What is superheating metalworking .

Non-regulatory elevation of body temperature, in which the setting point does not move, but is due to thermoregulation.

Disorders (such as damage to thermoregulatory centers), or impaired heat dissipation (ichthyosis.

and heat stroke caused by high ambient temperatures.

etc.), etc.) and abnormalities of thermogenic organs (e.g., hyperthyroidism.

The thermoregulation mechanism cannot control the body temperature at a level that is compatible with the setting point, which is a passive increase in body temperature. This type of elevated body temperature is called hyperthermia.

The phenomenon of heating a substance above the temperature at which a phase change normally occurs without a phase change. For example, a liquid that has been boiled for a long time can be heated above the boiling point without boiling (sometimes at a pressure of 1 atmosphere) after all the air dissolved in it has run away, and due to the lack of bubbles, that is, the lack of vaporized nuclei.

, the water temperature can rise to about 130, and in very special cases, it can also rise to 200).

Such a liquid is called a superheated liquid, and it is in a metastable state.

The bubble chamber used in nuclear physics experiments uses the instability of superheated liquids to create bubbles to show the trail of particles.

Interpretation. In some places in superheated liquids, due to fluctuations, the molecules have enough energy to push each other off, resulting in the formation of extremely small bubbles. The linearity of this bubble is only a few times the distance between the molecules of the liquid. Saturated vapor pressure within this fine bubble.

It is very small, even when the liquid temperature reaches the boiling point, the saturated vapor pressure inside the bubble cannot be greater than the pressure outside the bubble, so the bubble cannot expand.

When the superheated liquid continues to be heated to a temperature much higher than the boiling point, the saturated vapor pressure of the very small bubbles can exceed the pressure outside the bubbles. At this time, the bubble expands, and the saturated vapor pressure in the bubble also increases rapidly, making the bubble expand very quickly, and even blowing up the container, this phenomenon is called boiling.

In addition, in superheated liquids lacking vaporized nuclei, the artificial introduction of vaporized nuclei (e.g., fresh water containing air bubbles to superheated water) can also cause boiling. In terms of production, boiling is very harmful. In order to avoid boiling, for example, before heating the water in the boiler, it is necessary to add some fresh water dissolved with air, or put in some fragments of thin glass tubes with air and unglazed ceramic blocks.

If the heating temperature is too high, the grain of the metal will grow rapidly, which will reduce the mechanical properties of the metal and alloy materials, which is called overheating. Pay attention to distinguish the difference between overheating and overburning Overburning is that if the deformation temperature is further increased, when it is close to the melting point of the metal material, the metal grain boundary will oxidize or even melt, and the metal and alloy will produce cracks along the grain boundary during forging.

Metal heat treatment is a metal heat treatment process in which the workpiece is heated as a whole and then cooled at an appropriate rate to change its surrounding metallographic mechanism and thus change the overall mechanical properties. There are four basic processes for the overall heat treatment of steel: annealing, normalizing, quenching and tempering.

annealing:Annealing is to heat the workpiece to an appropriate temperature, adopt different holding times according to the material and the size of the workpiece, and then carry out slow cooling, the purpose is to make the internal structure of the metal reach or close to the equilibrium state, or to release the internal stress generated by the previous process, to obtain good process performance and use performance, or to prepare for further quenching. Taking No. 45 steel as an example, the metallographic after annealing is austenite, and it becomes too soft after annealing, and generally 45 steel is not annealed.

Professional explanation: The heat treatment process of heating the sub-eutectic steel workpiece to 20-40 degrees above AC3 (the final temperature at which ferrite is converted into austenite when heating), holding it for a period of time, and then slowly cooling it with the furnace (or buried in sand or lime cooling) to below 500 degrees and cooling in air.

Normalization:Normalizing is to heat the workpiece to a suitable temperature and then cool it in the air, the effect of normalizing is similar to annealing, but the resulting structure is finer, often used to improve the cutting performance of the material, and sometimes used for some parts with low requirements as the final heat treatment. The metallographic after No. 45 normalizing is austenite + pearlite.

