[Energy people are watching, click on the upper right corner to add 'Follow'] 1. Thermal powerplant (fossil—fired powerplant; thermal powerplant) Power facilities that use the thermal energy released by the combustion of fossil fuels to generate power, including fuel combustion,

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1, thermal powerplant (fossil—fired powerplant; thermal powerplant) Power facilities that use the thermal energy released by fossil fuel combustion to generate power, including all equipment, devices, instruments and devices for fuel combustion, heating, thermal energy conversion and electrical energy output, as well as buildings, structures and all ancillary facilities related to production and life for this purpose.

2, boiler (boiler) Mechanical equipment that uses the heat energy or other heat energy released by fuel combustion to heat feed water or other working fluid to produce steam, hot water or other working fluid (vapor) of specified parameters and quality. The boiler used for power generation is called a power station boiler. In power station boilers, the heat energy released by the combustion of fossil fuels (coal, petroleum, natural gas, etc.) is usually transferred to the working fluid-water in it through the metal wall of the heated surface, and the water is heated into steam with a certain pressure and temperature. The steam generated is used to drive the turbine, convert the heat energy into mechanical energy, and the turbine then drives the generator to turn mechanical energy into electrical energy for users. Power station boilers are also called steam generators.

3, Thermodynamics (thermo dynamics) A discipline that studies the properties of various energy (especially thermal energy) and their mutual conversion laws, as well as the relationship with the properties of matter, is a branch of physics. Thermodynamics focuses on studying the equilibrium state of matter and physical and chemical processes that are not very different from the equilibrium state. In modern times, it has expanded to the study of non-equilibrium state processes.

4, working fluid media substance that realizes the mutual conversion of thermal energy and mechanical energy is called working fluid. In order to obtain more work, the working fluid is required to have good expansion and fluidity, is cheap, easy to obtain, has stable thermal performance, and has no corrosion effect on the equipment. Water vapor has this performance, and power plants often use water vapor as the working fluid.

5, state parameters Any physical quantity that can represent the state characteristics of the working fluid is called a state parameter. For example: temperature T, pressure p, specific capacity ひ, internal energy u, enthalpy h, entropy s, etc. We often use these six, as well as state parameters such as fire use and fire without fire. The state parameters are different from what we usually call "parameters" such as flow rate and volume. They refer to physical quantities that represent the state characteristics of the working fluid. Therefore, pay attention to the concept of distinguishing the state parameters and cannot be confused with the "parameters" of habit.

6, pressure perpendicular force endured per unit area, also known as pressure. Pressure is a measure of intensity, and its value is independent of the size of the system. It is usually represented by the symbol P, and the unit is Pa (Pa). Pressure can be expressed in different forms such as absolute pressure, atmospheric pressure, positive pressure (called gauge pressure in engineering), negative pressure (called vacuum in engineering) and pressure difference.

7, specific volume unit mass substances. Indicated by symbol V. The specific volume is a measure of intensity, and its value is independent of the size of the system, and the unit is meters ³/kg (m³/kg). Another physical quantity commonly used in thermodynamics - density (ρ), is the inverse of the specific volume, that is, the mass of matter per unit volume.

8, temperature represents the physical quantity of the hot and cold of the object. According to the zeroth law of thermodynamics, temperature is a sign that measures whether a thermal system is in thermal equilibrium with other thermal systems. All systems with the same temperature are in thermal equilibrium state; otherwise, they are in unequal state. Temperature is an intensity measure, and the value is independent of the size of the system. The method of denoting the indexing of temperature is called a temperature scale or abbreviated as a temperature scale. The legal temperature scale in China uses the thermodynamic temperature scale in the international system of units, that is, the Kelvin temperature scale or absolute temperature scale, which is represented by the symbol T, and the unit is Kelvin (K). The temperature standards that have been used include Celsius temperature t (℃), Fahrenheit temperature t (°F), etc.

9, internal energy accumulates energy inside the thermal system. The internal energy is a extended amount, whose value is proportional to the mass, represented by the symbol U, and the unit is focal (J). The internal energy per unit mass is called the specific internal energy, expressed in u, and the unit is coke/kilogram (J/kg). From a microscopic perspective, internal energy includes kinetic energy, positional energy, chemical energy and nuclear energy that make up a large number of molecules in the system.In physical processes that do not involve chemical changes and nuclear reactions, chemical energy and nuclear energy may not be considered. At this time, the internal energy in the thermal system only involves molecular kinetic energy and positional energy. The internal energy of an ideal gas has nothing to do with pressure, but is just a function of temperature. The sum of the internal energy (U) and pressure potential energy (PV) possessed by the thermal system of enthalpy . Enthalene is a broad extension amount, represented by the symbol H, and the unit is focal (J). The enthalpy of a unit mass substance is called the specific enthalpy, expressed in h. The unit is coke/kg (J/kg).

