L. Lazic1, A. Durman2, S. Lazic3 HISTORY OF METALLURGY ON THE TERRITORY OF SISAK AND BANOVINA

1
Ladislav Lazic
METALLURGY ON THE TERRITORY OF REPUBLIC CROATIA
Prof. dr. sc. Ladislav Lazic, Faculty of
Metallurgy, University of Zagreb, Sisak, Croatia,
2
A BRIEF HISTORICAL OVERVIEW OF THE DEVELOPMENT OF
METALLURGY Metallurgy in the territory of
today's Sisak and Banovina, as a region of
Sisak-Moslavina County, was developed from
Vucedol as well as Celtic and Roman culture. The
manufacturing of basic metals and metal products
has a long tradition in Sisak. Since Halstatt
period onwards today's Sisak has continually been
settled and, in all historic periods, has been
closely connected with the production of iron and
iron products as its most important industrial
branch. Solid traces of an Illyrian settlement,
dating from the Halstatt period, can be found in
Sisak on the position called Pogorelec, on the
right-bank of the Kupa (around 800 BC). In the
Mt. Trgovi area the numerous craters and slag
heaps witness about intensive mining activity in
search of iron and silver-bearing lead ores
already in Illyrian times.
3
On the position of the former Halstatt
settlement on the right bank of the Kupa, the
Celts founded Segestica, the most important
settlement of that time in the southern Pannonia.
This center is actually the continuation of the
already established relations with the mines and
iron production from the previous period. Large
geological formations of iron ore are located in
this region, more precisely on the Mount Trgovi
(Trgovska gora), the western spur of the Mount
Zrinj (Zrinska gora), both in Croatia, and south
of the river Una on the Mountain Majdan
(Majdanska planina majdan, the Arabic word for
mine) in northwestern Bosnia (Fig. 1). Apart from
the iron ore, mainly limonite, there are deposits
of silver-bearing lead ore, as well as copper
ore.
4
Figure 1. Position of Trgovska gora
5
The Roman conquest of Pannonia began from the
year 35 BC. Oktavian August destroyed the Celtic
settlement Segestica and very soon a new
settlement Siscia was established on the
left-bank of the river Kupa, more precisely
between the flows of the Kupa and the Sava.
When, the Romans took over the already
established Celtic exploitation and manufacture
of iron at Mt. Trgovi, some forty kilometers to
the south of former Segestica, they also, whence
defeated and Maezeans, integrated the iron mines
located on the Maezean territory, some twenty
kilometers southward at Mountain Majdan. Roman
mines, slag accumulations and settlements in the
northeastern Bosnia, concentrated around the
Mountain Majdan (covering an area of 1200 km2)
confirm that. The quantities of the Roman age
slag found in Blagaj and Maslovare near the river
Japra amount to 2 million tons containing 50 of
iron.
6
In Roman times, Sisak (Siscia) and its wider
surroundings become one of the largest
metallurgical centres of the whole empire with
metallurgical workshops for making arms and
tools, and mints. There were established the
water and road communications for delivery of pig
iron in the form of forged pieces as well as
dispatch of finished products. The greatest part
of the processed iron ore ended up or at least
passed through Siscia in the form of forged
pieces. Part of it travelled by diagonal land
routes, from Japra to Sisak via Osjecenica (about
60 km), but the greatest part was transported by
rivers the Sana, Japra and Una downstream and
the Sava and the Kupa (4 kilometers) upstream -
totally 220 kilometers. Blacksmith workshops for
the production of iron products were distributed
all along this route, which can best be supported
by a find of 97 forged pieces, in the form of
semi-finished products (Fig. 2), 4 kilometres
downstream of Hrvatska Dubica. They were found in
1880 and 28 of them are kept today in the
Archaeological Museum in Zagreb.
7
Figure 2. Iron forged pieces found out in the
area of Hrvatska Dubica
8
After the fall of the Roman Empire the
metallurgical activity dies out to be renewed at
the end of 10th century upon arrival of the
Saxons. In the Middle Ages, together with opening
the mines of iron, silver-bearing lead ore and
copper ore, the first coin foundry and mint were
establish by the Count Petar Zrinski on the
territory of Banovina. With penetration of the
Turks these mining and metallurgical activities
die out to revive again in 18th century with
building up the copper foundries and the
stone-blast furnaces for production of pig iron.
9
Stone blast furnace in Bešlinac
10
Stone blast furnace in Vranovina
11
After the Second World War in the area of the
Mt. Zrinj and Mt. Trgovi the metal ore mining and
metallurgical production ceased.
12
"Sisak Ironworks" Prominent pre war metallurgist
ing. Milivoj Tomac also worked in Bešlinac for
two years. He was meritorious for building the
first modern blast furnace in Croatia. In fact,
in the late thirties of the last century the
production of steel in Europe was rapidly
increased, primarily because of intensive
preparation of fascist forces for war. This is
partly reflected in Croatia, which facilitated
the achievement of ing. Miroslav Tomacs long
time idea - the construction of blast furnaces
under his own design. Ing. Tomac could not
independently achieve this idea because of
financial reasons. Therefore, on his incentive
was established the Mining Association - Melting
Plant Caprag. Chosen location was based on four
essential factors nearness of the ore deposits,
convenient possibility of coke delivery as well
as dispatch of finished product and available
workforce. Building-up of the melting plant began
in the mid-1938 and the blast furnace was
celebratory started-up on 20th August 1939.
