“ Effect of MarTempering Heat Treatment on

Microstructure and Mechanical Properties of

Nodular Cast Iron”

U.V.PATEL COLLEGE OF ENGINEERING GANPAT UNIVERSITY

GUIDEDBY : Prof.N.A.MODI

PREPAREDBY:

CO-GUDIDED BY: Prof.V.P.PATEL Rathod Pratik.

(M11AMT013)

Industrial background Grey Nodules Pvt Ltd was established in the year 1992 in

Gujarat and located at kathwada GIDC, ahmedabad.

• Under the valuable headship of our CEO’s, Mr. Mukund

Shah & Mr. Kamlesh Patel, we have been able to done our

project with great knowledge and proper guidance.

Industrial Castings Products

Ductile And Cast Iron Castings For Pump

Ductile Iron Castings for Flanges

Electric Motor Body and Parts Castings

Gas and Petroleum Pump Products Castings

Grey Iron Castings

Iron Castings for Hydraulic and Pneumatic Components

• Cast irons usually contain 2 to 6.67% C but in general industry its

take 2.5 to 4.3% C.

• Cast iron also contain varying quantities Mn, Si and P.

• Additions of manganese, depending on the desired microstructure .

• Sulphur and phosphorus are also present in small amounts as

residual impurities.

Cast iron

Types of Cast Iron

• Gray cast iron

• Malleable Cast iron

• White cast iron

• Nodular cast iron

Ductile Cast Iron

• Ductile cast iron, also known as

Nodular iron or Spheroidal graphite (SG) iron,

is very similar in composition to grey cast iron, but the free graphite in

these alloys precipitates from the melt as spherical particles rather

than flakes.

• This is accomplished through the addition of small amounts of

magnesium or cerium to the ladle just before casting.

• The spherical graphite particles do not disrupt the continuity of the matrix

to the same extent as graphite flakes, resulting in higher strength and

toughness compared with grey cast iron of similar composition.

Average Composition of S.G. Cast Iron • Carbon – 3.0 - 4.0 %

• Silicon – 1.8 – 2.8 %

• Manganese – 0.1 – 1.00 %

• Sulphur – 0.03% max.

• Magnesium – 0.01 – 0.10 %

Properties of S.G Cast Iron • Easy to cast

• Tensile strengths of up to 900N/mm2

• Ductility

• Elongations of in excess of 20%

• Excellent Corrosion Resistance when compared to other ferrous metals.

• Ease of Machining

Steps in Production of S.G Iron

• Desulphurization: Sulphur helps to form graphite as flakes. Thus, the raw material for producing S.G Iron should have low sulphur

• Nodulising : Magnesium is added to remove sulphur and oxygen still present in the liquid alloy and provides a residual 0.04% magnesium, which causes growth of graphite to be Shperoidal.

• Inoculation: As magnesium is carbide former, ferrosilicon is added immediately as inoculants. Re-melting cause’s reversion to flake graphite due to loss of magnesium

Various grade of S.G. irons

Grade

Tensile

Strength

(N/mm2)

Hardness

(BHN)

Elongation

(%)

ISO 1083/JS/800-2/S 800 245-335 2

ISO 1083/JS/700-2/S 700 225-305 2

ISO 1083/JS/600-3/S 600 190-270 3

ISO 1083/JS/500-7/S 500 170-230 7

ISO 1083/JS/450-10/S 450 160-210 10

ISO 1083/JS/400-15/S 400 130-180 15

ISO 1083/JS/400-18/S 400 130-180 18

Types of Ductile Irons

Austenitic Ductile Iron.

Ferritic Ductile Iron.

Ferritic Pearlitic Ductile Iron.

Pearlitic Ductile Iron.

Martensitic Ductile Iron.

• Ferritic Ductile Iron: ferrite provide an iron with good ductility and affected resistance and with a yield and tensile strength equivalent to low carbon steel.

• Austenitic Ductile Iron : Alloyed to form an austenitic matrix, this ductile iron offers good corrosion and oxidation resistance and good strength and dimensional stability at elevated temperatures.

