بررسي تاثير زمان نگهداري بر تركيب شيميايي دماي خاتمه و مدت زمان استحاله يوتكتيك در چدن نشكن

The Influence of Holding Time on Temperature of Eutectic Ending, Duration of Eutectic Transformation and Chemical Composition in Ductile Iron

In the peresent research, different trends of temperature of eutectic ending and duration of eutectic transformation due to employment of different combinations of five types of inoculants and four types of nodularizers, with different fading resistances, were studied. Cooling curves and image analysis were used to characterize the influence of holding time, for 0, 5, 10, 15 and 20 min, on the samples prepared from the melt processed by 2.5 wt% nodularizer and 0.4 wt% inoculant and kept at 1320°C under nitrogen atmosphere. Chemical composition of 20 samples out of 100 attained by the means of emission spectrometry. While the dominant graphite morphology is spheroidal or flake, by succeeding of the fading phenomenon, temperature of eutectic ending and duration of eutectic transformation respectively decrease, increase and decrease again. When there is a combination of spheroidal, compacted and flake graphite, the above results are reverse. As long as the main graphite morphology is spheroidal, Mg,. S and Al content decrease by advancement of fading, nevertheless after this stage, Mg and Al content reach a steady state whereas S content slightly increases.