Abstract
Ductile iron bars (DIBs) with a diameter of 145 mm, used for plunger pump production, were made by the horizontal continuous casting (HCC). The microstructure of the samples cut at three locations with different distances away from the surface (∼20 mm from the surface, half of the radius and the center of the HCCDIBs) were investigated. The mechanical properties were measured by tensile and torsion tests. Results show that after the spheroidization of graphite, the iron matrix incorporates the nodules of Format I, Size 8 close to the surface, Format I, Size 7 at the half of the radius from the surface, and Format II, Size 6 in the centre of the bar, according to the ASTM A247 standard. The content of pearlite in the matrix changes from 55% (∼20 mm from the surface) to 70% (half of the radius) and 80% (the center of the HCCDIBs). The strengths in tension are 552, 607 and 486 MPa with the elongations of 12.5%, 10.5% and 5.8% in samples cut at these three locations from the surface to the centre, respectively. The strength in torsion is equal to 558, 551 and 471 MPa at corresponding torsion angles of 418°, 384° and 144° respectively to the same distance from the bar surface. Fracture in tension is manifested via crack propagation through the interface between graphite nodules and matrix (Mode I), while in torsion the fracture is caused by the shear of graphite nodules (Mode II). It is shown that the transition between two fracture modes is also dependent on the size of graphite nodule. Typically, fracture Mode I was observed for nodules of smaller diameter (less than 22.7 µm) and fracture Mode II was seen for nodules of greater diameter (more than 24.8 µm).
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Acknowledgements
This work was financially supported by the Shaanxi Provincial Science and Technology Achievement Transfer and Promotion Plan-absorb Achievement Transformation Project (No. 2017CGZH-XNGJ-03), Shaanxi Provincial Education Department Scientific Research Program Project-service Local Special Industrialization Cultivation Project (No. 17JF018), Xi’an Science and Technology Planning Project Science and Technology Innovation Guide Projects (No. 201805037YD15CG21(19)) and Xi’an University of Technology Scientific and Technological Achievement Transformation Project-technical Requirement Solving Project of Enterprises (No. 2018-1).
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Chun-jie Xu Male, born in 1971, Ph. D., Associate Professor. His research interests mainly focus on developing new preparation technics of metallic materials to expand their applications.
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Xu, Cj., Zhao, Z., Lei, Y. et al. Microstructure and properties of ductile iron bars for plunger pump prepared by horizontal continuous casting process. China Foundry 16, 118–125 (2019). https://doi.org/10.1007/s41230-019-8100-3
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DOI: https://doi.org/10.1007/s41230-019-8100-3
Key words
- horizontal continuous casting
- ductile iron bars
- plunger pump
- tension and torsion properties
- microstructure