Figure 1 and Figure 2 respectively show the graphite morphology and matrix structure of two kinds of gray cast iron in this test. Figure 1 shows that the graphite obtained by Cu alloying is relatively flat, thick and slender type a graphite with block type C graphite in the middle (Figure 1a). Compared with type a graphite, type C graphite is not conducive to tool lubrication and chip breaking, so as to increase the cutting force and lead to poor machining performance. The graphite obtained by multi-element additive alloying belongs to short and curved flake A-type graphite (Fig. 2b)), and the graphite content is 21.55%, and the graphite content of Cu alloying is 20.42%. In the same volume, because the graphite is small, the number of graphite is relatively large, and the graphite spacing is small, the plastic deformation of the material is relatively small in the local area to be cut, so it is easy to form banded chips with small bending degree, not easy to form “chip tumor”, weaken the “tool burning” phenomenon, and improve the cutting performance.

It can be seen from the matrix structure in Fig. 2 that there is little difference between the pearlite matrix of gray cast iron treated by multi-element addition and copper alloying. The influence of pearlite matrix on the processability of gray cast iron can not be well obtained from this test, but it can be obtained from the microhardness of pearlite matrix in the table, The microstructure of gray cast iron alloyed with multi alloying additives is more uniform than that alloyed with copper. The more uniform the microstructure, the better the machinability will be.