Basic introduction Chinese name: sintering definition: the process of transforming powdery materials into dense bodies: producing ceramics, powder metallurgy, refractory materials, etc. Obtaining the finished product: A Definition of polycrystalline material, sintering process, processing steps, manufacturing process, determination method, sintering significance, main uses, waste gas emission, definition Macro definition: At high temperature (not higher than the melting point), the solid particles of the ceramic body adhere to each other, and with the growth of the grains, the voids (pores) and grain boundaries gradually decrease. Through the transfer of substances, its total volume is reduced and its density is increased, and finally it becomes a dense polycrystalline sintered body with a certain microstructure. This phenomenon is called sintering. Micro-definition of sintered floor tiles: there is mutual attraction between molecules (or atoms) in solid state, and the process of heating makes particles get enough energy migration, makes powder particles bond, produces strength and leads to densification and recrystallization is called sintering. In the sintering process, when preparing inorganic solid compounds by solid-state reaction, the reaction rate is controlled by diffusion process, and high temperature is often needed to make the reaction effective. Other solid compounds are composed of solid phase and liquid phase, which will undergo decomposition reaction when melting, so sintering should generally be carried out below the melting point of the product to ensure uniform phase. But the sintering temperature should not be too low, otherwise the solid-state reaction rate will be too low. In many cases, sintering needs to be carried out in a specific atmosphere or vacuum. It is very important to control the partial pressure of gas phase in the sintering process, especially when the studied system contains valence-changing ions, the partial pressure of gas phase in the solid-state reaction will directly affect the composition and structure of the product. For example, in the synthesis of copper-based oxide high-temperature superconductors, the oxygen partial pressure must be strictly controlled in the sintering process to ensure that superconducting materials with definite structure, composition and copper state distribution can be obtained. Before blast furnace ironmaking production, all kinds of powdery iron-containing raw materials are mixed with appropriate amount of fuel and flux, and appropriate amount of water is added. After mixing and pelletizing, the materials undergo a series of physical and chemical changes on the sintering equipment and are sintered into blocks. Belt exhaust sintering machine is widely used to produce sinter. It mainly includes preparation of sintering raw materials, mixing of ingredients, sintering and product treatment. The processing step is an important step. PTFE preform must be sintered to become a useful product. Sintering is to heat the preform above the melting point (327℃) and keep it at this temperature for a certain time, so that the polymer molecules gradually change from crystalline to amorphous, and the dispersed resin particles are bonded into a continuous whole through mutual melting and diffusion. The fully sintered preform is cooled from a transparent colloid to a solid milky opaque product. Sintering process 1 is to heat treat sintered powder or compact at a temperature lower than the melting point of the main components, aiming at improving its strength through metallurgical bonding between particles. Sintering 2. In the process of pre-sintering or sintering, in order to isolate and protect the compact, the material in which the compact is buried. 3. Pre-sintering Pre-sintering heats the compact at a temperature lower than the final sintering temperature. 4. Pressurized sintering process of applying uniaxial pressure during pressure sintering. 5. Loose powder sintering and gravity sintering powder are directly sintered without pressing. 6. The liquid phase sintered powder or compact with at least two components is sintered in the state of forming a liquid phase. 7. Too high sintering temperature and/or too long sintering time lead to the deterioration of the final performance of the product. 8. Undersintering with too low sintering temperature and/or too short sintering time will lead to the products failing to achieve the required performance. 9. Infiltration sintering process of filling the pores of unsintered or sintered products with metal or alloy with melting point lower than that of molten products. 10, dewaxing, burning, and discharging organic additives (binders or lubricants) from the compact by heating. 1 1, mesh belt furnace Generally, the mesh belt protected by muffle realizes the continuous transportation of parts in the furnace. 12, walking beam furnace Walking beam furnace is a kind of sintering furnace, which transports the parts placed in the sintering plate into the furnace through the walking beam system. 13. The push rod furnace is a sintering furnace, in which parts are put into a combustion boat and transported in the furnace through a propulsion system. 14. Necks are formed during sintering, and neck-like connections are formed between particles. 15, bubbling and bubbling Due to the violent discharge of gas, the surface of sintered parts is bubbled. 