THE KROLL PROCESS AND REFINING TITANIUM

Imagine a material with the strength of steel, yet whose weight is comparable to that of aluminum. A material completely inert and non corrosive, making it hypo-allergenic and safe for virtually any application, even to the point of medical implants and surgical tools. A material that holds refractive properties which allow for extraordinary color options through proper manipulation. This material is titanium, a natural element that possesses these amazing traits and more.

Billions of years ago, a star in our vicinity spent its dramatic finale in a burst of light that gave birth to the element titanium. Titanium can only be created by the largest of cosmic explosions: the supernova. Its momentous origin underscores its superiority as a metal and foreshadows its undeniable allure.

One cannot simply stroll along the beach picking up specimens of this noble wonder of nature. In fact, it has taken decades of research and technology coupled with billions of dollars in equipment and testing to bring titanium to the forefront of metallurgy. A trace element commonly used in locating diamonds, titanium is typically found in the form of ores such as rutile and ilmenite. Before titanium can be used to create the huge array of products that have vastly improved our lives, it must first endure a costly and difficult process to extract the pure material from its ore state. The most common way that this is achieved is through a procedure called the Kroll process.

To produce a useable form of titanium, the basic ore, usually rutile, is converted to sponge by charging the ore in a chlorinator, then passing chlorine gas through the charge. This results in titanium tetrachloride. The oxygen is removed as CO or CO², resulting in a colorless liquid form of TiCl4 crude that is purified by continuous fractional distillation. It is then reacted with either magnesium or sodium under an inert atmosphere to yield a metallic titanium sponge and magnesium or sodium chloride. The chloride is then reprocessed and recycled.

The next stage of the process requires the titanium sponge to be crushed and pressed before being melted in a consumable electrode vacuum arc furnace at extreme heat. The melted ingot, each weighting as much as 12,000 lbs, is not poured but solidifies under vacuum conditions in the furnace.

Titanium was not discovered until the late 1700's. Remarkably, it wasn't until the early 1900's that it was isolated and named for the powerful mythological first sons of the universe - the Titans. Only within the last few decades has technology provided the means of extracting titanium from the Earth. Although it remains a costly and difficult process, the effort has provided a far greater positive impact on mankind than any material in recorded history. From the depths of the ocean to the far reaches of space, from the smallest medical implants to the largest passenger planes, titanium has become an indisputable part of human triumph. Its applications have spread throughout sports and automotive industries, industrial design and architecture. Ancient monuments were accented with gold. Today, many of our most modern architectural marvels, including the Guggenheim Museum in Bilbao, Spain are clad with titanium.

Once proclaimed to be the "metal of the future", titanium has seen that edict arrive and even evolve to the point of becoming an icon for uniqueness and superior quality. The explosion in demand for smaller more intricate products has given rise to development of new technologies based on modification of existing large format methodology for manufacturing processes.