What is the definition of pearlite? What are the main properties of pearlite?

Pearlite is made up of austenite.

Ferrite, which is precipitated at the same time as the eutectic transition occurs.

The structure of the cementite sheet is an iron-carbon alloy.

One of the five most basic types of organization. The code name is P. It is named after the discoverer.

Morphology. Its form is a layered complex with alternating layers of ferrite and cementite, also known as flake pearlite. Represented by the symbol p, the carbon content c=.

In pearlite, ferrite accounts for 88% and cementite accounts for 12%, and because the amount of ferrite is much larger than cementite, the ferrite lamellae are much thicker than cementite. Under the condition of spheroidized annealing, the cementite in the pearlite can also be granular, and such a pearlite is called granular pearlite.

After being etched by 2-4% nitric acid alcohol solution, the pearlite structure with different characteristics can be observed under the microscope at different magnifications. When the magnification is high, the wide ferrite and narrow cementite in the pearlite can be clearly seen. When the magnification is low, only a black line can be seen in the cementite in the pearlite; When the magnification continues to decrease or the pearlite becomes thinner, the lamellar structure of the pearlite cannot be distinguished, and the pearlite appears as a black mass.

Key features. The properties of pearlite are between ferrite and cementite, and the strength and toughness are better. its tensile strength.

750 900MPa, 180 280HBS, elongation.

is 20 25%, and the impact energy is 24 32j. Mechanical properties.

Between ferrite and cementite, the strength is high, the hardness is moderate, the plasticity and toughness are good B=770MPa, 180HBS, δ=20% 35%, AKU=24 32J).

The comprehensive mechanical properties of pearlite are better than those of ferrite or cementite alone. Mechanical properties of pearlite.

Between ferrite and cementite, it has moderate strength, hardness, and is not brittle, because the amount of cementite in pearlite is much smaller than that of ferrite.

The eutectic transformation of austenite is formed by the eutectic transformation of ferrite and cementite (p).

The properties of pearlite are between ferrite and cementite, and the strength and toughness are better. Its tensile strength is 750 900MPa, 180 280Hbs, elongation is 20 25%, and impact energy is 24 32J. The mechanical properties are between ferrite and cementite, with high strength, moderate hardness, good plasticity and toughness B=770MPa, 180HBS, δ=20% 35%, AKU=24 32J).

The comprehensive mechanical properties of pearlite are better than those of ferrite or cementite alone. The mechanical properties of pearlite are between ferrite and cementite, and the strength and hardness are moderate, and it is not brittle, because the amount of cementite in pearlite is much less than that of ferrite.

Temperature effects. 1. The distance between the centers of two adjacent cementite (or ferrite) sheets in the flake pearlite is called the sheet spacing of the pearlite.

2. Temperature is a major factor affecting the size of the piece spacing. With the increase of cooling rate, the austenite transition temperature decreases, that is, the supercooling degree increases, and the spacing of the pearlite formed by the transition decreases.

3. The relationship between the pearlite sheet spacing and the formation temperature of carbon steel and alloy steel. When the supercooling is very small, there is an approximate linear relationship, but in general it is nonlinear.

Organization. Pearlite is precipitated by the eutectic transformation of austenite, and the structure of ferrite and cementite flakes is one of the most basic five microstructures in iron-carbon alloys.

The average carbon content of the pearlite structure in carbon steel is about . Its mechanical properties are between ferrite and cementite, that is, its strength and hardness are significantly higher than ferrite, and its plasticity and toughness are worse than ferrite, but much better than cementite.

The phase structure of iron-carbon alloys is mainly as follows:

1. Ferrite, denoted by the symbol F or .

2. Austenite, represented by the symbol A or .

3. Cementite, its molecular formula is Fe3C, which is a gap compound with a complex crystal lattice, commonly used in the symbol CM

Pearlite, on the other hand, is a structure composed of cementite and ferrite, rather than a phase structure.

Spheroids are chemical compound tissues.

The so-called flake pearlite refers to the pearlite formed in the temperature range of A1 650, and the flake structure morphology of ferrite and cementite layers can be clearly distinguished under the optical microscope, and its sheet spacing is about 150 450nm.

Composition: Its form is a layered complex with alternating layers of ferrite and cementite thin layers, also known as flake pearlite. Represented by the symbol p, the carbon content c=. Among pearlites, ferrite accounts for 88%.

Cementite accounts for 12%, because the amount of ferrite is much larger than cementite, so the ferrite layer is much thicker than cementite, under the condition of spheroidization annealing, the cementite in the pearlite can also be granular, such a pearlite is called granular pearlite.

After being etched by 2-4% nitric acid alcohol solution, the pearlite structure with different characteristics can be observed under the microscope with different magnifications, and when the magnification is higher, the wide ferrite and narrow cementite in the pearlite can be clearly seen in parallel arrangement.