The Mystique Of Nodular Cast Iron
Nodular cast Iron (NDI), also called tubular iron, nodular cast iron or tubular steel iron is a form of cast iron found in the United States, developed by Keith Millis for use in the manufacture of jewelry and other metal products. It is primarily used in the United States in the production of metal stampings, metal fasteners, jewelry components, automotive parts, pipe fittings, pipe lines and roof shingles. It was first used to fabricate components for airplane frames, propeller shafts, landing gear and landing gear's assembly. The Tubular Iron construction made it ideal for use in automobile body building due to its strength and ability to hold immense weight.
During World War I, many metal workers lost their lives because of fatigue. Some of them had worked for over fifty years at the time of death and others had worked less than that. This was primarily due to the increased load on their tubular cast irons, which required additional fatigue strength and the consequent inability to work normally or efficiently under fatigue conditions. Lack of training in fatigue strength and design resulted in mass disasters at the time and caused great economic loss.
Keith was aware of this defect and later devised a simple design for the purpose of fatigue strength and design. A & I Company later evolved out of a desire to manufacture quality machinery and tools for the aviation industry. Initially, the firm used simple castings that were not difficult to manufacture. Gradually, improvements were made and nodular cast iron became a vital part of the manufacture of airplane wings. During World War II, the company received orders from the U.S. military to fabricate parts and components for the manufacture of fuel tanks and oil pipes for use in the fleet of Douglas DC - 3 engines.
The need for high strength and durability did not end with the war. The Second World War led to a serious reduction in the demand for labor as factories closed down. Keith designed a new design for the application of nodular cast iron components, which would meet the needs of aviation industries. To make the cylinder head of the wing airworthy, high strength steel of a minimum thickness of one inch was preferred. A threaded ring was also used as a bolt and was attached to the other end of the cylinder head by a tapering threads of high strength steel.
As soon as the alloy was introduced, the number of alloy producers increased drastically. At present, the market is flooded with nodular cast iron alloys having a range of applications ranging from roof shingles and cam tracks to valves and shaft seals. High strength, low bending strength and good heat resistance are its most important features. A few manufacturers in Japan to produce a limited amount of niigata steel of a high grade, which has high wear resistance capability.
It is evident that high strength and low wear resistance are one of the prime reasons for the tremendous popularity of nodular cast iron alloys. Being flexible and strong, it can be used in a variety of applications. Its ductility property ensures that it remains unaffected by chemical action and is capable of withstanding pressures of up to 500 pounds per square inch. However, its greatest benefit is that it provides adequate protection to man and material against extreme heat and weather conditions.
