1. Metals-Ferrous and Non Ferrous By Engr. Prof. Dr. Attaullah Shah.

Metals-Ferrous and Non Ferrous Metals-Ferrous and Non Ferrous By

Engr. Prof. Dr. Attaullah Shah

Ferrous Metals. Ferrous is an adjective used to indicate the presence of iron.

The word is derived from the Latin word ferrum "iron").

Ferrous metals include steel and pig iron (with a carbon content of a few percent) and alloys of iron with other metals (such as stainless steel).

The term non-ferrous is used to indicate metals other than iron and alloys that do not contain an appreciable amount of iron

All forms of iron and steel / manufactured to meet wide variety of specification

Chemical composition & internal structure is highly controlled during manufacturing.

Good strength and hard. Fabricated in shops to desired size & shape

Good quality control during manufacturing

Brief History: Iron age (12th century BC) (mostly wrought iron) – weapons made

with inefficient smelting methods. The best weapons? When iron combined with carbon!

Became more common after more efficient production methods were devised in the 17th century.

With invention of the Bessemer process in the mid-19th century, steel became a relatively inexpensive mass-produced good

IRON Basic constituent of steel. Most abundant metallic in the earth’s crust after aluminum Found in the form of ores as oxides, carbonates, silicates

& sulfides Produced in blast furnaces. It can be produced into 3 commercial

forms that is: a) wrought iron b) steel c) cast iron

Increase in the amount of carbon decreases the melting point of the metal.

Carbon exerts the most significant effects on the microstructure and properties of iron products.

Iron Ores Iron ores are rocks and minerals from which

metallic iron can be economically extracted. The ores are usually rich in iron oxides and

vary in color from dark grey, bright yellow, deep purple, to rusty red.

The iron itself is usually found in the form of magnetite (Fe3O4), hematite (Fe2O3), goethite (FeO(OH)), limonite (FeO(OH).n(H2O)) or siderite (FeCO3).

Hematite is also known as "natural ore", a name which refers to the early years of mining, when certain hematite ores containing up to 66% iron could be fed directly into iron-making blast furnaces.

Iron ore is the raw material used to make pig iron, which is one of the main raw materials to make steel.

98% of the mined iron ore is used to make steel. Indeed, it has been argued that iron ore is "more integral to the global economy than any other commodity, except perhaps oil.

Pig Iron Pig iron is the intermediate product of smelting iron ore with a high-carbon

fuel such as coke, usually with limestone as a flux. Charcoal and anthracite have also been used as fuel.

Pig iron has a very high carbon content, typically 3.5–4.5%, which makes it

very brittle and not useful directly as a material except for limited applications.

The Chinese were making pig iron by the later Zhou Dynasty (1122–256 BC).

An ingot is a material, usually metal,

that is cast into a shape suitable for further

processing.

WROUGHT IRON

Manufactured by melting & refining iron to a high degree of purity.

Then, molten metal is poured into a ladle and mixed with hot slag.

The fluxing action of the slag causes a spongy mass to form which is processed by rolling & pressing.

It is only iron-bearing material containing slag.

It’s a low carbon steel (less than 0.1% carbon by weight) containing a small amount of slag, usually less than 3%.

It contains small amount of manganese (less than 0.1%) and silicon (0.2%).

It’s ductility is lower than steel.

It’s tensile strength is lower.

It can be molded easily and has good resistance to corrosion.

It is used to make pipes, corrugated sheets, grills, bars, chains and other products.

It can be cold worked, forged and welded like steel.

Forging is working a metal to predetermined shape by one or more processes such as hammering, pressing and rolling at a temperature above the re-crystallization temperature.

Cold working is the process of working at a temperature that doesn’t alter the structural changes caused by the work or that is below the re-crystallization temperature.

Wrought iron is used extensively where corrosion resistance is needed.

Wrought Iron Gate & Wrought Iron Fence

Wrought Iron Rack

CAST IRON Manufactured by reheating pig iron (in a cupola) and

blending it with other material of known composition.

