Engineering Steels And Alloys

Phase DiagramPhase Diagram

The diagram which indicates the phases existing in the system at any temp. and composition known as equilibrium or phase diagram.

The co-ordinate system of binary phase diagrams uses temp. as the ordinate (Y-axis) and the wt. % of second element (X-axis).

DefinitionsDefinitions

System:A part of the universe under study is called as system.

Phase: Phase is homogeneous, physically distinct and mechanically separable part of the system under study.

Variables:A particular phase exists under various conditions of temp., Pressure and concentration. These parameters are known as variables of the phase.

Component:The element present in the system is called as component.

Alloys:

Alloy is a mixture of two or more elements having metallic properties.

The element which is present in the large amount is called as the base metal or parent metal or solvent andthe other element is called as alloying elements or solute.

Solid SolutionSolid Solution

It is an alloy in which the atoms of solute are distributed in the solvent and has the same structure as that of the solvent.

Ex: Sugar and Water, Salt and Water, etc.

Solid Solutions are of two types-

i) Substitutional andii) Interstitial.

Substitutional Solid SolutionSubstitutional Solid Solution

Substitutional solid solution means the atoms of solute are distributed at the atomic sites of solvent.

Depending on the distribution of solute atoms in solvent, substitutional solid solutions are classified into two types-

1)Regular or Ordered, and2)Random or Disordered.

In regular solid solution, the substitution of solute atoms in solvent is by a definite order shown in fig.

In random solid solution, the substitution of solute atoms in solvent is random or no definite order shown in fig.

Ordered Substitutional solid solution alloys in general are hard and require more energy for plastic deformation than disordered substitutional solid solution alloys.

In general solid solutions are soft, ductile and malleable and therefore they can be easily cold rolled, pressed and worked.

Interstitial Solid SolutionInterstitial Solid Solution

In interstitial solid solutions, the atoms of solute In interstitial solid solutions, the atoms of solute occupy the interstitial sites of solvent.occupy the interstitial sites of solvent.

Intermediate PhaseIntermediate Phase

When an alloying element is added to a given metal in such an amount that the limit of solid solubility is exceeded, a second phase appears with the solid solution. This second phase may be another solid solution or an intermediate phase.

Some intermediate phases have a fixed composition and they are called intermetallic compounds.

Intermetallic compounds are hard & brittle and have high melting point.

Gibb’s Phase RuleGibb’s Phase Rule

The Gibb’s Phase rule states that under equilibrium condition, the following relation must be satisfied,

P+F = C+2

Where, P = No. of phases existing in the system under

consideration. F = Degree of freedom i.e. the no. of variables such

as temp., pressure or concentration that can be changed independently without changing the no. of phases existing in the system.

c = No. of components in the system. 2 = represents any two variables out of above

three i.e. temp., pressure and concentration.

Most of the studies are done at constant pressure,Therefore-

P + F= C + 1

TYPES OF COOLING CURVES

1) For Pure Metals1) For Pure Metals

Apply Phase Rule,

In region AB,P+F = C+11+F = 1+1

F = 1In region BC,

P+F = C+12+F = 1+1

F = 0In region CD,

P+F = C+11+F = 1+1

F = 1

2) For Binary Solid Solution Alloys2) For Binary Solid Solution Alloys

Apply Phase Rule,

In region AB,P+F = C+11+F = 2+1

F = 2In region BC,

P+F = C+12+F = 2+1

F = 1In region CD,

P+F = C+11+F = 2+1

F = 2

3) For Binary Eutectic Alloys3) For Binary Eutectic Alloys

Apply Phase Rule,

In region AB,P+F = C+11+F = 2+1

F = 2In region BC,

P+F = C+13+F = 2+1

F = 0In region CD,

P+F = C+12+F = 2+1

F = 1

4) For Off- Eutectic Binary Alloys4) For Off- Eutectic Binary Alloys

Apply Phase Rule,In region AB,

P+F = C+11+F = 2+1

F = 2In region BC,

P+F = C+12+F = 2+1

F = 1In region CD,

P+F = C+13+F = 2+1

F = 0In region DE,

P+F = C+12+F = 2+1

F = 1

Plotting of Equilibrium DiagramPlotting of Equilibrium Diagram

Generally equilibrium or phase diagrams are plotted by the method of Thermal Analysis using the data obtained from cooling curves.

