Investigation of hardening processes of core mixtures with phosphate binders, including for additive sand molding

Шрифт:
40

https://doi.org/10.15407/steelcast2021.01.061

Met. litʹe Ukr., 2021, Tom 29, №1, P. 61-69

R.V. Liutyi1, PhD (Engin.), Docent, Associate Professor, e-mail: rvl2005@ukr.net, https://orcid.org/0000-0001-6655-6499
V.S. Doroshenko2, Dr. Sci. (Engin.), Senior Research Scientist, Leading Researcher, e-mail: doro55v@gmail.com, https://orcid.org/0000-0002-0070-5663
M.V. Tyshkovets1, Graduate student, e-mail: maria15021996@gmail.comhttps://orcid.org/0000-0001-9621-5249

1National Technical University of Ukraine "Igor Sikorsky Kyiv Polytechnic Institute (Kyiv, Ukraine)
2Physico-technological Institute of Metals and Alloys of the NAS of Ukraine (Kyiv, Ukraine)

Received 31.10.2020

UDK 621.742:661.862

The results of the study of the hardening dynamics and physical and mechanical properties of sand core mixtures with phosphate binder components with the addition of liquid chemical reagents of various natures to these mixtures are presented. 
The binder components in the mixtures are phosphates of silicon, aluminum, potassium and sodium, which are formed by the interaction of orthophosphoric acid with oxides or inorganic salts, which contain these elements. Core mixes contain ecologically safe and non-deficient components, provide high quality of castings from various foundry alloys. With thermal hardening, they are suitable for the manufacture of complex rods. Additive technologies for the production of foundry cores, which are actively developing, provide in particular layer-by-layer (up to 1 mm) application of molding material plus the fastest  possible strengthening of each layer. In this case, chemical reagents that show increased activity to the components of the sand-phosphate mixture and do not allow the mixing process, can be considered as promising hardeners of instant or rapid action. The actions of 30 different organic and inorganic chemical reagents on 8 core mixtures' properties has been studied and it has been shown that some of them do provide fast surface hardening. At the same time they do not lead to hardening of samples on all volume even after long endurance within several days. The results of the total strength (at compression in MPa) and surface strength (shedding in %) of the samples show that of the thirty chemical reagents studied, only two mixtures are promising for improvement in survivability parameters and curing time as cold-hardening mixtures and simple cores. 
The effects of rapid surface hardening in a number of compositions have been established, which is the basis for further development of additive technology based on them.

Keywords: Core mixture, binder component, orthophosphoric acid, phosphate, surface hardening, strength of sand mixture, additive technology, casting.

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