Pig iron

1. 5
th
International Advanced Technologies Symposium (IATS’09), May 13-15, 2009, Karabuk, Turkey
© IATS’09, Karabük Üniversitesi, Karabük, Türkiye
HIGH PURITY PIG IRON PRODUCTION BY USING STEEL SCRAP AND
COMPARISON WITH SORELMETAL®
ÇELİK HURDALARI KULLANILARAK YÜKSEK SAFLIKTA PİK DEMİR
ÜRETİMİ VE SORELMETAL®
İLE KIYASLANMASI
Gökhan ÖZER
a
, Nilüfer EVCİMEN
a
, Ahmet EKERİM
a
*
a
Yıldız Teknik Üniversitesi Kimya-Metalürji Fakültesi Metalürji ve Malzeme Mühendisliği Bölümü 34210
Esenler/İstanbul, Türkiye, E-posta: gozer@ yildiz.edu.tr, nevci@ yildiz.edu.tr, ekerim@ yildiz.edu.tr
ABSTRACT
Sorelmetal
®
(high purity iron ingots produced by QIT - Fer
et Titane Inc); is the most common charge material of
ductile iron production used in worldwide range. In this
study, high purity pig irons with different compositions were
produced from steel scrap instead of iron ore by using
electrical arc furnace. These products were compared with
Sorelmetal
®
, according to their chemical compositions and
microstructure observation.
Experimental studies were performed on pig irons to
examine the similarities to Sorelmetal
®
. For chemical
analyses optical emission spectrometry, for microstructural
observation optical light microscope have been used. In
addition, graphite sizes of the ductile iron were measured
by using image analyzer.
Depending on the obtained results, both structure and size
distribution of graphites resemblances to Sorelmetal®
.
Therefore this method can be used as a promising of
Sorelmetal®
Key words: Pig iron, Sorelmetal
®
, steel scrap, electrical
arc furnace.
ÖZET
Sorelmetal
®
(QIT – Fer et Titane Inc.’de tarafından üretilen
yüksek saflıktaki demir ingotları); küresel grafitli dökme
demir üretiminde dünya çapında en yaygın kullanım
alanına sahip şarj malzemesidir. Bu çalışmada yüksek
saflıktaki farklı kompozisyonlara sahip pik demir, demir
cevheri yerine çelik hurda kullanılarak elektrik ark fırınında
üretilmiştir. Üretilen pik demirler kimyasal kompozisyon ve
mikro yapı incelemeleri bakımından Sorelmetal
®
’le
kıyaslanmıştır.
Deneysel çalışmalar, pik demirler ile Sorelmetal
®
arasındaki benzerlikleri gözlemlemek amacıyla
gerçekleştirilmiştir. Kimyasal analizler için, optik emisyon
spektrometresi, mikro yapı incelemeleri için ise optik ışık
mikroskobu kullanılmıştır. Buna ek olarak grafit boyutları
imaj analiz cihazı kullanılarak tespit edilmiştir.
Elde edilen sonuçlar doğrultusunda küresel grafitli dökme
demirin hem yapısal hem de grafit boyut dağılımları
Sorelmetal
®
’ e uyum sağlamaktadır. Buna bağlı olarak bu
metot Sorelmetal
®
’e alternatif olarak gelecek vadeden bir
metottur.
Anahtar Kelimeler: Pik demir, Sorelmetal
®
, çelik hurdası,
elektrik ark fırını.
1. Introduction
The first iron castings to be made were cast directly from
the blast furnace. Foseco 23 Blast furnaces do not
produce steel, they produce pig iron. Primary, Iron
produced in the blast furnace is converted into the
following commercial products as steel, cast iron and pure
iron. Table 1.1. shows typical analysis of these products.
[1]
Table 1.1 Typical analysis of ferrous materials.
Pig
Iron(%)
Cast
Iron(%)
White Cast
Iron(%)
Steel(%)
C 3.5 – 4.25 2.5 – 3.75 1.75 – 2.7 0.10
Si 1.25 0.5 – 3.0 0.8 – 1.2 0.02
Mn 0.9 – 2.5 0.40 – 1.0 < 0.4 0.40
S 0.04 0.01 – 0.18 0.07 -0.15 0.03
P 0.06 – 3.0 0.12 – 1.1 < 0.02 0.03
Liquid iron from a blast furnace contains around 4 %C and
up to 2 %Si, together with other chemical elements derived
from the ore and other constituents of the furnace charge.
