What are the conditions and purposes of heat treatment?

Heat treatment conditions: the material is in the solid state, by means of heating, heat preservation and cooling; Objective: A metal thermal processing process to obtain the expected structure and properties.

Metal heat treatment is one of the important processes in machinery manufacturing, compared with other processing processes, heat treatment generally does not change the shape of the workpiece and the overall chemical composition, but by changing the internal microstructure of the workpiece, or changing the chemical composition of the surface of the workpiece, giving or improving the performance of the workpiece. It is characterized by an improvement in the intrinsic quality of the workpiece, which is generally not visible to the naked eye.

In order to make the metal workpiece have the required mechanical properties.

Physical and chemical properties, in addition to the reasonable selection of materials and various forming processes, heat treatment process.

is often essential. Steel is the most widely used material in the machinery industry, and the microstructure of steel is complex, which can be controlled by heat treatment, so the heat treatment of steel is the main content of metal heat treatment. In addition, aluminum, copper, magnesium, titanium, etc. and their alloys can also change their mechanical, physical and chemical properties through heat treatment to obtain different use properties.

Heat treatment is a process method in which a solid metal or alloy is heated in an appropriate way, kept warm for a certain time, and cooled at a certain cooling rate to change its structure, so as to obtain the required properties. Its purpose is to change the internal structure of steel through appropriate heat treatment process, to control the degree of structural transformation and the morphology of transformation products in the phase transformation process, so as to improve the properties of steel; The condition is that the alloy must have a solid phase transition before it can be heat-treated. View the original post

Purpose of Metal Heat Treatment:

1) Improve hardness, strength and increase wear resistance.

2) Reduce hardness and improve cutting performance.

3) Eliminate the internal stress generated in the process of casting, forging, welding, etc.

4) Improve surface wear resistance and corrosion resistance.

Metal heat treatment is a process in which the metal workpiece is heated to a suitable temperature in a certain medium, and after being kept at this temperature for a certain time, it is cooled in different media at different speeds, and its properties are controlled by changing the microstructure of the surface or interior of the metal material.

Integral 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 overall mechanical properties. There are four basic processes for the overall heat treatment of steel: annealing, normalizing, quenching and tempering.

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.

Normalizing or 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.

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. After quenching, the steel becomes hard, but at the same time brittle.

Heat treatment is a process in which the workpiece is heated to a certain temperature in a medium and kept warm for a certain time, and then cooled at a certain rate to change the microstructure of the metal, thereby changing its properties (including physical, chemical and mechanical properties). The purpose of heat treatment is to change the hardness and toughness of the workpiece, increase wear resistance, reduce brittleness, etc.

The heat treatment of steel is generally aimed at improving the mechanical properties or processing properties of steel. The details are as follows:

1.Annealing of steel.

Heating the steel to a certain temperature and holding it warm for a period of time and then allowing it to cool slowly is called annealing. Annealing of steel is a heat treatment method in which the steel is heated to a temperature where a phase change or partial phase change occurs, and then it is slowly cooled after heat preservation. The purpose of annealing is to eliminate microstructure defects, improve microstructure, homogenize composition, refine grains, improve the mechanical properties of steel, and reduce residual stress; At the same time, it can reduce hardness, improve plasticity and toughness, and improve cutting performance.

Therefore, annealing is not only to eliminate and improve the structural defects and internal stress left by the previous process, but also to prepare for the subsequent process, so annealing is a semi-finished product heat treatment, also known as pre-heat treatment.

2.Normalizing of steel.

Normalizing is a heat treatment method in which the steel is heated above the critical temperature, so that the steel is all transformed into homogeneous austenite, and then cooled naturally in the air. It can eliminate the reticulated cementite of the eutectic steel, and the crystal lattice can be refined for the normalization of sub-eutectic steel, and the comprehensive mechanical properties can be improved, and it is more economical to normalize instead of annealing process for parts with low requirements.

3.Quenching of steel.

Quenching is a heat treatment method that heats the steel above the critical temperature, keeps it warm for a period of time, and then quickly puts it into the quenching agent to reduce its temperature suddenly, and cools it rapidly at a speed greater than the critical cooling rate, and obtains an unbalanced structure dominated by martensite. Quenching can increase the strength and hardness of the steel, but reduce its plasticity. The quenching agents commonly used in quenching are:

Water, oil, alkaline water and salt solutions, etc.

