Transactions of Materials Processing (소성∙가공)

The Korean Society for Technology of Plasticity and materials processing (한국소성∙가공학회)
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A Study on High Temperature Deformation Behavior of Spray-Formed High Speed Steels

분무주조 고속도공구강의 고온변형 거동에 관한 연구

  • Ha, T.K. ;
  • Jung, J.Y. (Automobile Parts & Materials Research Center, Kyungpook National University)
  • 하태권 (강릉원주대학교 신소재금속공학과) ;
  • 정재영 (경북대학교 자동차부품소재연구소)
  • Received : 2018.02.21
  • Accepted : 2018.03.15
  • Published : 2018.04.01
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Abstract

In the present study, the mechanical behavior of the spray-formed high speed steel was investigated employing the internal variable theory of inelastic deformation. Special attention was focused on the effect of the microstructure evolution during the hot working process, such as the distribution of carbides to provide a basic database for the production condition of high speed steels with excellent properties. The billets of high speed steel ASP30TM were fabricated by a spray forming, and the subsequently hot-rolled and heat-treated process to obtain uniformly distributed carbide structure. As noted the spray-formed high speed steel showed relatively coarser carbides than hot-rolled and heat-treated one with fine and uniformly distributed carbide structure. The step strain rate tests and high temperature tensile tests were carried out on both the spray-formed and the hot-rolled specimens, to elucidate their high temperature deformation behavior. The spray-formed high speed steel showed much higher flow stress and lower elongation than the hot-rolled and heat-treated steel. During the tensile test at $900^{\circ}C$, the interruption of the deformation for 100 seconds was conducted to reveal that the recovery was a main dynamic deformation mechanism of spray formed high speed steel. The internal variable theory of the inelastic deformation was used to analyze data from the step strain rate tests, revealing that the activation energies for hot deformation of as-spray-formed and hot-worked steels, which were 157.1 and 278.9 kJ/mol, and which were corresponding to the dislocation core and lattice diffusions of ${\gamma}-Fe$, respectively.

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References

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