• Ferritic Pearlitic Ductile Iron: Properties are intermediate between ferritic and pearlitic grades, with good machinability and low production costs.

• Pearlitic Ductile Iron: pearlite result in an iron with good wear resistance, high strength and moderate ductility and impact resistant.

• Martensitic Ductile Iron: martensite matrix improves very wear resistance and high strength but with lower levels of ductility.

Heat Treatment

The heat treatments can be carried out on Spheroidal Graphite

Iron to achieve the following:

Increase toughness and ductility.

Increase strength and wear resistance.

Increase corrosion resistance.

Stabilize the microstructure, to minimize growth.

Equalize properties in castings with widely varying section sizes.

Improve consistency of properties.

Improve machinability and Relieve internal stresses.

• The most important heat treatments and their purposes are:

Stress relieving, a low-temperature treatment, to reduce or

relieve internal stresses remaining after casting.

Annealing, to improve ductility and toughness, to reduce

hardness, and to remove carbides.

Normalizing, to improve strength with some ductility.

Austempering, to yield a microstructure of high strength, with

some ductility and good wear resistance.

Surface hardening, by induction, flame, or laser, to produce a

locally selected wear-resistant hard surface.

Martempering, to increase hardness or to improve strength

and to reduce internal stress.

Martempering Process

• Martempering is a metallurgical production process intended to control martensite characteristics in ductile iron and alloys.

• Martensite is hard and brittle and require a reduction of the martensite characteristics to usable levels.

• The process of martempering is used to manipulating martensite levels and consists of heating and a sequential series of cooling cycles which gradually reduce the extent of martensite characteristics in the metal.

• It is beneficial to begin the process with a high level of martensite formation and to reduce the level gradually because the process minimizes distortion and cracking of the metal.

Steps in Martempering process

Microstructure of Martensite

Advantages Of MDI

• The advantage of martempering lies in the reduced thermal

gradient between surface and center.

• Residual stresses developed during martempering are lower

than those developed during conventional quenching.

• Minimize distortion

• Eliminate cracking

• it also greatly reduces the problems of pollution and fire

hazard as long as nitrate-nitrite salts are used rather than

martempering oils.

Literature Review • Oyetunji Akinlabi and Barnabas A. Was investigated on

“Development of Martempered Ductile Iron by Step-Quenching

Method in Warm Water” in 2012.

• S.G.iron normalized at 850˚C for 60 minutes. The normalized

specimens were subsequently heat-treated in muffle furnace at

850˚C for 30 min, then step-quenched in warm water at of 80˚C for

40 sec followed by tempering at tempering temp. (175˚C – 425˚C)

and times (30-180 minutes).

• The results showed that the developed MDI has a high hardness

value of 53 Rc at the lowest temperature, and 19.6 Rc at the highest

temperature.

• Metallographic analysis showed that untempered martensite was

obtained at holding temp. below 250˚C, tempered martensite at

250˚C to 325˚C, tempered martensite at holding temp. of 350˚C for

short holding times, above which the specimen is over-tempered.

• R. Aristizabal and R. Foley was studied on “Inter-critically

Austenized Quenched and Tempered Ductile Iron” in 2012.

• Ductile iron was produced using 0.7 wt % manganese and 0.5 wt %

nickel. Three different volume percentages of martensite (16, 24 and

37 vol. %) were formed by austenitizing then quenching in a

polymeric solution to room temperature.

• The material was austenitized at 900˚C for 480 seconds and then

quenched in water. Tempering was performed at 400-500˚C for 60 to

120 minutes.

• The results indicated that ferritic-martensitic microstructures in

ductile iron provided larger elongation than fully martensitic

microstructures. Also, strength and hardness increased and

elongation decreased as martensite increased. Tempering

significantly increased the elongation with only a small decrease in

the strengths.