11, Entropy (entropy) Entropy has no simple physical meaning and cannot be measured with an instrument. Its definition: The slight change in entropy is equal to the ratio of the tiny heat dq during the process to the absolute temperature T when heating. The slight change in entropy marks the heat exchange and heat transfer direction in the process. dS＜0, the thermal system absorbs heat, and the heat is negative; dS＞0, the thermal system exudes heat, and the heat is positive; dS=0, the thermal system has no heat exchange with the outside world. dS=dq/T, dq=ds×T.

Entropy Increase Principle: The entropy of an isolated system can increase (when an irreversible process occurs), can remain unchanged (a reversible process occurs), but cannot be reduced. The relationship between the entropy increase and functional force of

system: From the analysis of the unequal heat transfer process, it can be seen that the unequal heat transfer between the heat source and the working fluid causes the entropy increase of the system, and the loss of functional force in the system is equal to the entropy increase in the system multiplied by the temperature of the cold source. The occurrence of irreversible heat transfer increases the entropy of the system, which means that the loss of function power increases, and the ineffectiveness of discharge to the cold source increases. The loss of function power is proportional to the increase in entropy, so the increment of entropy in the system can be used as a measure of the irreversible process. When the heat carried by the working fluid in an actual thermodynamic device is constant, the more powerful the function is when the temperature is high, the more useful this high-temperature heat is. The entropy increase of temperature difference heat transfer in the boiler is the largest, so the loss of function is the greatest (high-temperature flue gas heat transfer to furnace water and steam). The original meaning of

entropy in foreign language is transformation, which refers to the ability to convert heat into work. The Chinese translation of "Entropy" is named by Professor Liu Xianzhou .

12. Fire is (exergy) The part of energy that can theoretically be converted into mechanical energy under given environmental conditions, also known as available energy or effective energy, represented by the symbol E. The unit is jing (J). The fire of unit mass is called the fire comparison, and is represented by the symbol e, and the unit is coke/kilogram (J/kg). Corresponding to the imbalance between the thermodynamic system and the environment, the use of fire in energy can be divided into physical fire and chemical fire. The use of enthalpy is the useless part of energy called fire without fire.

13, Equilibrium state When each part of the working fluid has equal pressure, temperature, specific capacity and other state parameters, it is said that the working fluid is in equilibrium state.

14, ideal gas (ideal gas) An ideal gas, which has no force in the molecules, and the size of the molecules can be ignored like geometric points. In fact, ideal gas does not exist, but under normal temperature and pressure, many simple gases, such as hydrogen, nitrogen, oxygen, etc., can be regarded as ideal gases, because under this condition, the gases are separated from each other and have weak interaction forces, which can be regarded as zero, and the average distance between molecules is much larger than the molecular diameter, so molecules can be regarded as particles that do not have volume.

15, specific heat (specificcheat) When the temperature of a unit amount of gas increases (or decreases) by 1°C, the heat absorbed (or) is called the unit heat capacity of the gas, or the specific heat of the gas. Indicated by the symbol c, the unit of specific heat is coke/(kg·open)[J/(kg·K)], which is a thermal property of the working fluid. The concept of

is first made by Scottish chemist J. Blake proposed in the 18th century.

16, the process of vaporizing substances from liquid to vapor. Including evaporation and boiling. Evaporation is a vaporization phenomenon performed on the surface of a liquid.

17, boiling vaporization inside the liquid. Under a certain pressure, boiling can only be carried out at a fixed temperature, which is called the boiling point. The pressure rises and the boiling point rises.

18 and saturated steam container total number of steam molecules no longer change and reaches dynamic equilibrium. This state is called saturated state, and the steam in the saturated state is called saturated steam; water in the saturated state is called saturated water; at this time the temperature of steam and water is called saturation temperature , and the corresponding pressure is called saturated pressure.

19, wet saturated steam mixture of saturated water and saturated steam.

20, dry saturated steam saturated steam without moisture.

21. Superheated steam The temperature of the steam is higher than the saturation temperature under the corresponding pressure, and the steam is called superheated steam.

22, superheat The temperature of the superheated steam exceeds the corresponding saturation temperature under the steam pressure, which is called superheat.

23, latent heat of vaporization The heat required to turn 1Kg of saturated water into 1Kg of saturated steam is called latent heat of vaporization or heat of vaporization.

24, dryness Mass percentage of dry saturated steam is contained in wet steam.

25, humidity Mass percentage of saturated water is contained in the wet steam.

