Syllabus for 1st term

Introduction(1). Introduction to manufacturing process and materials commonly used.(2). Classification of different metals and alloys(3). Mechanical properties of materials(4). Heat treatment processes

Casting process(1). Principle of metal casting, pattern, mould.(2). Pattern material, types and allowances.(3). Sand molding ,molding tools, molding materials, classification of moulds, cores.(4). Elements of gating system, casting defects.(5). Cupola construction and operation.(6). Permanent mould casting, die casting, hot chamber and cold chamber.(7). Centrifugal casting, investment casting.

Smithy and Forging(1). Introduction to smithy and forging, upsetting, fullering, flattering, swaging tools & appliances, drop forging and press forging.

Manufacturing ProcessManufacturing can be simply defined as value addition processes by which raw materials of low utility and value due to its inadequate material properties and poor or irregular size, shape and finish are converted into high utility and valued products with definite dimensions, forms and finish imparting some functional ability.

*

Manufacturing Process

Input: Raw material :Wood,Metal,Plastic etc.

Process :Casting, Welding, Forging, Machining, Sheet metal, Fitting etc.

Out put- desired product

*

Engineering Materials

*Pure Metals and AlloysMetal that are not mixed with any other materials are known as pure metals. Metals listed in the Periodic Table are pure metals E.g. Iron (Fe), Copper (Cu) and Zinc (Zn)Alloys are mixtures of two or more metals formed together with other elements/materials to create new metals with improved Mechanical Properties and other properties of the base metal.

E.g. Brass (Copper and Zinc), Stainless steel (steel and chromium)

Alloy = metal A + metal B + + other elements

*Ferrous Metals - Iron and SteelPure iron is soft and ductile to be of much practical use.But when carbon is added, useful set of alloys are produced.They are known as carbon steel.The amount of carbon will determine the hardness of the steel.The carbon amount ranges from 0.1% to 4%.

Ferrous Metals and AlloysPig Iron :It is the product of blast furnace and is obtained by the process of smelting (reduction of iron ore in to pig iron). The main raw material for pig iron includes iron ore, good quality coking coal and flux (like lime stone). Iron obtained from blast furnace picks more than 4 % carbon. This high amount of carbon in pig iron make it very hard and brittle and unsuitable for making use full articles. Thus it is again melted and refined to produce other varieties of iron and steel.

*Extraction of IronA blast furnace

Cast IronCast iron is produce by again melting pig iron with definite amount of lime stone, steel scrap in cupola furnace. it contains about 2 to 4 % of carbon and small percentage of silicon, sulfur, phosphorus and manganese and certain amount of alloying elements like nickel, chromium, molybdenum, copper, vanadium. Cast iron are of following types :

Grey cast iron (Carbon in free form)White cast iron (Carbon in compound form)Malleable Cast ironNodular Cast iron.

*Cast IronContains 2%-4% of carbon.Very hard and brittleStrong under compressionSuitable for castingEngine block, engineer vices, machine parts

Grey Cast ironIt is obtained by slow cooling of molten metal and on solidification iron contains greater part of carbon in form of graphite flakes. The cast iron is brittle and strength is much greater in compression than in tension.Advantages:It is cheaper.Low melting temperature.(1150 to 1200)Self lubricating propertyHigh fluidity

White Cast iron This contains carbon in compound form of iron carbide (cementite) and is obtained by rapid cooling of molten metal and large quantities of manganese with low quantity of silicon as manganese encourages carbide formation. It is very hard and brittle due to which it has limited engineering applications. It also have poor machining quality but it is widely used for manufacturing of wrought iron and malleable iron.

Malleable Cast ironMalleable irons are a class of cast irons with mechanical strength properties that are intermediate to those of grey cast irons. The microstructure provides properties that make malleable irons ideal for applications where toughness and machinability are required, and for components that are required to have some ductility so that theycan be bent or flexed into position without cracking.When compared with GCI are found to be less brittle and possesses toughness also.

