The oldest of all ferrous products is the gray iron. In-spite of many newer materials which are energetically promoted, gray iron has been used for applications wherein its properties have been proved to be most suitable. Virtually all foundry process produce gray iron castings. Only in recent times the metallurgy of this material has been understood clearly, through it is a very old material used widely in the process of engineering construction. Many molding processes have been used in producing gray iron casting.

Green sand casting is the most frequently used to produce casting as it is very economical. Due to introduction of high-pressure and an equipment with very rigid flask, dimensional accuracy is good in comparison with that obtained in shell molding. If these molds are not strong or hard, it results in wall movement in molds, due to which shrinkage and solidification defects develop. Although castings up to thousand pounds can be done with green sand, usually it is done for small or medium size castings. Blacking mix is sprayed and skin is dried to get a cleaner surface which is used often in engine blocks. Dry molds of sand are used to pour larger castings which withstands high ferrostatic pressures. Most often, the sand that was used in the green sand casting is employed, but another binder is used to increase the strength.

Shell molding can also be used to make cores which are most often used in other molds other than shell molds. The main advantage is because of its ability in hardening the core or mold when there is a contact with heated metal, which improves accuracy by which a mold or cast is made. Casting which is much cleaner can be produced than produced by any high production process. Though the binders and techniques for cold and hot processes are different from that used in shell mold process, the principle is the same. In the pipe industry, iron is casted in centrifugal casting in water cooled molds of metal. Refractory lining made of sand is used in the process of making liners of large cylinders.

Since freezing and cooling rate of the cast iron in permanent molds is high, a thinner section of the molding has cementite. The cementite is removed by the universal practice of annealing. Most used and economical composition of iron that is used in the castings of permanent mold is hypereutectic. This iron expands during solidification and due to the rigidness of the molds, the pressure that is developed during separation of graphite ensures to get a casting that is pressure tight. As the graphite usually occurs as type D, which has small flakes, it is possible to get a very fine finishing in permanent castings of mold. Due to this, graphite is used extensively in making the valve plates in refrigeration compressors. It is also used ideally to make bodies of hydraulic valves and brake cylinders. Though type D graphite along with ferrite matrix is used in permanent castings due to its high strength, it is not ideal for applications using borderline lubrication. These castings ideally perform well when operated in oil bath.