26, critical point As the pressure increases, the difference between saturated water and dry saturated steam becomes smaller and smaller. When the pressure rises to a certain value (22.115MPa), there is no difference between saturated water and dry saturated steam, and it has the same state parameters, which is called the critical point. The critical temperature of water is 374.15℃ and the critical pressure is 22.115MPa.

27, , , The gas pressure of the volume control process of is proportional to the absolute temperature, that is, P1/T1=P2/T2. During the volume setting process, all the heat added to the gas is used to increase the internal energy of the gas. Because the volume remains unchanged, no work is done. For example, when the internal combustion engine is working, the compressed gasoline and air mixture in the cylinder is ignited and suddenly burns. The pressure and temperature of the gas suddenly rise a lot in an instant, and the piston has no time to move. This process can be considered a process of volume fixation.

28. The process of constant pressure is carried out while the pressure remains unchanged, which is called the constant pressure process. Such as the vaporization of water in the boiler and the condensation of steam in the condenser . During the fixed pressure process, the specific capacity is proportional to the temperature, that is, ひ₁/T1=ひ₂/T2 The temperature decreases. The gas is compressed and the specific capacity decreases; the temperature increases, the gas expands, and the specific capacity increases. The heat during the constant pressure process is equal to the enthalpy difference between the final and initial states. Its T-S curve is a logarithmic curve with a positive slope.

29. The process of temperature fixation under the condition of constant temperature. P1ひ₁=P2ひ₂=Constant, that is, all the heat added during the process expands and performs work; all the work on the gas becomes heat and releases outward.

30. The process of thermal insulation in the absence of heat exchange with the outside world is called the thermal insulation process. Also known as isentropic process. In order to reduce heat loss, heat engines such as steam turbines and gas turbines are covered with insulation materials on the outside, and the working fluid expands very quickly, and there is no time to dissipate heat to the outside in a very short time, that is, the process of adiabatic expansion is approximately.

31, Therma1 power system; steam/water flow system) A device system that realizes thermal power conversion. Each related thermal equipment is composed of a working whole through pipeline connection and combination according to the specific functions and functions in the production process.

32, Thermodynamic system (thermodynamic system) The substance or space within a specific range selected as the analysis object in thermodynamic research, referred to as the thermodynamic system for short. In certain occasions, it is also referred to as the system. Materials or spaces other than thermal systems are collectively referred to as the environment (or outside world). The environment is only relative to the thermal system, and a part of the environment can also be drawn out to form another thermal system. The boundary between the thermal system and the environment is called the interface - the thermal system boundary. Any material or energy exchange between the thermal system and the environment is reflected in the boundaries of the thermal system. The interface can be real or imaginary, fixed or mobile.

33, Thermodynamic cycle (thermodynamic cycle) The working fluid starts from a thermal state, goes through a series of changes, and finally returns to the closed thermal process completed by the original thermal state.

34, positive cycle A thermal cycle If its net work is positive, that is, if its overall effect is to absorb heat from the heat source and perform work on the outside, the cycle is called a positive cycle.

35, reverse cycle A thermal cycle If its net work is negative, that is, if its overall effect is to consume external work and release heat to the heat source, the cycle is called a reverse cycle, such as the refrigeration process of the air conditioner.

36, reversible cycle If the process of forming the cycle is reversible, it is called a reversible cycle.

37, Irreversible cycle If any process that constitutes a loop is irreversible, it is called an irreversible cycle.

38. Zeroth law of thermodynamics (zeroth law of thermodynamics) The law in thermodynamics that establishes the concept of temperature based on the thermal equilibrium of thermodynamic systems. It is usually expressed as: each of the two systems is in thermal equilibrium with the third system, and the two systems must also be in thermal equilibrium with each other. Because this fact is first of all by C. When Clark Micswell stipulates that it is an empirical law, it is after the establishment of the first law of thermodynamics, so it is called the zeroth law of thermodynamics.

The law of zero shows that each system itself has a macro attribute that measures whether they are thermally balanced with each other - temperature. It is only related to the state of the system and is a state parameter of the system. According to the zero law, a thermometer can be established to measure temperature.

39. The first law of thermodynamics (first 1aw of thermodynamics) One of the basic laws of thermodynamics is a form of expression of the principle of conservation of energy. It is expressed as: an energy can be transferred between the thermodynamic system and the environment, or can be converted with other forms of energy. The total value of energy is conserved in the process of transmission and conversion and will not increase or decrease by itself. Another statement is that the first type of perpetual motion machine that can do work without consuming energy is impossible to achieve. It promotes the energy forms in the field of mechanics, linking various forms of energy such as thermal energy, internal energy and mechanical energy.

