How to identify the difference between ductile iron and gray cast iron

Ductile iron is a high-strength cast iron material with comprehensive properties close to steel. Ductile iron is obtained by spheroidizing and inoculating to obtain spheroidal graphite, which effectively improves the mechanical properties, plasticity and toughness of cast iron, thereby obtaining a higher strength than carbon steel.

Gray cast iron is a type of cast iron, which refers to cast iron with flake graphite. It is called gray cast iron because the fracture is dark gray when broken. Carbon exists in cast iron in the form of flake graphite. The fracture is gray. It has good casting and cutting properties and good wear resistance.

There are several ways to identify ductile iron and gray cast iron:

1. From the appearance of the knock fracture (not the surface that has been machined), the ductile iron has fine grains and is black-gray; the gray cast has relatively coarse grains, grayish white, and the crystal surface has a metallic luster.
2. From the processing surface, the processing surface of ductile iron parts is brighter than that of gray cast iron parts, and the structure is finer than that of gray cast iron parts.

3. Judging by the sound of knocking, ductile iron parts have a crisp sound and a long echo, and the knocking sound is similar to carbon steel; gray cast iron parts have no echo and the sound is muffled.
4. From the spark of the grinding wheel, the streamline of the spark beam of gray cast iron parts is thin and short, orange-red or dark red, and there is a feather-like tail at the tail.

Conclusion

Ductile iron parts have developed into a cast iron material second only to gray cast iron and widely used. The so-called "iron instead of steel" mainly refers to ductile iron.

The comprehensive performance of ductile iron is close to that of steel. It is precisely based on its excellent performance that it has been successfully used to cast some parts with complex forces and high requirements for strength, toughness and wear resistance. Ductile iron parts are a widely used cast iron material in the industrial sector.