Microstructure, Mechanical Properties, and Abrasive Wear Behaviour of Si-Mn-Cr-B Cast Steel as a Function of Carbon Concentration

The microstructures, mechanical properties and abrasive wear behaviour of five kinds of Si-Mn-Cr-B cast steels were studied. The steels investigated contained X wt.% C with X= 0.15, 0.25, 0.35, 0.45, 0.55, 2.5 wt.% Si, 2.5 wt.% Mn, 0.5 wt.% Cr, 0.004 wt.%B. The results showed that the A(c1) temperatures increased and A(C3) and M-s temperatures decreased with increasing carbon concentration. From the continuous cooling transformation (CCT) curves, it was discovered that the incubation period of pearlitic transformation was prolonged and the transformation curves of pearlite and bainite were separated significantly with rising carbon concentration. At lower carbon concentration, the normalized structure of Si-Mn-Cr-B cast steel consisted mainly of granular banite and M-A islands. The normalized microstructures of the cast steel changed from granular bainite gradually to needle-like bainite, upper bainite, and lower bainite with rising carbon concentration. The tensile strength and hardness of Si-Mn-Cr-B cast steel increased and impact and fracture toughness decreased with increasing carbon content. The wear testing results showed that the wear resistance of Si-Mn-Cr-B cast steel improved with higher carbon content but was obviously unchanged beyond the carbon concentration of 0.45%. The best balance of properties of Si-Mn-Cr-B cast steel is obtained at the carbon concentration range of 0.35-0.45%C.