What are the phases of steel?

Article by: Alba Solis | Last update: April 10, 2022
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The Fe-Fe3C phase diagram contains four solid phases; α-ferrite, austenite, cementite (Fe3C), and δ-ferrite. A description of each of these phases is presented below.

What do the lines A3 a1 and ACM mean?

A3, limit of the austenitic region for low carbon steels, that is, the limit γ/γ + α. Acm, equivalent limit for high carbon content steels, that is, the γ/γ+ Fe3C limit.

What is the difference between phase and constituent?

Important concepts: PHASE: is the portion of a chemically homogeneous structure. STRUCTURAL CONSTITUENT OR MICROCONSTITUENT: is the element of a structure that can be observed through optical microscopy.

What is the ferrite phase?

Ferrite-α: is an interstitial solid solution of carbon in the crystal lattice of iron BCC (body centered cubic). It can dissolve as a solid solution a maximum of 0.02% by weight of carbon at 723oC.

What is ferrite and its characteristics?

Ferromagnetic oxides, or ferrites as they are commonly called, are ceramic materials composed primarily of iron oxide combined with other metallic elements. They are ferromagnetic materials, that is, they can be magnetized or attracted by magnets.

29 related questions found

What is ferrite and pearlite?

Pearlite is a constituent that is approximately 86.5% ferrite and 13.5% cementite. Its microstructure is formed by alternating layers or sheets of the two phases (ferrite and cementite) during the slow cooling of a steel at eutectoid temperature.

What are SAE 4140 and 4340 steels?

B:Distinguish from the type of steel, 4140 steels and 4340 steel are all alloy steels. A: From composition analysis, they all contain chromium and molybdenum. B: Yes. But 4340 steel has nickel content while 4140 steel does not.

How are steels classified according to the SAE standard?

SAE classifies steels as: carbon, medium alloy, alloy, stainless, high strength, tool, etc.

What is a Micro Constituent?

Microconstituent: phase or mixture of phases that have formed at a given temperature. For example, the eutectic that forms in the Pb-Sn alloy at 183ºC, as we will see later. Composition: is the amount of each component that contains a phase, a microconstituent or an alloy.

How is the Spheroidite obtained?

Spheroidite is formed when the eutectoid transformation takes place slowly or when a spheroidization treatment is given after the formation of pearlite, cementite does not appear in lamellar form, but in globular form with lower energy content (lower surface area/volume ratio).

What are the constituents of steels?

It should be noted that steel has different constituents depending on its temperature, specifically, from higher to lower hardness, pearlite, cementite and ferrite; in addition to austenite (for more information consult the article Iron-carbon diagram).

What does the ACM line represent?

This line is called the upper critical temperature line, corresponding to the hypereutectoid zone, and is represented by Acm, and indicates the maximum amount of carbon that can dissolve austenite at each temperature.

What is the critical temperature of ac3?

Up to 911 °C (critical temperature AC3), ordinary iron crystallizes in the body-centered cubic system and is called α (alpha) iron or ferrite.

How do you interpret the iron carbon diagram?

Iron(Fe) carbon(C) diagram: Also called equilibrium or Fe-C phase diagram, it is used to represent the transformations that carbon steels undergo with temperature, admitting that heating (or cooling) of the mixture is takes place very slowly so that diffusion processes (…

What is SAE steel?

SAE 1020 is a low carbon content steel, easy to machine and with good weldability. Due to its carbon content, these steels are used for the manufacture of structural parts or medium resistance machinery.

What are SAE 4340 steels?

AISI / SAE 4340 steel is characterized by having a low alloy of chromium, nickel and molybdenum. This provides great hardenability, toughness and resistance to fatigue.

What type of steel is 4140?

4140 low alloy Chrome Molybdenum steel.

It is a steel with good hardening penetration and good hot stability characteristics up to 400°C, without tempering brittleness, very versatile and suitable for fatigue and torsion stresses in small and medium sections.

What is a treated 4140 steel?

Steel 4140 and 4140 T is a medium carbon steel alloyed with chromium and molybdenum with high hardenability and good resistance to fatigue, abrasion and impact. This steel can be nitrided to give it greater resistance to abrasion. It is susceptible to hardening by heat treatment.

Where is the ferrite found?

In metallurgy, ferrite or iron-α (alpha) is one of the crystal structures of iron. It crystallizes in the body-centered cubic (BCC) system and has magnetic properties.

Where is perlite found?

Location. In the Argentine Republic there are perlite deposits in the provinces of Catamarca, Jujuy, Mendoza, Río Negro, Chubut and Salta, the latter province being the one with the most productive deposits in the country. In Mexico there are several deposits, such as in Durango.

What structure does the ferrite have?

Ferrite a is a solid solution of carbon in iron a that also has a cc crystalline structure and has a very low carbon solubility, only 0.02% at eutectoid temperature and that decreases to 0.005% of C at room temperature.

How is ferrite made?

Ferrites are often produced in the form of powder, with which it is possible to produce pieces of great strength and hardness, previously molded by pressure and then heated, reaching the melting temperature, within a process known as sintering.

What kind of steel is ferrite?

Ferrite is the softest and most ductile constituent of steels. It crystallizes in a BCC structure. It has a hardness of 95 Vickers, and a breaking strength of 28 kg/mm2, reaching an elongation of 35 to 40%. In addition to all these characteristics, it has magnetic properties.

What does the Fe-C phase diagram measure?

The Fe-C diagram is characterized by several important points and lines: Point “A”: Represents the melting point of pure iron at 1536°C. Point “C”: Eutectic: It is called an invariant reaction and a concentration of 4.3% C at 1130°.

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