Spheroidal Graphite ironIt is also known as Nodular cast iron , it is obtained by adding one of the following elements like magnesium, calcium, zinc, boron. It is widely used in cast parts where pressure tightness is highly desirable eg. cylinder heads.In this, the graphite is in the form ofnodulesrather than flakes as it is ingrey iron. The sharp shape of the flakes of graphite create stress concentration points within the metal matrix and the rounded shape of the nodules less so, thus inhibiting the creation of cracks and providing the enhanced ductility .

Wrought IronIt is the purest form of iron contains 99 percent of iron .It is useful in forging operations and gives fibrous structure. It is tough, malleable, ductile and has good tensile strength.It is difficult to melt but at high temperature it becomes soft enough to be forged.It has good shock absorbing property.It can be neither hardened nor tempered like steel.It used for making chains, crane hooks, boiler tube etc.

Plain carbon steel & Its alloy Steel is an alloy of iron and carbon with the carbon content varying up to 1.8 % and is distributed through out the mass of the metal in a compound form.

Besides carbon it has sulphur, silicon, phosphorus, manganese etc.In steel ,iron is the quantity partner while carbon control the quality of steel.

Classification of Plain carbon steel On the basis of carbon content plain carbon steels are classified as:Low carbon or mild steel- 0.1 to 0.3 %Medium Carbon Steel- 0.3 to 0.6 %High Carbon Steel- 0.6 to 1.5 %Tool Steel- 0.9 to 1.5 %

Application:Mild steel are used mainly for structural steels forging etc. Medium carbon steel are used for connecting rod, crank shaft, axles.High carbon steel are used for rail, wire ropes, dies, hammer, locomotive wheels.Tool steel are used for drill, taps, knives, files, boring tool, bearings.

*Low Carbon SteelAlso known as mild steel. Contains 0.05% -0.32% carbon.

Tough, ductile and malleable.Easily joined and welded .Poor resistance to corrosion.Often used a general purpose materials.

Nails, screws, car bodies, Structural Steel used inthe construction industry.

*Medium Carbon SteelContains 0.35% - 0.5% of carbon.

Offer more strength and hardness butless ductile and malleable.

Structural steel, rails and garden tools.

High Carbon SteelAlso known as tool steel Contain 0.55%-1.5% carbon

Very hard but offers Higher Strength Less ductile and less malleable

Hand tools (chisels, punches) saw blades

Alloy SteelIt can be defined as steels to which elements other than carbon are added in sufficient amount to improve its properties .The most common alloying elements are chromium ,nickel manganese , silicon ,vanadium ,molybdenum ,tungsten etc.These alloying elements improves strength ,ductility and toughness.

Effects of alloying elements :Nickel : Improves toughness and corrosion resistance.Chromium: Improves hardenability ,toughness and corrosion resistance.Molybdenum: Improves hardenability ,tensile strength and creep strength at high temperature.Vanadium: Refine grain structure and act as deoxidiser.

Effect of the constituents on steelCarbon :Increases strength and hardness but reduces ductility and impact strength.Silicon : It act as a strong deoxidizer and prevent blow holes (0.05-0.3 %).Manganese : It act as deoxidizer and purifying agent as it combines with sulfur and decreases its harmful effect (0.3 1 %).Sulfur: As iron sulfide produces red shortness (brittleness at high temp) (0.02 -0.2)Phosphorus: It imparts cold shortness (brittleness at low or normal temp)(0.2 %).

*Stainless SteelSteel alloyed with chromium (18%), nickel (8%), magnesium (8%).On the basis of composition of these alloying elements it can be classified as:Austenitic Stainless Steel :15 to 20 % chromium and 7 to 10 % nickel.Martensitic Stainless Steel:10 to 14 % chromium Ferritic Stainless Steel: 14 to 30% chromium.Hard and tough, Corrosion resistanceComes in different gradesSinks, cooking utensils, surgical instruments

