The hardness and brittleness of cast iron is believed to be due to the presence of the cementite. Equilibrium phase diagram of the ironcarbon system. The iron carbon diagram there are two iron carbon equilibrium diagrams. A diagram that depicts existence of different phases of a system under equilibrium is termed as phase diagram. Thus, since the equilibrium phase diagrams are used to identify the phases and. Let us look at the effect of carbon content on the properties of iron carbon alloys. The fec phase diagram is a fairly complex one, but we will only consider the steel and cast iron part of the diagram, up to 6. Thus, each vertical dashed line, like the solid line in fig.
The traditional rist diagram has been combined with the present mathematical approaches like artificial neural network, to create a hybrid model to study the blast furnace. The part of ironcarbon alloy system diagram between pure iron and an interstitial compound, iron carbide fe3c, containing 6. Jan 05, 2014 principles of physical metallurgy by prof. Basic idea is to discuss both steels and the cast iron, because they are the two important. Slide 2 presents a sketch of iron carbon phase diagram. There are three main uses of the ellingham diagram. Since all steels will pass through the singlephase austenite. Were now going to focus in this lesson, on the ironcarbon system. Thus the feo phase diagram is perhaps the most thoroughly characterized because of its importance to the iron and steel industry. The iron carbon diagram provides a valuable foundation on which to build knowledge of both plain carbon and alloy steels in their immense variety. Cementite is a metastable phase, which decomposes to graphite if given long periods of time. Carbon is the most common alloying element in the iron which significantly affects the allotrophy, structure and properties of iron. On this diagram, the carbon percentage is shown on the xaxis and temperature on the yaxis.
With frame as pdf go to science of welding steel go to 8. A study of the constitution and structure of all steels and irons must first start with the iron carbon equilibrium diagram. It should first be pointed out that the normal equilibrium diagram really represents the metastable equilibrium between iron and iron carbide cementite. The iron carbon system 1 material technology and testing dr. Operating line prediction of corex ironmaking process. Iron carbon equilibrium diagram as used in engineering materials by mechanical engineers. It consists of atoms of at least two different types where solute atoms occupy either substitutionalor interstitial positions in the. Note that carbon lowers the freezing point of iron and that it broadens the tempera. Ironcarbon equilibrium diagram mechanical engineering. The fefe3c diagram is not the easiest thing to understand. Curie temperature temperature at which magnetism changes ferrite holds between 0. On the basis of this diagram iron carbon alloys having less than 2. Determine the ratio of carbon monoxide to carbon dioxide that will be able to reduce the oxide.
The phase diagrams are completely valid only under conditions of thermal equilibrium. In a glass of soda with ice, the soda is continuous and the ice is discontinuous. Nptel noc phase equilibria in materials nature and properties of ii mechanical engineering iron carbon equilibrium diagram metallurgy carbide phase example 1 22 because phase diagrams 1 binary eutectics. Bcc orthorhombic iron carbon phase diagram iron shows a eutectic with carbon allowing for a lower melting alloy body centered tetragonal. In their simplest form, steels are alloys of iron fe and carbon c. Davenport and edgar bain, is a phase that exists in steel.
Iron carbon phase diagram short cut method youtube. The proposed new version of the complete equilibrium phase diagram of the iron carbon system enables to reject the superposed version of the equilibrium and non equilibrium phase diagram of iron carbon and explains clearly the presence in the microstructure of iron carbon alloys at the room temperature of. Mechanical engineering best website for mechanical engineers with complete. They refer to the independent chemical species that comprise the system. Iron carbon phase diagram with eutectoid, eutectic.
Conventionally, the complete fe c diagram should extend from 100% fe to 100 % carbon graphite, but it is normally studied upto 6. Ironcarbon equilibrium diagram as used in engineering materials by mechanical engineers. Heat treatment of steel california state university. Iron carbon phase diagram in brief engineering insider. Often we use a phase diagram as a guide to processing.
It is also the basic understanding of the heat treatment of steels. Detailed notes on iron iron carbon equilibrium diagram. Equilibrium phase diagrams represent the relationships between temperature and the compositions and the quantities of phases at equilibrium. Steels with a carbon concentration less than about 0. Were now going to focus in this lesson, on the iron carbon system. Analysis of stable iron carbon and metastable iron ironcarbide ohase diagrams. It is very soft and ductile and is known as alpha iron by the metallurgists. Solid solution alloys a solid solution occurs when we alloy two metals and they are completely soluble in each other. The ironiron carbide equilibrium diagram practical maintenance. Ironcarbon phase diagram shown in figure16 is not a complete diagram.
The actual iron carbon diagram is far larger than the part shown here. Now in order for us to do that, lets go back and take a look at the iron carbon phase diagram. The iron carbon phase diagram in fig 2 actually shows two diagrams namely i the stable iron graphite diagram red lines, ii and the metastable fefe3c diagram. Ironcarbon phase diagram iron is ferromagnetic magnetism is dependent upon which crystalline structure is present due to carbon content and temperature. Iron carbon diagram shows the type of alloys formed under very slow cooling, proper heattreatment temperature and how the properties of steels and cast irons. Fe3c iron carbide called cementite because it is hard. Chapter 4 equilibrium phase diagrams and the ironcarbon system. Dmitri kopeliovich iron carbon phase diagram describes the iron carbon system of alloys containing up to 6.