The basic method of plotting the diagram by the use of cooling curves is explained below-

Let us consider a binary Cu-Ni system. Cu & Ni have 100% solubility in the liquid and solid state and they form a series of solid solutions.

Steps-Steps-

1. Prepare large no. of alloys of varying composition, with a variation of 10% Ni and mark them as below-

No. 1 & 11 are pure metals and No.2 to 10 are alloys.

2. Plotting cooling curves of the above materials. This is shown in fig. below-

%Cu 100 90 80 70 60 50 40 30 20 10 0

% Ni 0 10 20 30 40 50 60 70 80 90 100

Material No. 1 2 3 4 5 6 7 8 9 10 11

3. Note down the liquidus and solidus temperatures of these materials. Liquidus temperatures are marked as L1,L2,L3,L4,…..,L9,L10,L11 and solidus temperatures marked as S1,S2,S3,S4,…..,S9,S10,S11 resp.

Material No. 1 & 11 are pure metals, they solidify at constant temp. and hence their liquidus and solidus temperatures are same i.e. L1 = S1 and L11=S11 .

4. Transfer these temps. To temp. Vs composition graph as shown in fig. below, for materials 1 & 11i.e. for pure Cu & Ni we get only one pt. and for others we get two pts.

5. Draw smooth curves through the points L1 to L11

and S1 to S11 which represents liquidus and solidus of the diagram.

Above liquidus temp. all the materials are in the liquid state and below the solidus temp. they are in the solid state. Between the liquidus and solidus temps. The alloys are in the liquid plus solid state.

The resulting loop type of curve is called as the phase or equilibrium diagram.

At any temp. such as T, the avg. composition of the existing liquid is given by the pt. X and the avg. composition of the existing solid is given by the point Y, as shown in the above fig. The amounts of solid and liquid can be calculated by using lever arm principle or lever rule.

Lever RuleLever Rule

Amt. of liquid = Arm length FD Arm length CD

Amt. of Solid = Arm length CF Arm length CD

Amt. of liquid/Solid = Opposite Arm length Total Arm length

Various types of phase diagrams are obtained depending on the solubility of one metal into the another in liquid & solid states.

TYPES OF PHASE TYPES OF PHASE DIAGRAMSDIAGRAMS

• Isomorphous Systems• Eutectic Systems• Partial Eutectic Systems• Layer Type Systems

These diagrams are of loop type and are obtained for two metals having complete solubility in the liquid as well as solid state.

Ex: Cu-Ni, Au-Ag, Au-Cu, Mo-W, Mo-V, Mo-Ti, W- V, etc.

Isomorphous SystemsIsomorphous Systems

Amt. of liquid = Opposite Arm length Total Arm length

= Length 3N Length MN Amt. of Solid = Opposite Arm length Total Arm length

= Length 3M Length MN

These diagrams are obtained for two metals having complete solubility in the liquid state and complete insolubility in the solid state.

Ex: Pb-As, Bi-Cd, Th-Ti, etc.

Eutectic SystemsEutectic Systems

Partial Eutectic SystemsPartial Eutectic SystemsThese diagrams are obtained for two

metals having complete solubility in the liquid state and partial solubility in the solid state.

Ex: Ag-Cu, Pb-Sn, Sn-Bi, Pb-Sb,Cd-Zn, etc.

Layer Type SystemsLayer Type SystemsThese diagrams are obtained for two

metals having complete insolubility in the liquid as well as solid state.

Ex: Cu-Mo, Cu-W, Ag-W, Ag-Fe,etc.

Iron-Iron Carbide Iron-Iron Carbide Equilibrium Diagram Equilibrium Diagram

(Fe-Fe(Fe-Fe33C Diagram)C Diagram)

Phases Of Fe-FePhases Of Fe-Fe33C DiagramC Diagram

1. α(Ferrite):

Ferrite is an interstitial solid solution of carbon in low temp. B.C.C.α- iron. It is almost pure iron.

The solubility of carbon in α-iron at room temp. is 0.008% and increases with increasing temp. to about 0.025% at 7270C.

It is a relatively soft and ductile phase.

2. γ(Austenite):

Austenite is an interstitial solid solution of carbon in low temp. F.C.C.γ- iron.

It can dissolve up to 2.0% carbon at 11470C. The phase is stable only above 7270C.

It is a relatively soft, ductile, malleable and non-magnetic phase.

3. δ(δ-ferrite):

δ-ferrite is an interstitial solid solution of carbon in high temp. B.C.C.δ-iron.

