Development of Hypereutectoid Steel with Nodular Graphite

This work studies the formation of cast structures in hypereutectoid steel modified by alloying modifiers (Fe30Si55Mg7Ca2REM4, Fe34Si55Mg9Ca2 and Fe63Ni30Mg7) together with inoculants Fe20Si60Ba20. It is found that at spheroidizing by 0.7 % Fe63Ni30Mg7 and inoculation by 1.5 % Fe20Si60Ba20 causes the formation of inclusions of nodular graphite with nodularity exceeding 90 % and a structurally-free cementite structure is obtained. The mechanical properties of the steel with nodular graphite modified by Fe63Ni30Mg7 and Fe20Si60Ba20 are as follows: tensile strength (sigma(b)) 660-680 MPa, yield strength (sigma(0.2)) 520-540 MPa, percent elongation (delta) 5-8 %, impact strength (KC) 15-35 J/cm(2), Brinell hardness (HB) 241-255. After ferritic annealing these parameters were found to be sigma(b) =530-560 MPa, sigma(0.2)=400-430 MPa, delta =20-24 %, KC=160- 180 J/cm(2), 150-162 HB.