1. Look at the cutting surface
Gray iron: It is gray, the gloss is very dark, and the surface looks rough. Ductile iron: gray, brighter than gray iron, the surface roughness is like gray iron.
2. File test
Gray iron: The filing resistance is relatively low, and there is a "bashing" sound when filing. The file is rarely sticky. The end of the chip is gray-black with a small amount of silvery white highlights. The size of the particles is different, and the small particles are mainly fine. Grinding with fingers can easily make fingers black. Ductile iron: The resistance is slightly larger than that of gray iron when filing, and there is also a more obvious "sharp" sound, rarely sticking to the file, the dust is gray-black, with fine bright spots, and the particle size varies, but the large particles are used Mainly, use your fingers to grind the dust, which can make your fingers black, but it is lighter than gray iron.
3. Listen to percussion
Gray iron: The sound is deep and the duration is extremely short. Ductile Iron: The sound is crisp, with aftertones, and the duration is short.
4. Gray iron is gray cast iron, corresponding to nodular cast iron. Both are a type of cast iron.