Optimization of Ni and Cu additions in ADI cast iron in respect of cast cooling rate

The study analyzes the effect of Ni and Cu additions on the mechanical properties of ADI cast iron in casts with different wall thickness values. The applied experiment plan included the use of combinations of the Ni addition in the amount of 0.5% and 1.5% and the Cu addition in the amount of 0.5% and 1.0%. The content of the remaining elements equaled: C = 3.3-3.6%, Si = 2.2-2.6%, Mn = 0.10-0.13%, P max. 0.05%, S max. 0.020% (wt. %). Four cast iron melts were performed, by way of casting ingots with a thickness of 25 mm, 50 mm and 75 mm. The cast iron spheroidization was conducted by the flexible conduit method (steel envelope filled with magnesium). In the casting moulds, a special filtering-modifying system was applied. From each melt and each ingot, strength samples were prepared. After isothermal quenching, R_m and A₅ were measured. The approximating polynomials (R_m, A₅) = f(Ni,Cu) were elaborated. The polynomials make it possible to select the optimal Ni and Cu additions to obtain the required strength or plasticity. Based on the polynomials, three-dimensional diagrams illustrating the above relations were constructed.

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