Alternate layers of pig iron (with or without scrap steel) and

coke are charged into furnace.

Limestone is added to flux the ash from the coke.

Heat necessary for the smelting is supplied by the combustion of coke and air supplied by the blast.

Cupola function to purify iron and produce a more uniform product.

When sufficient metal is accumulated at the bottom of the furnace, it is tapped.

Composed primarily of iron, carbon and silicon Shaped by being cast in a mold

It has the greatest amount of carbon

Basically, the amount and form of carbon could affect the strength, hardness, brittleness and stiffness of cast iron.

Adding carbon to iron increases its hardness and strength but lowers the ductility.

Cast iron has high compressive strength but its tensile strength is low.

There are 2 types of cast iron that is: a) Gray Cast Iron b) White Cast Iron

Cast Iron Teapot

Cast Iron Pots

Cast Iron Bench

GRAY CAST IRON “Gray Cast Iron” also known as ordinary ast iron owing to

the color of fracture.

It contains free carbon (graphite flakes) that makes the metal weak and soft.

Contains high carbon content and large numbers of graphite flakes.

The flakes gives a gray appearance to a fractured surface

most widely used cast iron

Have poor ductility

Advantages of cast iron are as follows:a) Cheap b) Low melting pointc) Fluid – easy to cast, especially advantageous into large complex shapes.

d) Excellent bearing propertiese) Excellent damping properties (ability to absorb noise and vibration)

g) Can be heat threatenedh) Can be alloyed

White Cast Iron “White Cast Iron” is called in such name due to the fracture

surface that has a silvery white metallic color.

Carbon is combined chemically with iron in the form of cementite that makes this metal strong, hard and brittle.

harder and more resistant to wear from abrasion compared to gray iron.

Excellent wear resistance

High compressive stress

White Cast Iron Daybed

Steel Products

Steel – alloy consisting mostly of iron with a little carbon (0.2% - 2.04% by weight)

Cast iron = carbon content between 2.1% - 4.0% Iron = iron-carbon alloy with less than 0.005% carbon. Wrought iron – contains 1 – 3% by weight of slag in

the form of particles elongated in one direction – more rust resistant than steel and welds better

Steel Steel is an alloy that consists mostly of iron and has a carbon

content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten.

Steel with increased carbon content can be made harder and stronger than iron, but such steel is also less ductile than iron.

Steel is an alloy of iron and carbon. Pure iron’s strength remarkably increases when alloyed with carbon. The tensile strength increases with increasing carbon content but the ductility reduces. Steel having its properties because of the presence of carbon alone is called “Plain carbon steel”

Types of Plain Carbon steel Low carbon steel or mild steel:

The carbon content does not increases 0.25% Soft and ductile mostly used for construction purpose Uses ► Sheets, rods, wires, pipes, hammers, chains, shafts

et Medium-carbon steel :

The carbon content is 0.25 to 0.5 % Stronger than the mild steel slightly less ductile Uses ► Shafts, connecting rods and rails etc

High- carbon steel : Carbon content is above 0.5% Harder and stronger than mild steel and medium carbon steel Uses ► Keys, knifes, drills etc

The “abc’s” of Steel Making:

Raw Material:Carbon in the form of coke Iron ore (Fe2O3)

Limestone (CaCO3)

Air (lots of it!!)


CokeSolid residue product from the destructive

distillation of coal.About 80 to 95% C.Made by heating black coal in small ovens at

300 C for 24 hours in a coke plant.


The iron oreConsists of oxides in nature of iron and

oxygen Primarily magnetite (Fe3O4) or hematite (Fe2O3) The blast furnace basically separates the iron from

the oxygen in a reduction process

Mined primarily in Australia, Brazil and Canada.