• Y. Sahin , M. Erdogan and M. Cerah were investigated on

“Effect of martensite volume fraction and tempering time on

abrasive wear of ferritic ductile iron with dual matrix” in 2008.

• Austenitized in the two-phase region at temperatures of 795˚C and

815˚C for 20 min and then quenched in oil at 100˚C. The specimens

were subjected to tempering at 500˚C for 1 and 5 h.

• The results showed that weight loss resistance and strength

increased and ductility decreased with increasing MVF. At constant

MVF, weight loss increased with increasing tempering time.

• The lowest weight loss in sample having 90% MFV, while the

highest weight loss in sample having 25% MFV.

• The weight loss increased with increased applied load for all tested

samples. Abrasive wear has slight changes occurred with increased

tempering time.

• O. Eri, M. Jovanovi and D. Rajnovi was investigated on

“Microstructure and mechanical properties of CuNiMo austempered

ductile iron” in 2004.

• Samples were austenitized at 860˚C for 1h and then austempered at

320˚C and 400˚C in the interval from 0.5 to 5h.

• Austempering at 320˚C in between 2 and 5h, microstructure typical

for austempered ductile iron was produced, i.e. a mixture of free

bainitic ferrite and highly carbon enriched retained austenite.

• The characteristic of the whole range of austempering at 400 ˚C is

the appearance of martensitic structure.

• maximum volume of austenite that was obtained after 2.5 h of

austempering at 320 ˚C.

• The appearance of martensite during austempering at 400 ˚C is the

main cause for much lower tensile properties than at 320 ˚C.

• Mehmet Erdogan, Suleyman Tekeli were investigated on “The effect of martensite volume fraction and particle size on the tensile properties of a surface-carburized AISI 8620 steel with a dual-phase core microstructure” in 2003.

• This study is focused on the production of a dual-phase steel structure in the core of a surface-carburized steel and the effect of martensite volume fraction (MVF) and martensite particle size (MPS) on tensile properties.

• Experimental results showed that, compared with specimens with a fully martensitic microstructure in the core, those with a dual-phase microstructure in the core exhibited slightly lower tensile and yield strength but superior ductility without sacrificing surface hardness.

• In specimens with a dual-phase microstructure in the core, the tensile strength increased and ductility decreased with increasing MVF. Both the tensile strength and the ductility increased with decreasing MPS at constant MVF. The best combination of tensile strength and ductility was obtained with a fine MPS at a constant MVF of 25%.

Objective • From the literature review, MDI material has found increasing

applications over the years since its discovery because of its excellent

mechanical properties such as high strength, hardness, good wear

resistance and all that at low cost.

• The excellent mechanical properties of MDI material are due to its

unique microstructure which consists of high carbon martensite and

some amount of pearlite with graphite nodules dispersed in it.

achieving excellent mechanical properties depends on selection and

control of proper martempering time and temperature.

• Therefore, an attempt has been made in the present work to study the

effect of martempering temperature and time on the mechanical

properties of martempered ductile iron such as tensile strength, %

elongation and hardness by carrying out martempering treatment of

ductile iron at 60°C, 80°C, and 100°C oil temp. for 60, 120 & 180

second.

Design of Experimental

• The experimental procedure for the project work can be listed as :

• Sample casting.

• Specimen preparation.

• Heat treatment process.

• Mechanical testing.

• Micro structural observation.

Sand Casting

• Experiments were carried out in induction furnace with 500 kg Capacity

Crucible furnace.

• Metallic charge were composed of pig iron, commercially ferro silicon,

steel scrap .

• Nominal composition of the experimental alloy is given below.

Material C Si Mn P S Mg

SGI

(400/15) 3.680 2.030 .0380 0.030 0.014 0.038

Sand Preparation

Pattern making

Molding

Pouring

Final casting

Different Martempering condition

Austenitic

temperature

Oil

temperature

Time

(second) Tempering

850˚C

60˚C

60

300˚C

(for 1hr)

120

180

80˚C

60

120

180

100˚C

60

120

180

Result and Discussion

• The experiment has been carried out with an aim of

effect of mar-tempering heat treatment on mechanical

property and microstructure of the ductile iron. As per

the experimental process done on sample the result of

mechanical testing and microstructure is shown

Micro-structural observations • Before and after heat treatment, the samples were prepared for micro

structural analysis.