The presence of so much dissolved carbon etc. lowers the
melt point of the iron from 1536°
C (pure iron) to a eutectic
temperature of about 1150°
C (Fig. 1.1) so that blast
furnace iron is fully liquid and highly fluid at temperatures
around 1200°
C.

2. Özer ,G., Evcimen, N. and Ekerim, A.
Iron – Graphite ( - ) Iron- Carbide ( - - - )
Carbon
Content
(%C)
Temperature
( °
C)
Carbon
Content
(% C)
Temperature
( °
C)
A 2.09 1154 2.12 1148
B 4.25 1154 4.31 1148
C - - 6.68 1226
D 0.68 739 0.76 727
Figure 1.1 The iron–carbon phase diagram. [2]
While the solidification of the iron, most of the carbon is
thrown out of solution in the form either of graphite or of
iron carbide, depending on the composition of the iron, the
rate of cooling from liquid to solid and the presence of
nucleate. When the carbon is precipitated as flake
graphite, the casting is called ‘grey iron’. (Fig. 1.2) if as
carbide, the casting is said to be ‘white iron’. [3]
Figure 1.2 Random flake graphite, X100. [4]
Ductile iron has been known only since the late 1940s, but
it has grown in relative importance and currently
represents about 20 to 30% of the cast iron production of
most industrial countries. [5] Ductile iron, also known as
spheroidal graphite (s.g.) iron or nodular iron is made by
treating liquid iron of suitable composition with magnesium
before casting. This promotes the precipitation of graphite
in the form of discrete nodules instead of interconnected
flakes (Fig. 1.3). The nodular iron so formed has high
ductility, allowing castings to be used in critical applications
such as: Crankshafts, steering knuckles, differential
carriers, brake calipers, hubs, brackets, valves, water
pipes, pipe fittings and many others. [3]
Figure 1.3 Nodular graphite, X100. [4]
The spheroidal form of graphite that characterizes ductile
iron is usually produced by a magnesium content of about
0.04 to 0.06%. Magnesium is a highly reactive element at
molten iron temperatures, combining readily with oxygen
and sulfur. For magnesium economy and metal
cleanliness, the sulfur content of the iron to be treated
should be low (preferably <0.02%); this is readily achieved
in an electric furnace by melting charges based on steel
scrap or special-quality pig iron supplied for ductile iron
production, together with ductile iron returned scrap.
The contents of elements that affect the formation of
nodular graphite and promote the formation of carbide are
low according to the application of the grade concerned.
Higher-strength grades of ductile iron can be made with
common grades of constructional steel scrap, pig iron, and
foundry returns, but certain trace elements, notably, lead,
antimony, and titanium, are usually kept as low as possible
to achieve good graphite structure. Titanium in trace
amounts is beneficial to gray iron flake graphite, but is
detrimental to the nodular graphite forms needed in ductile
iron. [3]
Pig iron production from ilmenite, FeTiO3, process starts
with the mixing of is a certain amount of carbon which is
just enough to reduce the iron oxide component of the ore.
Then charged in an electrical furnace at 1650 °
C where
iron oxide is reduced to metal while titanium is separated
as a slag. The high purity iron ingots produced at the
metallurgical complexes of QIT - Fer et Titane Inc. (Sorel,
Canada) and Richards Bay Minerals (Richards Bay, South
Africa). Rio Tinto Iron & Titanium which markets
Sorelmetal®, guarantees the quality of this product as well
as the consistency, lot after lot, of its chemical
composition.
Figure 1.4 represents the selective reduction of ilmenite
process. A small amount of TiO2 is reduced to Ti2O3 and
will be found in the slag. The slag is mainly titanates of
iron, magnesium and calcium together with some calcium
and aluminum silicates. Its titanium dioxide content varies
between 72 and 98 %.

3. Özer ,G., Evcimen, N. and Ekerim, A.
Figure 1.4 Selective reduction of ilmenite. [6]
The analysis of iron produced at Sorel also known as
Sorelmetal® is given in Table 1.2. The slag is high in
titanium and low in iron and is therefore preferable to
ilmenite in manufacturing TiO2 pigment or titanium metal.
[6]
Table 1.2 Analysis of iron produced from Qebec ilmenite at
Sorel.
