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Material metallurgy progress
- Mar 16, 2018 -

Metallurgy refers to the process and process of extracting metal or metal compounds from ore and using various processing methods to make metal materials with certain properties. Metallurgical technology includes metallurgy, hydrometallurgy and electrometallurgy.

Pyrometallurgy refers to some or all of the minerals in the ore or concentrate at high temperature after a series of physical and chemical change, to generate another form of compound or simple substance, respectively enrichment in gaseous, liquid or solid products, achieve to extraction of metal from gangue and other impurities. Hydrometallurgy is made to extract metals into certain ions into the solution (cation or complex anion) form, to remove these impurities from the solution after through such means as replacement, reduction, electric product extracted from purifying liquid metal process. Electrometallurgical mainly include electric electrochemical two aspects of metallurgy, metallurgy and electric metallurgy is refers to the electrical energy into heat energy for smelting method, electrochemical metallurgy including electrolysis and electricity product, metal solution electrolysis in containing metal salt precipitation in the solution or melt. Can be included in the wet metallurgy type; The latter is known as the molten salt electrolysis, not only using electricity chemistry, but also the use of electrical energy into heat energy, so as to heat the metal salts into the melt, it can also be included in the pyrometallurgy category.

The material has a wide extension, according to the chemical composition of the materials can be divided into metal materials, inorganic non-metallic materials, polymer materials and composite materials; According to material use can be divided into structural material and functional material. The material metallurgy proposed in this course refers to the use of metallurgy to solve the material problems. When it comes to metallurgy, the scope is limited to metal materials.

The properties of metal materials are generally divided into two categories: process performance and use performance. The so-called process performance refers to the performance of the metal materials in the process of processing and manufacturing. The process performance of metal material determines its adaptability in the process of manufacturing. Due to different processing conditions, the required process performance is different, such as casting performance, weldability, malleability, heat treatment performance, machinability and so on. Performance refers to the performance of mechanical parts under the conditions of use, including mechanical properties, physical properties and chemical properties. The performance of metal material determines its use range and service life. The mechanical properties of metal materials are the properties of materials, which are the main basis for the design and selection of the parts. Different loading properties (such as stretching, compression, torsion, impact, cyclic loading, etc.), the mechanical properties required for metal materials will also be different. Common mechanical properties include strength, plasticity, hardness, impact toughness, multiple impact resistance and fatigue limit.

Between atoms in the material combination and arrangement to a large extent determines the macroscopic properties of materials, the bonding between the atoms are: ionic bond and covalent bond, metallic bonding, molecular bonds and hydrogen bond; In the formation of metal crystal defects in the crystal structure is also due to the crystal growth, processing each link, such as the internal arrangement of atoms in crystal deviates from the ideal location, or arrangement of chaotic regions.

With the development of science and technology, many performance cannot meet the requirements of a single element material, so most of the materials are composed of a variety of elements, different elements blend into new materials, due to the physical and chemical interaction between elements, the formation of crystal structure and can be the phase composition, phase refers to the material in the same structure, composition and performance are in separate part of the interface, along with all the materials, the number of phase, size, etc. With the chemical composition, preparation technology and other changes, the influencing factors of phase structure are: electronegative element, atomic size factor, electron concentration factors.

In the process of solidification and crystallization of materials, the transformation of material liquid to solid state is a basic phase transition process, where the solidification theory of pure metals is the basis of solidification theory. Liquid metal X-ray, said of the liquid metal between neighboring atoms have a close to the crystal structure of arrangement rule, but this arrangement to the crystal, the regularity of can't extend to over long distances. Therefore, in the small range of liquid phase, there are small groups with close contact and regular arrangement of atoms, which are called short - range or short - range order. The study also shows that the short-range ordered group of liquid metals is not fixed and immutable, but is constantly changing. The thermal motion of atoms at high temperature is intense, and short - range ordered group can only maintain a short time, while the new short - range ordered atomic group appears at the same time. This is a dynamic balance between those disordered atoms. This phenomenon is known as the structure or fluctuation of the liquid metal. These undulating, short-range, orderly groups provide the conditions for the nucleation, which is developed by these short-range ordered groups. In a cold liquid metal, once the nucleus is formed, the crystals grow. The main means of crystal nucleus and crystal grew up with liquid-solid two phase interface structure and temperature distribution on the liquid-solid two phase boundary in front, metal solidification after the completion of the organization depends on the nucleation and growth process, two crystal nucleus of how many decide how much to the grain or grain weight, crystal grew up mainly affect organizational form. Traditional materials science has the following general law: law of crystallographic structure, material defects and fracture strength, material phase transformation principle, the deformation and fracture of rules, the material strength of the principle (solid solution strengthening, fine-grain strengthening, second phase strengthening, phase transformation toughening glass phase precipitation, grain boundary strength. By studying and grasping these rules, the properties of the material are controlled.

In the process of metallurgy, there are several links, the principle and process of each link, and discuss its influence on material preparation.

Drying: despite the moisture of raw materials, the drying temperature is 400-600 ℃ in general. Roasting is the metallurgical process where the ore or concentrate is heated to below their melting point temperature, and occurs in the process of oxidation, reduction or other chemical changes. The purpose is to change the chemical composition of the object extracted from raw materials to meet the requirements of smelting. According to the different atmosphere of roasting process, it can be divided into oxidizing roasting, reduction roasting, sulfuration roasting, chlorinated roasting and so on. Calcining is the process of decomposing the mineral materials of carbonate or hydroxide into the air, removing carbon dioxide or water and becoming oxides. Sintering and pellets are the main methods for the powder ore forming by mixing the different powder mines and heating roasting, solidifying into porous blocks or spherical materials. In the above process, chemical changes such as oxidation and reduction occur, and the bond between atoms has changed, affecting the properties and properties of the materials.

Melting is to point to will handle good ore or other materials, through the REDOX reaction at high temperature, metal and impurities in the ore separation into two liquid layer is the process of liquid metal and slag, also called smelting. The smelting conditions can be divided into reduction smelting, matte smelting, oxidation blowing and so on. Refining is to further process the smelting of coarse metal containing a small amount of impurities to improve its purity. Blowing smelting, is the essence of oxidation is made of matte matte smelting of melt, generally in the converter with the aid of oxygen-enriched air blowing oxygen in the air or the iron oxide, sulfur and other impurities element or slag or volatile with the principal part of metal separation and metal. Distillation refers to the method of separating certain components of smelting materials by using the characteristics of different volatiles of various substances at a certain temperature under the condition of indirect heating. So-called leaching is the solid material to the fluid in the solvent, make one or several valuable metals in solid material dissolves in the solution, slag and gangue and some main metal into, make the extraction metal and gangue, and some separation of impurities.

Aqueous electrolysis: it is to point to in the aqueous electrolyte, insert the two electrodes, the cathode and anode, bubbled into direct current, REDOX reaction in the aqueous electrolyte, this process is called electrolytic solution. Because of the different anodes, there is a soluble anode and an insoluble anode. The former is called electrolytic refining and the latter is an electrolytic deposition. Molten salt electrolysis is used as electrolyte electrolysis process, mainly used to extract light metals. This is because the chemical activity of these metals is very high, and electrolysis of these metals is not metal.

Metallurgy is a precursor to materials science, from the Angle of metallurgy, look for ways to solve the problem of material science is a process for traceability, more microscopic, it is easier to control characteristics, such as the preparation of ultrafine metal pipe, biological material preparation, material metallurgy will provide new ideas for the development of material science.