• slice of 4 mm is cut to determine the microstructure. These slices are

firstly polished in SiC paper of different grades then in 1 µ m cloth

coated with diamond paste.

• The samples were etched using 2% nital.

• Then the microstructures were taken for different heat treated

specimen by using Image Analyzer microscope.

Microstructure and Phase analysis of casting at 60°C of oil temp.

At 120 sec At 180 sec At 60 sec

Microstructure and phase analysis of casting at 80°C of oil temp.

At 60 sec At 120 sec At 180 sec

Microstructure and phase analysis of casting at 100°C of oil temp.

At 180 sec At 120 sec At 60 sec

Microstructure of casting as cast condition

Hardness Testing Result

Austenitic

temperature

Oil

temperature

Time

(second) Tempering

Hardness

(BHN)

850˚C

60˚C

60

300˚C

(for 1hr)

395

120 427

180 444

80˚C

60 461

120 470

180 512

100˚C

60 458

120 465

180 470

Without heat treatment 166

Hardness vs. oil temperature

Austenitic

temperature

Oil

temperature

Time

(second) Tempering

Tensile

strength

(N/mm²)

850˚C

60˚C

60

300˚C

(for 1hr)

840

120 955

180 1033

80˚C

60 981

120 1228

180 1204

100˚C

60 1279

120 1546

180 1635

Without heat treatment 400

Tensile Strength Testing Result

Tensile strength vs. oil temperature

Austenitic

temperature

Oil

temperature

Time

(second) Tempering

Elongation

(%)

850˚C

60˚C

60

300˚C

(for 1hr)

0.82

120 0.65

180 0.16

80˚C

60 0.90

120 1.03

180 0.53

100˚C

60 0.89

120 0.77

180 1.51

Without heat treatment 15

Percentage of Elongation

Elongation vs. oil temperature

Micro structural Result

Austenitic

temperature Oil temp.

Time

(second) Tempering

Pearlite and

martensite

(%)

Ferrite

850˚C

60˚C

60

300˚C

(for 1hr)

95.64 4.36

120 98.01 1.98

180 98.81 1.19

80˚C

60 97.37 2.36

120 97 3

180 98.8 1.2

100˚C

60 96.7 3.3

120 98.67 1.34

180 97.36 2.64

Without heat treatment 4.95 95.05

Martensite and pearlite vs.

oil temperature Ferrite vs. oil

temperature

Conclusion

• Due to the Mar-tempering Heat treatment at 60˚C oil

temperature at different time phase, hardness are 395, 427 and

444 BHN with respect to 60, 120 and 180 sec and UTS are

840, 955 and 1033 N/mm² at 60, 120 and 180 second time

period.

• At 80˚C oil temperature and different time period of

martempering heat treatment, Hardness value are 461, 470

and 512 BHN and UTS are 981, 1228 and 1204 N/mm² with

respect to 60, 120 and 180 sec time phase.

• At last 100˚C oil temperature heat treatment process, hardness

value are 458, 465 and 470 BHN and UTS are 1279, 1546

and 1635 N/mm² with respect to 60, 120 and 180 sec.

• The microstructure in as cast condition shows the pearlitic and

ferrite matrix with graphite nodules in both grades of samples,

while after quenching and tempering the matrix converted into

the martensite and tempered pearlite. Thus, the strength and

hardness was increased in tempered samples, but elongation

decreases.

• The martempering temperature is moderate the hardness value is

maximum. ( 80 degree temperature).

• As the martempering period of holding time increase percentage

of martensite increase before the transfer to the tempering

process.

• The martempering temperature is higher, it’s give best result of

the tensile strength.(100 degree)

• Percentage increase in pearlite transformation increase the value

of tensile strength.