40, The second law of thermodynamics (second law of thermodynamics) One of the basic laws of thermodynamics is usually expressed as that heat can be spontaneously transferred from hotter objects to colder objects, but it is impossible to spontaneously transferred from colder objects to hotter objects; it can also be expressed as: the result of the frictional effect of two objects converting work into heat, but it is impossible to convert this frictional heat into work and does not have other effects. The second law of thermodynamics is an important supplement to the first law of thermodynamics.

41, Carnot cycle (Carnot cycle): A thermal cycle consisting of four completely reversible thermal processes - isothermal endothermic, isentropic expansion, isentropic exothermic and isentropic compression between a high-temperature heat source and a low-temperature heat source. Historically, it is the embodiment of the second law of thermodynamics.

was proposed by French S. Carnot in 1824 and is an ideal thermal cycle. An ideal cycle without any energy loss.

42. Kano's theorem is expressed as: ① The efficiency of the heat engine working between two constant temperature heat sources cannot exceed the efficiency of the Kano heat engine, ② All Kano heat engines working between two constant temperature heat sources have equal efficiency.

43. Third law of thermodynamics (third law of thermodynamics) One of the basic laws of thermodynamics reflects the regularity of absolute zero and its adjacent areas of thermal phenomena. It is usually expressed as: No matter what method is used, it is impossible to make the temperature of the object reach absolute zero through finite steps. German chemist W. in 1906. Walter Nernst first proposed the "thermal theorem", and later, after the development of F.E. Simon and others, it became the third law of thermodynamics. When the thermodynamic temperature tends to zero, the entropy change of the condensation system in the reversible isothermal process tends to zero.

44, Rankine cycle The basic cycle of steam power device, the working fluid performs heat absorption, expansion, heat release and compression in boilers, turbines, condensers, water supply pumps and other thermal equipment, which absorbs heat, expands, extrudes heat, and compresses the four processes of heat energy continuously converting heat energy into mechanical energy. This cycle is called Rankine cycle. 45, Heat transfer (heattransfer) A discipline that studies the laws of heat transfer. Heat transfer is one of the common phenomena in nature and engineering practice. The second law of thermodynamics points out that heat always spontaneously transfers from high temperature to low temperature, and heat transfer is a science that studies this phenomenon. There are three basic heat transfer methods: heat conduction , heat convection and heat radiation.

46, heat conduction (heatconduction) The heat transfer phenomenon that occurs due to direct contact between parts of objects with different temperatures or between two objects with different temperatures is also called heat conduction. Heat conduction is a phenomenon analysis from a macroscopic perspective, that is, matter is regarded as a continuous medium, with no relative displacement between the parts. Heat conduction is one of the three basic methods of heat transfer, and the study of thermal conductivity laws is an important part of heat transfer. The task of thermal conductivity theory is to find out the temperature, that is, the temperature field, or the heat flow flux [heat flow density] in various places in the object at any time.

47, Fourier's law (Fourier Law) The basic law of thermal conductivity is expressed as: In a continuous and uniform isotropic medium at any time, the heat flow vector q transferred on site at each point is proportional to the local temperature gradient, that is,

q=-λgradΤ

where λ is the thermal conductivity of the medium; grad T is the temperature gradient; the negative sign indicates that the heat flow vector and the temperature gradient vector are collinear but inverse, and are both perpendicular to the isothermal surface passing through the point, that is, the heat flow vector is towards the direction of temperature reduction. It is consistent with the second law of thermodynamics.

48. The thermal conductivity coefficient λ is an indicator that measures the thermal conductivity of an object. Its size indicates the quality of thermal conductivity (thermal insulation) performance. All were determined by the experiment. In engineering design, the thermal conductivity is the basis for rational selection of materials.

49. The temperature conduction coefficient a affects the physical quantity of the unstable thermal conduction process, and its numerical size indicates the ability of the object to propagate temperature changes. It is proportional to the thermal conductivity of an object and inversely to the thermal storage capacity of an object. Materials with large temperature conductivity have a fast temperature change during unstable thermal conductivity, and the time to achieve uniform temperature is short. Otherwise, the opposite.

Thermal conductivity and thermal conductivity are two concepts that are both different and related. The thermal conductivity only refers to the thermal conductivity of the material, reflecting the magnitude of the heat flow, while the temperature conductivity comprehensively considers the thermal conductivity of the material and the amount of heat required to increase the temperature, reflecting the speed of temperature change. The temperature conductivity coefficient of the stable thermal conductivity process is meaningless, only the thermal conductivity affects the process; the unstable thermal conductivity process determines the temperature distribution of the object due to continuous heat absorption or heat exothermicity.

