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Experiment No.: 06 Date: / /200JOMINY END QUENCH TEST

AIM: Measure hardenability of the material with the help of Jominy EndQuench Test.

APPARATUS:Jominy end quench hardness test with quenching fixture and

muffle furnace.

THEORY:Hardenability is the ease with which a steel piece can be

hardened by martensitic transformation or it is the depth of hardeningproduced under the given conditions of cooling. It is evaluated bydetermining the minimum cooling rate to transform an austeritiessteel to a structure that is predominantly or entirely martensitic, or bydetermining the thickness of the largest steel section that can beconverted to such a structure under the given conditions of cooling.Hardenability is most commonly measured by the Jominy End Quench

Test. In this test, the specimen dimensions and test conditions arestandardized and are as below:

The specimen is of cylindrical shape with 25.4 mm (1.0 inch) diameterand approximately 102 mm (4.0 inch) in length and has a machinedshoulder (or a fitted detachable collar ring) at one end. The abovespecimen is austerities at a constant temperature for a fixed time andquickly transferred to a fixture (quenching jig), Fig. Water is allowedto flow on the bottom end through a pipe having inside diameter of 12.7 mm (1/2 inch) for about 20 minutes. The distance between thepipe and the bottom end of the specimen is 12.7 mm (1/2 inch). Thepressure should be adjusted such that the free height of water isapproximately 64 mm (2.5 inch). At this pressure, water forms acomplete umbrella over the bottom surface of the specimen. Thetemperature of water should be between 21 and 27C.

The cooling rate is maximum at the quenched end of the specimenwhere usually full hardening occurs and diminishes steadily towardsthe air cooled end where the structure is nearly equivalent to thatproduced by normalizing i.e. all possible rates of cooling, from waterquenching to air cooling are obtained on a single test piece. Thecooling rates along the length of the bar are essentially independentof the composition of the bar and because the specimen is of standard size and the test procedure is maintained constant, thecooling rate at the same position on different samples is the same. Itis therefore possible to compare the hardenability of various steelsfrom their microstructures at similar locations from the quenched end.

METALLURGY Prof. Ms. G. S.PATIL

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After quenching, two flat surfaces are ground (about 1.6 mmdepth) opposite to each other along the length of the specimen. Thehardness (VPN or Rc) is measured at intervals of 1.6 mm (1/16 inch)distance from the quenched end. The hardness values are plotted asfunction of distance from the quenched end and the resulting curve iscalled as Jominy harden ability curve. A typical curve is shown in Fig.9.60. The hardness changes most rapidly at a location where thestructure is 50% martensite. This distance from the quenched end isreported in terms of points (1 point = 1/16 inch distance) as hardenability.

Decarburization of the sample should be avoided during heatingby using controlled atmosphere in the furnace. Alternatively, thesample can be placed in a steel tube with cast iron chips all around.and heated. Slight decarburization will show first and sometimessecond reading of hardness on the lower side, but the harden abilityvalue as such does not get affected. However, appreciabledecarburization may affect the hardenability value.

Hardenability of a steel is directly related to its critical coolingrate or to the distance of the nose of I.T. diagram from the Y-axis. If the critical cooling rate is high, the steel must be cooled rapidlyduring hardening to prevent pearlite or bainite formation above M g ,and its hardenability becomes low. If the critical cooling rate is low,the steel can be cooled slowly to produce martensitic structure andits hardenability becomes high. Any factor which reduces the criticalcooling rate will increase the hardenability. An increase in carboncontent increases the shift of the LT. diagram to the right sidedecreasing the critical cooling rate, subsequently increasing thehardenability. Fig. shows the effect of carbon on the critical coolingrate.

The hardness obtained after hardening heat treatment dependson the carbon content and alloying elements in the steel. Both thecarbon and alloying elements increase the hardness, but the increasein hardness due to carbon is more significant than due to the alloyingelements. Therefore, the hardness of hardened steels (i.e. martensitephase) is mainly controlled by carbon content in the steel (i.e. inaustenite). In other words, the maximum hardness that can beobtained in steel largely depends on its carbon content whereas, itshardenability depends on the content of alloying elements.

