What is quenchability? What is the principle of quenching

Generally refers to the ability of steel to obtain martensite through quenching.

Steel grades with high hardenability, such as high-alloy steel, have strong hardenability, and do not need too high cooling rate during quenching to obtain a hard martensitic structure, so oil can be used as a quenching medium.

Steel grades with low hardenability, such as mild steel, have poor hardenability, and must have a high cooling rate during quenching to obtain martensitic, so it is necessary to use water or even salt water and alkaline water as the quenching medium.

For aluminum alloys.

The quenching principle of aluminum alloy is to form a solid solution of more alloying elements at high temperature, and after rapid cooling (quenching), and then carry out "aging" treatment, due to the reduction of solid solubility, there will be diffuse phase precipitation, or the formation of atomic segregation, to achieve the strengthening effect.

The quenching sensitivity here refers to whether the strengthening effect can be achieved through the quenching + aging process.

For example, binary aluminum-silicon, aluminum-manganese, aluminum-magnesium, aluminum-zinc alloy, the solid solubility is very large, even if the solid solubility is reduced after quenching, there is no effect, so the above method is strengthened, the effect is very small, that is to say, the quenching sensitivity is low.

Quenching, a heat treatment process for metal and glass. The quenching of steel is a heat treatment process in which the steel is heated to a critical temperature of AC3 or above AC1, kept warm for a period of time, and all or part of the austenite is 1, and then the martensite transformation is carried out at a cooling rate greater than the critical cooling rate to below MS. Solution treatment of materials such as aluminum alloys, copper alloys, titanium alloys, tempered glass, etc., or heat treatment processes with a rapid cooling process are usually referred to as quenching.

The main function of the wheel flange is to get stuck on the track and not to run the rail, and the accurate role is that if the two tracks are parallel to the crane (overhead crane) during installation, the role of the wheel flange is mainly to prevent the running rail.

The principle of quenching: the metal workpiece is hammered and then heated, and it is quickly put into ice water, so that it instantly enters the cooling state from the high temperature state, after this process, the hardness of the metal workpiece will rise, and the performance will be better and more stable. In psychology, the theory that applies the same principle is called the "quenching effect".

Quenching process.

Degreasing - rust removal - coating protectant - cool drying - furnace - heating - isothermal - heating - heat preservation - quenching - (water or oil or other) - inspection - (tempering, see tempering process).

Application of the principle of quenching in pedagogy.

The quenching principle is equivalent to "cold treatment" and "frustration education" in pedagogy. For troublesome matters or contradictions that have intensified, you may wish to adopt "cold treatment" and let it go for a period of time, so that you will think more thoroughly and your methods will be more secure. For students who have been praised for a long time and have some hot heads, it is advisable to set up a small obstacle and apply "frustration education", and after several exercises, their psychology will become more mature and their psychological tolerance will be stronger.

During the presentation, leave some blank space appropriately to achieve a good presentation effect. When criticizing, cold treatment is equivalent to a blank effect, which is to provide students with an opportunity to think and introspect.

"Cold treatment" is relative to "heat treatment". The so-called "heat treatment" is to focus on positive education, understand it with reason, move it with emotion, and influence students. When students make mistakes, they should be pointed out in a timely manner, and educational corrections should be given to curb the further development of the situation, and the students' misunderstandings and behaviors should be corrected, so that they can develop healthily.

Quenching is a heat treatment process method that heats the steel above the critical temperature, keeps it warm for a certain time, and then cools it at a temperature greater than the critical cooling rate, so as to obtain an unbalanced structure dominated by martensite (bainite or single-phase austenite is also obtained as needed). Quenching is the most widely used process method in steel heat treatment process.

The supercooled austenite is transformed into martensite or bainite to obtain martensite or bainite structure, and then tempered at different temperatures to greatly improve the rigidity, hardness, wear resistance, fatigue strength and toughness of steel, so as to meet the different requirements of various mechanical parts and tools. It can also meet the special physical and chemical properties of some special steels such as ferromagnetism and corrosion resistance through quenching.

Notes:

When quenching, the most commonly used cooling media are brine, water and oil. The workpiece quenched by salt water is easy to obtain high hardness and smooth surface, and it is not easy to produce soft spots that are not hardened, but it is easy to make the workpiece seriously deformed and even cracked. The use of oil as quenching medium is only suitable for the quenching of some alloy steels or small-sized carbon steel workpieces with relatively large stability of supercooled austenite.

The quenching method in which the workpiece is locally heated to the austenitization temperature and then cooled according to the usual method, or cooled by jetting the heating part with a water stream, so as to harden the workpiece locally is called local quenching. In production, flame heating, induction heating or salt bath heating are commonly used to achieve local quenching of workpieces. In recent years, an ideal local quenching method for laser heating quenching has been developed and has been applied in production.

Quenching is a method of heat treatment of the workpiece, which can make the workpiece obtain a certain special property. Usually the metal workpiece is heated to a certain temperature and then immersed in a coolant (oil, water, etc.) and cooled rapidly to increase the hardness. It is commonly known as dipping fire.