It is similar to α-Ferrite except its occurrence at high temp.

4. Fe3C(Cementite):

It is an intermetallic compound of iron and carbon with a fixed carbon content 0f 6.67% by wt.

It is extremely hard and brittle phase.

Transformations of Fe-Fe3C Diagram

Peritectic TransformationPeritectic Transformation

In general Peritectic transformation is – S1 + L S2

Where, S1 and S2 are two different solids.

L = Liquid.

Peritectic Region of Fe-FePeritectic Region of Fe-Fe33C Diagram C Diagram

δ + L 14920C γ (of 0.1%C) (of 0.55%C) (of 0.18%C)

δ of 0.1%C combines with liquid of 0.55%C at 14920C and forms γ of 0.18%C. The amounts of δ and L can be found out by applying lever rule-

Amt. of δ = 0.55-0.18 0.55-0.1 = 82.2% Amt. of Liquid = 0.18 – 0.1 0.55-0.1 = 17.8%

For Hypo-peritectic Steels

δ + L 14920C γ + δ

For Hyper-peritectic Steels

δ + L 14920C γ + L

Eutectoid TransformationEutectoid TransformationIn general Eutectoid transformation is – S1 S2 + S3

Where, S1,S2 and S3 are different solids.

Eutectoid Region of Fe-FeEutectoid Region of Fe-Fe33C Diagram C Diagram

γ 7270C α + Fe3C

(of 0.8%C) (of 0.025%C) (of 6.67%C)

Austenite of 0.8%C decomposes at constant temp. of 7270C and forms a mixture of ferrite of 0.025%C and Cementite of 6.67%C.

This eutectiod mixture of ferrite and cementite is called as pearlite.

The amounts of ferrite and cementite can be found out by applying lever rule-

Amt. of Ferrite = 6.67 - 0.8 6.67-0.008 = 88.1%Amt. of Cementite = 0.8 – 0.008 6.67-0.008 = 11.9%

Eutectic TransformationEutectic TransformationIn general Eutectic transformation is – L S1 + S2

Where, S1 and S2 two different solids.

L = Liquid.

Eutectic Region of Fe-FeEutectic Region of Fe-Fe33C Diagram C Diagram

L 11470C γ + Fe3C (of 4.3%C) (of 2.0%C) (of 6.67%C)

Liquid of 4.3%C transforms at constant temp. of 11470C and gives an eutectic mixture of austenite of 2.0%C and Cementite of 6.67%C.

This eutectic mixture of austenite and cementite is called as ledeburite.

The amounts of ferrite and cementite can be found out by applying lever rule-

Amt. of Ferrite = 6.67 – 4.3 6.67-0. 8 = 40.4%Amt. of Cementite = 4.3 – 0.8 6.67-0.8 = 59.6%

Critical Temperatures of Fe-FeCritical Temperatures of Fe-Fe33C Diagram C Diagram Sr.No

Critical Points (Symbols)

Temp oC Significance during Heating

01 Ao

Curie temp. of cementite210 Cementite becomes

paramagnetic.

02 A1

Lower Critical temp.727 Pearlite starts transforming to

austenite.

03 A2

Curie temp. of ferrite768 Ferrite becomes paramagnetic.

04 A3

Upper Critical temp. for hypo eutectoid steels

727-910 Completion of ferrite to austenite transformation.

05 Acm

Upper Critical temp. for hyper eutectoid steels

727-1147 Completion of cementite to austenite transformation.

06 A4 1400-1492 Completion of austenite to δ-ferrite transformation

Microstructure of Slowly Cooled Steels

Microstructure of Hypo-Eutectoid SteelsMicrostructure of Hypo-Eutectoid Steels

Apply Lever Rule at Room Temp.Apply Lever Rule at Room Temp.

Amt. of α = 0.8 - 0.2 0.8-0.008 = 75%

Amt. of Pearlite = 0.2 – 0.008 0.8 - 0.008 = 25%

Variation of Ferrite & Pearlite with CarbonVariation of Ferrite & Pearlite with Carbon

Ferrite appears white and pearlite appears dark under microscope.

