructures of High Heat Input Welded Tandem EGW Joint in EH36-TM Steel)

  • 정홍철;박영환;안영호;이종봉
    • Journal of Welding and Joining
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    • 제25권1호
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    • pp.57-62
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    • 2007
  • In the coarse grained HAZ of conventional TiN steel, most TiN particles are dissolved and austenite grain growth easily occurrs during high heat input welding. To avoid this difficulty, thermal stability of TiN particles is improved by increasing nitrogen content in EH36-TM steel. Increased thermal stability of TiN particle is helpful for preventing austenite grain growth by the pinning effect. In this study, the mechanical properties and microstructures of high heat input welded Tandem EGW joint in EH36-TM steel with high nitrogen content were investigated. The austenite grain size in simulated HAZ of the steel at $1400^{\circ}C$ was much smaller than that of conventional TiN steel. Even for high heat input welding, the microstructure of coarse grained HAZ consisted of fine ferrite and pearlite and the mechanical properties of the joint were sufficient to meet all the requirements specified in classification rule.

GTAW-SMAW와 SAW를 이용한 고장력강관의 용접에 대한 연구 (A Study on the Welding Process of High Strength Steel Pipe in GTAW-SMAW and SAW)

  • 이철구;조선근
    • Journal of Welding and Joining
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    • 제12권4호
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    • pp.41-49
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    • 1994
  • This study is to compare the welding quality of API 5L-X65 Steel- pipe's for natural gas transmission piping applied by SAW at shop and by GTAW-SMAW at site. The results can be summarized as follows; 1) Tensile strength of the welded zone by SAW(611.5 MPa) and by GTAW-SMAW(608.6 MPa) was maintained greater than that of the base metal(583.5 MPa). 2) Hardness of the welded zone and HAZ by SAW(Hv 194.8) & GTAW-SMAW (Hv 196.1) was slightly increased above that of the base metal (Hv 168.8), but less than the maximum allowable hardness(Hv 248). 3) Impact value of the welded zone by SAW(126.8 J) & GTAW-SMAW(88 J) became lower than that of the base metal(282.5 J), but was above the requirement of API 5L(68J). 4) Microscopic structure of the welded zone and HAZ by both SAW & GTAW-SMAW became fine-grained.

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고강도-고인성 라인파이프강 개발 동향 (Developing Trend of High Strength and Good Toughness Linepipe Steel)

  • 유장용;강기봉
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2004년도 춘계학술대회
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    • pp.216-221
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    • 2004
  • Linepipe steels with a low carbon acicular ferrite microstructure have been recently developed to accommodate the current transportation condition of the gas and oil industry, and they are finally applied to West- East pipeline project in China. By adopting acicular microstructure, both better formability and better toughness could be obtained due to low yield ratio and fine grained microstructure. Mechanical properties of pipe are not greatly different from those of base plates or hot coils with a microstructure of acicular ferrite. Merits of introducing higher strength steels are well known, i.e., reducing the gauge of pipe and the material cost, increasing the welding speed and decreasing construction cost because of reducing the construction period. Threfore, gas and oil industry has required higher strength steel than APIX70 grade steel. Under this background, API-X80 steel has been developed and shall be applied to the several projects. In this paper, developing stage of API-X80 steel is also presented and discussed.

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