Future Work • Engineering applications of ductile iron in as cast and different heat treated

conditions are growing day by day. MDI’s application has increased

tremendously in many industrial areas.

• MDI is increasingly the material of choice of designers and engineers

because of their cost effective performance. It has started to replace steel in

some structural applications.

• It has also found its tremendous applications in automobile sector which

includes crankshafts, disc-brake calipers, axle housings, roller, gear etc.

• For all these applications, we need to take into consideration many other

mechanical properties like, wear and erosion resistance, impact resistance,

fracture toughness, creep resistance, noise reduction and energy saving

properties, etc.

• So in future, we can measure the above mentioned mechanical properties to

optimally select a material for its specific application. We can also add

inoculants into sample for better result and then measure above mechanical

properties.

References

• http://en.wikipedia.org/wiki/Metal

• A. K. Chakravati, “Casting Technology and Cast Alloy”

• O. P. Khana, “Material science”

• http://eprints.iisc.ernet.in/id/eprint/14622

• http://www.materialsengineer.com/E

Steel%20Properties%20Overview.htm

• Oyetunji Akinlabi and Barnabas A. A., on “Development of

Martempered Ductile Iron by Step-Quenching Method in Warm

Water”, The Federal University of Technology, Akure Nigeria in

2012

• R. Aristizabal and R. Foley, “AUSTENITIZED QUENCHED AND

TEMPERE D DUCTILE IRON”, University of Antioquia, Medellin,

Colombia in 2012

• C. Hakan Gür, Melika OZER and Mehmet ERDOGAN,”The Evaluation of

Structure – Property Relationships in the Dual Matrix Ductile Iron by Magnetic

Barkhausen Noise Analysis”, Middle East Technical Univ., Metallurgical &

Materials Eng. Dept. Ankara, Turkey in 2008

• Sudhanshu Shekhar and Amit Jaiswal, “HEAT TREATMENT OF S.G CAST IRON

AND ITS EFFECTS”, National Institute of Technology Rourkela in 2008

• Y. Sahin , M. Erdogan and M. Cerah, “Effect of martensite volume fraction and

tempering time on abrasive wear of ferritic ductile iron with dual matrix”, Faculty

of Engineering, Bahcesehir University, Besiktas, Istanbul in 2008

• O. Eri, M. Jovanovi, L. Šidjanin and D. Rajnovi, “MICROSTRUCTURE AND

MECHANICAL PROPERTIES OF CuNiMo AUSTEMPERED DUCTILE IRON”,

Instute of Nuclear Sciences “Vinca” in 2004

• Mehmet Erdogan and Suleyman Tekeli, “The effect of martensite volume fraction

and particle size on the tensile properties of a surface-carburized AISI 8620 steel

with a dual-phase core microstructure”, Faculty of Technical Education, Gazi

University in 2003

• A.S.M.A. Haseeb and Md. Aminul Islam, “Tribological behaviour of quenched and

tempered, and austempered ductile iron at the same hardness level”, Department of

Materials and Metallurgical Engineering, Bangladesh University of Engineering

and Technology, Dhaka in 2000

• Ali M. Rashidi and M. Moshrefi-Torbati,”Effect of tempering

conditions on the mechanical properties of ductile cast iron with

dual matrix structure DMS”, Mechanical Engineering Department,

Razi UniÍersity, Kermanshah, Iran in 2000

• S. Yazdani, M. Ardestani, “Effect of sub-zero cooling on

microstructure and mechanical properties of a low alloyed

austempered ductile iron”, Faculty of Materials Engineering, Sahand

University of Technology, Tabriz, IRAN \

• O. P. Khana, “Foundry Technology”

• James H Davidson, Microstructure of steel and cast irons, New

York, Springer-verlag, 2003, ISBN 3-540-20963-8, Part 3, chapter

21,

• AVNER Sidney H ,Introduction to Physical Metallurgy, Second

Edition, MCGRAWHILL INTERNATIONAL EDITIONS, chapter

11,