Iron carbon phase diagram with detailed explanation. So, apart from fefe3c diagram, your concepts in heat treatment may be weak. By far the most widely used material for building the worlds infrastructure and industries, it is used to fabricate everything from sewing needles to oil tankers. Iron carbon diagram free download as powerpoint presentation. Introduction to ironcarbon equilibrium diagram structures in fec diagram ironcarbon equilibrium diagram fig. L liquid phase a ferrite bcc structure ferromagnetic fairly ductile d bcc structure. Microstructure in iron carbon alloys eutecticpearlite hypoeutectoid alloys hypoeutectoid steel. The study of the constitution and structure of iron and steel start with the iron carbon phase diagram. They are also used to troubleshoot quality problems. Iron cementite diagram is not a true equilibrium diagram, since equilibrium means no change of phase with time, however long it may be. Recall that it tells us about the structure of alloys under equilibrium rate of cooling. Steel, alloy of iron and carbon in which the carbon content ranges up to 2 percent with a higher carbon content, the material is defined as cast iron. Iron which contains little or no carbon is called ferrite. If a solid solution alloy is viewed under a microscope only one type of crystal can be seen just like a pure metal.
In general practice it is sufficient to consider only solid and liquid phases, thus pressure is. Cementite is metastable, and the true equilibrium is to be between iron and graphite c. Now, we are going to start with the classic iron carbon phase diagram. Phase diagrams are useful to metallurgists for selection of alloys with a specific composition and design and control of heat treatment procedures that will produce specific properties.
Because of the absence of graphite, it has a light appearance. A map of the temperature at which different phase changes occur on very slow heating and cooling in relation to carbon, is called iron carbon diagram. Ghosh,department of metallurgy and material science,iit kharagpur. It increases with increase in carbon % as reflected in fec equilibrium diagram. The ironcarbon equilibrium diagram total materia article. Phase diagrams definitions and basic concepts phases and microstructure binary isomorphous systems complete solid solubility binary eutectic systems limited solid solubility binary systems with intermediate phasescompounds the ironcarbon system steel and cast iron. This graph, which is known as iron carbon equilibrium diagram has the following important points. It also provides knowledge of various heat treatment processes such as hardening or annealing. What is an intuitive explanation of the ironcarbon phase. Iron carbon phase diagrams free download as powerpoint presentation. A metallic alloy is a mixture of a metal with other metals or nonmetals. Teach yourself phase diagrams and phase transformations. The part of iron carbon alloy system diagram between pure iron and an interstitial compound, iron carbide fe 3 c, containing 6.
White cast iron is unique in that it is the only member of the cast iron family in which carbon is present only as carbide. A phase is a portion of a substance possessing a welldefined structure, uniform composition, and distinct boundaries or interfaces. Determine the relative ease of reducing a given metallic oxide to metal. Introduction to materials science chapter 9, phase diagrams 5 a system is at equilibrium if at constant temperature. Graphitisation, however, rarely occurs in steels and may take years to form. Equilibrium phase diagrams represent the relationships between temperature and. What is ferrite, cementite, pearlite, martensite, austenite. The one at 727c is known as eutectoid transformation where austenite decomposes into a mixture of ferrite and cementite. White cast iron has high compressive strength and retains good hardness and strength at. Determine the partial pressure of oxygen that is in equilibrium with a metal oxide at a given temperature. The iron carbon phase diagram provides a foundation for understanding both carbon steels and alloy steels. The main structures, significance of various lines and critical. The fec phase diagram is a fairly complex one, but we will only consider the steel part of the. Austenite has a cubicclose packed crystal structure and tends to decompose into ferrite bodycentered cubic and cementite fe 3 c.
When molten cast iron solidifies some of the carbon precipitates as graphite, forming tiny, irregular flakes within the crystal structure of the metal. When we look at the phase diagram over a range of different temperatures, what we see is iron melts at a temperature of 1538 c. Ferrous alloys fec phase diagram the vast majority of steels are in the austenitic condition at temperatures in excess of 900 c. Introduction to iron carbon equilibrium diagram structures in fec diagram. Scribd is the worlds largest social reading and publishing site. An example of a commonly used phase diagram is the iron carbon phase diagram. The iron iron carbide fefe3c phase diagram in their simplest form, steels are alloys of iron fe and carbon c. Due to the high lattice distortion, martensite has high residual stresses. An alloy in this state shows no tendency to change it is thermodynamically. When we look at the phase diagram over a range of different temperatures, what we see is iron melts at a. Jul 18, 2019 phase diagram nptel pdf posted on july 18, 2019 by admin nptel noc phase equilibria in materials nature and properties of ii mechanical engineering iron carbon equilibrium diagram metallurgy carbide phase example 1 22 because phase diagrams 1 binary eutectics. In their simplest form, steels are alloys of iron fe and.
The iron carbon diagram also called the iron carbon phase or equilibrium diagram is a graphic representation of the respective microstructure states depending on temperature y axis and carbon content x axis. Gray iron gray iron was the original cast iron, and is an iron alloy characterized by its relatively high carbon content usually 2% to 4%. A word to keep in mind throughout our discussion is equilibrium. Martensite non equilibrium bct phase from quench of. Nov 01, 2017 in their simplest form, steels are alloys of iron fe and carbon c. The equilibrium constitution is the state of lowest gibbs free energy g, for a given composition, temperature and pressure. The ironcarbon diagram there are two iron carbon equilibrium diagrams. Iron carbon diagram iron iron carbide phase diagram iron iron carbide phase diagram features of iron iron carbide diagram phases present. The main structures, significance of various lines and critical points are discussed as. Oct 11, 2017 iron carbon equilibrium diagram, ttt diagram and heat treatment 1.
Its best way to draw and remember iron carbon equilibrium diagram in heat treatment chapter. Iron carbon phase diagram in their simplest form, steels are alloys of iron fe and carbon c. The fec phase diagram is a fairly complex one, but we will only consider the steel part of the diagram, up to around 7% carbon. Pure iron at room temperature consists of grains of ferrite.
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