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Rolled ring forgings process is used to make ring shaped objects with less than an inch in diameter to cylindrical shapes that have diameters measuring hundreds of inches. A wide range of industrial products for nuclear reactors, pressure vessels, off-road equipment, bearings and gears weighing just a few pounds to hundreds of metric tonnes are made using this process.The process can be used for most metals used in high temperature applications. Understanding the process The rolling ring process is done on rolling mills where a metal that are heated above the recrystallization temperature are rolled till a ring of desired wall thickness is achieved. The metal is first shaped into a donut like structure and then placed on an idler roller. The idler roller continuously presses against another roller called the drive roller. The metal is kept in place using axial rollers. As the idler roller presses against the drive, the thickness of the metal decreases in an uniform manner due to high speed rotation. The process continues till a seamless ring of desired thickness is achieved. Rolled ring forgings can be of varying of diameters as well. Metal specifications Commonly used industrial grade metals for making rings are Carbon low alloy, stainless steel, aluminium and titanium. Each of these metals produces rings with varying specifications. While the inner diameter can range from 10 inches, the maximum outer diameter normally does not exceed 120 inches for aluminium and titanium while the other two metals allow making slightly larger rings with outer diameters measuring 128 inches. A major difference in application is that titanium cannot be used to make tall rings. The maximum height of forgings that can be made of titanium is 10 inches. Carbon also stands out as it can be used for making rings that weigh as much as 6,500 lb, nearly the max weight of ring that can be made of stainless steel which is the most commonly used alloy for rings. Advantages Rolled rings forgings are strong as they do not have welds and are single piece design. Rolling is a cost saving compared to other processes like machined bar as it does not produce wastage and requires considerably less machining to make rings. Rings of large sizes can be made and the grade flexibility is also higher compared to other processes. The rings have consistent metallurgical properties and reduce dependence on labour for inspection and quality control.
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