The relationship between the number of graphite balls and the properties of 45 ° sector block is shown in Figure 1. Compare the performance of 45 ° fan-shaped block at different positions: the tensile strength is 371 MPa? The results show that the minimum value and maximum value are about 2% in the range of 380MPa; the yield strength is about 3% in the range of 233mpa-240mpa; the elongation is 19.5% – 23.5%, and the maximum value and minimum value are 17%; the impact value at room temperature is 17.9j.cm- 9 j.cm, the difference between the maximum value and the minimum value is 25.1%; the impact value of – 40 ° C fluctuates in the range of 5.4 j.cm-8.0 j.cm, the difference between the minimum value and the maximum value is 32.5%. From the analysis of fluctuation range, the fluctuation range of – 40 ° C impact value is the largest.

The spheroidization rate and the number of graphite balls are analyzed. It is found that the spheroidization rate varies from 85.4% to 90.9% on the cross section of 45 ° fan-shaped block, and the difference between the maximum value and the minimum value is 6%; the number of graphite balls varies from 50 / mm ~ 2 to 125 / mm ~ 2, and the difference between the maximum value and the minimum value is 60%.

The results show that the tensile strength, yield strength, elongation and other conventional mechanical properties of the 45 ° fan-shaped block have little change on the whole section, the spheroidization rate of the 45 ° fan-shaped block at different positions has little fluctuation, and the impact property, especially the impact property of – 4 (TC) has a large fluctuation range; in addition, the number of graphite balls changes significantly on the section of the 45 ° fan-shaped block. The analysis shows that the influence of spheroidization rate of graphite ball number on conventional mechanical properties such as tensile strength, yield strength and elongation of ductile iron and impact property is not obvious; the influence of graphite ball number on conventional mechanical properties such as tensile strength, yield strength and elongation of ductile iron is not obvious, but it has great influence on impact property, as shown in Figure 2.

The fluctuation range of impact value at -40 ° C (32.5%) is larger than that at room temperature (25.1%). The change of impact value at – 40 ° C is shown in Figure 3.

When the sampling position moves from the inner side to the inner 1 / 8 position, the number of graphite balls decreases from 100 / mm ~ 2 to 75 / mm ~ 2, and the impact property at – 40 ° C decreases from 7.8 J / cm ~ 2 to 5.4 J / cm ~ 2; when the sampling position moves from the outer side to the center, the number of graphite balls decreases from 125 / mm ~ 2 The impact value at – 40 ° C decreases from 8.0j/cm2 to 5.9j/cm2. Due to the deviation of sampling position, the – 40 ° C impact value at the inner quarter is higher than that at both sides. By analyzing the relationship between – 40 ° C impact value and graphite ball on the whole section of 45 ° sector block, it can be concluded that – 40 ° C impact value decreases with the decrease of graphite ball number. The number of graphite balls in the inner quarter is the least, and the size of graphite balls is the largest. Therefore, it is considered that the weak position of – 40 ° C impact property is near the inner quarter.