The original definition of forging is the "mechanical deformation of metal when heated to a plastic state". However, in recent years it has come to include similar operations done in the cold or room temperature state as well. Titanium is an alloy of the future and therefore titanium forging is an important process. It is essential to find the optimal forging process for titanium.Techniques for press and hammer forging of titanium are essentially the same as for low-alloy steels. Good handling methods and plant layout will reduce the number of reheats necessary, minimizing contamination during forging. Because of the rapid cooling and the fairly narrow hot working range, the chilling effect of tools should be reduced to a minimum by keeping contact time as short as possible. Preheating the tools also helps. Repeated light blows, or attempts to continue forging at too low a temperature, may promote internal cracking and should be avoided. Moreover, a large number of reheats with only a small amount of deformation between heats is also detrimental, because it leads to a coarsening of the microstructure and consequently poor mechanical properties. In drop forging, die contours should have larger radii and fillets than those used for steel; the lower thermal contraction of titanium requires a smaller shrinkage allowance. Trimming should be carried out hot; furnace, drop hammer and trimming press should be as close together as possible to minimize preheating and avoid wasting time and heat. A final stress-relief anneal is recommended
Hot working treatment- titanium and its alloys can be readily hot worked at temperatures generally somewhat lower than those used for steels. To minimize surface contamination, titanium should be held at high temperatures for only a short time before forging. The rate of contamination, relatively low up to 700°c, increases rapidly with increase of temperature. All forging furnace atmospheres contain free or combined oxygen, and some absorption of this element inevitably occurs. In addition to visible scaling, diffusion of oxygen results in hardening of a relatively shallow underlying layer. The effect of nitrogen is not usually significant at preheating temperatures. Subsequent operations such as machining will remove the hardened surface layer, and the final product will have hardness similar to forging stock.