Professional explanation: the steel or steel parts are heated to the critical point AC3 (for sub-eutectic steel) or ACCM (the final temperature of the secondary cementite dissolved into austenite when heated, for per-eutectic steel) above 30 -50, and after the appropriate time of heat preservation, the heat treatment process of uniform cooling in free-flowing air is normalizing. After normalization, the sub-eutectic steel is F+S, the eutectic steel is S, and the per-eutectic steel is S+Fe3C The main difference between normalizing and complete annealing is that the cooling rate is faster, and the purpose is to normalize the steel structure, also known as normalization.

Quenching:Quenching is to heat and keep the workpiece warm, and then quickly cool it in a quenching medium such as water, oil or other inorganic salt solutions, organic aqueous solutions, etc. The rear steel becomes harder, but at the same time brittle.

In the case of No. 45 steel, it is rarely quenched alone because it is difficult to get the desired hardness. Professional explanation: The heat treatment process of cooling the steel after steel austenitization at an appropriate cooling rate, so that the workpiece can undergo martensite and other unstable microstructure transformation in all or a certain range within the cross-section.

TemperingTempering is to reduce the brittleness of steel, and the quenched steel is kept warm for a long time at an appropriate temperature higher than room temperature and lower than 650, and then cooled, this process is called tempering. Professional Explanation:

The quenched workpiece is heated to an appropriate temperature below the critical point AC1 (the starting temperature of the pearlite to austenite transition when heated) for a certain period of time, and then cooled in a manner that meets the requirements to obtain the desired structure and properties.

Metal heat treatment is to heat the metal workpiece to a suitable temperature in a certain medium, and after maintaining it at this temperature for a certain time, it is cooled at different speeds.

Tempering: The structure obtained by high temperature tempering is tempered sostenite. Tempering is generally not used alone, tempering is carried out after quenching of parts, the main purpose is to eliminate quenching stress and obtain the required structure, tempering is divided into low temperature, medium temperature and high temperature tempering according to the different tempering temperatures.

Tempered martensite, drossite, and soxenite were obtained, respectively. Among them, the heat treatment combined with high temperature tempering after quenching is called quenching and tempering treatment, and its purpose is to obtain comprehensive mechanical properties with good strength, hardness, plasticity and toughness. Therefore, it is widely used in automobiles, tractors, machine tools, etc., such as connecting rods, bolts, gears and shafts.

After tempering, the hardness is generally HB200 330.

Annealing: The annealing process occurs in a pearlite transition, and the main purpose of annealing is to bring the internal structure of the metal to or near equilibrium in preparation for subsequent processing and final heat treatment. Stress relief annealing is an annealing process that eliminates residual stresses caused by plastic deformation processing, welding, etc., as well as within castings.

There is internal stress in the workpiece after forging, casting, welding and cutting, if it is not eliminated in time, the workpiece will be deformed in the process of processing and use, and the accuracy of the workpiece will be affected. It is important to use stress-relieving annealing to eliminate the internal stresses generated during machining. The heating temperature of the stress-relieving annealing is lower than the phase change temperature, so that no microstructure transformation occurs throughout the heat treatment process.

Internal stresses are mainly eliminated naturally by the workpiece during heat preservation and slow cooling. In order to make the stress in the workpiece more completely relieved, the heating temperature should be controlled when heating. Generally, it is fed into the furnace at a low temperature and then heated to a specified temperature at a heating rate of about 100 h.

The heating temperature of the weldment should be slightly higher than 600. The holding time depends on the situation, usually 2 4h. The upper limit of the holding time of the stress relief annealing of the casting is taken, the cooling rate is controlled at (20 50) h, and the cooling is below 300 before the furnace can be air-cooled.

Aging treatment can be divided into natural aging and artificial aging two kinds of natural aging is to place the casting in the open field for more than half a year, so that it occurs slowly, so that the residual stress is eliminated or reduced, artificial aging is to heat the casting to 550 650 for stress relief annealing, it saves time than natural aging, and the residual stress is removed more thoroughly.

The major of metal materials and heat treatment is generally affiliated with the School of Materials, and the major of metal materials and heat treatment is also called the Department of Materials Science or Materials Science and Engineering in some schools.

It's not easy to say what you have learned, I'll give you a concept, engineering colleges generally have a school of materials, and below, there is a department called materials science, which can also be called metallurgy and heat treatment (the name of the beginning of liberation).

The School of Materials is also divided into three majors: forging, welding, and casting, which together add up to material processing engineering or material forming and control.

