Iron carbonates

Carbon dioxide (CO2) is a very common contaminant in hydrocarbon fluids, especially in gases and gas condensate, and is a source of corrosion problems. CO2 in the gas phase dissolves in any water present to form carbonic acid (H2CO3) which is highly corrosive. Its reaction with iron creates iron carbonate (FeCOg) ... 

The corrosion rate of steel in carbonic acid is faster than in hydrochloric acid Correlations are available to predict the rate of steel corrosion for different partial pressures of CO2 and different temperatures. At high temperatures the iron carbonate forms a film of protective scale on the steel s surface, but this is easily washed away at lower temperatures (again a corrosion nomogram is available to predict the impact of the scale on the corrosion rate at various CO2 partial pressures and temperatures). 

Mittemeijer E J, Cheng L, der Schaaf P J V, Brakman C M and Korevaar B M 1988 Analysis of nonisothermal transformation kinetics tempering of iron-carbon and iron-nitrogen martensites Metall. Trans. A 19 925... 

Iron carbide process Iron-carbon alloys Iron castings... 

Fig. 1. Iron—carbon phase diagram, where a is the body-centered cubic (bcc) a-iron, y is the face-centered cubic y-iron, and Fe C is iron carbide(3 l)...

Titanium Iron Carbon Other white oxides... 

It was not until the eighteenth century that carbon was recognized as a chemical element, and it is quite certain that no early metallurgist was aware of the basis of the unique properties of steel as compared to those of wrought iron. Carbon can be alloyed with iron in a number of ways to make steel, and all methods described herein have been used at various times in many locaUties for perhaps 3000 or more years. 

The ash content is 0.2—0.5% by weight for temperate woods and 0.5—2.0% by weight for tropical woods. The principal elemental components of wood ash are calcium and potassium with lesser amounts of magnesium, sodium, manganese, and iron. Carbonate, phosphate, sUicate, oxalate, and sulfate are likely anions. Some woods, especiaUy from the tropics, contain significant amounts of sUica. 

The iron—carbon system contains the orthorhombic iron carbide (3 1) [12011 -67-5] which melts congmendy and represents the cementite in... 

Listed metallic materials Ductile iron, malleable iron. Carbon steel, ASTM A36, ASTM A283 1. No additional requirements. 1. Shall not be used. 

The iron-carbon solid alloy which results from the solidification of non blastfurnace metal is saturated with carbon at the metal-slag temperature of about 2000 K, which is subsequendy refined by the oxidation of carbon to produce steel containing less than 1 wt% carbon, die level depending on the application. The first solid phases to separate from liquid steel at the eutectic temperature, 1408 K, are the (f.c.c) y-phase Austenite together with cementite, Fe3C, which has an orthorhombic sttiicture, and not die dieniiodynamically stable carbon phase which is to be expected from die equilibrium diagram. Cementite is thermodynamically unstable with respect to decomposition to h on and carbon from room temperature up to 1130 K... 

Figure 6.3 The iron-carbon phase diagram showing the alternative production of iron and cementite from the liquid alloy, which occurs in practice, to the equilibrium production of graphite...

Figure 6.4 The time-temperature-transformation diagram of the iron-carbon system, beginning at the composition of austenite...

In order to answer these questions as directly as possible we begin by looking at diffusive and displacive transformations in pure iron (once we understand how pure iron transforms we will have no problem in generalising to iron-carbon alloys). Now, as we saw in Chapter 2, iron has different crystal structures at different temperatures. Below 914°C the stable structure is b.c.c., but above 914°C it is f.c.c. If f.c.c. iron is cooled below 914°C the structure becomes thermodynamically unstable, and it tries to change back to b.c.c. This f.c.c. b.c.c. transformation usually takes place by a diffusive mechanism. But in exceptional conditions it can occur by a displacive mechanism instead. To understand how iron can transform displacively we must first look at the details of how it transforms by diffusion. 

Fig. 11.1. The left-hand part of the iron-carbon phase diagram. There ore five phases in the Fe-FejC system L, 5, y, or and Fe3C (see Table 1 1.1).

Figure A1.37 shows the iron-carbon phase diagram up to 6.7 wt% carbon (to the first intermetallic compound, FejC). Of all the phase diagrams you, as an engineer, will encounter, this is the most important. So much so that you simply have to learn the names of the phases, and the approximate regimes of composition and temperature they occupy. The phases are ...

The iron-carbon system has a eutectic find it and mark it on the diagram (Fig. A1.37). At the eutectic point the phase reaction, on cooling, is... 

Ammonia, Anhydrous Cast Iron Cast Iron Carbon Steel Carbon Steel Mechanical Mall. Iron NOTE ... 

Ethylene Ethylene Dichloride Cast Steel Cast Iron Carbon Steel Cast Iron Carbon Steel Steel Carbon Steel K Monel Mechanical Mechanical Cast Iron Mall. Iron K Monel ... 

Styrene Cast Iron Cast Iron Carbon Steel 13% Chrome Steel Ring Packing Cast Iron Mall. Iron... 

The polymorphism of certain metals, iron the most important, was after centuries of study perceived to be the key to the hardening of steel. In the process of studying iron polymorphism, several decades were devoted to a red herring, as it proved this was the P-iron controversy. P-iron was for a long time regarded as a phase distinct from at-iron (Smith 1965) but eventually found to be merely the ferromagnetic form of ot-iron thus the supposed transition from P to a-iron was simply the Curie temperature, p-iron has disappeared from the iron-carbon phase diagram and all transformations are between a and y. 

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