Ductile iron, also known as nodular cast iron，spheroidal graphite cast iron, and SG iron. It is obtained by adding a certain amount of nodularizer and graphitizer in the molten iron before casting to help with the crystallization of spherical graphite, which has high strength, good toughness and plasticity, and is a good material with advantages of both steel and cast irons.
Steel square tube refers to a square steel pipe, made of carbon steel, cast steel or other materials, is what traditional winding machine manufacturers use to make machine base. So what's the difference between the two materials?
1. Ductile iron's yield strength is higher than steel square. Ductile iron's yield strength ratio is 0.6～0.65 and steel's is only 0.5～0.55. The yield strength means that the external force above this limit will cause permanent deformation of parts.Therefore, steel square's ability to resist pressure is weaker, prone to plastic deformation, and ductile iron is more suitable for carrying the high-speed operating impact of winding machines.
2. Ductile iron contains a large amount of graphite, which per sehas a lubricating effect. The hollows formed by graphite falling can adsorb and store lubricants, which gives castings good wear resistance. Graphite can also prevent the transmission of movements，so ductile iron's shock resistance is 10 times of steel's， which makes it particularly suitable for vibration-bearing machine base.
3. Ductile iron can give full play to the material potential through heat treatment，which has excellent mechanical properties. Its tensile strength is the highest of all kinds of cast iron. So it's often used instead of carbon steel to carry heavy and complex parts. And steel square may have brittle fractures, or thick plate layer tearing in low temperature or some other conditions.
4. The carbon content of ductile iron is generally 4.3～4.7%. And the carbon content of steel is generally 0.4～0.5. Because of the high stability of carbon, the corrosion resistance of ductile iron is more than 10 times times that of steel. However, manganese content of steel is high and the stability of manganese is very poor. Therefore, the steel's resistance to chemical corrosion is poor, easy to rust with fakes brokening off, which is not goood for the long-term maintenance of the machine.
With reference to all the factors mentioned above, ductile iron makes the best material choice for Ascend's machine base because of its excellent toughness, wear resistance, pressure-bearing and shock resistance.