50, convective heat transfer (heattransfer by convection; confidentialheat transfer) The heat transfer process generated by direct contact between the fluid and the surface of an object with different temperatures. It is the result of the combined effect of two basic heat transfer methods, heat conduction and heat convection, also known as convection and heat release.

51, thermal resistance (thermal resistance) The ratio of the heat transfer pushing force formed by the temperature difference and the radiation force difference to the heat flow or heat flow flux during the heat conduction, convective heat transfer and radiation heat transfer is a parameter that comprehensively reflects the ability to prevent heat transfer.

52. Forced motion The fluid movement caused by external mechanical force is called the forced motion of the fluid .

53. Free movement The movement caused by different density of each part of the fluid is called free movement of the fluid .

54, Laminar flow When the flow rate of the fluid is very small, all particles of the fluid flow in parallel with the axis direction of the tube, and all parts of the fluid do not interfere with each other. This flow state is called laminar flow.

55, turbulent If the flow rate of the fluid gradually increases, when it increases to a certain critical value, it will be found that the various parts of the fluid are mixed with each other, and even vortexes appear. This flow state is called turbulent .

56. Boiling heat transfer in tube (boiling heat transfer in tubes) The boiling medium (liquid) is forced to move along the pipeline under the action of external force (pressure difference), and is boiling at the same time, which is a flowing boiling heat transfer. If the medium in the tube does not flow, unless the inner diameter of the tube is very small and is very close to the bubble size generated, it can generally be treated as boiling heat exchange in the tank.

57, membrane boiling (fi1mboiling) Under certain conditions, the water or steam-water mixture in the evaporated heating surface of the subcritical pressure boiler is separated from the pipe wall by a layer of steam film, resulting in a sharp drop in the heat transfer coefficient, a sharp increase in the temperature of the pipe wall, and even an overburning phenomenon occurs. Membrane boiling is also known as heat transfer deterioration, and is divided into two categories according to mechanism.

58, radiation heat transfer (radiation heat transfer) The heat exchange process between two objects or media that are not in contact with each other and are not of equal temperatures through electromagnetic waves is one of the important topics in heat transfer research.

radiation is a transmission process that emits and absorbs energy in the form of electromagnetic waves. Various electromagnetic waves propagate in space at the same speed as the speed of light, but the properties of electromagnetic waves of different wavelengths or frequencies are different.

59, radiation angle coefficient (radiative ang1efactors) The energy emitted by one surface can directly reach the share of the other surface during radiation heat exchange, referred to as the angle coefficient, represented by the symbol F_a-b. The lower corner mark _a—b means that radiation energy will be projected from surface a to surface b. It is directly related to the geometry and relative positions of the two objects studied, and is an indispensable factor for calculating surface radiation heat exchange.

60, radiation selectivity (selectivity of radiation) The performance of gas selectively absorbing or radiating radiation energy in certain wavelength ranges by adding or releasing a certain energy stored in the molecule. It is one of the unique radiation characteristics of gases.

61, blackness (blackness) The ratio of the actual radiation force of an object to the radiation force of absolute bold body (abbreviated as bold body) at the same temperature, also known as the emissivity. It reflects the inherent radiation capacity of the object surface that is close to the bold body and is an important parameter in radiation heat exchange.

62, infrared detection (infra—red inspection) Non-destructive detection technology that uses the method of measuring infrared radiation to detect the surface temperature or temperature distribution of the component to determine whether there are internal defects in its operating state. Infrared is an electromagnetic wave. The surface of the component radiates infrared rays, and its power is proportional to the fourth power of the temperature. When the component is defective, whether it has a heat source itself, or additional heating (such as using current, plasma gun, flame spray gun, infrared lamp, etc.), cooling will lead to abnormal temperature distribution.

63, absolute bold object whose absorption rate is equal to 1.

64. The fourth power of radiation The magnitude of the radiation force of the absolute blackbody is proportional to the fourth power of its absolute temperature.

E_o=C_o(T/100)⁴ C_o——Radiation coefficient of absolute bold body

65, water circulation (boiler circuit) The circulation flow of water and soda mixture in the water-cooled wall of the furnace. After the feed water enters the steam drum through the economizer, it is distributed to the water-cooled wall through the downward pipe and the connecting box. The water is heated in the water-cooled wall to generate steam, forming a steam-water mixture and then returns to the steam drum; the pot water after the steam is separated enters the water-cooled wall through the downward pipe and the connecting box to continue to flow circulating. Poor water circulation will cause water-cooled walls to overtemperature bursts, so normal water circulation is one of the important conditions for the reliable operation of the boiler.

66, circulating flow rate corresponds to the speed of saturated water calculated according to the pipe cross-section under the working fluid flow rate. The circulating flow rate of a natural circulation boiler is related to pressure.

