study of ductile iron

1. A SEMINAR ON
“STUDY OF DUCTILE IRON’’
 NIAJ AHMED

2. INTRODUCTION:-
 DUCTILE IRON IS THE NAME GIVEN TO THAT CAST –IRON,
WHERE THE GRAPHITE IS PRESENT IN THE MATRIX IN THE
FORM OF SPHEROID OR GLOBULES OR NODULES. HENCE IT
IS ALSO CALLED AS NODULAR IRON AND BECAUSE OF ITS
EXCEPTIONALLY HIGH DUCTILITY (WITH ELONGATION SOME
TIMES AS HIGH AS 22%) IS ALSO REFERRED TO AS DUCTILE
IRON.

3. PRORERTIES OF DUCTILE IRON :-
 HIGH STRENGTH (IN SOME CASES EVEN GREATER THAN THE STEEL)
 ADEQUATE DUCTILITY.
 SUPERIOR CAST ABILITY.
 EXCELLENT MACHINABILITY.
 LOWER DENSITY THEN THAT OF STEEL.
 SUPERIOR SURFACE LUBRICATION PROPERTIES.
 BETTER DAMPING CHARACTERISTICS.
MICROSTRUCTURE:-

4. COMPOSITION OF DUCTILE IRON :-
GRADES OF DUCTILE IRON:
 350/22
 400/18
 400/15
 450/10
 500/7
 600/3
 700/3
 800/2
 900/2
COMPOSITION PERCENTAGE
CARBON 3.0-4.0
SILICON 2-3
MANGANESE 0.15-0.25
SULPHUR 0.015
PHOSPHOROUS 0.05 MAX.
MAGNESIUM 0.015-0.05

5. PRODUCTION OF DUCTILE IRON:-
MELTING OF BASE IRON.
 DE –SULPURIZATION.
Mg- TREATMENT.
POST INOCULATION.
MELTING OF BASE IRON CONSIST OF:-
 PIG IRON.
 STEEL SCRAP.
 CAST IRON SCRAP.
 FOUNDRY RETURNS.

6. DESULPHURIZATION:-
IT IS A PROCESS TO REDUCED THE SULPHUR% IN THE
MELT BASE GREY IRON IN S.G IRON PRODUCTION.
THIS PROCESS ONLY REQUIRED IN ACID LINE
CUPOLA FURNACE AND OTHER ALL TYPES OF
FURNACE ARE NOT REQUIRED.
DESULPURIZING AGENT:-
 CALCIUM OXIDE (CaO)
 SODIUM CARBONATE(Na₂CO₃)
 CALCIUM CARBIDE(CaC₂)

7. Mg TREATMENT:-
MAGNESIUM PLAYS THE MOST IMPORTANT ROLE IN
THE DUCTILE IRON PRODUCTION.
THE TECHNIQUES OF MG TREATMENT ARE AS
FOLLOWS:-
 OPEN LADLE TRANSFER METHOD.
 SANDWICH METHOD.
 TUNDISH COVER METHOD.
 PLUNGING METHOD.
 CONVERTER PROCESS.
 IN-MOULD TECHNIQUES.

8. OPEN LADLE TRANSFER METHOD
 IT IS ALSO KNOWN AS POUR
OVER METHOD.
 IN THIS ALLOY PLACED IN
OPEN LADLE.
 DENSITY ALLOY IS NEEDED.
 TAPPING RATE 15 SECOND/
TON.
 SIMPLE AND GOOD FOR
SMALL BATCHES.
 Mg RECOVERY IS 20%-25%.

9. SANDWICH METHOD
 IT IS ALSO CARRIED OUT IN
OPEN LADLE.
 IN THIS THE MAGNESIUM
ALLOY PLACED IN A POCKET
IN THE BOTTOM OF THE
LADLE AND COVERED WITH
STEEL SCRAP OR STEEL
PLATES.
 THIS IS SIMPLE AND
FLEXIBLE METHOD.
 Mg RECOVERY IS 40%-45%

10. TUNDISH COVER METHOD
 OXIDATION OF Mg IS
REDUCED.
 REDUCTION IN CARBON
LOSS.
 REDUCED IN
TEMPERATURE LOSS.
 Mg RECOVERY IS 60%-65%.
 90% FUMES REDUCTION.

11. PLUNGING METHOD
 SUITABLE FOR LIGHTER
MAGNESIUM MATERIAL.
 TREATMENT TIME IS
LONGER AND
TEMPERATURE LOSS IS
HIGHER WHEN PLUGING
AND THERE IS VERY LITTLE
FLEXIBILITY IN CHANGING
THE QUANTITY OF IRON
TREATED.
 Mg RECOVERY IS 50%

12. CONVERTER PROCESS
 IT IS ALSO KNOWN AS
GEOGE FISCHER
CONVERTER METHOD.
 THE REACTION CHAMBER IS
CHARGED WITH PURE
MAGNESIUM.
 BASE IRON WITH HIGH
SUPHUR CONTENT 0.2%-0.3%
CAN BE USED BECAUSE OF
HIGH EFFICIENCY OF
MAGNESIUM USED.
 Mg RECOVERY CAN BE HIGH
AS 70%.