16, the phenomenon of liquid phase exudation when the green body is heated and sweated. 17, sintered shell sintered skin, a surface layer formed on the sintered part, its performance is different from the inside of the product. 18. The ratio of the relative density of a porous body to the density of a material with the same composition in a non-porous state is expressed as a percentage. 19, radial crushing strength The fracture strength of sintered cylinder samples is determined by applying radial pressure. 20. The ratio of the volume of all pores in a porous body to the total volume. 2 1. Diffusion pore: a pore formed by diffusion of one component into another due to the Kirkendall effect. 22. Pore size distribution The percentage of pore sizes in materials calculated by quantity or volume. 23. Apparent Hardness The hardness of sintered materials measured under specific conditions includes the influence of pores. 24. The hardness of a certain phase or particle or a certain area of a sintered material measured under specific conditions does not include the influence of pores. 25. Bubble point pressure The minimum pressure required to force a gas through a liquid impregnated product to produce the first bubble. 26. Fluid permeability The amount of liquid or gas passing through a porous body per unit time measured under specific conditions. Determination method: put the test paper into an oven and dry it to constant weight at 105~ 1 10℃. Cool to room temperature in the dryer for use. Weigh the dried sample on the balance. After fully absorbing kerosene, weigh the sample in kerosene. Sample weight in air after saturated kerosene. Put the weighed sample into an oven at 105~ 1 10℃ to remove kerosene until the kerosene in the sample is exhausted. Put the samples into a high-temperature furnace according to the numbering sequence, and sprinkle a thin layer of calcined quartz powder or Al2O3 powder between the bottom of the furnace and the samples. After installation, start heating, heat up according to the heating curve, and sample at the predetermined sampling temperature. Keep the temperature at each sampling temperature for 65438 05 minutes, then take the sample out of the electric furnace and quickly bury it in preheated quartz powder or Al2O3 powder to ensure that the sample will not burst during cooling. After cooling to near room temperature, record the sample number and sampling temperature in the table, and check whether the sample has cracks, sand sticking and other defects. Then put it into an oven at 105~ 1 10℃ and dry it to a constant weight. Take out the sample, put it in a dryer and cool it to room temperature. The samples are divided into two batches, the first batch is below 900℃, the second batch is above 900℃, and the samples are the first batch and the second batch respectively. After calculating the results of each temperature point according to the formula, the curves of shrinkage and porosity are drawn with temperature as abscissa and porosity and shrinkage as ordinate, and the sintering temperature and sintering temperature range are determined by the curves. Sintering significance The temperature in the sintering process is called sintering temperature, and the temperature range between sintering temperature and starting overburning temperature is called sintering temperature range. If the sintering temperature and sintering temperature range continue to increase during the sintering process, the green body will begin to deform, soften and burn, resulting in sintering accidents. Hazard sources: high temperature, dust, high-speed mechanical rotation, toxic and harmful gases and logistics injuries, aerial work and other hazards; Accident types: mechanical injury, falling from a height, object strike, lifting injury, burn, electric shock, poisoning, pneumoconiosis; Cause of the accident: equipment defect, technical process defect, protective device defect, bad working environment, imperfect rules and regulations, and illegal operation. Since 1970s, China's iron ore powder briquetting industry has made great achievements. Before 1970, the types of sintering machines in China were all below 75m2. After the 1970s, especially in 1985, Baosteel imported a 450m 2 large sintering machine from Japan, and relied on and organized domestic sintering plants to design, produce and manufacture the 130 m 2 sintering machine, exhaust ring cooler and more than 20 corresponding supporting equipment, which made China's large sintering machine reach a higher level. During this period, the key problems of sinter cooling (vibration cooling and disc cooling) and adding cushion material were solved, and the sintering technology of high alkalinity sinter thick bed was popularized in sintering plants all over the country. During the "steelmaking" period from 65438 to 0958, drum-ground sintering, commonly known as "flat blowing", began to develop in Longyan area where iron ore was concentrated. 