Hardenability also depends on the grain size of austenite.Coarse grained austenite has better hardenability than fine grainedaustenite. This is because the grain boundaries reduce the coolingrate. Also, since pearlite is nucleated at austenite grain boundaries,fine grained austenite tends to transform to pearlite more rapidlythan coarse grained austenite because of more grain boundary area.


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Inhomogeneous austenite shows less hardenability thanhomogeneous austenite. The presence of carbides, nitrides, borides,inclusions, etc. in austenite will also reduce the hardenability. Typical

jominy curves of high harden ability steels (deep hardening steels)such as high carbon alloy steels, low hardenability steels (shallowhardening steels) such as plain carbon steels with more than 0.6%carbon, and non-hardenable steels such as plain carbon steels withless than 0.2% carbon are shown in Fig.

PROCEDURE:1. Take the given specimen and heat the specimen above austenitic region.2. Soak at this temp.3. Hot specimen is quickly transferred to the water tank. Water is made to

strike the bottom end of specimen to form an umbrella as shown in fig.Quenching is done for 10 minutes.

4. After quenching is over, two dimensionally opposite flat surfaces areground longitudinally on the specimen.

5. Fix the specimen on the jominy fixture and measure hardness at theinterval of 1/16 from the quenched end to the collared end.

6. Plot the graph of hardness versus distance from quenched end and drawthe hardenability curve.

RESULT:

Sr.No.

Distance fromquenched end

(mm)

Hardness (Rc)

01 0.502 1.003 1.504 2.005 2.506 3.007 3.508 4.0

CONCLUSIONS:Plot the graph Hardness Vs Distance from quenched end.Avg. Hardenability value of the given specimen is = ___________ Rc.


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Experiment No.: 02 Date: / /200TENSION TEST

AIM: To conduct tensile test on the given specimens.

APPARATUS: Universal Testing Machine, Specimen.

THEORY: This test is widely used to determine strength, ductility,

resilience, toughness and several other material properties. A test specimenof circular, square or rectangular cross-section of a suitable size is preparedfrom the material to be tested is shown in the above fig. During preparationof the specimen, care should be taken to avoid sharp changes in section toreduce stress concentration. This reduces the chances of failures of

specimen at low stress values.

TYPICAL TENSION SPECIMENS


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EVALUATION OF PROPERTIES : This test is used to evaluate the following properties of the materials.

i) Proportional Stress (P.S.) : It is the highest value of the stress up to which stress isproportional to strain.

ii) Elastic Limit or Stress (E.L.) : It is the highest value of the stress up to which thedeformations are elastic or temporary and beyond which they are plastic orpermanent. This stress is slightly higher than the proportional stress.

iii) Ultimate Tensile Stress (U.T.S.) : It is the highest value of the stress that the material canbear or sustain without fracture.

iv) Breaking Stress (B.S.) or Fracture Stress (F.S.) :It is the stress value at the point of fracture or failure.


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v) Yield Stress (Y.S.) : It is the stress at which the material yields i.e. showsappreciable plastic deformation at almost constant stress without any strainhardening. This stress exists in some materials like low carbon steels andmild steel.

vi) Proof Stress :Proof stress is reported for those materials which do not show

yield point or well defined straight line portion on their stress- straindiagrams and is an equivalent term to the yield stress or elastic stress. Proof stress is defined as the stress at which the material shows a specifiedamount of plastic deformation or permanent set.


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vii) Resilience:It is the total energy absorbed by the material during its

elastic deformation. It is the area up to the elastic load in a load extensiondiagram and is shown in fig.

ENGG. LOAD EXTENSION DIAGRAM ENGG. STRESS STRAINCURVE

SHOWING RESILIENCE SHOWING MODULUS OFRESILIENCE

Modulus of resilience = ResilienceVolume

Modulus of resilience = 1 2

2EWhere, 1 = Elastic Stress

E = Modulus of Elasticity.

viii) Toughness :It is the total energy absorbed by the material prior to its

fracture. This energy is the sum of elastic energy and plastic energy. It is thetotal area under theload extension diagram as shown in fig.