As the primary sources of metal, natural ores deplete
consistently, there is an obvious recognition that the total
supply of any metal on Earth is finite. It is evident that the
metals have to be recycled from "scrap" to maintain a
steady supply to meet the demands of industry and
wherever else metals are used., recycling of metal from
secondary sources (scrap of relatively abundant metals
like iron, steel and aluminum) is an established industry,
motivated by both economic as well as environmental
factors. [7] According to this approach, improvements on
iron- steel industry in process steps are accelerated. [8]
In this study, experiments were carried out by bringing a
new, different point of view on high purity pig iron
production. An alternative method of production was
investigated by using steel scrap instead of iron ore.
2. EXPERIMENTAL METHODS
Experimental studies started with selecting the
conformable steel scrap. Chemical composition of the
scrap was determined by optical emission spectroscopy on
a HILGER Analytical.
According to the determination of steel scraps, sawdust
was prepared from them as small as possible in laboratory
conditions. Graphite powders were used as a carbon
source for transforming steel scrap to pig iron. Carbon
tenor of graphite powder is % 99.5. Furthermore, pressing
process was applied on both graphite powders and steel
scrap to obtain convenient samples for melting operations.
Additional carbon content amount was determined by
using Equation 2.1 [9]
G
xM
C
B
A
)
( −
=
(Equation 2.1)
A= Amount of charge C (kg) E=Percentage of
experimental C (%)
B= Percentage of exist C (%) M= Mass of steel scraps
(kg)
G=Percentage of graphite
tenor (%)
Melting process was realized on atmosphere controlled,
single electrode, direct current electrical arc furnace as
laboratory scale. Picture and schematic illustration of
vacuum arc furnace has shown in Figure 2.1 a and b.
(a) (b)
Figure 2.1 Vacuum arc furnace (a) Picture (b) Schematic
illustration [10]
After melting process both chemical composition and
metallographic analyses were done on prepared samples.
The specimens were grinded and then polished with Al2O3
paste. 2% nital was used to etch the samples. The
microstructures of the samples were observed up to the
magnification of 1000X in a light microscope with LEICA
DFC280 Image Analyzer.
3. RESULTS and DISCUSSION
3.1. Chemical Analysis of Steel Scrap
Acquirement of high purity pig iron, choosing the
convenient steel scrap according to its chemical
composition has great importance. The amount of Sulfur
(S), Titanium (Ti), Magnesium (Mn) and Silicon (Si) must
be as lower as possible. Chemical composition of selected
steel scrap is shown in Table 3.1.
C S P2O5 MnO
1.8-2.5 0.11 0.025 Trace
V2O5 Cr Si TiO2
0 0.05 0.08 Trace

4. Özer ,G., Evcimen, N. and Ekerim, A.
Table 3.1 Chemical composition of selected steel scrap.
Fe C Si Mn P S Cr
98.70 0.13 0.250 0.476 0.007 0.18 0.027
As B Co Cu Nb Pb Sn
0.006 0.00 0.004 0.040 0.006 0.00 0.024
Mo Ni Ti V Al W
0.00 0.02 0.00 0.00 0.052 0.04
The results as shown in Table 3.1, suitability of selected
steel scrap that would be used in experimental study.
3.2. Determination of Charge Amount
Mass of charge steel scrap was determinate as 20 g
according to melting furnace conditions. Additionally,
amount of charge carbon was measured by using Equation
2.1. Percentage of exist carbon content was taken as 4.00
and experimental was 0.134 (from Table 3.1). As
mentioned before carbon tenor of graphite powder was
taken as % 99.5.
By placing, these dates in Equation 2.1, Equation 3.1 was
achieved.
( ) ( )
( )
g
g
A 780
.
0
5
.
99
20
134
.
0
00
.
4
≅
×
−
=
( 3.1)
According to Equation 3.1 amount of charge carbon was
determinate as 0.78g. After pressing the samples with
pressing mold (Figure 3.1.(a)), shapes of samples became
like Figure 3.1(b).
(a) (b)
Figure 3.1 View of (a) pressing mold, (b) pressed sample.
3.3. Chemical Analysis of Samples
Firstly, chemical analysis of Sorel pig was done as shown
in Table 3.2.
Table 3.2 Chemical analysis of Sorel pig.