1in March, 1968, the first18m2 sintering machine of No.3 Steel started construction. /kloc-0 was completed and put into operation in April, 970. Modern sintering production is made up of iron ore powder, flux, fuel, substitute and returned ore in a certain proportion, mixed with appropriate amount of water, granulated and sintered from top to bottom on the exhaust sintering machine trolley. The whole sintering bed (600 mm ~ 700 mm) can be divided into: sintering bed, combustion bed, preheating bed and cooling bed. 1989-2007, China's sintering industry developed rapidly, and a large number of new processes, technologies and equipment were introduced one after another. China has entered the advanced ranks of the world sintering industry. Its development and related achievements are as follows: (1) Since 1978 Masteel successfully tackled the key problems of cold burning technology, a number of key enterprises and local key enterprises basically completed the transformation from hot burning to cold burning during the Sixth Five-Year Plan and the Seventh Five-Year Plan. A considerable number of enterprises have built and used raw material neutralization and mixing fields, and most production enterprises have realized automatic batching, mixer-enhanced granulation, segregation distribution, cooling screening, grading technology and paving technology. (2) Since the "Seventh Five-Year Plan" and "Eighth Five-Year Plan", a number of new processes and technologies have been developed on the basis of traditional sintering technology, and they have been popularized and applied in major domestic iron and steel enterprises, such as high alkalinity sintering technology, pellet sintering technology, small pellet sintering technology, low temperature sintering technology and low silicon sintering technology. (3) Large-scale and automation of equipment. Before the early 1970s, the largest sintering machine in China was 75m2. In the early 1980 s, China introduced Baosteel's 450m 2 large sintering machine and its supporting equipment, and introduced its manufacturing technology. Up to 2007, China has built 72 180 m 2 sintering machines and their supporting facilities in Baosteel, Angang and WISCO. The total sintering area reached 221216m2, and the average area of a single sintering machine was 295m2. Since 1989, the technology, equipment and automation level of large and medium-sized sintering machines put into production in China have been improved, and relatively perfect process detection and control have been realized. The computer control system is used to automatically operate, monitor, control and manage the production process. (4) Improvement of sintering production index and product quality. The quality of sinter in China has been significantly improved, and the energy consumption of sintering process has been greatly reduced. 1986 to 2007, China's sintering industry has been further developed, mainly in the following aspects: (1) designing and manufacturing complete sets of large sintering machines; Large and medium-sized enterprises have built a comprehensive raw material yard to stabilize the chemical composition of sintering raw materials; A large number of new processes, technologies and equipment have been developed (direct-drag automatic weight batching equipment, various additives for sintering efficiency and energy saving, fuel addition, pellet sintering, various forms of preheating sintering mixture, new energy-saving ignition and holding furnace, high iron and low silicon sintering, ultra-thick bed sintering, etc.). ) The quality of sinter in China has been greatly improved, and more advanced domestic enterprises, such as Baosteel, WISCO No.4 Sintering Plant and Jigang, have controlled the FeO content of sinter at around 7%. In many sintering plants, FeO content is 8% ~ 10%, TFe is 57% ~ 60%, and SiO2 _ 2 content is reduced to 4.5% ~ 5%, thus realizing low silicon sintering. The strength of ISO roller is 79% ~ 83%. China's iron and steel enterprises still have great room for development, but the competition at home and abroad is fierce, and the sintering plant is also facing the adjustment of market economy. At present, the urgent problem to be solved is to improve the quality of sinter; The development trend of sintering production is to gradually realize the large-scale sintering machine; Adopting raw material mixing technology to improve the grade of sinter concentrate; Improve the level of automation and productivity, and strive to reduce the cost of sinter; Strengthen environmental protection management; Accelerate the growth of pellet consumption and improve the burden structure of blast furnace in China; Adopt pellet sintering process to further strengthen sintering production; Continue to transform and update old equipment; Insist on producing high basicity sinter; Make full use of iron ore resources at home and abroad; Adjust and improve the layout of sintering production; Implementing the strategy of sustainable development and building a clean factory. The main raw materials of sintering production line in generalized iron and steel industry enterprises are iron concentrate and coal. Because coal contains sulfur, sintering will emit harmful gas product sulfur dioxide, so flue gas desulfurization must be carried out. Other gas emissions are mainly nitrogen oxides and carbon dioxide. Using bag filter or electrostatic precipitator, the discharge can reach the standard during normal work. The dust discharged after dust removal is basically less than PM2.5, and the standard is only the harmonious product of macro-economy and national health environment. Reaching the standard does not mean that it has no impact on human beings and the environment. Because of the high sintering temperature, the sinter can not be sent to the blast furnace by heating. Even if some waste heat is recovered, a lot of waste heat will still be discharged.