Titanium is roughly half the weight of steel and twice the strength of aluminum. It also withstands much higher temperatures, and is far more inert than either. The downside is it can cost 10 times as much per pound as aluminum and 40 times that of steel. The high cost is not much because of its rarity, but rather the energy-intensive process of refining from ore. In an effort to find a better way to extract this precious material, the US Energy Department has just funded a group at Case Western Reserve (CWR) to the tune of $ 675,000.
The reason for the department’s sudden vigor to improve titanium refining is not entirely clear. In the past, Russia has always been two reasons that titanium has been considered a strategic material. On the one hand, militarily speaking, putting the most titanium in the air is roughly equivalent to having air superiority. On the other hand, most the planet’s titanium, conveniently (for them) is produced in Russia.
Traditionally, the main cost in extracting titanium has been the requirement for sacrificial magnesium, itself a light and expensive metal. A new direct electrolytic process, called electrowinning, is capable of extracting commercially pure titanium straight from its molten ore. The funding will be used to build a proposed electrochemical reactor at CWR, which will use electrowinning to produce titanium without any need for sacrificial magnesium.
It is important to note here that getting your hands on titanium is only half the battle. Those same properties that make titanium so desirable — and hard to extract — also make it really hard to machine or otherwise produce a finished part. For example, titanium’s notorious toughness dulls cutting tools in a fraction of the time other metals do. The heat generated by cutting tends to stay in the tool rather than transferring to the metal part — so as the tool heats up, it easily erodes and deforms.
Titanium and its useful alloys tend to work-harden immediately, much like stainless steel. That can become a problem if, for example, you have to drill a deep hole. It is often preferable to drill the hole straight off to full diameter on the first pass rather than trying to enlarge a pre-drilled hole that has work-hardened walls. We should mention that for most aerospace and medical applications, the common titanium alloy used is Ti6ALV. It has aluminum and vanadium mixed in to give it much greater strength than the commercially pure variety.
Titanium also sparks brightly and readily when struck, recalling its god-like name (Titan). This is something to keep in mind when pallets of titanium start showing up in glorious affordable bulk. The urge to call out titanium for a part in a design should be tempered with the practicalities of bending it to your will. Unmanned machining environments require built-in fire detection and extinguishing systems, particularly when oil-based or flammable cutting fluids are used. Welding is another story altogether. Normally to fuse metal with a process such as TIG welding, you supply inert shielding gas to the hot area to prevent oxidation. When welding titanium, you instead supply oxygen to yourself and do your welding in a huge room entirely under inert atmosphere.
Finding an economical process to extract titanium is the first step towards securing a titanium future. New manufacturing processes, like 3D metal printing, are rapidly bringing in a range of potential new titanium applications. Composite materials have taken some of the immediate pressure off of the need for cheap titanium. Yet although they can be both light and tough, without sufficient hardness, no one will be tapping threads in a composite that must withstand any substantial pull-out force — or fly a craft made of them to close to the sun.