Chemical Composition of Iron & Steel

MaterialCarbon %Silicon%Manganese%Sulfur%Phosporus%Pig Iron3-40.5-30.1-10.02-0.10.03-2G.C.I2.5-3.751-2.50.4-10.06-0.120.1-1M.C.I.2.2-3.61.1-1.40.1-0.40.03-030.1-0.2W.C.I.1.75-2.30.85-1.20.1-0.40.12-0.350.05-0.2Wrought Iron0.02-0.030.1-0.20.02-0.10.02-0.040.05-0.2Steel0.05-20.05-0.30.3-10.02-0.20.02-0.15

NonFerrous Metals & AlloysNonferrous metals are those which do not contain iron as base. They have low melting point then ferrous metals also suffer from hot-shortness . Properties of non-ferrous metal are as:Good corrosion resistance.Good electrical and magnetic properties.Softness.Ease of casting.Good formability.Low density.Various nonferrous metals used are Aluminum ,Copper ,Zinc ,Nickel , lead etc.

Aluminium & Its AlloysAluminum is extracted from bauxite ore. Its melting point is 658.It is extensively used as light and non corrosive metal in aircraft and automobile industries.In pure form it is soft but when mixed with small amount of other metals it becomes hard and rigid.It has good electrical conductivity and high resistance to corrosion. Its nontoxicity make it suitable for cooking utensils.Alloy Duralumin:( 3.5 to 4.5% Cu ,0.4 to 0.7% Mn ,0.4 to 0.7% Mg and rest as aluminum).It has age hardening property so after working the metal is allowed to age for 3 to 4 days it will be hardened.

Copper and Its AlloyCopper is extracted from copper pyrites ore. It is of red colored.It is soft ,malleable ,ductile and tough.It is a good conductor of heat and electricity second to silver.It is largely used in wire and sheet form for electrical purposes.It is non- corrosive and resist weather very effectively.Melting point of copper is 1083.AlloyBronze: It is an alloy composed of copper (75 to 95 %) and tin(5 to 25 %).It has good wear resistance.It has good corrosion resistance.It is used in hydraulic fittings, utensils, bearings, sheets ,rods ,wire etc.

BRASSESIt is the most widely used alloy composed of copper and zinc.The maximum percentage of zinc in brass is about 50.Melting point of brass ranges from 800 to 1000 .It has good corrosion resistance property.It has soft, ductile and has good tensile strength .It is non magnetic and poor conductor of electricity.It is used in hyraulicfittings, bearing and bushes etc.

Properties of materials Mechanical properties of materialsStrength, Toughness, Hardness, Ductility, Elasticity, Fatigue and CreepChemical propertiesOxidation, Corrosion, Flammability, Toxicity, Physical propertiesDensity, Specific heat, Melting and boiling point,Thermal expansion and conductivity, Electrical and magnetic properties

Mechanical Properties of Metals

How do metals respond to external loads? Stress and Strain Tension Compression Shear Torsion Elastic deformation Plastic Deformation Yield Strength Tensile Strength DuctilityToughness Hardness

*Stress-Strain Testspecimenmachine

How materials deform as a function of applied load IntroductionStress, (MPa)Strain, (mm / mm)

*Tensile Test

Stress and Strain(For Tension and Compression)To compare specimens , the load is calculated per unit area. Stress: = F / Ao F: is loadA0: cross-sectional area A0 perpendicular to F before application of the load.Strain: = l / lo ( 100 %)l: change in length lo: original length.Stress / strain = /

Elastic deformationE = Young's modulus or modulus of elasticity (same units as , N/m2 or Pa) Hooke's law for Tensile StressStressStrainLoadSlope = modulus ofelasticity EUnload = E Higher E higher stiffness

Stress-Strain Diagram Strain ( ) (DL/Lo)41235Stress (F/A)Elastic RegionPlasticRegionFractureultimatetensile strength

Slope=EElastic region slope =Youngs (elastic) modulus yield strengthPlastic region ultimate tensile strength strain hardening fractureneckingyieldstrength

After yielding, the stress necessary to continue plastic deformation in metals increases to a maximum point (M) and then decreases to the eventual fracture point (F). All deformation up to the maximum stress is uniform throughout the tensile sample. However, at max stress, a small constriction or neck begins to form. Subsequent deformation will be confined to this neck area. Fracture strength corresponds to the stress at fracture. Tensile Strength, TS

*Stress-strain behavior found for some steels with yield point phenomenon.

