1. The graphite of gray iron is flat and flake, and the graphite of ductile iron is spherical. If the spheroidal graphite cast iron is hit with a sound similar to that of carbon steel, it indicates that the spheroidal graphite cast iron is well spheroidized. But the sound of gray iron percussion sounds dull.

2. Regarding the spheroidization rate, it can be said that the same nodular cast iron products have different spheroidization rates, so the quality is different, and the price is also very different. Generally, the factory has a spheroidization rate of 85% and it is a qualified product. The spheroidization rate is below 85% because the molten iron temperature is low due to the lack of spheroidization during casting, and the bearing pressure of the manufactured product does not meet the requirements.

3. From the appearance of the fracture (not the machined surface), ductile iron and gray iron can be easily distinguished. Observed with the naked eye, the crystal grain of the fracture of gray iron is relatively coarse, gray-white, and the crystal surface has metallic luster. The fractured grains of ductile iron are very small, black-gray, if the spheroidization is good, there is almost no metallic luster, if there is a whitish luster.

4. In terms of smelting method, ductile iron is added with inoculant and spheroidizing agent to gray iron during smelting to make graphite change from dispersed flocculent to spherical, in order to reduce the fragmentation of ferrite and increase its strength. , Mentioned performance to achieve.

5. In terms of mechanical properties, the mechanical properties of gray cast iron are lower than that of ductile iron. The range of mechanical properties of gray cast iron is 100-350MPa, while the mechanical properties of ductile iron are 350-700MPa. In addition, ductile iron also has elongation. Requirement, and gray cast iron rarely has this requirement.