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Titanium Submarines

In 1789, while studying the chemical composition of a magnetlc sand from the village of Manaccan, the English scientist W. Gregor found a new earths, which he named manaccanitic earth. In 1795, M. Klaproth found a hitherto unknown metal in the mineral rutile and named it titanium; two years later, he himself established the identity between rutile and manaccanitic earth. In 2910, M. Hunter prepared a relatively pure and ductile titanium. As late as 1948, titanium was still being described as a brittle metal useful chiefly for alloying and dioxidizing steels.

The scientific and technical basis for the wide use of Titanium are the following properties of titanium and especially its alloys: low specific weight, high strength, corrosion resistance in many agressive media, suitability for industrial production, weldability, resistance to the corrosion under stress, to concentrated stress and many others. Titanium metal and its alloys are desirable materials for ship hulls and other structures because of their high strength, light weight and corrosion-resistance. If constructed in titanium, Navy ships would have lighter weight for the same size—allowing for a bigger payload—and virtually no corrosion.

But because titanium costs up to nine times more than steel and is technically difficult and expensive to manufacture into marine vessel hulls, it has been generally avoided by the shipbuilding industry. Titanium needs a totally different manufacturing process; shipyard workers must be retrained; construction halls must be reconfigured; and bending and shaping of heavy plates of titanium alloy are far more difficult compared to steel. Titanium proved to be very difficult to work with. Its extreme hardness caused problems in machining and shaping the material. Drills broke and tools snapped, and new ones had to be devised. Titanium also was very sensitive to contaminants, such as chlorine and cadmium.

Industrial production of titanium was set up in the Soviet Union in the early 1950s. For several decades, titanium had been used by the Soviets in the manufacture of stainless steel, but only since 1952 had the Soviet press published articles on research in the development and use of titanium metal. The USSR assigned high priority to the expansion of production of titanium because of growing requirements and, to a lesser extent, because of the almost complete embargo on shipments of titanium from the Free World to the Communist countries [the country with the largest known reserves was the Soviet Union]. Soviet production of titanium sponge increased by about 70 percent from 1958 to 1962, but in September 1962 a Soviet journal reported that production of titanium "still lagged behind requirements." The uses for titanium included parts for the manufacture of aircraft and space vehicles and for production of corrosion-resisting equipment used in certain chemical processing industries.

In accordance with plans for the development of the national economy and scientific work in the USSR, a great deal of research was done starting in the early 1950s in the field of metallurgy of titanium, the theory of titanium alloys; many compositions for titanium alloys were developed, and production processes for industry; work was done on the design and creation of unique industrial machinery, plants, apparatus, and testing and series operational testing was carried out. The technical and economic efficiency of using titanium and its alloys in a number of branches of industry were demonstrated.

This huge work was done by many scientific and industrial collectives of research institutes and factories of a number of ministries (non-ferrous metallurgy, aviation and ship building industries, general machine design, chemical and oil machine construction, the chemical industry and others). Institutes of the Academy of Sciences of the USSR participate creatively in research on metallurgy, physical metallurgy, the metal chemistry of titanium, and in developing new titianium alloys, their testing and adoption in industry.

The directives of the Twenty-third Congress of the Communist Party of the Soviet Union in connection with the 1966-1970 Five-Year Plan for development of the USSR's national economy provided for an additional sharp increase in the production of new, progressive materials and their extensive introduction into the economy. These materials include titanium. The Soviet Union was a world leader in metallurgy, metal working and metal thermal treatment, enabling production of very strong and unique alloys of titanium and steel. Some Soviet submarines, such as Alfa-class submarines, broke ground with construction entirely of titanium and mastered the technique of titanium welding as early as the late 1950.

In 1970 the deployment of the Alfa SSN surprised the U.S. Navy with a 45 knot speed and 2000-2500 foot operating depth. Alfa used a high power density, liquid metal reactor plant to increase the power-to-weight and volume ratios of her propulsion plant, while simultaneously reducing the hull weight needed for extreme operating depths by using a titanium pressure hull. Alfa had a sister, the Papa SSGN, which appeared to employ these same submarine design technologies for the antiship mission. These submarines, assuming they were the lead boats of new submarine classes, threatened American ASW weapons with obsolescence.