Quenching is one of the basic means to strengthen steel, quenching steel into martensite, followed by tempering to improve toughness, is the traditional method to make steel obtain high comprehensive mechanical properties. In order to fully exploit the strength of steel, the steel must first be completely converted into martensite, i.e. it must be cooled at a rate fast enough to avoid the decomposition of austenite into structures such as ferrite, pearlite or bainite during quenching, which is called the critical cooling rate, also commonly known as the critical cooling rate.

Some high-alloy steels such as precipitation-hardening stainless steel (17-7PH steel, etc.), or non-ferrous metals such as duralumin alloy (Al-Cu-MG alloy), etc., are also subjected to fast cooling treatment similar to quenching, but their purpose is to keep the high-temperature phase (austenite and solid solution respectively) to room temperature, so that it is supersaturated, and then need to be aged to harden the material, this kind of quenching is called solution heat treatment.

From the point of view of the process, the choice of quenching temperature and quenching medium is an important factor affecting the quenching effect, and these depend on the properties of the steel and alloy. In terms of the properties of steel, the ability of steel to form martensitic in quenching depends on the critical cooling rate of the steel (hardenability of the steel). The hardenability of steel is determined by the composition of the austenite and some other factors, such as the grain size of the austenite, the uniform distribution of alloying elements in the austenite, etc.

It is crucial to determine the hardenability of the steel, which is an important basis for selecting the parameters of the quenching process.

Hardenability of steel:

Hardenability is one of the fundamental properties of steel. It differs from hardenability, which refers to the hardness value of martensitic and is mainly determined by the amount of carbon in the steel. The magnitude of hardenability is measured by the ideal critical diameter di, which is the diameter of the steel rod when it is cooled in a medium with a cooling intensity of (see below) and the core forms 50 martensite.

When cooled in other quenching media (such as water, oil, etc.), the obtained critical diameter DC is smaller than that of Di. Of these, 50 martensitic transitions have been artificially selected for ease of measurement and can be determined by metallographic examination and hardness measurements. The curves in Figure 3 show the relationship between hardness values and carbon content when the hardened layer contains different percentages of martensitic.

When a certain size of round bar is quenched, the cooling rate of the surface and the core is obviously different, and the relationship between the cooling rate of different parts of the workpiece and the continuous cooling transition diagram of the steel is shown in Figure 4; The part of the heart where the cooling rate exceeds the critical cooling rate is transformed into martensite (hatched part), and the core that is less than the critical cooling rate is transformed into non-martensitic tissue (chromatic part).

Obviously, the depth of the hardened layer depends on the magnitude of the critical cooling rate, so the critical cooling rate of the steel can be reduced by adding alloying elements, so that the depth of the hardened layer of the steel can be increased. The most commonly used method for determining the hardenability of steel is the top quenching test.

When the steel is heated to a certain temperature, the internal structure of the steel is rapidly cooled to obtain a more rigid form.

In the past, when striking iron, the iron was burned red (900 or so) and inserted into the pool to cool, and then the process (forging, quenching) was repeated, as if the red iron was "dipped in" in water, so the word in the industry was pronounced as dipping fire.

What does normalizing, annealing, quenching, and tempering mean? Have you figured it all out?

What does normalizing, annealing, quenching, and tempering mean? Have you figured it all out?

Quenching is a heat treatment process that heats the steel to a certain temperature, so that the internal structure of the steel is quickly cooled to obtain a more hardness form When the iron is struck before, the iron is burned red (up and down 900) and inserted into the pool for cooling, and then the process is repeated (forging, quenching), just like the red iron is "dipped in" in water, so the word industry is pronounced as dipping fire.

Quenching is a heat treatment technology for metal materials, which heats the workpiece to the appropriate temperature, and then rapidly cools its surface to form a hard, ductile and strong metal structure. This technology can improve the hardness of the material, increase its tensile strength, elasticity and toughness at the same time, and better meet the needs of wear, corrosion, friction and other aspects.

Special attention needs to be paid to the speed and temperature of heating and cooling during the quenching process to ensure the quality and effect of the workpiece. Commonly used quenching methods include water quenching, oil quenching, salt quenching, gas quenching, etc., each of which has a different scope of application and effect.

Quenching is widely used in machinery manufacturing, steel production, automobile manufacturing, aerospace and other fields. By using the right quenching technology, the material can have better performance and a longer service life. Therefore, quenching technology is regarded as a very important metal processing technology, which is of great help to improve the technical level and development of China's manufacturing industry.

Quenching is a heat treatment process method that heats the steel above the critical temperature, holds it for a certain time, and then cools it at a cooling rate greater than the critical cooling rate, so as to obtain an unbalanced structure dominated by martensite leakage (there are also bainite or single-phase austenite that is maintained as needed).

The purpose of quenching is to make the supercooled austenite carry out martensite or bainite transformation to obtain martensite or bainite structure, and then cooperate with tempering at different temperatures to improve the rigidity, hardness, wear resistance, fatigue strength and toughness of steel with a large search width, so as to meet the different requirements of various mechanical parts and tools.