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Development of Water-Soluble Composite Salt Sand Cores Made by a Hot-Pressed Sintering Process

Yang Xiaona, Zhang Long, Jin Xin, Hong Jun, Ran Songlin, Zhou Fei

Archives of Foundry Engineering

2023

Vol. 23, iss. 3

51--58

A wide variety of water-soluble cores are widely used in hollow composite castings with internal cavities, curved channels, and undercuts. Among them, the cores made by adding binders of inorganic salts in the form of aqueous solutions have excellent solubility in water. However, excellent collapsibility is often accompanied by poor moisture absorption resistance. In this study, a water-soluble core with moderate strength and moisture absorption resistance was prepared by hot pressing and sintering the core sand mixture of sand, bentonite, and composite salts, and a tee tube specimen was cast. The experimental results showed that the cores with KCl-K2CO3 as binder could obtain strength of more than 0.9 MPa and still maintain 0.3 MPa at 80±5% relative humidity for 6 hours; the subsequent sintering process can significantly improve the resistance to moisture absorption of the hot pressed cores (0.6 MPa after 24 hours of storage at 85±5% relative humidity); the water-soluble core prepared by the post-treatment can be used to cast tee pipe castings with a smooth inner surface and no porosity defects, and it is easy to remove the core.

Effects of metal-ceramic anticorrosion coating on the performance of ballastless tracks at high temperature

Zhang Jiwen, Jiang Hailou, Ding Feng, Zhang Pingze, Zhou Fei, Li Tao, Duan Ning

Archives of Civil and Mechanical Engineering

2020

Vol. 20, no. 4

329--342

A highly reflective metal-ceramic anticorrosion coating is proposed to address temperature-induced track arching and concomitant damage of the China Railway Track System II ballastless tracks. The term ceramic refers to the inorganic phosphate coating binder and the metal pertains to the aluminite powder filler. Its thermal properties were studied through finite element modeling and heat radiation testing of uncoated and coated concrete samples and 1:1 ballastless track slab models. The metal–ceramic anticorrosion coating microstructure and constituent characterization were considered in its cooling efficacy analysis. The insulation temperature of the concrete test pieces increased as the thickness of the primer layer increased. At a primer layer thickness of 100 μm, 200 μm, and 300 μm, the corresponding insulation temperature was 8 °C, 18 °C, and 25 °C, respectively. Moreover, the temperature gradient, longitudinal stress, and vertical displacement of a track slab coated with a 300-μm metal-ceramic anticorrosion coating layer decreased by 29%, 57%, and 51.9%, respectively, which agreed well with the simulation results. The reduction in temperature transfer to the substrate, realized by the metal-ceramic anticorrosion coating, holds great promise for application in the construction industry.