The fast, deep diving nuclear submarine threat proved in many ways to be a false alarm. Alfa did not enter serial production until later in the 1970s and only a total of six were deployed before the program was canceled. Likewise, only one PAPA was ever deployed. Instead, the Soviets focused on building more traditional boats. Recent Russian submarines have not been constructed with titanium hulls, presumably for reasons of cost.

Titanium and titanium alloys have become important structural metals due to an unusual combination of properties. These alloys have strength comparable to many stainless steels at much lighter weight. Additionally, they display excellent corrosion resistance, superior to that of aluminum and sometimes greater than that of stainless steel. Further, titanium is one of the most abundant metals in the earth's crust, and as production methods become more economical, will be employed in ever growing applications.

Many titanium alloys have been developed for aerospace applications where mechanical properties are the primary consideration. In industrial applications, however, corrosion resistance is the most important property Since titanium metal first became a commercial reality in 1950, corrosion resistance has been an important consideration in its selection as an engineering structural material. Titanium has gained acceptance in many media where its corrosion resistance and engineering properties have provided the cor rosion and design engineer with a reliable and economic material. Titanium metal's corrosion resistance is due to a stable, protective, strongly adherent oxide film. This film forms instantly when a fresh surface is exposed to air or moisture.

Titanium alloys are considered to be "reactive metal," i.e., they react with atmospheric gases, such as oxygen as well as nitrogen, when at elevated temperature. Because of this, titanium processing such as melting and casting are typically performed in a vacuum or in an inert gas environment. Contamination with oxygen or nitrogen will embrittle the titanium. Similar considerations are used when welding titanium alloys.

Welding procedures for titanium that dictate complete shielding of welds until cooled using inert argon gas. One such common procedure is manual gas tungsten arc welding, which is a slow and laborious process. In addition, inspecting for weld discoloration, is another step in the process that generally results in more rework. These requirements are onerous, requiring that welding small parts be conducted inside an inert gas chamber, to building dedicated local inert gas shields for each weld joint, to adding cumbersome "trailing shields" behind the torch that continue to cover the hot weld metal with inert gas until the weld has cooled sufficiently. All these techniques restrict access and the ability of the welder to manipulate the torch to achieve good weld quality. And, the necessity to use these devices increases the difficulty and time required to produce a weld. Due to these more stringent requirements, labor hours required to weld a given weldment design are a minimum of five times more than required for a similar steel component.

Contamination of titanium with oxygen or nitrogen, and thus the quality of the weld from a strength standpoint, has traditionally been determined by the color of the weld surface. The reaction with oxygen and/or nitrogen creates a thin oxide or nitride (?) layer on the surface with the thickness of the layer being related to the color, and therefore the amount of contamination. For instance, a shiny silver colored weld indicates no contamination, straw or gold color indicates there is a minor amount of contamination and blue or purple indicates significant levels and brown or grey indicates gross contamination. Inspectors must be provided with weld color standards used for comparison purposes. Other methods of assessing contamination include portable hardness test methods and eddy current non-destructive inspection methods. This is the current state of the art in titanium welding.

Weldments produced using the conventional Gas Metal Arc Welding (GMAW) process are done without the use of additional auxiliary shielding devices, such as trailing shields, glove boxes, purge chambers, back-up shields or other shielding devices. Deposited weld metal and heat affected zones are not additionally shielded from the atmosphere by inert gas, except by gas supplied by the torch through the standard gas cup associated with conventional GMAW welding torches. The resultant weld surface color is not an indicator of the weld properties. Any weld color from shiny silver, to blue, grey or brown and scaled, is acceptable by this process.

For centuries, man attempted to descend into the oceans for scientific observation, salvage and rescue operations, animal and mineral harvesting, and attacking enemy ships in times of war. Often, such activities require vessels capable of submerging to great depths. Thus, the foremost concern in designing and fabricating the hull of a submergence vessel is that the hull be strong enough to resist the large crushing forces resulting from hydrostatic pressure. For this reason, submarines have been typically constructed of welded steel that is several inches thick.

