Titanium

From Combat Robot

Titanium is a chemical element with the symbol Ti and atomic number 22. It is recognized for its high strength-to-weight ratio. It is a strong metal with low density that is quite ductile, lustrous, and metallic-white in color. Titanium is non-magnetic and a poor conductor of heat and electricity.

The two most useful properties of the metal form are corrosion resistance and the highest strength-to-weight ratio of any metal. In its unalloyed condition, titanium is as strong as some steels, but 45% lighter. Titanium is 60% more dense than aluminium, but more than twice as strong as the commonly used 6061-T6 aluminium alloy.

Titanium can be alloyed with iron, aluminium, vanadium, molybdenum, among other elements, to produce strong lightweight alloys. Titanium alloys are fairly hard although not as hard as specific grades of heat-treated steel. The stiffness of titanium alloys are not as great as aluminium alloys, so it is used less for structures which require high rigidity. Grade 5 alloy, also known as Ti6Al4V, Ti-6Al-4V or Ti 6-4, is the most widely commonly used. It has a chemical composition of 6% aluminium, 4% vanadium, 0.25% (maximum) iron, 0.2% (maximum) oxygen, and the remainder titanium. Grade 5 is significantly stronger than commercially pure titanium while having the same stiffness and thermal properties. This grade is an excellent combination of strength, weldability, fabricability, and is heat treatable.

Grade 5 alloy has a density of roughly 4500 kg/m3, Young's modulus of 110 GPa, and tensile strength of 1000 MPa. By comparison, annealed type 316 stainless steel has a density of 8000 kg/m3, modulus of 193 GPa, and tensile strength of only 570 MPa. Tempered 6061 aluminium alloy has 2700 kg/m3, 69 GPa, and 310 MPa, respectively.

Machining requires precautions, as the material will work harden if sharp tools, proper pressure, and correct cooling methods are not used. The metal can be machined using the same equipment and via the same processes as stainless steel.

All welding of titanium must be done in an inert atmosphere of argon or helium in order to shield it from contamination with atmospheric gases. Contamination will reduce the integrity of the assembly welds and lead to joint failure.

The best prices for titanium are to be found on the surplus market. Some places sell it as low as $8 a pound, although it sometimes can reach as much as $30, and thats not counting the hardening process.