Silicon Alloyed Ductile Cast Iron and Its Application

Processy litʹâ, 2020, Tom 139, №1, p.20-29

Abstract

Received 24.12.2019

UDK 669.15:546.28

Currently, many countries are actively working on the use of silicon alloying to create new grades of ductile cast iron with improved mechanical properties and machining. The article presents experimental data on the effect of silicon (up to 4 %wt.) on the structure formation and level of ductile cast iron with spheroidal graphite mechanical properties. The efficiency of alloying with silicon depends on the composition of the base melt, the modifier, on the modifying method, on the castings cooling rate. It is shown that alloying with silicon eliminates the chilling in castings and provides the formation of strengthened ferritic metal base. As a result, the strength and ductility of ductile cast iron are both increased. It is established that, compared to ladle modifying, at in-mold modifying the density of spheroidal graphite inclusions distribution is increased by 3–5 times, while the amount of ferrite in the structure – by 1.8−2.0 times. Silicon-alloyed ferritic ductile cast iron, obtained by in-mold modifying, is characterized by high values of strength (Rm = 550−620 MPa, Rp0,2 = 420–500 MPa) and ductility (A = 11−17 %). In terms of strength, the developed ductile cast iron is far superior to the standard ferritic grades and plasticity – to ferritic-pearlitic, with a relatively lower (up to 2.9 %wt.) silicon amount. An important advantage of silicon-alloyed ductile cast iron is the even distribution of castings hardness and improvement of their machinability by cutting. The combination of these indicators can significantly improve the quality of cast products made of ductile cast iron and increase their competitiveness.