Titanium alloy melting method
1, vacuum consumable arc furnace melting method (referred to as VAR method)
With the development of vacuum technology and the application of computers, the VAR method soon became a mature industrial production technology for titanium. Titanium and its alloy ingot today are mostly produced by this method. VAR method is characterized by low power consumption, high melting speed and good quality reproducibility. VAR ingot melting with good crystalline structure and uniform chemical composition. In general, the finished ingot should be produced by the VAR method. At least after two remelting. Production of titanium ingot VAR method, the world's manufacturers use similar processes, the difference is perhaps that the use of different electrode preparation methods and equipment. Electrode preparation can fall into three categories, one by using a continuous pressing of the total feed electrode, excluding the electrode welding process: the second is a single electrode pressing, welding welded consumable electrode. And through plasma arc welding or vacuum welding into one; third is the point of other melting method casting electrode.
Modern advanced VAR furnace technical features and advantages: (1) full coaxial power input, that is completely coaxial throughout the furnace height, said the coaxial power supply 'to reduce the segregation phenomenon; (2) the crucible The internal electricity school can be fine-tuned in the X-axis / Y-axial direction; (3) With an accurate electrode weighing system, the melting rate is automatically controlled to achieve constant speed melting. Ensure the quality of the melting; (4) ensure the repetitiveness and consistency of each melting; (5) flexibility, that is, a furnace can produce a large number of ingots and large ingots, which can greatly improve the productivity; ) Has good economy. The "coaxial feed" approach avoids magnetic leakage due to an imbalance in the current supplied by the crucible. Reduce and eliminate the adverse effects of induction magnetic fields on smelting products. And improve the electrical efficiency, so as to obtain a stable quality ingot. The purpose of "Constant Speed ??Melting" is to improve ingot quality and to control the condensation process by ensuring that the arc length and melting rate are constant during the smelting process using advanced electronic control systems and weight sensors. Segregation can effectively prevent the ingot to ensure the inherent quality. In addition to the above two major features, the VAR furnace for modern titanium smelting also enables the large-scale production of VAR furnaces. Modern VAR furnaces can smell large ingots with a diameter of 1.5 m and a weight of 32 t. The vAR method is a standard industrial smelting method for modern titanium and titanium alloys. There are the following techniques are adjusted. First, the electrode preparation method. Preparation of the electrode process is expected to be very cumbersome. An expensive pressure is required to compress the titanium sponge, master alloy, and return debris into an integral electrode or a single small electric wrench. Monolithic electrodes need to be welded into consumable electrodes. At the same time in order, to ensure uniformity of consumable electrode composition, also need to configure the fabric, said material, mixing and other appropriate facilities. Second, occasional segregation and other metallurgical defects. Such as component segregation and solidification segregation. The former is introduced owing to the uneven distribution of impurity elements or alloying elements in the electrode. The time to finish melting is too late for the solidification; the latter is caused by the occasional introduction of high-density inclusions (HDI) and low-density inclusions (LDI) from raw materials or processes that can not be completely dissolved during melting Lead to great harm caused by inclusions and other metallurgical defects.
2, non-consumable vacuum arc furnace melting method (Jane your method)
At present, the water-cooled copper electrode has replaced the tungsten industry in the initial stage of titanium industry, electricity or graphite tungsten electroplating pull to solve the problem of industrial pollution, making the NC method to become an important method of smelting titanium and titanium alloy, several tons of NC furnace has been operating in Europe and the United States. There are for two types of water-cooled copper electrodes: one is self-rotating and the other is rotating the magnetic field, which aims to prevent the burning of the electrode against the arc. NC furnace can also be separated into two kinds: one is in the water-cooled copper crucible melting raw materials, casting in water-cooled copper mold into ingots; the other is in the water-cooled copper crucible continuous investment in raw materials, melting and solidification. The advantages of NC melting are: ① can eliminate the pressing electrode and the welding electrode process; ② can make the arc stay in the material for a long time, so as to improve the uniformity of ingot composition; ③ can use different shapes and sizes of raw materials, Melting process can also add 100% residue, to achieve the recycling of titanium. NC method as a melting, from the recovery of residual material and decrease costs point of view is quite favorable. Usually, NC furnace and VAR furnace are used together to give full play to their respective advantages.