However, there are many disadvantages of such construction. The thickness of the hull makes rolling and welding operations extremely difficult. Also, the resulting weight of the welded steel structure is immense and it impacts buoyancy and maneuverability. Furthermore, the substantially tubular, elongated structure of a typical submarine hull is impossible to shape without specialized components.

High-strength titanium is one of the most promising new hull materials. It weighs approxiraately Z76 lb/cu ft compared to a weight of 490 lb/cu ft for steel. Some alloys with yield strengths of 120,000 psi may be welded in thin sheets if extreme care is used to prevent contamination. Non-weldable alloys with yield strengths to 175,000 psi and greater are also available.

Any vessel made from magnetic materials has a Magnetic Anomaly Detectors (MAD) signature. It decreases as the cube root of distance, and does not propagate like a wave. There are significant natural and man-made noise sources. It is a good sensor for close-in detections. There has been interest in the use of non-magnetic steels (German Type 205 and 206 submarines) and building non-steel submarines (the Russian Alfa had a titanium hull). Non-magnetic steel has not been popular in more recent submarines for unknown reasons.

The high strength-to-weight ratio and outstanding seawater corrosion resistance of titanium alloys have long been recognized and have marked titanium as an important structural material in future ocean systems. A specific application in which alloy titanium has several potential advantages over high-strength steels is in the construction of pressure hulls for submarines and deep submergence vehicles.

Titanium is half as dense as steel and non-magnetic, but has major disadvantages, including inadequate resistance to brittle fracture (especially at low temperatures found in the deep ocean). Reluctance to use titanium in ship hulls was grounded in two solid facts: aircraft grade titanium was outrageously expensive and converting to titanium in a historically steel and aluminum shipyard would potentially slow welding speeds by an order of magnitude.

Prior to utilizing alloy titanium for this application, however, definite advances were needed in fabrication technology to provide more economical procedures for joining titanium into structural components. Specific factors which control the economics of joining titanium alloys include the need for extreme cleanliness and careful gas shielding to prevent harmful contamination during fusion welding, the high cost of available weld filler materials (approximately $40 per pound), and the unavailability of an electrode for shielded-metal-arc welding (SMAW). Welding titanium on a shipyard production basis is possible using lower cost, marine grades of titanium to fabricate the hull. Aerospace grade titanium used in aircraft is about nine times more expensive than steel. But “fit-for-purpose” ship hull or marine grades of titanium could be made less costly — perhaps only three times as expensive as steel — by changing the processing and finishing requirements. Although well established, the existing titanium welding processes are too slow for ship hull construction which typically requires miles of welds.

The world's only extant titanium sculpture is the well-known 42.5 meters tall monument in Moscow to first cosmonaut Yuri Gagarin. On April 12, 1961 Yuri Gagarin began his epic journey into space on board the Vostok-1 spaceship. Gagarin, who died in a 1968 plane crash, is commemorated by a number of monuments, sculptures, busts and obelisks. The monument to his achievement, situated on Moscow’s Gagarin square (till 1968 – Kaluzhskaya zastava square), was unveiled on July 4, 1980 when the Olympic Games were being held in Moscow. The monument was created by sculptor – P.I. Bondarenko, architects – Ya.B. Belopolsky, F.M. Gazhevsky, and designer - A.F. Sudakov. The Monument to Gagarin features an inspirational design with Gagarin in his space suit, arms partially raised as if he were about to leap into the sky. One of the highest monuments in Moscow, the monument is situated exactly at that place, where it should be seen even from Moscow MKAD Ring Road.

The Sverdlovsk Region is home to the world's largest producer of titanium, a metal widely used in aviation and other manufacturing. The Titanium Valley Zone has been established to attract Russian and international industrial groups interested in access to unique industrial resources and also prepared to invest in the Russian economy. Titanium Valley Special Economic Zone is a Russian government-backed project that aims to attract major international industrial groups by offering them tax incentives and access to Russia's mining, refining and manufacturing facilities.



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