The limestoneActs as a flux – converts impurities in the ore

into a fuse able slag


AirPreheated by fuel gas from the coke ovens to

about 1000 C.Delivered to the blast furnace at 6,000 m3/minPasses through furnace and burns the coke to

produce heat required and also generates the carbon monoxide.


Typical blast furnace:1.6 tons of iron ore0.18 tons of limestone0.6 tons of coke2 -3 tons of preheated air


Step 1 – The Blast Furnace:Stands 300 feet tallDesigned to run continuously for 4 -5 years before

being relined.Heat generated by burning coke in the preheated

air.Coke acts as reducing agent and changes to

carbon monoxide (the reducing agent) which removes the oxygen from the iron oxide.


Step 1 – The Blast Furnace:Four primary zones – the bottom zone (zone

4) reaches temperature of 1800 C – this is where iron is tapped off.

The top zone (zone 1) – where coke is burned and moisture driven off.

Zone 2 – slag coagulates and is removed.


Step 1 – The Blast Furnace: Two important chemical reactions:

Oxidation of the carbon from coke:

COOC 22 2

• Reduction of iron ore:

233 323 COFeCOOFe


Step 1 – The Blast Furnace:Products from the blast furnace:

Iron stored in steel shelled ladles Pig iron (brittle w/ 4% carbon)

Step 2: Manufacturing of Steel from Iron

Two common methods: Bessemer Furnace = Ingots = molten steel

poured into molds to create ingots which then go through forging press and roughing mill to create billet, bloom or slab, OR:

Continuous cast – continuous process to again create a billet, bloom, slab or “as cast semis”

Step 2 – The Bessemer converter:Used for REFINEMENT:

Takes pig iron with high C content and removes C. Removes impurities such as Si and Mn (via

oxides)

Much smaller furnace (vs. Blast furnace)Lowered cost of steel makingPoured into molds to form ingots

Replaced by basic oxygen process and electric arc furnace.

Steel Ingots

Heat treatment of Steel: To develop steel of particular structure or conditions best

suited for particular work. Basis of heat treatment:

At certain temperature called critical temperature, all alloys undergo reversible constituent change or inversions.

At heating the critical point differs from that in the cooling. Holding of material at elevated temperature may help it to

establish equilibrium of constituents. Slow cooling from an elevated temperature above critical point

permits natural constitutional change. Rapid cooling or quenching completely inhibits the natural

change and so tends to retain the particular structure.

Heat Treatment process of steel. Hardening process:

The degree of hardness of steel depends on proportions of these three forms: For steel containing less than 0.85% carbon, the hardening temperature must

be above 885C0 to ensure that ferrite is dissolved. In case of steel having more than 0.85% of Carbon, comentite itself is very hard

and needs temperature slightly above 730C0 For steel with very low carbon, to harden the steel.

Quenching: Rapid Cooling:

Tampering: When a piece of steel is hardened by heating above the critical range and then

quenched, it is too hard for practical purpose. Drawing:

At comparatively higher temperature and below critical temp, the steel is drawn and cooled softens steel.

Annealing: Heating above the critical Temp, and then very slowly cooling it making it

more ductile and tough. Normalizing:

Steel is heated above the critical Temp but cooled rapidly, which refines the grains of the steel.

• Steel is marketed in a wide variety of sizes and shapes, such as rods, pipes, railroad rails, tees, channels, and I-beams.

• These shapes are produced at steel mills by rolling and otherwise forming heated ingots to the required shape. The working of steel also improves the quality of the steel by refining its crystalline structure and making the metal tougher.

• The basic process of working steel is known as hot rolling. In hot rolling the cast ingot is first heated to bright-red heat in a furnace called a soaking pit and is then passed between a series of pairs of metal rollers that squeeze it to the desired size and shape. The distance between the rollers diminishes for each successive pair as the steel is elongated and reduced in thickness.

