Journal of Welding and Joining

The Korean Welding and Joining Society (대한용접접합학회)
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Effect of Peak Temperature on the Grain Growth in Simulated HAZ of Cr-Mo-V Steel(T24)

Cr-Mo-V강(T24)의 재현 HAZ의 결정립 성장에 미치는 피크온도의 영향

  • Lee, Kyong-woon (Corporate R&D Institute, Doosan Heavy Industries) ;
  • Lee, Seong-hyeong (Dept. of Applied Hybrid Materials, Graduate School of Convergence Science, Pusan National University) ;
  • Na, Hye-sung (Dept. of materials Science and Engineering, Pusan National University) ;
  • Kang, Chung-Yun (Dept. of materials Science and Engineering, Pusan National University)
  • Received : 2016.11.01
  • Accepted : 2016.12.15
  • Published : 2016.12.30
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Abstract

Recently developed ferritic heat resistance steel, T24 was used to evaluate microstructure characteristics of simulated heat affected zone. Also, correlation between the prior austenite grain size and amount of $M_{23}C_6$ carbide dissolution was discussed. With the increasing of peak temperature, Grain size steadily increased up to $1050^{\circ}C$ and then rapidly increased at $1150^{\circ}C$. Of the peak temperature $950{\sim}1050^{\circ}C$, amounts of $M_{23}C_6$carbide dissolution are low. But Most of $M_{23}C_6$ carbide that is inhibited grain growth were dissolved above $1050^{\circ}C$ and decreased volume fraction of carbide. This indicates that grain growth may be achieved through dissolution of carbide in the base material. As of welding, due to very rapid heating rate, $M_{23}C_6$ carbide exists above equilibrium solution temperature that is $800^{\circ}C$, even at $1050^{\circ}C$. So, It was confirmed that close correlation between carbide dissolution in the base material and grain growth. Calculated grain size has a linear relationship with peak temperature, on the other hand, measured grain size discontinuously increased between $950{\sim}1050^{\circ}C$ and above $1050^{\circ}C$. Grain size of heat affected zone at $1350^{\circ}C$ peak temperature showed maximum 67um and minimum 4um. Also, The number of side showed 3 to 10.

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References

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