This document discusses a study on the effect of martempering heat treatment on the microstructure and mechanical properties of nodular cast iron. Martempering was performed at oil temperatures of 60°C, 80°C, and 100°C for durations of 60, 120, and 180 seconds. Microstructural analysis found the presence of martensite decreased with longer times at higher temperatures. Hardness increased with higher oil temperatures and longer times, with a maximum of 512 BHN. Tensile strength and hardness also increased with higher oil temperatures and longer times, reaching a maximum of 1635 N/mm2, while elongation generally decreased with these conditions except at 100°C for 180 seconds.

1. “ 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)

2. 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

3. •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

4. Types of Cast Iron
•Gray cast iron
•Malleable Cast iron
•White cast iron
•Nodular cast iron

5. 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.

6. 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

7. 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

8. 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

9. Types of Ductile Irons
 Austenitic Ductile Iron.
 Ferritic Ductile Iron.
 Ferritic Pearlitic Ductile Iron.
 Pearlitic Ductile Iron.
 Martensitic Ductile Iron.

10. •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.

11. 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.

12. •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.

13. 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.

14. Steps in Martempering process

15. Microstructure of Martensite

16. 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.

17. 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.

18. •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.

19. •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.

20. •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.

21. •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%.

22. 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.

23. 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.

24. 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

25. Sand Preparation
Pattern making
Molding
Pouring
Final casting

26. 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

27. 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

28. 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.

29. Microstructure and Phase analysis of casting at 60°C of oil temp.
At 120 sec
At 180 sec
At 60 sec

30. Microstructure and phase analysis of casting at 80°C of oil temp.
At 60 sec
At 120 sec
At 180 sec

31. Microstructure and phase analysis of casting at 100°C of oil temp.
At 180 sec
At 120 sec
At 60 sec

32. Microstructure of casting as cast condition

33. 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

34. Hardness vs. oil temperature

35. 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

36. Tensile strength vs. oil temperature

37. 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

38. Elongation vs. oil temperature

39. 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

40. Martensite and pearlite vs. oil temperature
Ferrite vs. oil temperature

41. 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.

42. •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.

43. 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.

44. 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

45. • 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

46. •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,