Vu The Ha’s research while affiliated with Long Island University and other places

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Publications (3)


Effects of Ce Addition on Solidification Structure of a Low-Carbon 42CrMo4 Steel
  • Article

July 2021

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33 Reads

Advanced Materials Research

Vu The Ha

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Effects of Cerium (Ce) addition on solidification structure of a low-carbon 42CrMo4 steel was investigated. The addition of up to 0.067 wt.% of Ce in the steel produced greatly improved solidification structure with a suppressed columnar grain zone, finer grain size in an equiaxed grain zone and zero area fraction of casting shrinkage cavity. The added Ce occurred in the steel both in the form of Ce oxy-sulfide inclusions and as dissolved atomic Ce segregated together with other elements at prior austenite grain boundaries and at interdendritic spacing. The Ce oxy-sulfide inclusions were found to play a major role in the observed improved grain structure meanwhile dissolved Ce had pronounced effects on morphology of dendritic networks. The fraction of Ce dissolved in the melt appeared to bring about increase in fluidity of the molten steel, leading to total elimination of interdendritic shrinkage porosity in solidification structure of the steel with added Ce. Ce addition can be considered as a potential solution for grain structure refinement in heavy-weight castings of 42CrMo4 steel grade.


Structural Characteristics of Cr-Mo Steels Microalloyed with Cerium
  • Article
  • Full-text available

June 2015

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81 Reads

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1 Citation

MANUFACTURING TECHNOLOGY

The results of an experimental study on influence of cerium addition on structural characteristics of 42CrMo4 steel are presented. Alloying with cerium was carried out using profile filled with powdered mixture of mischmetal. The samples were taken from two ingots cast in the VHM's steelworks with standard time of casting of about 14 minutes. Three steel bars from one of the produced ingots were prepared by forging. Chemical composition, macro- and microstructure, X-ray EDX chemical microanalysis, hardness of the all steel samples were obtained. Cerium addition resulted in the formation of micrometer size inclusions which can be utilized for controlling the grain size structure of steel castings. The majority of the particles have settled at the bottom part of the casting, indicating that the convection flow during solidification was very weak. The cerium addition slightly diminished hardness of the steel. A segregation phenomenon causing inhomogeneous distribution of cerium over entire volume of as-cast samples after relatively rapid crystallization process of the steel was revealed.

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Influence of Non-Ferrous Metals and Rare-Earth Elements on Structural Characteristics of Cr–Mo Steels

April 2015

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36 Reads

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2 Citations

Advanced Science Engineering and Medicine

Theoretical and experimental study on influence of addition of selected non-ferrous metals and mischmetal on microstructural characteristics in special Cr–Mo steels were performed. A number of binary iron-admixture systems were theoretically studied and equilibrium distribution coefficients were recently computed. Cast samples of Cr–Mo steel with Ce addition were prepared using a plasma furnace and an induction furnace. Microstructure investigations of the cast steel samples revealed that the addition of rare-earth metals (REM) to liquid steels brought about formation of cerium oxy-sulfide inclusions prior to steel solidification. The inclusions have acted as active heterogeneous nucleation sites for grain nucleation during solidification processes and grain structure in final as-cast microstructure was remarkably refined. The performed REM addition produced positive effects on grain structure of the cast steel samples.

Citations (1)


... Operational experiments were designed on the basis of available literature and the results of our previous experimental activities [59][60][61][62][63]. Experiments were realized in two stages, when two trial heats (marked A, B) of low-alloy structural Cr-Mo steels, which were alloyed by REMs in the form of Mischmetal with a composition of 59.3 wt.% of Ce, 36.5 wt.% of La, 0.2 wt.% of Fe, and 0.4 wt.% of Mg, were gradually produced in the electrical steel plant. ...

Reference:

The Effect of Rare Earth Metals Alloying on the Internal Quality of Industrially Produced Heavy Steel Forgings
Influence of Non-Ferrous Metals and Rare-Earth Elements on Structural Characteristics of Cr–Mo Steels
  • Citing Article
  • April 2015

Advanced Science Engineering and Medicine