Metallurgy Interview Questions and Answers

1 :: What is Iron Ferrite, what is it used for, and where is it found?

Well, a few definitions match your question. First, "ferrite" is the name metallurgists give to the body-centered-cubic phase of iron and its alloys. The 'body-centered-cubic' phrase refers to the way the atoms are arranged in the lattice, to distinguish it from "austenite" which is the face-centered-cubic arrangement. Generally, ferrite is a pretty pure iron- the core iron used in electrical transformers, for example, is ferritic-but there are also some stainless steels that are ferritic. These iron-chromium alloys would have 12 to 18% chromium in them, and used for expensive exhaust systems in automobiles, for example. Iron is not found in nature, as are, say, chunks of copper, but must be refined by a blast furnace or other smelting technique.

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2 :: Which metals do not react with lithium Bromide ad why?

For solving the problem you should have the electro negativity of Li and B and calculate the difference between the two quantities, and for the next step for any metal, you should calculate the difference between its electro negativity and bromine's. Then if the result was higher than first value, one may say that this metal will react with the material otherwise it will not. However, you should have this in mind that the given procedure is true only in standard condition. However, in practice, many other factors will affect. Now I give you the calculations:

Electro negativity for Li = 1

Electro negativity for Br = 1.14

1.14 - 1 = .14

Now we consider a metal, let say Mg. Its Electro negativity is 1.2, so the difference is 1.2-1.14= .06, which is less than .14, so it will not react in standard conditions. Let say Fe, its Electro negativity is 1.8, the difference is 1.8 - 1.14 = .64 which is greater than .14, and it may react and form FeBr2.

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3 :: What is widman statten structure?

Primary Widman statten ferrite either directly grows from the austenite grain surfaces, whereas secondary Widmanst¨atten ferrite develops from any allotriomorphic ferrite that may be present in the microstructure.

Widmanst¨atten ferrite can form at temperatures close to the Ae3 temperature and hence can occur at very low driving forces; the under cooling needed amounts to a free energy change of only 50 J mol. This is much less than required to sustain diffusion less transformation. Because Widmanst¨atten ferrite forms at low under cooling (and above the T0 temperatures),

It is thermodynamically required that the carbon is redistributed during growth.

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4 :: Why duplex or super duplex stainless steels are welded with low heat input type electrode?

Duplex and super duplex stainless steel; but in general it's true for welding of all types of austenitic stainless steels -and you must know that we can assume duplex s. steels as austenitic s. steels cause the amount of austenite is 50% of the matrix equal to ferrite- to use a low heat input process. In addition, the reason is general in austenitic s. steels as well. That is because the weld decays. Austenitic s. steels containing about 0.1% carbon or more are often susceptible to inter granular corrosion in the weld HAZ, which is known as "Weld Decay". In these types of S .Steels the higher the heat input, the more severe the weld decay. However, here is a fact that all duplex stainless steels have a carbon content of less than 0.1%. Therefore, the severity of weld decay may be lighter, but still exists, and sensitization takes place more rapidly as the carbon content is increased.

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5 :: For what reason would an aluminum casting, when applied with a powder coated paint finish, cause a poor finish to the paintwork.

Porosity is related to air or gas entrapment during the melting or casting process. When the metal cools and solidifies a small hole is left in the casting. Good out gassings of the melt and good foundry practice can eliminate much of this. Porosity can also be caused by lack of flow into the mold, which is a function of the alloy, superheat (temperature above the melting point), complexity of the mold and a few other factors. Another problem might be entrapment of impurities or slag in the melt. This results in a "dirty" casting. Some aluminum alloys can be particularly prone to these problems. Porosity can be eliminated by careful slag control in the melt, filters, and pour techniques.

I am not sure if the problems are particularly Indian versus British but the people who are doing the casting. I have seen excellent Indian, British, U.S., and Mexican castings as well as bad ones for these nations.

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