Determining rational complex modifying and alloying additives to improve the mechanical characteristics of gray cast iron

The object of this study is the mechanical properties and parameters of the cast iron microstructure. The task to solve was to ensure high mechanical properties of cast iron for mechanical engineering part. To this end, a working hypothesis was put forward, which assumed the possibility of increasing mechanical properties by selecting complex additives based on modifiers and alloying ferroalloys. The effect of 4 groups of additives was investigated: group 1 – ferrochrome (FeCr025) and silicocalcium (SiCa-30), group 2 – ferrotitanium (FТі35) and ferroboral (FEB6), group 3 – ferrotitanium (FТі35) and ferrochrome (FeCr025), group 4 – ferroboral (FEB6) and silicocalcium (SiCa-30). They were introduced into the liquid metal in different percentages in the amount of 3 % of the mass of liquid cast iron. The following mechanical characteristics were selected: flexural strength (σ, MPa), tensile strength (UTS, MPa), deflection arrow (f, mm), hardness (HB), and whitening. It was determined that the strength characteristics of cast iron treated with ferroalloys of group 1 reach a maximum at about 40 % silicocalcium in the composition of the additive. The tensile strength of cast iron reaches about 320 MPa, the bending strength is about 710 MPa, the deflection arrow is 4.5 mm, and the hardness corresponds to the HB250 level. The fact of competition of hardness and other mechanical properties was established in the range of silicocalcium content in the modifier composition up to 40 %. Thus, it was established that it is the combination FeCr025+SiCa-30 with the ratio of components of 40:60, respectively, that is rational. The revealed regularities of changes in the amount of carbides, the size of graphite, and the amount of ferrite when using different additives allow us to explain patterns in the formation of mechanical properties of cast irons. Owing to this, it becomes possible to identify the mechanism of formation of properties, ensuring purposeful regulation of the quality of cast iron