67, mass flow rate working fluid flow rate per unit flow section of the pipe, unit is kg/(m².s). Under subcritical pressure, to avoid deterioration of heat transfer, the allowable minimum mass flow rate should be determined according to the thermal load.

68, circulation ratio The ratio of the circulating water volume entering the dropping tube to the steam volume at its outlet. The high school pressure boiler is limited by the water-cooled wall salt accumulation, and the circulation ratio must be large enough.The circulation ratio is related to the structure of the circulation system and the heating strength of the riser. Under certain conditions of the cross-sectional ratio and structure of the descending pipe and the rising pipe, the thermal load increases, and the circulating flow rate increases accordingly at the beginning, and the circulating rate also increases, showing self-compensation ability; but when the heat load increases again, the circulating flow rate increases slowly or even no longer increases, and the circulating rate no longer increases, and the self-compensation ability is lost. If the thermal load increases again, the circulating rate decreases instead, and the circulating rate that no longer increases, and the circulating rate is called the boundary circulating rate.

DC boiler designed for cycle magnification is 1. The concept of circulating water system circulation magnification is different from the concept of circulating water magnification in boilers. The circulating water system circulation magnification refers to the ratio of the circulating water volume to the exhaust steam entering the condenser. The circulation ratio designed by our factory's circulating water system is 50.

69, water vapor (steam) is a gaseous substance formed by water vaporization or ice sublimation.

70. Saturated state Place a certain amount of water in a closed pressure-resistant container, and then drain the air left in the container. At this time, water molecules escape from the water. After a certain period of time, the water vapor fills the space above the entire water surface. At a certain temperature, the pressure of this water vapor will automatically stabilize at a certain value. At this time, the number of molecules leaving the water surface is the same as the number of molecules returning to the water surface, that is, the dynamic equilibrium state is reached, that is, the water and water vapor are in a saturated state. Water and steam in a saturated state are called saturated water and saturated steam respectively. The pressure of saturated steam is called the saturation pressure, and the corresponding temperature in this state is called the saturation temperature. There is a certain correspondence between saturation pressure and saturation temperature.

71, basic structure of steel (fundamental microstructure of steel) The basic microstructure types in steel include austenite , ferrite , pearlite , bainite , martensite and carbides. Among them, austenite, ferrite and martensite are solid solution (two or more components dissolve each other in liquid state, and also dissolve each other in solid state to form a single uniform phase. According to the different positions of the atoms of the dissolved elements, they are divided into three solid solutions, including replacement, gap and absence formula. Austeite, ferrite and martensite are all interstitial solid solutions), pearlite and bainite are mechanical mixtures (the two components are insoluble in each other in solid state, and do not form compounds, and have their own lattice and properties of phases), and carbides are compounds (combined with each other in a certain atomic ratio, and can be represented by a simple chemical formula). cementite in steel is iron carbon compound.

72, austenite carbon or other alloy elements dissolved into gamma iron. It is a face-centered cubic lattice, non-magnetic, with good plasticity and toughness. Generally, austenite exists at high temperatures in steel. After the steel is quenched, some austenite remains at room temperature, which is called residual austenite. Adding alloy elements such as Ni, Mn, etc. to the alloy steel that expands the γ region can keep the austenite energy below room temperature, which is called austenite steel.

73, ferrite carbon or other alloy elements dissolve into the solid solution formed by α iron. It is a body-centered cubic lattice with good plasticity and toughness. Ferrite is the main microstructure of low and medium carbon steels and low alloy steels. Generally speaking, as the ferrite volume increases, the plasticity and toughness of steel increase and the strength decreases. Adding alloy elements of reduced γ zones, such as Si, Ti, Cr, etc. to the steel, can obtain ferrite structures at high temperatures and room temperatures, called ferrite steel.

74, pearlite is a mechanical mixture composed of ferrite and cementite. Usually a sheet-like structure. It is a product of eutectoid transformation below the temperature of A1 and has high strength and hardness. The strength and plasticity of medium-carbon steel and low-alloy steel depends on the number of pearlite and the spacing of the sheets. The smaller the spacing, the higher the strength. As the pearlite transition temperature decreases, coarse-sheet pearlite, fine-sheet pearlite, soxantite, and quenite can be formed respectively. They all belong to pearlite tissue, but the spacing between the layers is different.