Fe C Mn S P Ni
95.1 3.72 0.03 0.025 0.023 0.05
Cr Cu Mo Al Sn As
0.00 0.01 0.005 0.005 - -
B V Nb Ti Si W
- 0.05 0.007 0.003 0.032 0.00
Chemical analysis results of five samples are given in
Table 3.3, 3.4, 3.5, 3.6 and 3.7.
Table 3.3 Chemical analysis of Sample 1.
Table 3.4 Chemical analysis of Sample 2.
Table 3.5 Chemical analysis of Sample 3.
Table 3.6 Chemical analysis of Sample 4.
Table 3.7 Chemical analysis of Sample 5.
3.4. Microstructure Analysis
Microstructure analyses with magnification of 100X are
shown in Figure 3.2.
Fe C Mn S P Ni
95.5 4.32 0.038 0.010 0.005 0.00
Cr Cu Mo Al Sn As
0.02 0.04 0.005 0.021 - -
B V Nb Ti Si W
- 0.00 0.006 0.003 0.007 0.013
Fe C Mn S P Ni
95.5 4.09 0.146 0.031 0.007 0.00
Cr Cu Mo Al Sn As
0.00 0.00 0.002 0.025 - -
B V Nb Ti Si W
- 0.00 0.007 0.00 0.066 0.001
Fe C Mn S P Ni
94.5 4.13 0.293 0.031 0.007 0.008
Cr Cu Mo Al Sn As
0.075 0.00 0.003 0.031 - -
B V Nb Ti Si W
- 0.00 0.010 0.00 0.22 0.099
Fe C Mn S P Ni
95.4 4.18 0.054 0.028 0.08 0.00
Cr Cu Mo Al Sn As
0.00 0.025 0.002 0.054 - -
B V Nb Ti Si W
- 0.00 0.006 0.001 0.07 0.017
Fe C Mn S P Ni
95.1 4.20 0.124 0.026 0.018 0.00
Cr Cu Mo Al Sn As
0.036 0.044 0.002 0.043 - -
B V Nb Ti Si W
- 0.00 0.015 0.00 0.331 0.048

5. Özer ,G., Evcimen, N. and Ekerim, A.
(a) (b)
(c) (d)
(e) (f)
Figure 3.2 (a) Sorelmetal
®
, (b) Sample 1, (c) Sample 2, (d)
Sample 3 ,(e) Sample 4 ,(f) Sample 5 microstructures.
The microstructures of the samples shown in Figure 3.2
could be compared with sorel pig (Figure 3.2 (a)).
However, structures were changed according to sample
chemical compositions, they pointed similarities with
Sorelmetal
®
pig structure.
4. CONCLUSION
In this study, an alternative material, in comparison with
sorel pig (most commonly used in production of spherical
graphite cast iron known as ductile iron) has been
investigated. During production process instead of using
iron ore, high quality steel scrap has been employed. High
quality pig iron production has been obtained by adding
extra carbon into the steel scrap and melting in electrical
arc furnace with repeating the operation three times.
After melting process, completed similar results between
samples and sorel pig were obtained in both chemical
compositions and microstructures.
According to this achievement, the pig irons produced by
this alternative method could be used as an alternative of
sorel metal pig.
Furthermore, this method improves the recycling of steel
scrap that provides environmental and economical
benefits.
References
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The Metal Industry Ferrous Metals, Wiley-VHC, 1997.
[2] Elliott, R., Cast Iron Technology, Butterworth-
Heinemann, reproduced by permission of the
publishers, 1988.
[3] J. R. Brown, Foseco Ferrous Foundryman’s Handbook,
Butterworth Heinemann, 2000.
[4] T. SJOGREN and I. L. SVENSSON, The Effect of
Graphite Fraction and Morphology on the Plastic
Deformation Behavior of Cast Irons ,Metallurgıcal And
Materials Transactions A, Vol. 38A, 840-847, 2007
[5] ASM Metal Handbooks, Vol.15, ASM International,
1988.
[6] www.sorelmetal.com
[7] S. R. Rao, Resource Recovery and Recycling from
Metallurgical Wastes, Elsevier, 2006.
[8] M. Yanmaz, İklim Değişikliği ve AB Uyum Yaklaşımının
Demir Çelik Sektörüne Etkileri, Erdemir Sürdürülebilir
Çevre Grubu, Kasım 2005.
[9] N. Aras, Küresel Grafitli Demir Dökümü, MMO, Yayın
No:45, 1970.
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Titanyum Üretim Koşullarının Termodinamik
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