1, vacuum self-consumption electric arc furnace melting method (referred to as VAR method)
With the development of vacuum technology and the application of computers, VAR method soon became the industrial production technology of titanium casting. Today's titanium and titanium alloy ingot melting the vast majority of the use of vacuum self-consumption arc furnace melting method. var method is characterized by low power consumption, high melting speed and good quality reproducibility. var method of melting ingot has a good crystalline organization and uniform chemical composition. Generally speaking, the finished ingots produced by VAR melting should be melted at least twice.
2, non-self-consuming vacuum arc furnace melting method (referred to as NC method)
At present, the water-cooled copper electrode has replaced the titanium industry The beginning of the tungsten - thorium alloy or graphite electrode, to solve the problem of industrial pollution, thus making the NC method has become one of the important methods of melting titanium and titanium alloys, several tons of NC furnaces have been operating in Europe and the United States. Water-cooled copper electrode is divided into two types; one is self-rotating, the other is a rotating magnetic field.NC furnace can also be divided into two kinds: one is in the cold water copper crucible melting raw materials, in the water-cooled copper mold casting into ingots; the other is in the water-cooled copper crucible continuous input of raw materials, melting and solidification.
3,Cold hearth melting method (CHM method for short)
Pollution of raw materials and melting process abnormalities will cause titanium and titanium alloy ingot metallurgical inclusions defects, this problem has been affecting the application of titanium and titanium alloy in the aerospace field. In order to eliminate the metallurgical inclusions in the rotating parts of titanium alloy aircraft engines, the cold hearth melting technology came into being.CHM method. The main feature is the separation of melting, refining and solidification processes, that is, the charge to be melted into the cold hearth ** line melting, and then into the cold hearth refining zone for refining, . . and then solidified into ingots in the crystallization zone. Ingot can be round ingot, flat ingot and hollow ingot. Flat ingots can be rolled directly into plates, shortening the production cycle and reducing product costs.CHM method is also divided into electron beam cold hearth smelting method and plasma cold hearth smelting method.
(1) Electron beam cold hearth melting method (EBCHM method for short)
Electron beam melting is the use of high-speed electron energy, so that the material itself generates heat to melt and refine the industrial process, the melting furnace is called EBCHM furnace. EBCHM method can effectively remove tantalum, molybdenum, tungsten, tungsten carbide and other high-density inclusions (HDI) and titanium nitride, titanium oxide, and other low low-density inclusions (LDI) E-beam smelting can be ** the purity of the ingot, and even reach pure. However, because the electron beam melting in a high vacuum work, so the vapor pressure of the higher alloying elements volatilization loss is serious, to control the chemical composition of the alloy has brought difficulties. Alloy ingot after a melting must also be used VAR in the melting once, while for industrial pure titanium, the ingot produced by this method, due to the good surface quality, subcutaneous porosity shallow and less, a ingot can be followed by pressure processing.
(2) Ion cold hearth melting method (PACHM method for short)
PACHM method using inert gas ionization generated by the plasma arc as a heat source, can be in a low vacuum to near atmospheric pressure within a wide range of pressure to complete the melting. The distinctive feature of this method is that alloy components with different vapor pressures ** can be melted without significant burnout, and both high density inclusions (HDI) and low density inclusions (LOI) can be eliminated. The method has the performance of providing improved properties of conventional alloys, and can realize the melting of multiple alloys, which is a more economical method of conventional melting. Using this method of melting, for titanium and titanium alloys, a melting can be obtained in the composition of uniformity of the ingot is more ideal, but the ingot of the subsurface porosity tends to be more and deep.
4, cold crucible melting method (referred to as CCM method)
In the 1980s, the U.S. ferrosilicon company developed a slag-free induction melting process, the CCM method to industrial production applications for the production of titanium ingots and titanium precision castings. In recent years in some developed , CCM method has begun to step into industrialized production scale, ingot. The large diameter of 1 meter, length of 2 meters, the development prospects are impressive. CCM method melting in a non-conductive water-cooled arc block or steel pipe each other in the metal crucible, this combination of. The big advantage is that the gap between each two blocks is an enhanced magnetic field, the magnetic field produces a strong stirring so that the chemical composition of the alloy and the temperature is consistent, thus improving the quality of the product.CCM method both VAR method and refractory materials crucible induction melting characteristics, do not need refractory materials, do not have to prepare electrodes can be obtained at a time of melting the composition of the uniformity of high-quality ingots without crucible contamination. Compared with VAR method, CCM method has the advantages of low equipment cost and easy operation, but the technology is still in the development stage.
5, electric slag melting method (referred to as ESR method)
ESR method uses the current through the conductive slag with the mutual collision of charged particles, and will be converted into thermal energy, that is, with the slag resistance generated by the thermal energy of the furnace material melting and refining. ESR method using self-consumption electrode in the inactive material (CaF2) in the slag melting, which can be directly melting and casting into different shapes of ingot billet, and has a good surface quality, suitable for the next process of direct processing.