75, bainite supersaturated ferrite and cementite, two-phase mixture is an unbalanced structure. The bainite form in steel depends on the transition temperature and alloy elements, including upper bainite, lower bainite, granular bainite and carbon-free bainite.The bainite feather-like on

consists of parallel strip ferrite ferrite and cementite distributed between strips, sheet-like or short rod-like and parallel to ferrite. The dislocation density in ferrite is high, that is, the strength is high, but the toughness is poor. The bainite supersaturated ferrite under

is in the shape of a needle sheet, and the needle sheets are distributed at a certain angle, and many uniform and fine carbides are precipitated inside it. The supersaturated ferrite in lower bainite has a high-density dislocation cell substructure and uniformly dispersed carbides, so it has high strength and good wear resistance.

76, supersaturated solid solution of martensite carbon. It is a body-center cubic lattice, which is the product of supercooled austenite non-diffusion phase transformation. The martensite form in steel varies with carbon content. Low-carbon martensite is strip-shaped, distributed in parallel bundles, and is strip-shaped under a metallographic microscope. Low-carbon martensite has good toughness and high strength and hardness. High carbon martensite is sheet martensite. Flake martensites are always distributed at certain angles to each other. After low temperature tempering, martensite turns black, while the residual austenite remains white. The sheet-like martensite substructure is mainly fine twins and has high hardness.

77, alloy steel (alloysteel) In order to improve certain properties of steel, an appropriate amount of alloy elements is added to the basis of carbon steel . Alloy steel has better performance than carbon steel in terms of mechanics, physics, chemicals, heat resistance and certain process properties.

78, carbon steel (carbon steel 1) Iron-carbon alloy with carbon content less than 1.35% and contains limited amounts of impurities such as manganese, silicon, phosphorus, sulfur and trace residual elements and trace elements. Carbon content is the main factor determining the performance and use of carbon steel. Carbon steel is widely used in components with working temperatures not exceeding 450℃ in thermal power plants.

Carbon steel can be divided into low carbon steel, medium carbon steel, and high carbon steel according to chemical composition; it can be divided into ordinary carbon steel, high-quality carbon steel and high-quality carbon steel according to the quality of steel; it can be divided into carbon structural steel and carbon tool steel according to the purpose.

79, heat-resistant steel (heatresistant steel) has sufficient high temperature strength, good oxidation resistance and corrosion resistance, and long-term structural stability at high temperatures. Heat-resistant steel is mainly alloy steels that add alloy elements such as chromium (Cr), silicon (Si), aluminum (A1), molybdenum (Mo), vanadium (V), tungsten (W), niobium (Nb), titanium (Ti), boron (B) and rare earth (Re).

80, metal heat treatment (heattreatment of metal) uses the phase change law of solid metal and uses heating, insulation and cooling methods to improve and control the required structure and properties of metal (physical, chemical and mechanical properties, etc.). According to the difference between heating and cooling, metal heat treatment can be divided into annealing, normalizing, quenching, back-tempering, tempering, etc. The most important things in the heat treatment process are: the selection of process parameters and the prevention of heat treatment defects, etc.

81, annealing (annealing) A metal heat treatment process that heats the metal component to a higher or lower critical point, maintains it for a certain period of time, and then slowly cools, thereby obtaining a structure and performance close to the equilibrium state. The purpose is to soften the material, increase plasticity and toughness, uniformize the chemical composition, remove residual stress or obtain expected physical properties, etc.

82, normalizing (normalizing) A simple and economical heat treatment process for heating the steel parts to a temperature of 40-60℃ or higher above the upper critical point, and cooling in the air after the insulation reaches complete austenitization. Commonly known as Constant. Its main purpose is to refine the grains to improve the mechanical properties of the steel and can be used for final heat treatment. It can also be used to improve the tissue to improve the cutting performance of steel.

83, quenching (hardennine; quenching) Heat the steel to the austenitization temperature and maintain it for a certain period of time, and then cool at a speed greater than the critical cooling to obtain a non-diffusion transformation structure, such as martensite, bainite and austenite, a heat treatment process, commonly known as dipping fire. The purpose is usually to increase the strength and hardness of steel. The quenching process includes three aspects: selection of quenching temperature, determination of heating time and selection of cooling medium. The requirement is to achieve the required performance, with small deformation and no cracking.

84, tempered (tempering) A heat treatment process that heats the quenched steel at a certain temperature, keeps it in heat and then cools it down.

85, corrosion (corrosion) Deterioration and damage caused by chemical, electrochemical reactions and physical actions of metals with the surrounding environment. Chemical corrosion is the direct chemical reaction of the surface of a material or device and its surrounding medium, causing the metal to be damaged by the damage, which mostly occur in a gaseous environment. During the metal corrosion damage process, electric current is called electrochemical corrosion.

86, comprehensive corrosion damage caused by chemical or electrochemical reactions with surrounding media on the entire surface of a material or device or on a large area. Although comprehensive corrosion will not significantly shorten the service life of the equipment, when metals are corroded on a large area, corrosion products will be produced. When these corrosion products are brought into the pot and deposited on the pipe wall, it will cause damage to corrosion under the sediment.