3, cold hearth melting method (referred to as CHM method)
The metallurgical inclusion weaknesses of titanium and titanium alloy ingots caused by the pollution of raw materials and the abnormal melting process have been affecting the application of titanium and titanium alloy in the aerospace field. In order to eliminate the metallurgical inclusion in the rotating components of titanium alloy aircraft engines, cold hearth melting technology came into being. CHM method is the biggest characteristic of the separation of melting, refining and solidification process, that is, the melted charge into the Ling furnace bed after the first melting, and then into the cold hearth refining zone refining, and finally solidified into ingots in the crystallization zone. A significant advantage of CHM technology is the formation of a condensed shell on the bed wall of a cold hearth. It's "sticky zone" captures high-density inclusions (HDI) such as WC, Mo, Ta. In the meantime, (LDI) particles in the high temperature liquid retention time, to ensure the complete dissolution of LDI, which effectively remove inclusion. That is to say. Cold hearth smelting purification mechanism can be separated into two kinds of gravity separation and melting separation.
3.1 electron beam cold hearth melting (EBCHM method) Electron beam melting (EB), is the use of high-speed electronic energy, so, that the material itself generates heat to smelt and refining process. EB furnace with cold hearth, called EBCHM. The EBCHM method has the admirable function that the traditional melting method does not have: (1) Effective removal of high-density inclusions (HDI) and titanium nitride such as tantalum, molybdenum, tungsten, tungsten carbide. Titanium dioxide and other low-density inclusions (LDI); (2) can accept a variety of feeding methods, titanium residue recovery easier, you can use other smelting can not use the waste, still can be pure titanium ingots, greatly reduced Product cost; (3) can be directly from the liquid metal sample analysis and testing; (4) can produce shaped billet, reduce production processes, reduce raw material consumption and improve the yield; EBCHM method has the following disadvantages: (1) smelting needs Under high vacuum conditions, it can not be used directly with titanium sponge titanium smelting; (2) alloying elements volatile, it is difficult to control the chemical composition.
3.2 cold jealous bed melting methods (tube called PCHM method)
The PCHM method uses a plasma arc generated by the ionization of an inert gas as a heat source and can be melted over a wide pressure range from a low vacuum to near atmospheric pressure. This method is distinguished notably by the fact that it is possible to guarantee alloying compositions with different vapor pressure and is not evident in the smelting process. This method offers the ability to improve the habitual table metal properties, enables the smelting of a wide range of alloys and is a more economical alternative to conventional smelting processes Smelting method. Melting using this method, for titanium and titanium alloys, a meeting can be the ideal ingot. The advantages of the modern PCHM method lie in: ① low investment in equipment, easy operation, safe and reliable; ② different types and forms of raw materials can be used, the residual material recovery rate is high; ③ the chemical composition of the diversified alloy is ensured; ④ the expensive noble gas Recycling, reducing production costs. The disadvantage of PCHM method is lower electrical efficiency. The difference between EBCHM and PCHM is that both HDI and LDI can be eliminated. The widespread use of the former smelting pure titanium is more appropriate; and for the alloy, the latter is more appropriate. As with the VAR method, the above two methods implement a wide range of process automation controls, including process parameters (smelting speed, temperature distribution during melting and solidification, composition changes during smelting, removal of insoluble inclusion, etc.) and mass.
4, cold crucible melting method (referred to as CCM method)
In the 1980s, Ferrosilicon developed a slag-free induction melting process and pushed CCM to industrial production for the production of precision castings of titanium ingots and titanium. In recent years in some economically developed countries, the CCM method has begun to scale mechanized production scale, ingot maximum diameter of lm, length 2m, its development prospects are remarkable. The CCM method smelting process is conducted in a metal crucible that is not electrically conductive with either a water-cooled arc block or a copper tube. The greatest benefit of this combination is that the gap between every two blocks is an enhanced magnetic field that produces a strong magnetic field Stirring the chemical composition and temperature, thereby enhancing product quality. The CCM method combines the VAR method and induction melting of crucible with refractory material without the use of refractory materials. The CCM method can obtain a high quality ingot with a homogeneous melting component and no crucible contamination without making an electrode. Compared with the VAR method, the CCM method has the advantages of low equipment cost and simple operation, but the technology is either still in the development stage at present.
5, electroslag melting method (referred to as ESR method)
ESR method is the point of current through the conductive slag when charged particles collide with each other, while the electrical energy into heat. That is, the heat generated by slag resistance will melt and refinish the charge. The ESR method uses a consumable electrode for electroslag melting in an inactive slag (CaF2), which can be directly cast into a ballet of the same shape and has a good surface quality and is suitable for direct processing in the next step. The advantages of this method are: (1) the complete coaxiality of the ESR furnace ensures the reproducibility of the best quality ingot; (2) the ingot is crystallized in the axial direction with dense and uniform microstructure; (3) the electrode with very high precision Weighing system and melting rate control system; (4) the device is simple, easy to operate. The disadvantage is that the flag cannot be paved on the ingot pollution.