Steel Products:

•The first pair of rollers through which the ingot passes is commonly called the blooming mill, and the square billets of steel that the ingot produces are known as blooms. From the blooming mill, the steel is passed on to roughing mills and finally to finishing mills that reduce it to the correct cross section. The rollers of mills used to produce railroad rails and such structural shapes as I-beams, H-beams, and angles are grooved to give the required shape.

•Modern manufacturing requires a large amount of thin sheet steel. Continuous mills roll steel strips and sheets in widths of up to 2.4 m (8 ft). Such mills process thin sheet steel so rapidly, before it cools and becomes unworkable. A slab of hot steel over 11 cm (about 4.5 in) thick is fed through a series of rollers which reduce it progressively in thickness to 0.127 cm (0.05 inc) and increase its length from 4 m (13 ft) to 370 m (1210 ft).

Continuous mills are equipped with a number of accessory devices including edging rollers, de-scaling devices, and devices for coiling the sheet automatically when it reaches the end of the mill.

The edging rollers are sets of vertical rolls set opposite each other at either side of the sheet to ensure that the width of the sheet is maintained. De-scaling apparatus removes the scale that forms on the surface of the sheet by knocking it off mechanically, loosening it by means of an air blast, or bending the sheet sharply at some point in its travel. The completed coils of sheet are dropped on a conveyor and carried away to be annealed and cut into individual sheets.

A more efficient way to produce thin sheet steel is to feed thinner slabs through the rollers. Using conventional casting methods, ingots must still be passed through a blooming mill in order to produce slabs thin enough to enter a continuous mill.

By devising a continuous casting system that produces an endless steel slab less than 5 cm (2 in) thick, German engineers have eliminated any need for blooming and roughing mills. In 1989, a steel mill in Indiana became the first outside Europe to adopt this new system.

Pipe Cheaper grades of pipe are shaped by bending a flat strip, or skelp, of hot steel into cylindrical form and welding the edges to complete the pipe. For the smaller sizes of pipe, the edges of the skelp are usually overlapped and passed between a pair of rollers curved to correspond with the outside diameter of the pipe. The pressure on the rollers is great enough to weld the edges together. Seamless pipe or tubing is made from solid rods by passing them between a pair of inclined rollers that have a pointed metal bar, or mandrel, set between them in such a way that it pierces the rods and forms the inside diameter of the pipe at the same time that the rollers are forming the outside diameter.

Tin Plate By far the most important coated product of the steel mill is tin plate for the manufacture of containers. The “tin” can is actually more than 99 percent steel. In some mills steel sheets that have been hot-rolled and then cold-rolled are coated by passing them through a bath of molten tin. The most common method of coating is by the electrolytic process. Sheet steel is slowly unrolled from its coil and passed through a chemical solution. Meanwhile, a current of electricity is passing through a piece of pure tin into the same solution, causing the tin to dissolve slowly and to be deposited on the steel. In electrolytic processing, less than half a kilogram of tin will coat more than 18.6 sq m (more than 200 sq ft) of steel.

For the product known as thin tin, sheet and strip are given a second cold rolling before being coated with tin, a treatment that makes the steel plate extra tough as well as extra thin. Cans made of thin tin are about as strong as ordinary tin cans, yet they contain less steel, with a resultant saving in weight and cost. Lightweight packaging containers are also being made of tin-plated steel foil that has been laminated to paper or cardboard.

Other processes of steel fabrication include forging, founding, and drawing the steel through dies.

Figure 9-12: processing of refined steel into products.

F 9-13 – The whole spectrum of steel products!

Classifications of Steel Steels are grouped into five main classifications.

Carbon Steels More than 90 percent of all steels are carbon steels. They contain varying amounts of carbon and not more than 1.65 percent manganese, 0.60 percent silicon, and 0.60 percent copper. Machines, automobile bodies, most structural steel for buildings, ship hulls, bedsprings, and bobby pins are among the products made of carbon steels.

Alloy Steels These steels have a specified composition, containing certain percentages of vanadium, molybdenum, or other elements, as well as larger amounts of manganese, silicon, and copper than do the regular carbon steels. Automobile gears and axles, roller skates, and carving knives are some of the many things that are made of alloy steels.