* Another ductility measure: Ductility may be expressed as either percent elongation (% plastic strain at fracture) or percent reduction in area. %AR > %EL is possible if internal voids form in neck. Ductility, %ELDuctility is a measure of the plastic deformation that has been sustained at fracture:A material that suffers very little plastic deformation is brittle.

*c07f13ToughnessLower toughness: ceramicsHigher toughness: metalsToughness is the ability to absorb energy up to fracture (energy per unit volume of material).

A tough material has strength and ductility.

Approximated by the area under the stress-straincurve.

*HardnessHardness is a measure of a materials resistance to localized plastic deformation (a small dent or scratch).The depth or size of the indentation is measured, and corresponds to a hardness number.The softer the material, the larger and deeper the indentation (and lower hardness number).

* Resistance to permanently indenting the surface. Large hardness means: --resistance to plastic deformation or cracking in compression. --better wear properties.Adapted from Fig. 6.18, Callister 6e. (Fig. 6.18 is adapted from G.F. Kinney, Engineering Properties and Applications of Plastics, p. 202, John Wiley and Sons, 1957.)Hardness

*c07tf05

*Heat TreatmentA process used to alter the properties and characteristics of metals by heating and cooling.Three stages of heat treatment1. Heat the metal to the correct temperature2. Keep it at that temperature for a the required length of time (soaking)3. Cool it in the correct way to give the desired propertiesCold working induce stress in metal lead to work hardening prevent further work from taking place

Cooling curveIron may exist in several allotropic forms like ,,, in solid state. the existence of one form to the other depends upon the temperature to which the iron is heated.As shown in fig. the first horizontal step appears on this curve at a temperature of1535 .(which is the melting point of pure iron).above this metal is in molten state and upon freezing delta() iron is formed.(BCC structure.)

At temperature 1400 ,delta iron transform in to Gamma iron.(FCC)

At temperature 910 , Gamma iron transform in to non magnetic alpha iron .(BCC)

At temperature 768 , nonmagnetic alpha iron transform in to magnetic alpha iron which exist at room temperature.

Heat Treatment of Steel

METHODS OF HEAT TREATMENTAnnealingNormalisingHardeningTempering Case hardening a. Carburising b. Cyaniding c. Nitriding

*AnnealingAnnealing is the process whereby heat is introduced to mobilize the atoms and relieve internal stressAfter annealing, it allows the metal to be further shapedIt involves the re-crystallization of the distorted structure

Annealing Purpose of annealing is to obtain the following effects.Soften the steelImprove machinabilityIncrease toughnessRelieve internal stressRefine grain size

Different type of annealing.Full AnnealingProcess Annealing.Spheroidise AnnealingIsothermal Annealing

Full Annealing This process completely remove the traces of previous structure by complete phase recrystallization.The process consist of:Heating steel above the critical point.(30 to 50 above Ac3 point for hypo eutectoid steel and 30 to 50 above Ac1 point for hyper eutectoid steel.Holding at this temp. for considerable period.(3 to 4 minutes per mm section.Slow cooling in furnace.This slow cooling helps to decompose austenite in to ferrite and pearlite structure in hypo eutectoid steel and pearlite and cementite for hyper eutectoid steel.

Process Annealing This process is used to restore ductility of steel when it is cold worked. This process consist of :

Heating the steel to a temp. below Ac1 point (500 to 700).Holding at this temp for considerable time.Slow cooling. This helps to come back the distorted grains in to normal state.Specially used for low carbon steel in deep drawing and as intermediate process in wire drawing.

Spheroidise Annealing This process is used for enhancing the machinability of high carbon steel by producing globular pearlite structure. this process includes:

Heating of steel slightly above Ac1 point(730 to 770 )Holding at this temp for considerable time.Slow cooling in furnace up to 550 and then air cooling.

