INTRODUCTION

Titanium has been recognized as an element (Symbol Ti; atomic number 22; and atomic weight 47.9) for at least 200 years. However, commercial production of titanium did not begin until the 1950’s. At that time, titanium was recognized for its strategic importance as a unique lightweight, high strength alloyed that was a structurally efficient metal for critical, high-performance aircraft, such as jet engines and airframe components. The worldwide production of this originally exotic, “Space Age” metal and its alloys has since grown to more than 50 million pounds annually. Increased metal sponge and mill product production capacity and efficiency, improved manufacturing technologies, and a vastly expanded market base have dramatically lowered the price of titanium products. Today, titanium alloys are common and readily available engineered metals that compete directly with stainless and specialty steels, copper alloys, nickel-based alloys and composites.

As the ninth most abundant element in the Earth’s Crust and fourth most abundant structural metal, the current worldwide supply of feedstock ore for producing titanium metal is virtually unlimited. Significant unused worldwide sponge, melting and processing capacity for titanium can accommodate continued growth into new, high-volume applications. In addition to its attractive high strength-to- density characteristics for aerospace use, titanium’s exceptional corrosion resistance derived from its protective oxide film has motivated extensive application in seawater, marine, brine and aggressive industrial chemical service over the past fifty years. Today, titanium and its alloys are extensively used for aerospace, industrial and consumer applications. In addition to aircraft engines and airframes, titanium is also used in the following applications: missiles, spacecraft, chemical and petrochemical production, hydrocarbon production and processing, power generation, desalination, nuclear waste storage, pollution control, ore leaching and metal recovery, offshore marine deep sea applications, and Navy ship components among others.

Attractive Mechanical Properties

Titanium and its alloys exhibit a unique combination of mechanical and physical properties and corrosion resistance which have made them desirable for aerospace, industrial, chemical and the energy industry.

Corrosion and Erosion Resistance

Titanium alloys exhibit exceptional resistance to a vast range of chemical environments and conditions provided by a thin invisible but extremely protective surface oxide film. This film, which is primarily TiO2, is highly tenacious, adherent, and chemically stable. It can spontaneously and instantaneously re-heal itself if mechanically damaged if minor traces of oxygen or moisture are present in the environment. Titanium is known for its elevated resistance to localized attack and stress corrosion in aqueous chlorides. Titanium alloys are also recognized for their superior resistance

Other Attractive Properties

Titanium’s relatively low density, which is 56% to that of steel and half that of nickel and copper means twice as much metal volume per weight and much more attractive mill product costs when weighed against other metals on a dimensional basis. Together with higher strength, this obviously translates into much lighter and/or smaller components for both static and dynamic structures & components.

Titanium alloys exhibit a low modulus of elasticity which is roughly half that of steels and nickel alloys. This increased elasticity (flexibility) means reduced bending and cyclic stresses, making it ideal for springs, bellows, body implants, dental fixtures, dynamic offshore risers, drill pipes, and various sports equipment. Titanium’s inherent non-reactivity (nontoxic, nonallergenic and fully biocompatible) with the body has driven its wide use in prosthetic devices and jewelry. Stemming from the unique combination of high strength, low modulus and low density, titanium alloys are intrinsically more resistant to shock and explosion damage than most other engineering materials. These alloys possess coefficients of thermal expansion which are significantly less than those of aluminum, ferrous, nickel and copper alloys. This low expansivity allows for improved interface compatibility with ceramic and glass materials and minimizes warpage and fatigue effects during thermal cycling. Titanium is essentially nonmagnetic and is ideal where electromagnetic interference must be minimized. When eradicated, titanium and its isotopes exhibit extremely short radioactive half-lives and will not remain “hot” for more than several hours.

Heat Transfer Characteristics

Titanium has been a very attractive and well-established heat transfer material in shell/tube, plate/frame, and other types of heat exchangers for process fluid heating or cooling, especially in seawater coolers. Exchanger heat transfer efficiency can be optimized because of the following beneficial attributes of titanium:

• Exceptional resistance to corrosion and fluid erosion
• An extremely thin, conductive oxide surface film
• A hard and smooth surface
• A surface that promotes condensation
• Reasonably good thermal conductivity
• Good strength

Although unalloyed titanium possesses an inherent thermal conductivity below that of copper or aluminum, its conductivity is still approximately 10- 20% higher than typical stainless steel alloys. With its good strength and ability to fully withstand corrosion and erosion from flowing, turbulent fluids, titanium walls can be thinned down dramatically to minimize heat transfer resistance (and cost). Titanium’s smooth, noncorroding, hard-to-adhere to surfaces maintains high cleanliness over time. This surface promotes drop-wise condensation from aqueous vapors, thereby enhancing condensation rates in cooler/condensers compared to other metals as indicated .