13. IN-MOULD TECHNIQUES
 THE TECHNIQUE OF
ADDING MAGNESIUM
ALLOYS IN THE MOULD
CAVITY, WELL KNOWN
AS THE IN-MOULD
PROCESS.
 POURING TIME TO BE
CONTROLLED.
 SUITABLE FOR MASS
PRODUCTION.
 Mg RECOVERY IS
MAXIMUM UPTO 75%.

14. Mg% to be added= desired % Mg + Base iron S%
%Mg recovery X 0.01
 Mg Recovery % = 0.76 x (S% in base metal – S% residual) + residual Mg%
• Mg% added
The amount of nodulizer required is given by the formula :
 % nodulizer alloy = %Mgr + %Mgs
%Mga X %E
Where
 Mgr = residual magnesium
 Mgs = The amount of magnesium that will reacts with
sulphur
(% Mgs = 0.75 x % of sulphur in base Iron)
 Mga = Magnesium in the alloy
 E = Efficiency of the processes.

15. POST INOCULATION
 SINCE IN THE CASE OF PRODUCTION OF DUCTILE IRON, INOCULATION IS DONE
AFTER SOME TREATMENT i.e DESULPURIZATION & Mg TREATMENT.
 AS WE KNOW THAT INOCULATION PROVIDES MORE NUCLEATION CENTRE FOR
GRAPHITIZATION & REDUCES THE CHILLING TENDENCY.
 FOR S.G IRON INOCULATION GRADE FERRRO SILICON (3-5%) IS USED AS A
INNOCULANT WHOSE CHEMICAL COMPOSITION IS ≈ 70% Si+0.1%(Ca, Ce, Sn, Ba,
Al) + BALANCE Fe.
 THE IMPURITIES PROVIDES EXTRA NUCLEATION FOR NODULIZERS.
 AFTER INOCULATION, TREATED MELT SHOULD BE POURED IN THE MOULD
BETWEEN 4- 10 MINUTE.
 STORING INNOCULANT FOR LONGER TIME PERIOD CREATS TWO PROBLEM.
1. MOISTURE PICK UP, WHICH WHEN EXCESSIVE CAN GREATLY INCREASES
HYDROGEN CONTENT IN THE MELT, CAUSING PINHOLE.
2. THE OTHER PROBLEM IS INOCULANT DETORIATION CAUSED MOST LIKELY
BY OXIDATION OF THE ACTIVE INOCULATING ELEMENT.

16. EFFECT OF INOCULANT:-
 SIZE:
1. SMALLER SIZE CAUSES OXIDATION/ BURNING OF
INNOCULANTS.
2. GREATER SIZE CAUSES INCLUSION & DISSOLUTION
PROBLEM.
 TIME:
1. EARLIER ADDING CAUSES DISSOLUTION PROBLEM
2. LATE ADDING CAUSES REVERSIBILITY.
 AMOUNT:
1. LESSER AMOUNT CAUSES CHILLING TENDENCY
2. MORE AMOUNT CAUSES CHANGE IN CHEMICAL
COMPOSITION.

17. APPLICATIONS OF DUCTILE IRON:-
THE APPLICATION OF THE S.G IRON HAVE INCREASED TREMENDOUSLY IN
RECENT TIMES AS CAN BE SEEN FROM THE LIST OF THE COMPONENTS
WHICH ARE BEING MADE.
 ENGINE CRANK SHAFT
 BRAKE CALIPER, DISC BRAKE ANCHOR, BRAKE ANCHOR PLATE.
 MACHINE- TOOL BED
 ELECTRICAL INSULATOR POST AND CAP.
 STEERING KNUCKLE
 RACK AND PINION OF STEERING ASSEMBLY
 PISTON FOR IMPACT DRILLS.
 ROLLING MILL ROLLS.
 MOULDING BOXES AND MOULD BOX CLAMPS
 BRAKE SHOE FOR HEAVY DUTY BRAKES.
 SPACER CAGE FOR ROLLING BEARING.
 PISTON RINGS.
 WIND MILL ITEMS

18. CONCLUSION:-
THE DUCTILE IRON FINDS WIDE ENGINEERING
APPLICATION BECAUSE OF ITS EXCELLENT
COMBINATION OF CASTABILITY AND MECHANICAL
PROPERTY. IT HAS ALSO VERY GOOD
MACHANIABILITY, CORROSION RESISTANCE, WEAR
RESISTANCE AND THERMAL SHOCK RESISTANCE. IT
FINDS APPLICATION IN GEARS, DIES, VALVE AND
PUMP BODIES, PINION, CRANK SHAFT ETC. IT IS A
WIDELY ACCEPTABLE CAST IRON BECAUSE OF HIGH
STRENGTH AND GOOD DUCTILITY. THE PROBLEMS
FACED DUE TO LOWER MELTING AND BOILING
POINT OF MG HAVE BEEN ENCOUNTER BY USING
VARIOUS MAGNESIUM TREATMENT PRACTICES.