1. Definition and characteristics of high-purity metallic materials
High-purity metal materials are metal materials with extremely high levels of purity (usually above 99.999%). Its main characteristics include highly complete crystal structure, very low impurity content and excellent electrical and thermal conductivity. The preparation of high-purity metallic materials is demanding and usually involves multiple process steps, such as vacuum smelting and electrochemical purification, to ensure a high degree of purity.
2. Areas of application for high-purity metallic materials
High purity metal materials are widely used in many fields, of which the electronics industry is one of the main application areas. In the integrated circuit manufacturing process, the use of high-purity metals as the basic material can ensure the reliability and high performance of electronic devices. The medical field also utilizes the biocompatibility of high-purity metals to prepare high-purity metal implants, such as artificial joints and dental restorative materials. In addition, in the field of optoelectronics, semiconductor manufacturing, solar cells, etc., high-purity metal materials also play an important role and have important application value. At the same time, these application fields also put forward extremely high requirements on the purity, stability and conductivity of high-purity metal materials, which promote the continuous development and innovation of high-purity metal material preparation technology.
Second, the vacuum melting technology overview
1.Vacuum melting basic principle
Vacuum melting is an important method of metal preparation, the basic principle is to place the metal samples in a high vacuum or very low pressure environment, through the heating of the metal melting and then cooling and solidification, in order to obtain high-purity, low-gas content of the metal materials. The core of the process is to utilize the vacuum environment to avoid the metal reacting with oxygen, nitrogen and other impurities in the air, thus reducing the mixing of impurities. Vacuum melting not only requires a highly pure process environment, but also precise control of temperature, pressure and other parameters to ensure the purity and uniformity of the metal material.
2. Classification and characteristics of vacuum melting
Vacuum melting can be divided into vacuum arc melting, vacuum induction melting and vacuum electron beam melting according to different process characteristics and application areas. Vacuum arc melting is the use of electric arc high temperature effect of the metal sample melting process. Vacuum induction melting utilizes the principle of induction heating to generate induction current on the surface of metal samples through electromagnetic induction to heat and melt them. Vacuum electron beam melting is a high-energy electron beam directly on the surface of the metal samples will be heated and melted process. Different types of vacuum melting methods have their own characteristics, but all of them are in a high vacuum environment to realize the purity of the metal melting. Vacuum melting technology has become one of the most important means for the preparation of high-purity metals due to its highly pure preparation process and the excellent properties of the prepared materials.
Third, the key technology in the vacuum melting
1. Vacuum environment control technology
Vacuum environment control technology mainly includes high vacuum maintenance and gas control. In vacuum melting, maintaining a high vacuum environment is the basis for ensuring the high purity of metal materials. High vacuum maintenance is through the advanced vacuum pump and sealing technology to ensure that the melting process within the system gas concentration is very low. Precise gas control is essential to prevent external gas impurities from entering the metal material. By introducing inert gases or gas mixtures into the melting chamber and monitoring them in real time using online monitoring equipment such as mass spectrometers, the composition of the gases can be effectively controlled, which helps to avoid oxidation reactions and other contamination processes and ensures high purity of the metal.
2. Melting equipment and process parameters control technology
Electric furnace is one of the core equipments of vacuum melting, which directly affects the heating and cooling of metal in the melting process. It is very critical to design the furnace structure reasonably to ensure that the metal samples are heated evenly. Advanced furnace control system can ensure the temperature stability of the metal during melting and solidification by precisely controlling the temperature. The cooling rate directly affects the crystal growth rate and lattice structure. By adjusting the cooling rate, the size and shape of the metal crystals can be controlled, thus improving the mechanical properties and structural homogeneity of the metal material. A highly controllable cooling rate is a key process parameter in vacuum melting technology.
3. Slag-liquid separation and purification technology
In the process of vacuum melting, there may be some solid dross insoluble in the molten metal, such as oxides, inclusions and so on. The slag-liquid separation and purification process aims to remove the impurities from the molten metal to improve the purity of the metal. Through the reasonable design of the furnace structure, can make these slag liquid and metal effective separation, common methods for the use of cyclone, magnetic field and other equipment to separate the slag liquid from the metal.
4. Refining and purification technology
Chemical refining is through the addition of appropriate amount of reducing agent, oxidizing agent and other chemical substances, so that the impurities in the molten metal and its reaction, the formation of volatile gases or dissolved in the slag, and ultimately realize the removal of impurities. Chemical refining requires precise measurement and control of the amount of chemicals added and the reaction conditions to ensure the refining effect.