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Modulus of toughness = ToughnessVolume

Modulus of Toughness = 2/3 u x e f Where,

u = Ultimate tensile stress.e f = Strain at the fracture point.

ix) Stiffness :It is defined as the resistance of a material for its deformation.

Stiffness is also defined as force per unit deflection. Sometimes it isexpressed by Youngs modulus of elasticity. It is denoted by K and its unit isN/mm.

E = True Stress True Strain


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x) Ductility :

It is defined as the ability of a material to undergo plasticdeformation under tensile loading before its fracture. Ductility expressed by,

% elongation = Change in lengthOriginal length

% reduction in area = Change in cross- sectional area Original cross-sectional area

xi) Malleability :Malleability is defined as the ability of a metal to be formed by

hammering or rolling. It is the capacity of a material to withstanddeformation under compression without failure.


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xii) Strain Hardening Coefficient (n): This coefficient gives an idea about the ability of a material for

hardening due to straining or plastic deformation. The approximate equation applicable for deformation behavior in

the plastic region up to necking is:

T = K n

Where,

T = True Stress = True Strainn = Strain Hardening Coefficient K = Material Constant (Strengthcoefficient)

Above equation is applicable from 1 to u in the fig. below-

PROCEDURE:1. Prepare the specimen of circular, square or rectangular c/s of a

suitable size from the material to be tested.2. Make two permanent marks on the specimen at appropriate distance

i.e. original gauge length.3. Held the specimen by suitable means between two heads of a testing

machine.4. Apply the progressively increasing tensile load until the specimen

fractures.5. Note down the fracture load.6. Measure the total elongation after fracture.7. See the type of fracture.


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8. Then calculate the tensile properties by analytical method using theexperimental data.

CONCLUSIONS:

Conducting tensile test on the given specimen, calculate tensile

properties and see the types of fractures.

Experiment No.: 03 Date: / /200COMPRESSION TEST

AIM: To conduct compression test on the given specimens. APPARATUS: Universal Testing Machine (UTM), Specimen.

THEORY:

PROCEDURE:1. Prepare the specimen of circular, square or rectangular c/s of a

suitable size from the material to be tested.2. Held the specimen by suitable means between two heads of a testingmachine.

3. Apply the progressively increasing compressive load until thespecimen fractures.

4. Note down the fracture load.

CONCLUSIONS:

Conducting compressive test on the given specimen and see the typesof fractures.

CONCLUSIONS:


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Experiment No.: 05 Date: / /200

NON DESTRUCTIVE TEST

AIM: To conduct dye penetrant test on the given specimen.

APPARATUS: Dye penetrant test kit, Specimens.

THEORY:Invisible cracks, porosity and other defects on the surface of

components can be easily detected by this technique. Component may beferrous, non-ferrous, ceramics, glass and plastic.

PROCEDURE:1. Cleaning the surface (Grease, oil or any other extraneous material

such as scale must be removed by a suitable solution).2. Drying of surface.3. Applying dye-penetrant on clean and dry surface by dipping, brushing

or any other suitable technique. The dye penetrant is allowed topenetrant in the surface flaws. Depending upon the type of defect, thetime may be anywhere between few seconds to several hours.

4. Removing excess penetrant by a soft and clean cotton.5. Applying developer on the surface. This pulls out the dye from the

flaws and the flaws are revealed by color of the dye.

CONCLUSIONS:

Detect the cracks, porosity with the help of this test.


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ILLUSTRATION OF A TENSILE TESTING MACHINE


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VARIOUS TYPES OF FRACTURES IN A TENSILE TEST


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TYPES OF FRACTURES OF BRITTLE MATERIALS UNDER COMPRESSIVE LOAD


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Jominy End Quench Test


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Dye Penetrant Test


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