FEATURES OF ALLOYING INFLUENCE ON DUCTILE CAST IRON STRUCTURE FORMATION AND MECHANICAL PROPERTIES IN CASTINGS

Procesi littâ, 2024, Vol 4 (158), 25-35

Abstract

Ductile cast iron has an increased tendency to carbide phase forming during crystallization. Therefore, it is effective to increase the ductile cast iron strength characteristics via alloying with non-carbide-forming elements, which also are copper and nickel. The work investigates the regularities of alloying with copper and nickel influence on the ductile cast iron structure formation
and mechanical properties in castings. It is shown that at ductile cast iron alloying with copper, compared to alloying with nickel, the perlite amount in metal base and tensile strength Rm increases while the relative elongation A decreases. Technological parameters that ensure the production of alloyed ductile cast irons with mechanical properties that significantly exceed the requirements of DSTU EN 1563:2018 standard for perlitic cast iron single (Rm ≥ 800 MPa, A ≥ 2%) have been developed. It was established that high-quality pig iron use allows to reduce the FeSiMgCa master alloy consumption for modifying from 2.5 % to 1.5 % (from liquid cast iron weight) and promotes to cast metal plasticity increasing by more than 2 times at a sufficiently high level of alloyed ductile cast irons strength. A short-term process of more economical heat treatment has been developed which provides a significant increase of alloyed ductile cast iron strength: in thin-walled products made of ductile cast iron alloyed with copper (1 %wt.) the tensile strength Rm reaches 950 MPa at a relative elongation A = 6.6 %, alloyed with nickel (1 %wt.) – up to 875 MPa at A = 9.1%. That is, ductile cast iron alloying with nickel is more effective for plasticity  increasing while alloying with copper is more effective for strength increasing. The results of the conducted research expand
the database for development of advanced technologies of products obtaining from alloyed ductile cast iron with increased mechanical and special properties for modern technic.