1, vacuum consumable arc furnace melting method (referred to as VAR method)
With the development of vacuum technology and the application of computers, the VAR method soon became a mature industrial production technology for titanium. Titanium and its alloy ingot today are mostly produced by this method. VAR method is characterized by low power consumption, high melting speed and good quality reproducibility. VAR ingot melting with good crystalline structure and uniform chemical composition. In general, the finished ingot should be produced by the VAR method. At least after two remelting. Production of titanium ingot VAR method, the world's manufacturers use similar processes, the difference is perhaps that the use of different electrode preparation methods and equipment. Electrode preparation can fall into three categories, one by using a continuous pressing of the total feed electrode, excluding the electrode welding process: the second is a single electrode pressing, welding welded consumable electrode. And through plasma arc welding or vacuum welding into one; third is the point of other melting method casting electrode.
Modern advanced VAR furnace technical features and advantages: (1) full coaxial power input, that is completely coaxial throughout the furnace height, said the coaxial power supply 'to reduce the segregation phenomenon; (2) the crucible The internal electricity school can be fine-tuned in the X-axis / Y-axial direction; (3) With an accurate electrode weighing system, the melting rate is automatically controlled to achieve constant speed melting. Ensure the quality of the melting; (4) ensure the repetitiveness and consistency of each melting; (5) flexibility, that is, a furnace can produce a large number of ingots and large ingots, which can greatly improve the productivity; ) Has good economy. The "coaxial feed" approach avoids magnetic leakage due to an imbalance in the current supplied by the crucible. Reduce and eliminate the adverse effects of induction magnetic fields on smelting products. And improve the electrical efficiency, so as to obtain a stable quality ingot. The purpose of "Constant Speed ??Melting" is to improve ingot quality and to control the condensation process by ensuring that the arc length and melting rate are constant during the smelting process using advanced electronic control systems and weight sensors. Segregation can effectively prevent the ingot to ensure the inherent quality. In addition to the above two major features, the VAR furnace for modern titanium smelting also enables the large-scale production of VAR furnaces. Modern VAR furnaces can smell large ingots with a diameter of 1.5 m and a weight of 32 t. The vAR method is a standard industrial smelting method for modern titanium and titanium alloys. There are the following techniques are adjusted. First, the electrode preparation method. Preparation of the electrode process is expected to be very cumbersome. An expensive pressure is required to compress the titanium sponge, master alloy, and return debris into an integral electrode or a single small electric wrench. Monolithic electrodes need to be welded into consumable electrodes. At the same time in order, to ensure uniformity of consumable electrode composition, also need to configure the fabric, said material, mixing and other appropriate facilities. Second, occasional segregation and other metallurgical defects. Such as component segregation and solidification segregation. The former is introduced owing to the uneven distribution of impurity elements or alloying elements in the electrode. The time to finish melting is too late for the solidification; the latter is caused by the occasional introduction of high-density inclusions (HDI) and low-density inclusions (LDI) from raw materials or processes that can not be completely dissolved during melting Lead to great harm caused by inclusions and other metallurgical defects.
2, non-consumable vacuum arc furnace melting method (Jane your method)
At present, the water-cooled copper electrode has replaced the tungsten industry in the initial stage of titanium industry, electricity or graphite tungsten electroplating pull to solve the problem of industrial pollution, making the NC method to become an important method of smelting titanium and titanium alloy, several tons of NC furnace has been operating in Europe and the United States. There are for two types of water-cooled copper electrodes: one is self-rotating and the other is rotating the magnetic field, which aims to prevent the burning of the electrode against the arc. NC furnace can also be separated into two kinds: one is in the water-cooled copper crucible melting raw materials, casting in water-cooled copper mold into ingots; the other is in the water-cooled copper crucible continuous investment in raw materials, melting and solidification. The advantages of NC melting are: ① can eliminate the pressing electrode and the welding electrode process; ② can make the arc stay in the material for a long time, so as to improve the uniformity of ingot composition; ③ can use different shapes and sizes of raw materials, Melting process can also add 100% residue, to achieve the recycling of titanium. NC method as a melting, from the recovery of residual material and decrease costs point of view is quite favorable. Usually, NC furnace and VAR furnace are used together to give full play to their respective advantages.