87, galvanic corrosion Corrosion phenomenon occurs when two metals with different potentials contact each other (or are connected through conductors) and the presence of an electrolyte solution is also called heterometal contact corrosion. Such as metal corrosion at the expansion joint between the condenser copper alloy tube and the copper tube plate during operation.

88. Point corrosion is also called pore corrosion. A part of the metal is corroded into some small and deep point holes. The more concentrated the corrosion products and media are at the bottom of the corrosion point, the more effective the effect, the deeper the corrosion hole, and sometimes even perforation occurs.

89, Crack corrosion Corrosion occurs in the local range of the gap when the member has a gap or covers the surface of the deposit exposed to the corrosive medium. Such as corrosion at metal riveting, bolting connection and under metal surface deposits.

90. Intergranular corrosion Metal materials In some corrosion media (such as NaOH), the dissolution rate of the grain boundary is much greater than the dissolution rate of the grain itself, selective local corrosion along the grain boundary will occur.

91. Selective corrosion refers to the selective detachment of the highly active components in the alloy during the electrochemical process. Such as brass dezincification, bronze detincification, etc.

92. Stress corrosion is caused by the special damage caused by the synergistic effect of corrosive media and mechanical stress. Such corrosion may lead to the generation and development of cracks. The forms of stress corrosion caused by boiler equipment, etc. include: ① Stress corrosion fracture. It is metal fracture failure caused by the synergistic action of stress and corrosive media. ② Corrosion fatigue It is material damage caused by the synergistic action of alternating stress and corrosive media. ③Cacious embrittlement It is a special stress corrosion form of boiler metals, mainly due to the embrittlement of metals caused by sodium hydroxide solution. ④ Hydrogen embrittlement The material plasticity decreases, cracks or damage caused by hydrogen (absorbing during welding and pickling) in metal materials.

93. Grinding (pulling) damage caused by the synergistic effect of corrosion and wear in corrosive media. Continuous wear (erosion) removes the re-formed protective oxide film, causing re-corrosion, forming a vicious cycle.

94, low-temperature corrosion on the fire side) The corrosion phenomenon caused by the condensation of anhydride on the low-temperature heating surface of the boiler when burning high-sulfur coal. Air preheaters (especially their cold ends) are the most likely parts of low-temperature flue gas corrosion. They often coexist with ash blockage, affecting the circulation of flue gas and air. Not only increases resistance and smoke exhaust losses, reduces boiler efficiency, but also limits the output of the boiler in severe cases.

95, high-temperature corrosion on the fire side. Corrosion of the metal pipe wall on the water-cooled wall of the boiler furnace and the heated surface of the superheater. Generally, it occurs when burning solid slag discharge furnaces with high ash and low volatile coal. When the heat load in the furnace is too concentrated and slightly positive pressure, high-temperature flue gas corrosion of the furnace water-cooled wall will also occur.

96, primary stress stress caused by non-self-limiting loads. Such as the internal pressure, external pressure, gravity, explosive force, seismic force, wind force and snow load of the compressed element.Loads that act for a long time (such as gravity, internal pressure, external pressure, snow load, etc.) are called constant loads, while loads that act for a short time (such as seismic force, wind force, explosive force, etc.) are called instantaneous loads.

97, secondary stress stress caused by self-limiting load. Such as uneven temperature field, stress caused by loads such as constrained displacement and interference assembly. These stresses will disappear on their own after the constraint is relaxed, so they are confined to a system. The secondary stress damages the component much less than the primary stress.

98. Peak stress The stress distribution is extremely uneven (i.e., stress concentration) due to sudden changes in the stiffness of the element or internal defects. The high stress that appears locally on it is called peak stress. It does not cause immediate damage to the element, but under the repeated action of this high stress, cracks will occur there and fatigue damage.

99, salt deposit (saltdeposit) Various substances carried by steam are precipitated due to changes in temperature and pressure, causing their solubility to decrease and deposit in the steam flow part of the thermal equipment. Different steam parameters and different salts carried by steam are also different. The higher the parameters, the more serious the harm of salt accumulation. The salt accumulation areas are mainly superheaters and turbine blades, and metal brittleness (brittleness of metal). The characteristic of metal materials absorbing only less mechanical energy when they break, which is characterized by the failure without macroscopic plastic deformation. Metal brittleness is commonly characterized by impact values ​​and their changes. According to the conditions for metal brittleness, it is often divided into red and hot brittleness, cold brittleness, temper brittleness, hot brittleness, aging brittleness, etc.

(Source: Baidu Wenku Power Plant Chemical Exchange Learning)

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