Titanium is a lustrous, silvery coloured metal that is known to have particularly high strength and low density. It was first discovered in Cornwall in 1791 and takes it names from Greek mythology, after the Titans.
Titanium is used in a wide number of industries including aerospace and jewellery making, and it is valued for being highly resistant to corrosion particularly from chlorine and seawater. But why is it so expensive?
Titanium cannot be extracted by using carbon to reduce the ore as it forms titanium carbide making the metal very brittle. Instead, the extraction process involves several stages that are referred to as the Kroll Process. It is the complexity of this process and the energy expended in production that gives titanium its high market price. The metal must first be turned into a porous form, or titanium sponge as it is sometimes called. From this ingots can be formed by slowly melting the porous metal and these ingots can then be turned into smaller products such as bills, bars, sheets, strips and tubes. Successive re-melting of the metal still produces a high quality metal.
Because titanium has such a high melting point, the temperatures required for this process are extremely high and it is thought that the conversion of the metal to ingots accounts for around 30% of the cost of the entire process. A lot of energy is needed and the process is labour intensive. The strength of titanium means the process is slow and once the finished product is done around 90% of the original material has been lost. When used in the aerospace industry, for example, 1kg of finished titanium has come from almost 11kg.
Welding is the process of joining together materials, usually metals, but fusing them together through melting the surface points. Two pieces of metal can then be joined to form a single piece. Welding is used for all sorts of reasons from creating metal structures such as bridges and sculptures, to repairing damaged metal structures such as ships.
Hyperbaric welding is a specialist form of welding that requires elevated pressure to work. It is usually performed underwater for this reason. The process can be performed either ‘wet’ or ‘dry’. Wet is when it is performed in the water, and dry is when it takes place in a positive pressure enclosure, or isolation chamber, which gives an increased level of pressure. It is most commonly referred to as hyperbaric welding but when performed in a wet environment it can also be called underwater welding. Hyperbaric welding can be used to repair ships, oil rigs and underwater pipes, and steel is the main material that is used.
Dry hyperbaric welding, as we touched on above, involves the process being carried out in an environment with increased pressure, in a sealed chamber. There will usually be a gas mixture around the chamber. Wet welding is less commonly used and is a skill that less people possess. The welder must also be able to dive, and they are exposed to the risk of electric shock whilst they do this. To prevent this all equipment must be properly insulated and the welding current should be well controlled.
The benefits of this type of welding are that things like oil rigs and ships that are submerged in water can be easily repaired. This makes their maintenance much easier, and more cost effective, as well as enabling the repair to be carried out more quickly than if the structure had to be removed from the water.
Metal detectors are electronic instruments that are used to detect the presence of metal if it is in close proximity. They can be particularly useful for finding metal that may be underground or hidden and are often used for archaeological purposes.
Different metal detectors can work in different ways, depending on their uses, but in a simple form they usually consist of a transmitter coil, through which electricity flows to create a magnetic field. This turns the metal detector into an electromagnet. By moving the detector, the magnetic field that has been created is moved too and when it comes close to another metal a second magnetic field is created which is what the detector is looking for. There is another coil, called a receiver coil, on the detector that will usually emit a noise when it comes into contact with the magnetic field. Generally, the stronger the magnetic field is the louder the noise will be to indicate how close you are to the metal object.
Metal detectors are also used for security purposes in places such as government buildings and airports. Since the 1970s, metal detectors have been largely used across the world in airports to screen passengers before they board a flight. In addition to this, security officials are often in possession of smaller hand-held devices that can be swept over the body to detect metal.
Anyone can own a metal detector and in England and Wales their use is not prohibited, providing that permission has been granted by the landowner of the area they are to be used on. The only exclusions are if the area in question is a Scheduled Ancient Monument, an SSSI (site of special scientific interest) or falls under the Countryside Stewardship Scheme.