Microstructure of Hyper-Eutectoid SteelsMicrostructure of Hyper-Eutectoid Steels

Apply Lever Rule at 727Apply Lever Rule at 72700CC

Amt. of Fe3C = 1.2 - 0.8

6.67-0. 8 = 6.8%

Amt. of Pearlite = 6.67 – 1.2 6.67-0. 8 = 93.2%

Maxm amt. of = 2.0 – 0.8Fe3C in Steel 6.67-0.8

= 20.4% (at 11470C)

Variation of Ferrite & Pearlite with CarbonVariation of Ferrite & Pearlite with Carbon

Cementite appears white and pearlite appears dark under microscope.

Non-Equilibrium CoolingNon-Equilibrium Cooling

Factors of Non Equilibrium CoolingFactors of Non Equilibrium Cooling

Following factors govern the formation of Widmanstatten Pattern-

• Composition of Steel• Grain size of Austenite• Cooling Rate.

Property Variation with carbon in steelProperty Variation with carbon in steel

Classification and Applications of SteelsClassification and Applications of Steels

The various criteria for the basis of classification are as follows-

1)Amount of Carbon2)Amount of alloying element and carbon3)Amount of deoxidation4)Grain coarsening characteristics5)Method of manufacture6)Depth of hardening7)Form and use.

1. On the basis of amount of Carbon1. On the basis of amount of Carbon

Plain carbon steels are classified into three groups-

a)Low carbon steels (0.008 - 0.30%C)b)Medium carbon steels (0.30 - 0.60%C)c) High carbon steels (0.60 – 2.0%C)

Low Carbon SteelsLow Carbon Steels

They are soft, ductile, malleable, tough, machinable, weldable and non- hardenable by heat treatment.

They are good for cold working purpose.

Applications: They are used for Wires, nails, rivets, screws, panels,

welding rods, ship plates, boiler plates & tubes, fan blades, gears, valves, cam shafts, crank shafts, connecting rods, railway axles, fish plates, cross-heads, tubes for bi-cycles & automobiles and small forgings.

Medium Carbon SteelsMedium Carbon SteelsThese steels have intermediate properties to those

of low carbon and high carbon steels.

They are medium hard, not so ductile and malleable, medium tough, slightly difficult to machine, weld and harden. They are also called as Machinery Steels.

Applications: They are used for bolts, axles, lock washers, large

forging dies, springs, wires, wheel spokes, hammers, rods, turbine rotors, crank pins, cylinder liners, railway rails and railway tyres.

High Carbon SteelsHigh Carbon SteelsThey are hard, wear resistant, brittle, difficult to

machine, difficult to weld and can be hardened by heat treatment.

These steels can’t be cold worked and hence hot worked. They are also called as Tool Steels.

Applications: They are used for forging dies, punches, hammers,

springs, clips, clutch discs, car bumpers, chisels vice jaws, shear blades, drills, leaf springs, music wires, razor blades, knives, balls & races for ball bearings, mandrels, cutters, files, wire drawing dies, reamers and metal cutting saws.

2. On the basis of Alloying Elements2. On the basis of Alloying Elements

Alloying elements such as Ni, Cr, Mn, W, Mo, V, etc. are added to p-lain carbon steels in certain amounts to increase the desired properties. Such steels are classified on the basis of total alloy content in the following manner-

a)Low alloy steels (less than 10% alloying elements)

b)High alloy steels (more than 10% alloying elements)

Carbon Content Total content of alloying elements

Low (< 0.3%) Low (<10%)

Medium (0.3-0.6%) High (>10%)

High (0.6-2.0%)

3. On the basis of Deoxidation3. On the basis of Deoxidation

Depending on the deoxidation, steels are classified as –

a)Rimmed steels b)Killed steelsc) Semi-killed steels .

Rimmed SteelsRimmed Steels

A molten steel contains large amount of dissolved oxygen and other gases. The solubility of gases is more in the liquid than in the solid metal & hence the dissolved oxygen along with other gases tries to go out as CO during solidification. The thin solidified layer is called as rim (skin), therefore the steels are called as rimmed steels.

These steels are used for deep drawing and forming.

Killed SteelsKilled Steels

The dissolved oxygen from the melt is completely removed by the addition of strong deoxidizing agents like Al, Si or Mn.

These deoxidizers are added to the steels in furnace or in the ladder prior to pouring into the mould.

These steels are used for the components which have to be forged, carburized or heat treated.

Semi-Killed SteelsSemi-Killed Steels

In these steels part of the dissolved oxygen is removed by the addition of deoxidizers.

They show intermediate grain coarsening characteristics to those of rimmed and killed steels.

They are used for sheets, plates, structural shapes, etc.