3, cold hearth melting method (referred to as CHM method)
The metallurgical inclusion weaknesses of titanium and titanium alloy ingots caused by the pollution of raw materials and the abnormal melting process have been affecting the application of titanium and titanium alloy in the aerospace field. In order to eliminate the metallurgical inclusion in the rotating components of titanium alloy aircraft engines, cold hearth melting technology came into being. CHM method is the biggest characteristic of the separation of melting, refining and solidification process, that is, the melted charge into the Ling furnace bed after the first melting, and then into the cold hearth refining zone refining, and finally solidified into ingots in the crystallization zone. A significant advantage of CHM technology is the formation of a condensed shell on the bed wall of a cold hearth. It's "sticky zone" captures high-density inclusions (HDI) such as WC, Mo, Ta. In the meantime, (LDI) particles in the high temperature liquid retention time, to ensure the complete dissolution of LDI, which effectively remove inclusion. That is to say. Cold hearth smelting purification mechanism can be separated into two kinds of gravity separation and melting separation.
3.1 electron beam cold hearth melting (EBCHM method) Electron beam melting (EB), is the use of high-speed electronic energy, so, that the material itself generates heat to smelt and refining process. EB furnace with cold hearth, called EBCHM. The EBCHM method has the admirable function that the traditional melting method does not have: (1) Effective removal of high-density inclusions (HDI) and titanium nitride such as tantalum, molybdenum, tungsten, tungsten carbide. Titanium dioxide and other low-density inclusions (LDI); (2) can accept a variety of feeding methods, titanium residue recovery easier, you can use other smelting can not use the waste, still can be pure titanium ingots, greatly reduced Product cost; (3) can be directly from the liquid metal sample analysis and testing; (4) can produce shaped billet, reduce production processes, reduce raw material consumption and improve the yield; EBCHM method has the following disadvantages: (1) smelting needs Under high vacuum conditions, it can not be used directly with titanium sponge titanium smelting; (2) alloying elements volatile, it is difficult to control the chemical composition.
3.2 cold jealous bed melting methods (tube called PCHM method)
The PCHM method uses a plasma arc generated by the ionization of an inert gas as a heat source and can be melted over a wide pressure range from a low vacuum to near atmospheric pressure. This method is distinguished notably by the fact that it is possible to guarantee alloying compositions with different vapor pressure and is not evident in the smelting process. This method offers the ability to improve the habitual table metal properties, enables the smelting of a wide range of alloys and is a more economical alternative to conventional smelting processes Smelting method. Melting using this method, for titanium and titanium alloys, a meeting can be the ideal ingot. The advantages of the modern PCHM method lie in: ① low investment in equipment, easy operation, safe and reliable; ② different types and forms of raw materials can be used, the residual material recovery rate is high; ③ the chemical composition of the diversified alloy is ensured; ④ the expensive noble gas Recycling, reducing production costs. The disadvantage of PCHM method is lower electrical efficiency. The difference between EBCHM and PCHM is that both HDI and LDI can be eliminated. The widespread use of the former smelting pure titanium is more appropriate; and for the alloy, the latter is more appropriate. As with the VAR method, the above two methods implement a wide range of process automation controls, including process parameters (smelting speed, temperature distribution during melting and solidification, composition changes during smelting, removal of insoluble inclusion, etc.) and mass.
4, cold crucible melting method (referred to as CCM method)
In the 1980s, Ferrosilicon developed a slag-free induction melting process and pushed CCM to industrial production for the production of precision castings of titanium ingots and titanium. In recent years in some economically developed countries, the CCM method has begun to scale mechanized production scale, ingot maximum diameter of lm, length 2m, its development prospects are remarkable. The CCM method smelting process is conducted in a metal crucible that is not electrically conductive with either a water-cooled arc block or a copper tube. The greatest benefit of this combination is that the gap between every two blocks is an enhanced magnetic field that produces a strong magnetic field Stirring the chemical composition and temperature, thereby enhancing product quality. The CCM method combines the VAR method and induction melting of crucible with refractory material without the use of refractory materials. The CCM method can obtain a high quality ingot with a homogeneous melting component and no crucible contamination without making an electrode. Compared with the VAR method, the CCM method has the advantages of low equipment cost and simple operation, but the technology is either still in the development stage at present.
5, electroslag melting method (referred to as ESR method)
ESR method is the point of current through the conductive slag when charged particles collide with each other, while the electrical energy into heat. That is, the heat generated by slag resistance will melt and refinish the charge. The ESR method uses a consumable electrode for electroslag melting in an inactive slag (CaF2), which can be directly cast into a ballet of the same shape and has a good surface quality and is suitable for direct processing in the next step. The advantages of this method are: (1) the complete coaxiality of the ESR furnace ensures the reproducibility of the best quality ingot; (2) the ingot is crystallized in the axial direction with dense and uniform microstructure; (3) the electrode with very high precision Weighing system and melting rate control system; (4) the device is simple, easy to operate. The disadvantage is that the flag cannot be paved on the ingot pollution.
