Ferrous Production

8/8/2019 Ferrous Production

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FERROUS PRODUCTION-II

PREPARED BY:MR.TAYYAB TARIQ

(2008-MET-04)

DEPARTMENT OF METALLURGICAL AND MATERIALS ENGINEERING

UET,LAHORE.


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QUESTIONS /ANSWERS

Q#1-What is a steel and how chemical composition of steel divides steel?

Ans: Steel is essentially a malleable alloy of iron and one or more of other elements like carbon,

chromium, nickel, vanadium, tungsten or almost any active element ( other than gas).

The chemical composition of steels broadly divides them into two major groups

1. Plain carbon steels

2. Alloy steels

The plain carbon steels are essentially alloy of iron and carbon only whereas, if one or more of elements

other than carbon are added to steel in significant amounts to ensure specific properties such as better

strength, ductility, electrical and magnetic properties, corrosion resistance and so on it is known as alloy

steel. These specially added elements are known as alloying additions in steels.

Q#2- what are the impurities in steel?

Ans: Steels may contain many other elements such as Al, Si, Mn, S, P, O etc. which are not added

specially for any specific purpose but are always present because of their association in the process of

iron and steel making and cannot be totally eliminated during the known process of iron and steel making.

These are known as impurities in steel. Every attempt is made to minimize them during the process of

steel making. For cheaper variety of steels their contents are at high level.

Q#3- How plain carbon steels are classified?

Ans: Plain carbon steels are broadly subdivided into four major types based on their carbon contents.This division is definitely useful.

Soft or low carbon steels up to 0.15%C

Mild steels in the range 0.15-0.35%C

Medium carbon steels in the range 0.35-0.65%C

High carbon steels in the range 0.65-1.75%C

Q#4- How alloy steels are classified?

Ans: The alloy steels are broadly sub-divided into three groups on the basis of the total alloying elementspresent.

Low alloy steels up to 5% total alloying contents

Medium alloy steels 5-10% total alloying contents

High alloy steels above 10% total alloying contents


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Q#5- Write down the applications of various steels.

Ans: Steels are very versatile in terms of their engineering properties. With appropriate thermo-

mechanical treatments properties of steels can be altered significantly to obtain variety of combinations of

mechanical, electrical and chemical properties. Very broadly in steels, hardness and strength increases

with carbon contents as well as alloying contents

Steels ApplicationsMild steels ConstructionalHigh carbon steels Cutting tools because of better hardnessLow carbon steels For the production of thin sheets, flats because of

better malleability

Q#6- What are the impurities in pig iron and in sponge iron?

Ans:In liquid state pig iron may contain inevitably several impurities like C, Si, P, Mn, S etc.

In solid state the sponge iron may contain the gangue oxides of the iron ore like Al 2O3, SiO2, CaO, MgOetc as inevitably impurities.

Q#7- What are the steps of steel making?

Ans:Steel is produced from iron ores in minimum two stages

Production of iron from iron ores by smelting and reduction

Refining of molten iron

Q#8- What are the processes steps of steel making?

Ans:The overall process includes

1. Charge calculations

2. Melting

3. Refining

4. Finishing

Q#9- What are the products of steel plants?

Ans:The products of steel plants are in the form of structural shapes such as I-sections, channels,

angles, plates, rails, sheets, axles and wheels for railways, merchant products like rounds, hexagons,

squares, strips etc.


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Q#10- What are the raw materials for steel making?

Ans: The chief raw materials for steel making are as follows

Sources of metallic iron

Oxidizing agents

Fluxes Sources of heat

Deoxidizers and alloying additions

Furnace refractories

Q#11- What is meant by acid and basic iron?

Ans: If the iron contains less than 0.05% phosphorus then it is called acid iron or hematite or Swedish

iron. For this iron acid steel making process is adopted. If the iron contains more than 0.05% phosphorus

then it is called basic iron and basic steel making process is needed to refine this iron. A special category

of basic iron that contains more than 1.5% phosphorus is known as Thomas iron and special basic steel

making process have been developed to refine this iron.

Q#12- What are the sources of metallic iron for steel making?

Hot metal (pig iron)

Sponge iron

Mill scale (iron ore/oxides of iron)

Steel scrap

Q#13- Write down the processes name of steel making?

Ans:

Steel making process NameConventional processes Bessemer, open hearth, electric arc steel

making.

Oxygen steel making processes LD, Kaldo, Rotor

Q#14- What are the oxidizing agents for steel making?