4. On the basis of Grain Coarsening 4. On the basis of Grain Coarsening CharacteristicsCharacteristics

Depending on the grain coarsening characteristics steels are classified into two types-

a)Coarse Grained Steels b)Fine Grained Steels.

5. On the basis of Method of 5. On the basis of Method of ManufactureManufacture

According to the method of manufacture, the steels are classified as-

a)Basic Open Hearthb)Electric furnacec) Basic oxygen processd)Acid Open Hearthe)Acid Bessemer.

6. On the basis of Depth Of Hardening6. On the basis of Depth Of Hardening

The steels are classified on the basis of depth of hardening are as below-

a)Non- hardenable steels,b)Shallow hardening steels, andc) Deep hardening steels.

a) Non- hardenable steelsa) Non- hardenable steels

These steels contain less carbon and almost no alloying elements.

These steels are suitable for fabrication by cold working and welding.

They have applications similar to those of low carbon steels.

b) Shallow hardening steelsb) Shallow hardening steels

These steels are medium carbon with or without alloying elements, and are intermediate to those of non-hardening and deep hardening types.

These steels get hardened only at the surface and hence sometimes used for gears, camshafts and such other applications.

c) Deep hardening steelsc) Deep hardening steels

These steels contain more carbon and alloying elements.

They are used for where depth of hardening required is more or throughout hardening is necessary and have application similar to those of high carbon steels.

7. On the basis of Form and Use7. On the basis of Form and Use

Some of the steels are classified according to their use-

a)Boiler Steels:They are suitable for the construction of boilers. The steels are low carbon steels with less than 0.25% C.

b) Case Hardening Steels:They are suitable for case hardening purpose. For case carburizing & hardening, low carbon steels containing less than 0.20% C are used.

c) Corrosion and Heat Resistant Steels:They are alloy steels having high corrosion & oxidation resistance and used for corrosive & high temp. conditions.

Ex: Stainless steels & high chromium steels.

d) Deep Drawing Steels:They are suitable for deep drawing purposes due to their high formability. They are used for automobile bodies, stoves, refrigerators, etc. These steels contain carbon less than 0.10%.

e) Electrical Steels:These steels have good electric characteristics and are used for the manufacture of electrical equipments. They contain Si and the carbon is usually less than 0.05%.

f) Free Cutting (machining) Steels:These steels can be easily machined & are used for the manufacture of nuts, bolts, screws, etc. Elements like S, P, Se, Te, & Pb increase machinability and hence these steels contain more than one of the above elements.

g) Machinery Steels:They are used for the manufacture of automotive and machinery parts and the carbon content is between 0.3-0.55%.

h) Structural Steels:These steels are used in the construction of ships, cars, building, bridges, etc. & contain carbon from 0.15-0.3%.

i) Tool Steels:They are used as tools for machining or cutting of metals and contain carbon above 0.6%.

Specification Of Steels

Specification Of SteelsSpecification Of Steels

Steels are classified on the basis of certain criteria like the method of manufacture, chemical composition, heat treatment, mechanical properties, quality, etc.

Majority of the specifications are based on chemical composition.

Indian Standard Designation SystemIndian Standard Designation System

Indian standard code for designation of steel was adopted by the Indian Standards Institutes (ISI).

This standard is revised in two parts-Part -1

Designation of steel based on letter.Part –2

Designation of steel based on numerals.

Examples:Examples:

1) Fe 400Steel with minimum tensile strength of 400N/mm2.

2) Fe E 225Steel with minimum yield strength of 225N/mm2.

3) Fe 410KKilled steel with minimum tensile strength of 410N/mm2.

4) St 42Steel with minimum tensile strength of 42 Kg/mm2.

5) St E 200Steel with minimum yield strength of 200 Kg/mm2.

6) C 20Steel with avg. carbon of 0.2%.

7) C 40Steel with avg. carbon of 0.4%.

8) 25 C 5Steel with avg. carbon of 0.25% & Mn of 0.5%.

9) 80 T 11Plain carbon tool steel with avg. carbon of 0.8% & Mn of 1.1%.

10) 15 Ni 13 Cr 1 Mo 12 Steel with avg. composition as- C - 0.15 %

Ni – 1.3 % Cr – 1 % Mo – 0.12 %.

