What are the advantages of cast iron?

Cast iron is one of the most extensively used alloys of ferrous. It is made from pig iron by the process of casting and hence the name. Pig iron is placed in the furnace along with other alloying elements and melted until the molten mixture is obtained. The molten mixture is then poured in casts or molds​ of required dimension and left to solidify. The resultant solid obtained is the cast iron which finds its use in a myriad of industries.

Advantages:

1. Good castability (low Tm, good fluidity)
2. Good machinability (graphite cast irons)
3. Antivibration properties
4. Low-stress concentration
5. Sensibility

 

Types of cast iron

The properties of iron casting can vary according to the alloying elements added. The cast iron’s properties can be manipulated by varying the alloying constituents. The main alloying elements added to the cast iron are carbon and silicon. Based on the amount of the alloying elements added, the cast iron can be classified into grey iron or white iron. They are differentiated by the color of the casting when it is fractured.

White cast iron, when fractured, allows the crack to pass right through the cast product. On the other hand, grey cast iron deflects a crack but at the same time initiates numerous other cracks because of the presence of the graphite structure. As grey cast iron has a high amount of silicon in it, it has a graphite structure that brings in characteristics characteristic to the cast iron. White cast iron is harder and so exhibits less machinability than grey cast iron. White cast iron also contains less amount of silicon than the grey cast iron. White cast iron also has carbide impurities in them.

Additionally, cast iron can also be classified into malleable and ductile cast iron. When white cast iron is heated, its properties change and this improved type of cast iron are called as malleable cast iron. When alloying elements like magnesium or ceriumare added to pig iron when it is melted, they form ductile cast iron with a different structure compared to other cast irons.

The grey cast iron has good casting properties, good vibration damping, good wear resistance, good machinability and low notch sensitivity. However, its tensile strength and elongation are very low, so only can produce some metal parts with low physical requirements, such as protective cover, cover, oil pan, hand wheels, frame, floor, hammer, small handle, base, frame, box, knife, bed, bearing seat, table, wheels, cover, pump, valve, pipe, flywheel, motor blocks etc. As for the higher grades, grey cast iron can withstand greater load and a certain degree of tightness or corrosion resistance of the more important castings such as cylinder, gear, base, flywheels, bed, cylinder block, cylinder liner, piston, gear box, brake wheel, coupling Plate, medium pressure valve, etc. 

 

Strength 

Cast iron has higher strength at reduced costs. They also have higher strength and ductility and are stiffer than pure iron. The strength of cast iron is what makes it a workable material for various industries. It has a low melting point and greater fluidity.

 

Castability 

Cast iron is used in an array of industries because of the ease of its castability. The cast iron can be molded into various shapes and sizes based on the industrial needs. The cost of production and the minimal usage of tools make it a viable manufacturing material.

 

Machinability 

Cast iron can be easily machined into final products. The properties of a metal like hardness, tensile strength and microstructure alter its machinability. Hence, it can be used in a number of industries for manufacturing numerous products.