Refractory metals are a group of metals that show superior heat and wear resistance. Which exact metals belong to the group differs. However, the most common definition of refractory metals include the elements niobium, molybdenum, tantalum, tungsten and rhenium. A wider definition includes 12 elements, which includes titanium, vanadium and chromium, only to name a few.
The most common applications are glass-melting electrodes, furnace parts and heat sinks. Further, refractory metals are commonly applied in the aerospace and defense industry.
Ferroalloy refers generally to alloys of iron which contain a high proportion of one or more other elements than carbon. These include elements such as chromium, manganese or aluminium. The steel industry is the largest consumer of ferroalloys, as they impart various properties to steel. In addition, ferroalloys play an important role in the production of the metal. For example, ferroalloys prevent the negative effects of sulphur in the production and improve the corrosion resistance in steels.
In general, ferroalloys are produced in a blast furnace or an electric arc furnace, whereby the importance of the latter method declined steadily in the 20th century.
Other possibilities for the production of ferroalloys are by carbothermic reactions, the addition of elements into molten iron and by direct reduction.
Like other alloys, titanium alloys consist of a mixture of chemical elements. They are characterized by a very high tensile strength, toughness and corrosion resistance. In Addition, titanium alloys are able to resist extremely high temperatures of up to 760° C (1400 °C) and are density low compared to steel and other superalloys. Therefore, titanium alloys are comparably light. However, on the other hand, these advantages are offset by high production and material costs.
Pure titanium exist in form of β-phase at temperatures above 885 °C (1625 °F) and in form of α-phase at temperatures below 885 °C. The alloying elements may either stabilize the α- or β-phase. Alloys that stabilize α-phase include aluminium, oxygen and nitrogen. Molybdenum, tungsten and tantalum stabilize β-phase.
Annealing is a heat treatment process. The main goal of the procedure is to alter the microstructure and therefore the physical and chemical properties of metals. In steels, annealing reduces hardness, and internal stresses on the one hand and increases ductility on the other. Therefore, the process makes the material more formable and workable and prevents it from brittle failure.
The hardness of a material is the quality of being able to withstand localized permanent or plastic deformation, penetration, scratching or bending. If hardness increases, so does the resistance to wear, on the one hand. However, hard materials on the other hand are hard to change in shape. Therefore, hardness is an important property of metals.