Isothermal Annealing

Isothermal annealing is carried out aa for ordinary annealing to form austenite It is then rapidly cooled in air to a temp. of 50 to 100 below Ar1 line i.e. to 600 to 700 .Holding isothermally at this temp. during a certain period of time for decomposition of austenite in to pearlite.

Normalising Normalising is done for the following purposes:To eliminate coarse grain structure.To remove internal stresses caused by working .To improve mechanical properties.

The process of normalising consist of :Heating the metal from 40 to 50 above Ac3 and Acm line.Holding at this temp. for a short period(15 minutes)Cooling in air This produces ferrite and pearlite for hypo eutectoid steel, pearlite for eutectiod and pearlite and cementite for hyper eutectoid steel. This improves the yield point, tensile strength, impact strength, but reduces machinability and ductilty to some extent.

HardeningThe hardening process is used for all tools and some machine parts in heavy duty services. the purposes of hardening are:To develop high hardness to resist wear and to enable it to cut other metal.To improve strength and toughness.

The process consist of :Heating the steel to a temp. above critical point (30 to 50 above Ac3 point for hypo eutectoid steel and 30 to 50 above Ac1 point for hyper eutectoid steel.)(ferrite & Pearlite and pearlite & cementite structures are formed for both the steels.)Holding at this temp. for considerable period.Quenching in water, oil, molten salt bath.

*TemperingTempering is the process to reduce hardness and brittleness slightly of a hardened steel work piece.It helps to produce a more elastic and tough steel capable of retaining the cutting edge after temperingTempering of cold chiselGuidelines for tempering

TemperingAs quenching makes steel hard, brittle with internal stresses. So objectives of tempering are as follows:To reduce the internal stresses.To reduce hardness.To increase ductility.To increase toughness and shock resistance. Tempering treatment involves:Reheating the steel after hardening to temp below Ac1 point.Holding it for considerable time.Slow cooling tempering can be classified as :Low temp. tempering.(150 to 250)Medium Temp. tempering(350 to 450)High Temp. tempering.(500 to 650)

*Case/ Surface HardeningCase hardening is a process used with mild steel to give a hard skinThe metal is heated to red hot state and is dipped in carbon powder. It is then repeated 2-3 more times before quenching the metal in water to harden the skin.This allows the surface of mild steel to be able to subject to wear but the soft core is able to subject to sudden shock e.g. the tool holders

Case Hardening Case hardening: This is the oldest method of producing a hard surface on steel. the steel used for this purpose is usually a low carbon steel of about 0.15 % carbon that can not be heat treated. this process increases the carbon content in outer surface by 0.9 to 1.2 %.Various steps involved are as follows: Heating of steel to red hot state (above or close to critical temperature) in contact with some carbonaceous material like wood, bone, charcoal etc. Some energizers like sodium, calcium or barium carbonates to increase the concentration of carbon monoxide which improves the carburizing rate. All this happens because at critical temp. iron has an affinity for carbon. Thus carbon enters the metal to make outer surface high carbon steel.

Surface Hardening MethodsCarburizingNitridingCynidingFlame hardeningInduction heating

*CarburizingCarburizing involves placing the mild steel in box packed with charcoal granules, heated to 950 C (1742 oF) and allowing the mild steel to soak for several hours.It achieves the same purpose of case hardening

Nitriding This process is used for case hardening of alloy steel only. The process includes.

Heating of steel in atmosphere of ammonia gas at temp. of 500 to 650 where ammonia dissociate and nascent nitrogen combines in the to form nitrides which gives extreme hardness to the surface. this process is generally performed on forging component as final operation.

CyanidingIt is the process of producing hard surface on low carbon or medium carbon steels. this process includes:

Immersion of steel in to molten salt bath (one third each of sodium chloride, sodium carbonate and sodium cyanide) maintained at 800 to 900 .

Quenching the steel in water or oil. Hard surface produced due to presence of compounds of carbon as well as nitrogen.

*****