(1) Raw materials
The main ingredients for preparing molten iron in the experiment are Q10 pig iron, scrap steel, spheroidizing agent, inoculant, etc. the raw material ratio of the three groups of nodular cast iron designed is shown in Table 1.
(2) Sample preparation
Melting: the experimental materials are melted in an industrialized 25 kg medium frequency induction furnace. In order to ensure the accuracy of the basic composition of the sample, the alloy composition is adjusted by melting pig iron and scrap first, and then adding alloy elements. The infrared temperature measuring gun is used to monitor the temperature of molten iron in real time to ensure that the discharge temperature is about 1500 ℃ ~ 1520 ° C.
Spheroidizing and inoculation treatment: preheat the ladle in advance, put 2% low magnesium spheroidizing agent into the groove on one side of the ladle bottom, evenly cover the surface of the spheroidizing agent with 0.4% silicon barium calcium inoculant in the ladle, and carry out spheroidizing and inoculation treatment on the liquid metal by the flushing method. During the experiment, the infrared temperature measuring gun is used to monitor the molten iron temperature in real time, and the pouring temperature is controlled between 1425 ~ 1450 ℃. The molten iron is poured into the sand mold. In order to prevent the decay of inoculation, 0.15% inoculant is added with the flow during pouring for secondary inoculation. Finally, a cylindrical test bar with a bottom diameter of 60 mm and a height of about 200 mm is obtained as shown in the figure. The composition of the prepared nodular cast iron was analyzed. Among them, elements C and s are determined by carbon sulfur analyzer (cs-8800, China), and other elements are determined by fluorescence analyzer (xrf-1800, Japan). Table 2 shows the measured actual alloy composition values of three groups of cast test bars. In order to prevent too many pouring defects at both ends of the test bar from affecting the experimental accuracy, the subsequent test samples are taken from the middle of the test bar.