High-Strength Low-Alloy Steels Called HSLA steels, they are the newest of the five chief families of steels. They cost less than the regular alloy steels because they contain only small amounts of the expensive alloying elements. They have been specially processed, however, to have much more strength than carbon steels of the same weight. For example, freight cars made of HSLA steels can carry larger loads because their walls are thinner than would be necessary with carbon steel of equal strength; also, because an HSLA freight car is lighter in weight than the ordinary car, it is less of a load for the locomotive to pull. Numerous buildings are now being constructed with frameworks of HSLA steels. Girders can be made thinner without sacrificing their strength, and additional space is left for offices and apartments.

Stainless Steels Stainless steels contain chromium, nickel, and other alloying elements that keep them bright and rust resistant in spite of moisture or the action of corrosive acids and gases. Some stainless steels are very hard; some have unusual strength and will retain that strength for long periods at extremely high and low temperatures. Because of their shining surfaces architects often use them for decorative purposes. Stainless steels are used for the pipes and tanks of petroleum refineries and chemical plants, for jet planes, and for space capsules. Surgical instruments and equipment are made from these steels, and they are also used to patch or replace broken bones because the steels can withstand the action of body fluids. In kitchens and in plants where food is prepared, handling equipment is often made of stainless steel because it does not taint the food and can be easily cleaned.

Tool Steels These steels are fabricated into many types of tools or into the cutting and shaping parts of power-driven machinery for various manufacturing operations. They contain tungsten, molybdenum, and other alloying elements that give them extra strength, hardness, and resistance to wear.

Alloys of Steel:

Most of the steel used in the buildings Engineering is purposefully alloyed with one or more elements to modify its properties.

By the terms alloying, it is understood that some other element other than carbon is added to iron. The ordinary steel containing carbon is termed as alloy of Carbon and Iron.

Usually metals like nickel, chromium, manganese, vanadium, are added to steel for making alloys.

Nickel steel: The amount of nickel varies from 1 to 4.5 % and Carbons

varies from 0.1% to 0.4%.

Nickel improves the tensile strength and reduces brittleness and imparts hardness and ductility to steel.

Rust formation is resisted with higher content of nickel. Nickel steel having 3 to 4.5% nickel is frequently used for

long span bridge construction, shafting, rifle barrels, bearings, castings.

Steel alloys having 36% nickel and 0.5% carbon is called

Invar which is used for measuring tapes and pendulum of clocks, where change in dimensions is minimum.

Steel alloy with 46% nickel and very little carbon is known

as Platinite, which has same thermal coefficient as glass.

Chrome Steel: 0.5% to 2% Chromium, 0.2% to 1.5% carbon are

used for parts where great hardness, high strength and fair degree of toughness is required.

Steel with 0.5% chromium and 0.6% to 0.9% carbon are generally used for manufacturing of chisels, drills, razors and saw blades.

Tungsten Steel: Oldest of steel alloys, used for permanent

magnets.With 3% Tungsten, it becomes suitable for lath

tools. With about 1% carbon, it produces good steel for

use in springs. Tungsten forms essential part of high speed tools.

Molybdenum steel: MB used in small quantity 0.3% in combination with

Chromium and Manganese, makes high tensile steel suitable for automobile parts.

Silicon steel: Used for Transformer cores and dynamos.

High Speed Steel: It may run at red heat without losing its hardness 15-20%Tungsten, 3-5% Cr, 0.5-2% Vanadium,0.6-

0.8% Carbon with silicon, sulphur, and phosphorous. Used in parts which withstands high heat and wear

as required for exhaust valves.

1. Metals-Ferrous and Non Ferrous By Engr. Prof. Dr. Attaullah Shah.

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Transcript of 1. Metals-Ferrous and Non Ferrous By Engr. Prof. Dr. Attaullah Shah.