The definition of heat treatment is a metal thermal processing process that heats, insulates and cools metal materials in a certain medium, and controls their properties by changing the metallographic structure on the surface or inside the material.

Therefore, the purpose of heat treatment is to change the properties of the workpiece by changing the surface or internal structure of the material to obtain the mechanical properties we need. For example, quenching:

Improve the mechanical properties of finished metal or parts. For example, improve the hardness and wear resistance of tools and bearings, improve the elastic limit of springs, and improve the comprehensive mechanical properties of shaft parts.

Improve the material properties or chemical properties of certain special steels. For example, improve the corrosion resistance of stainless steel, increase the permanent magnetism of magnets, etc.

Heat treatment is the process of heating a metal or alloy to a given temperature and holding it for a period of time, and then cooling it at a selected rate and method to obtain the desired microstructure and properties, which is called heat treatment.

Heat treatment includes annealing, normalizing, quenching, tempering, etc.

Annealing: The workpiece is heated to a temperature above the critical point (AC1 or AC3), left for a certain period of time (heat preservation), and then slowly cooled (cooled with the furnace), this process is called annealing.

Purpose of annealing:

1.Reduced hardness for easy cutting of workpieces.

2.Improve the microstructure and mechanical properties of materials.

3.Improve the tissue structure and prepare it for later quenching.

4.Relieves internal stress.

5.Fine crystals are obtained.

Normalizing: A heat treatment operation in which the workpiece is heated to 30-50 above AC3 or ACM, and after heat preservation, it is taken out of the furnace and cooled in air. (Normalizing cools much faster than annealing).

After normalizing, its strength and hardness are higher than those of annealing, and the plasticity is slightly lower, so that the number of pearlite increases, and the improvement of the structure ensures that higher mechanical properties are obtained, and the productivity is high due to cooling in air.

Quenching is the heating of the workpiece above the critical point (AC3 or AC1), and the rapid cooling after heat preservation to obtain a martensitic structure (there is also a certain amount of residual austenite), this heat treatment operation is called quenching. After quenching, the outstanding characteristics of steel in performance are high hardness and low plasticity.

Purpose of quenching:

1.Increase the hardness and wear resistance of steel workpieces.

2.Quenching and subsequent tempering at medium or high temperatures can achieve good overall properties of the workpiece.

Tempering: It is to heat the quenched workpiece to a temperature below AC1, keep it warm for a period of time, and then cool it down in water, oil or air. (Tempering is carried out immediately after quenching, and tempering includes low temperature tempering, medium temperature tempering and high temperature tempering).

The purpose of tempering: to reduce or eliminate the internal stress caused by the workpiece during quenching, and improve the plasticity and toughness, so as to obtain the mechanical properties required and possible to achieve when the workpiece is used.

The purpose of heat treatment is to improve the mechanical properties or processability and energy of steel.

Heat treatment refers to a metal thermal processing process in which the metal material is heated in a solid state by means of heating, maintaining reputation and cold cold, changing the chemical composition and structure of the material surface or inside to obtain the required properties.

As early as 770 BC to 222 BC, the Chinese have discovered in production practice that the properties of copper and iron will change due to the influence of temperature and pressure deformation, and the softening of white cast iron is an important process for making agricultural tools.

Industry status: With the continuous development of heavy industries such as parts and machinery, heat treatment has an important supporting role in the revitalization and development of China's machinery manufacturing industry, and the development of machinery manufacturing industry will also drive the rapid development of China's heat treatment industry.

The Twelfth Five-Year Plan specifically points out that it is necessary to make full use of the industry information platform, promote new technologies, guide enterprise innovation, vigorously develop energy-saving heat treatment, give full play to the advantages of technology research and development service platform, and provide support for energy conservation and emission reduction in the industry. <>

1) Place the cartridge in room temperature water and heat it slowly so that the water temperature rises to the boiling point within 1 2 hours, maintain it for 15 minutes, and let it cool naturally.

2) Place the box in 70 degrees of constant temperature water to maintain the small Ladan, then rise to the boiling point, and maintain it for another 30 minutes to let it cool naturally.

3) Place the cartridge in warm water, heat to boiling point within 30 minutes, maintain for 30 minutes, and let it cool naturally.

4) Place the box in cold water, slowly heat it to 65 rock points, maintain it for 1 hour, then heat it to the boiling point, and then maintain it for 30 minutes to let it cool naturally.