The reserves of titanium in the earth's crust are second only to iron, aluminum, and copper, ranking fourth among metal elements. Moreover, titanium alloys have a series of excellent properties, so they are more and more widely used. According to its application background, titanium alloys can be divided into three types: high-temperature titanium alloys, structural titanium alloys, and functional titanium alloys. In addition to casting, the forming methods of titanium alloys include forging, superplastic, welding, and other methods.
Melting process of cast titanium alloy
Titanium is a very active metal, which reacts very quickly with oxygen, nitrogen, hydrogen, and carbon in liquid state, so titanium alloy melting must be carried out under the protection of higher vacuum or inert gas (Ar or Ne). The crucibles used for smelting are all water-cooled copper crucibles. There are three main methods for the specific smelting process:
Non-consumable electrode arc melting alloy melting is carried out under the protection of vacuum or inert gas. This process mainly prepares electrodes by smelting consumable electrodes.
Vacuum consumable electrode arc melting uses an electrode made of titanium or titanium alloy as the cathode, and a water-cooled copper crucible as the anode. The molten electrode enters the crucible in the form of droplets, forming a molten pool. The surface of the molten pool is heated by the electric arc, and it is always in a liquid state, and the bottom and the periphery of the crucible are forced to cool, resulting in bottom-up crystallization. The molten metal in the molten pool solidifies and becomes a titanium ingot.
Vacuum consumable electrode shell melting furnace is developed on the basis of a vacuum-consumable electrode arc. It is a furnace type for casting special-shaped parts that combines smelting and centrifugal casting. Its biggest feature is that there is a thin titanium alloy solid shell between the water-cooled copper crucible and the metal melt. The so-called solidified shell, this layer of the solidified shell of the same material is used as the inner lining of the crucible to form a molten pool to store titanium liquid, avoiding the pollution of the crucible to the titanium alloy liquid. After pouring, a layer of solidified shell left in the loss can continue to be used as the inner lining of the crucible.
In recent years, with the development of science and technology and the needs of production, new methods and equipment for smelting titanium alloys and other active metals have been researched and developed, mainly including electron beam furnaces, plasma furnaces, vacuum induction furnaces, etc., and have obtained a certain degree of application. However, from the comparison of technical and economic indicators such as power consumption, melting speed, and cost, consumable electrode electric arc furnace (including shell furnace) smelting is still the most economical and applicable smelting method.
At present, the quality control before the furnace adopts the NB-800 series photoelectric direct reading spectrometer, which can quickly and conveniently detect the content of each element in the titanium alloy, which greatly facilitates the on-site quality control of the furnace workers!