SolveSolve11) 35 S 1812) 35 Mn 1 S 1813) 20 Mn 214) 20 Mn Cr 115) 95 Cr 5 Mo 116) 35 Ni Cr 6017) 20 Ni 55 Cr 50 Mo 2018) 17 Mn 1 Cr 9519) T 75 W 18 Cr 4 V 120) T 105 Cr 1 Mn 60 21) T 85 W 6 Mo 5 Cr 4 V 222) T 35 Cr 5 Mo 1 V 3o

11) 35 S 18 Steel with avg. carbon of 0.35% and S of 0.18%.12) 35 Mn 1 S 18 Steels with avg. carbon of 0.35%, Mn of 1% and

Sulphur 0.18%.13) 20 Mn 2 Steels with avg. carbon of 0.2% and Mn 2%.14) 20 Mn Cr 1 Steels with avg. carbon of 0.2%, Mn of 1% and

Chromium 1%.15) 95 Cr 5 Mo 1 Steels with avg. carbon of 0.95%, Chromium 1% and

molybdenum 1%.

16) 35 Ni Cr 60 Steels with avg. carbon of 0.35%, Nickel 1% and chromium 0.6%.

17) 20 Ni 55 Cr 50 Mo 20 Steels with avg. carbon of 0.2%, Nickel 0.55%, chromium 0.5% and molybdenum 0.2%.

18) 17 Mn 1 Cr 95 Steels with avg. carbon of 0.17%, Mn 1% and chromium 0.95%.

19) T 75 W 18 Cr 4 V 1 Tool Steel with avg. composition of

C – 0.75 % W – 18% Cr – 4% V – 1%

20) T 105 Cr 1 Mn 60 Tool Steel with avg. composition of C – 1.05 % Cr – 1% Mn – 0.6 %21) T 85 W 6 Mo 5 Cr 4 V 2 Tool Steel with avg. composition of C – 0.85 % W – 6% Mo – 5% Cr – 4% V – 2 %22) T 35 Cr 5 Mo 1 V 3o Tool Steel with avg. composition of C – 0.35 % Mo – 1 % Cr – 5% V – 0.3 %

AISI/SAE Designation SystemAISI/SAE Designation System

American Iron and Steel Institute (AISI) and Society of Automotive Engineers (SAE), London.

The method of designation of steel is based on the chemical composition .

This method consist of designating the steel with four or five numerical digits.

The first digit (from Left) indicates the type of steel as follows-

1- Carbon Steels2- Nickel Steels3- Ni-Cr Steels4- Molybdenum Steels5- Chromium Steels6- Cr-v Steels7- Tungsten steels8- Ni-Cr-Mo Steels9- Si-Mn Steels

For simple alloys, the second digit indicates the approximate percentage of the alloying elements and for others, it indicates modification of the alloy in that alloy group.

The last two or three digits divided by 100 usually indicate the avg. percent carbon in the steel.

ExamplesExamples

1040 – Plain carbon steel with 0.4% carbon.2440 – Nickel steel with 4 % Nickel & 0.4 % C.9260 – Silicon Steel with 2 % Silicon & 0.6 % C.

In addition to numerals, AISI specification may include a letter prefix to indicate the mfg. process of that steels as-

A – Basic open hearth alloy steel. B – Acid bessemer carbon steel. C – Basic open hearth carbon steel. D – Acid open hearth carbon steel. E – Electric furnace steel.

Some Important AISI/SAE steel Some Important AISI/SAE steel Designation Designation Sr.No.

Details of the Steel AISI/SAE Group

01 Carbon Steels i) Plain Carbon Steelii) Free Cutting Steeliii) Manganese Steels

1XXX10XX

11XX,12XX13XX

02 Nickel Steelsi)0.50% Niii)1.5% Niiii)3.5% Niiv)5.0% Ni

2XXX20XX21XX23XX25XX

03 Nickel-Chromium SteelsVarious combinations of Ni & Cr

3XXX31XX to 34XX

04 Molybdenum Steelsi) Cr-Moii) Cr-Ni-Mo (High)iii) Ni-Mo

4XXX41XX43XX

46XX to 48XX

Sr.No.

Details of the Steel AISI/SAE Group

05 Chromium Steels 5XXX

06 Chromium - vanadium Steels 6XXX

07 Tungsten Steels 7XXX

08 Ni-Cr-Mo Steels(low) 8XXX

09 Silicon Steels 92XX

British Standard Designation SystemBritish Standard Designation System

British system of designation of steels is known as En Series.

The En no. of a steels has no correlation with composition or mechanical properties of steel.