Title of Thesis
EFFECTS OF HEAT TREATMENT AND ALLOYING
ELEMENTS ON CHARACTERISTICS OF AUSTEMPERED DUCTILE IRON
MUHAMMAD ASHRAF SHEIKH
Department of Metallurgical & Materials Engineering, University of
Engineering and Technology Lahore
Metallurgy & Materials
|Number of Pages
|Keywords (Extracted from title, table of contents and abstract of thesis)
HEAT TREATMENT, ALLOYING ELEMENTS, AUSTEMPERED, DUCTILE IRON
The effect of three variables on
ductile iron has been investigated in this study. The first variable
was the effect of austempering time on ductile iron. The second
variable was the effect of austenitizing temperature and the third
major variable was the effect of alloying additions on ductile iron.
The alloying elements selected for this purpose were copper, nickel,
a combination of copper and nickel and lanthanum.
The initial study was conducted on unalloyed ductile iron
castings. The effect of austempering time was examined by varying
austempering time in the range of 30 minutes to 90 minutes, while
keeping austenitization temperature and austempering temperature
constant. It was found that with the increase of austempering time,
the tensile strength increased significantly. However, at 90 minutes
the tensile strength decreased. The optimum temperature was found to
be 60 minutes. The second variable was the effect of austenitization
temperature on ductile iron. Based on the result of the first
experiment, the austempering was carried out for 90 minutes. The
austempering temperatures were kept at 270 oC and 370 oC. The
austenitization temperature was varied from 850 oC to 925 oC. The
study revealed that tensile strength increased at 900 oC but it
decreased at 925oC. The third major variable involving the effect of
alloying additions on ductile iron, was studied by adding copper
with three different values i.e. 0.5 wt. %, 1.0 wt. % and 1.5 wt. %.
The fourth melt was without the addition of copper. It was found
that with the increase of copper the tensile strength continued to
increase up to 1.5 wt. %. The second alloying addition was nickel.
One melt was made without nickel while the remaining three melts
were made with the addition of 1.0 wt. %, 2.0 wt. % and 3.0% x
nickel. The tensile strength increased correspondingly with the
increase in the addition of nickel to 3.0 wt. %. The effect of a
combination of copper and nickel on ductile iron was also examined.
The effect of the last alloying element which was studied was
lanthanum. Four melts were made for this study. The first melt was
without the addition of lanthanum while the remaining three had
0.006 wt.%, 0.02 wt.% and 0.03 wt.% lanthanum. The results indicated
that the tensile strength increased with the increase of lanthanum
content with and without austempering. Furthermore, the highest
nodule count was obtained with 0.03 wt.% lanthanum while the
nodularity remained almost unchanged.
Thus, it was observed that the addition of alloying elements
results in an increase of tensile strength. The optimum austempering
time was 90 minutes and the optimum austenitizing temperature was
found to be 900 oC.