| FENG Zhi-guo,ZHAO Xun-feng,LIU Jing.Effects of Electromagnetic Induction Vacuum Transform-pulse on Carburizing Structure and Performance of 20CrMnTi Steel[J],47(12):76-82 |
| Effects of Electromagnetic Induction Vacuum Transform-pulse on Carburizing Structure and Performance of 20CrMnTi Steel |
| Received:July 25, 2018 Revised:December 20, 2018 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2018.12.011 |
| KeyWord:electromagnetic induction vacuum carburizing transform-pulse boost-diffusion EBSD microstructure |
| Author | Institution |
| FENG Zhi-guo |
1.Guizhou University, Guizhou , China |
| ZHAO Xun-feng |
1.Guizhou University, Guizhou , China |
| LIU Jing |
2.Guizhou Normal University, Guizhou , China |
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| Abstract: |
| The work aims to study grain coarsening behavior and microstructure on the carburized layer of 20CrMnTi steel by controlling the distribution of “boost” and “diffusion” pulses in the process of vacuum pulse carburizing. An electromagnetic induction vacuum pulse carburizing was used to prepare carburized layers on 20CrMnTi steel through four processes of “original pulse”, “variable boost”, “variable diffusion” and “variable pressure” respectively. Meanwhile, the microstructure, crystal phase transition, hardness gradient and surface residual stress of the carburized layers were analyzed deeply through SEM, EBSD, automatic microhardness tester and XRD residual stress tester. Through the comparison and analysis of four processes, the thickness of the carburized layer of 20CrMnTi steel reached 1450 μm, but there was still a large amount of massive Fe3C in the carburized layer after the process of “variable boost”. The Fe3C, the retained austenite and the thickness in carburized layer of 20CrMnTi steel treated by the “variable diffusion” process decreased to 3.88%, 7.32% and 1320 μm respectively. In addition, the hardness of the carburized layer in the depth of 0 to 60 μm increased to 780 HV0.5 and the surface residual compressive stress increased to -231 MPa. From the results, the “variable diffusion” could provide the optimum structure property. “Variable boost” process increases the carbon concentration difference between the surface layer and the interior during the early stage of carburization and improves the diffusion driving force of carbon atoms, which is favorable for the growth of the carburized layer. Moreover, the “variable diffusion” process further dissolves the carbides in the late stage of carburization, which facilitates the full diffusion of carbon atoms into the interior of the carburized layer and reduces carbide precipitation and formation of residual austenite in the carburized layer. |
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