According to the names of several other majors in the same college, you can get a general idea of metallurgy and heat treatment.

That is to say, your classmates in the same college are engaged in forging, welding, casting, that is, the hot processing technology of metal materials, and what you want to do is similar to this, which is the purification, smelting and modification of materials.

Let me give you a typical learning content: the study of iron-carbon phase diagrams.

The content goes on its own.

This content is familiar to all material people, and it is a classic in the heat treatment discipline.

In fact, after graduating from the bachelor's degree, the work is generally in steel mills, smelters (such as Baosteel, Shougang and other steel plants), and heat treatment workshops in the metal manufacturing industry.

It is mainly responsible for the smelting and purification of metals, the heat treatment control of the composition temperature and time according to the phase diagram of the smelting process of metals, and the microstructure analysis of specimens.

It is the most basic discipline of materials science, so the employment of undergraduates is not as good as several other majors (casting, forging and welding) when looking for jobs, but in scientific research, it is the only discipline that can be called science in the School of Materials (others are called engineering), such as reading a doctorate, and publishing literature will be better than other disciplines.

That is to say, metallurgy and heat treatment majors are not easy to employ, and they belong to the disciplines of theoretical research in engineering, which are more suitable for further study.

According to the different schools and the content of further study, there are more nanomaterials or composite materials at the doctoral level.

I've heard of this.

Hello, I'm glad to answer for youA: The advantage of heat treatment of metal materials is the principle of metal heat treatment: a comprehensive process in which a metal or alloy is heated to a certain time in a certain medium under a solid state and cooled down at a certain speed.

Metal heat treatment: 1. Significantly improve the mechanical properties of the material and prolong the service life of the metal. 2. It can eliminate various deficiencies caused by casting, forging, Korean and other processing technologies.

3. Improve the processing performance of metal. 4. Make the surface of metal processing have special chemical and physical functions such as anti-wear and corrosion resistance 5. Eliminate the defects of the embryo and improve its process performance.

The upstairs has already answered better, add:

1. Annealing can be divided into spheroidization annealing, complete annealing, incomplete annealing, diffusion annealing, homogenization annealing, recrystallization annealing, stress relief annealing, dehydrogenation annealing, etc., there are many, about 20 kinds, for example, spheroidization annealing is divided into ordinary spheroidization annealing, isothermal spheroidization annealing, periodic spheroidization annealing, cyclic spheroidization annealing, etc.

2. Quenching is divided into: single medium quenching, multi-medium quenching, graded quenching, isothermal quenching, spray quenching, and local quenching.

3. Induction heating and quenching are divided into: high-frequency induction heating and quenching, ultra-audio induction heating and quenching, medium frequency induction heating and quenching, and power frequency induction heating and quenching.

In addition, resistance heating and quenching, laser heat treatment, electrolytic heat treatment, vacuum heat treatment, ion nitriding, seepage, boronization, metal infiltration TD treatment, chemical vapor deposition (CVD), physical vapor deposition (PVD) and so on are all heat treatments.

Surface heat treatment is a metal heat treatment process that only heats the surface of the workpiece to change the mechanical properties of the surface. In order to only heat the surface of the workpiece and not let too much heat pass into the workpiece, the heat source used must have a high energy density, that is, a large heat energy is given to the workpiece per unit area, so that the surface or local layer of the workpiece can reach high temperature in a short time or instantaneously. The main methods of surface heat treatment include laser heat treatment, flame quenching and induction heating heat treatment, and the commonly used heat sources are flames such as oxyacetylene or propylene oxide, induced current, laser and electron beam.

Answer]: The performance of heat treatment process mainly refers to the permeability, deformation and cracking tendency and oxidation and decarburization tendency of the quenching draft. Steel, aluminum alloys, and titanium alloys can all be strengthened by heat treatment.

The heat treatment process performance of alloy steel is better than that of early carbon steel. Important parts with complex shapes or large sizes and high load-bearing capacity should be made of alloy steel. The higher the carbon content of carbon steel, the greater its tendency to quench deformation and cracking.

When selecting carburizing steel, it is necessary to pay attention to the overheating sensitivity of the steel; When selecting quenched and tempered steel, it is necessary to pay attention to the high-temperature tempering brittleness of the steel; When choosing spring steel, it is necessary to pay attention to the oxidation and decarburization tendency of the steel.