Ans:The oxidizing agents used for steel making are iron oxide, air and oxygen gas. Iron oxide is used in

the form of lumpy hematite ore and mill scale. Mill scale is the oxide of iron produced during hot

fabrication of steel and is readily available in an integrated steel plant.


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Q#15- What is the purpose of flux in iron and steel making?

Ans: A flux is a substance added during smelting and refining

To bring down the softening point of the gangue materials Reduce the viscosity of slag (increase the fluidity)

To decrease the activity of some components to make it stable in the slag phase

Lime/limestone is generally added during steel making to make the slag basic enough to retain

phosphorus and sulphur. Fluorspar and bauxite are added to decrease the viscosity of refining slags.

Q#16- What are the sources of heat in steel making?

Ans:As the processes like Bessemer and the BOF s are autogeneous since enough heat is generated

during refining by the exothermic oxidation of impurities. These processes need hot metal preferably of asuitable composition, as a charge to run the process. The amount of heat generated is always more than

necessary so that scrap and iron ore is required to keep the bath temperature within required limits.

The sources of heat are

Chemical:

Solid .. Pulverized fuel

Liquid oils, tar, etc

Gas. Producer, water, coke oven, natural and blast furnace gasses

Electrical:

Induction heating

Resistance heating

Arc heating

Q#17- What is sponge iron?

Ans:Sponge iron is a product obtained from direct reduction of iron ore. Direct reduction is carried out in

solid state and no fusion takes place. The oxygen in the iron ore is removed leaving void space and the

whole mass becomes porous and spongy. Hence it is referred to as sponge iron. It is also known as DRI

(direct reduced iron)

There are two processes for manufacture of sponge iron on the basis of reductant used. These are

Coal based sponge iron using coal as reductant

Gas-based sponge iron using natural gas as reductant

As a gangue materials present in the ore remains in the sponge, the volume of slag is usually larger when

a part of scrap is substituted by sponge iron.


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Q#18-Differentiate between electric arc furnace and induction furnace.

Ans:

Q#19- What are the major parts of Electric Arc Furnace?

Ans:The Electric Arc furnace has the three major parts

Hearth

Shell walls

Roof

Q#20- What are the refractroies used in the Hearth, shell walls and Roof?

Ans: The hearth is lined with the dolomite refractory. The steps are

First the fireclay bricks are provided against the steel shell of electric arc furnace for thermal

insulation

Dolomite bricks are introduced and made the stadium type construction

Finally the dolomite powder rammed on it

The shell is lined with magnesite-carbon bricks

The roof is lined with high alumina (fireclay) and silica bricks.

Q#21- What is the importance of carbon boil in Electric Arc Furnace?

Ans: When all the metallic charge is melted down then a basic slag is formed on the surface of molten

metal. The slag contains various oxides like FeO, CaO, SiO 2, MnO, Al2O3 etc. The refining takes place

under the influence of this basic oxidizing slag. Fluorspar (CaF2) is added to maintain adequate fluidity in

the slag. Silicon is oxidized to silica which passes into the slag. Evolution of CO gas stirs the bath and the

phenomenon is known as carbon boil. Dephosphorization is favoured by a basic oxidizing slag. Fresh

lime and iron ore are charged to continue the refining reactions. As the carbon-oxygen reaction rate picks

up the intensity of the carbon boil also increases. The slag may froth. So the carbon boil in the electric arc

furnace refines the molten metal.

Electric arc furnace Induction furnace

It is a steel making unit It is steel melting unit

Graphite electrodes are used for heating charge Induction coil is used


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Q#22- Explain the phenomenon of diffusion deoxidation.

Ans: Those grades of steels which have a more sulphur specification a second reducing slag is usually

made after the first oxidizing slag. In order to form the reducing slag, the flux materials usually consist of

burnt lime, sand and fluorspar and pulverized coke is added to this slag. Under the influence of the arc

the following reaction takes place

CaO + 3C CaC2 + CO

A typical carbide slag is gray in colour and it disintegrates into powder on cooling. The formation of the

carbide in the slag may be verified by quenching a slag sample in water. The presence of carbide may be

detected by the typical smell of acetylene. The carbide helps to maintain a low oxygen potential in the

slag by a process known as diffusion deoxidation. It is well known that the iron oxide partition coefficient

kFeO = Fe/FeO is a constant at constant temperature. CaC2 reacts with FeO in the slag according to the

reaction

CaC2 + 2FeO CaO + Fe + 2CO

In diffusion deoxidation the product is CO gas which escapes from the system. The reducing slag favoursdesulphurization according to the reaction

CaO + FeS CaS + FeO

Ferrous Production

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