Particularly it should be emphasized that the
blast furnace, although of a low capacity, was
originally designed and built with welded shell,
which provoked interest and foreign experts.
Afterwards the same technique was applied in
other countries. Initial production of the
melting plant was about 40 tons a day. Blast
furnace in Caprag in 1939 can be considered as
the first metallurgical plants on the territory
of todays Croatia, in the industrial sense of
the word.
13
In 1950 Željezara Sisak/ Sisak Ironworks
commenced the production of seamless steel tubes
and castings. In the period until 1990 "Sisak
Ironworks" was the only manufacturer of seamless
pipes among 34 countries in the world, with an
annual production of about 150.000 t, an
important manufacturer of welded pipes of over
200.000 t per year and cold processing pipes
(drawing, pilgering) of about 10.000 t per year.
Steel production with 2 Siemens-Martin furnaces
and 1 electric arc furnace together with 2 blast
furnace of 150 m3 was about 360.000 t per year.
Up to 850.000 t coke per year was produced in
Coke Plant Bakar. Production development has
been accompanied by the establishment of the
institution of higher education. Namely, in 1960,
the Faculty of Metallurgy was founded in
Sisak. During the Croatian War of Independence
(1991-1995) the production was drastically
falling. Thus, e.g. in 1994 the production of
welded pipes was about 28.000 t/year, seamless
pipes below 70.000 t/year and cold processing
pipes about 2.000 t/year. Afterwards the Coke
Plant Bakar, both blast furnaces with
agglomeration, both SM furnaces as well as the
strip and billet rolling mill with 2 pusher type
reheating furnaces were dismantled.
14
After two unsuccessful privatization process
(Truboimpeks, Mechel) the basic metals industry
in "Sisak Ironworks" was owned by CMC SISAK
d.o.o., Sisak. Annual steel production was at the
level of about 18.500 t seamless pipes, 16.000 t
welded pipes and 2.000 t cold processed pipes.
Today's owner of steelmaking in Sisak is
Italian company A.B.S. Sisak d.o.o. They have
electric steelmaking technology with continuous
casting of round products from ? 210 mm to ? 410
mm and billets 160x160 and 170x170 mm. The
furnace has capacity of 75 t of steel
scrap. Željezara Split (Steelworks Split) was
specialized in production of rolled reinforcing
steel. On two electric furnaces the steel
production was up to 120,000 t per year. Up to
80.000 tons of steel per year was processed in
the hot rolling mill and to almost 30.000 t in
the cold rolling mill. The steel plant was
reconstructed in the following way one electric
furnace with the ladle furnace of capacity up to
190.000 t per year and the rolling mill with
equal capacity. However, production has been
suspended for a long period.
15
A.B.S. Sisak d.o.o. has the contemporary process
route primary steelmaking in the electric arc
furnace, after that, removal of oxygen as well as
subsequent adjustment of composition and
temperature in a vessel (ladle furnace) beyond
the primary steelmaking furnace (so-called the
secondary metallurgy or ladle metallurgy
steelmaking), and vacuum process for degassing
operations, i.e. removing dissolved gasses from
the melt. The operations of secondary
metallurgy, carried out in a vessel beyond the
primary steelmaking furnace, increase the
economics and maximize the productivity of
steelmaking. Composition and cleanliness control
invariable follow primary steelmaking owing to
the increased demand of a diverse range of
high-quality steels. Downstream continuous
casting process operations demand stringent
control of composition, cleanliness, and
temperature. The total duration of secondary
steelmaking (i.e. deoxidation, alloying, heating,
degassing, etc.) operations is long and often
exceeds that of primary steelmaking.
16
Despite being a modern plant for the production
of high quality steel, there are many
opportunities to improve existing technological
processes that could be achieved with scientific
research projects in cooperation of scientific
educational institutions and the
steelmakers. Modeling in steelmaking process
analysis, design, optimization, and
control Higher productivity and superior product
quality are interlinked with efficient process
control. Because of that, the development of an
adequate measuring devices and an increasing of
process models for effective control and
automation technology in steelmaking have special
importance. Modelling is a well-established
scientific technique with demonstrated
capabilities and finds widespread application in
engineering process analysis, design, control,
and optimization. Physical modelling - The key
objective in physical modelling is to measure and
visualize one or many characteristics of the real
system, rather inexpensive and conveniently.
Obtained results can be applied to validate a
mathematical model.
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• Mathematical modelling
• A mathematical model is a set of equations,
  algebraic or differential, which may be used to
  represent and predict certain phenomena. As the
  steelmaking is a complex process which involves
  multiphase turbulent flow, heat and mass transfer
  as well as chemical reactions among slag, metal,
  gas, and solid, numerical idealizations are
  applied to formulate reasonable realistic process
  models in steelmaking. Mathematical modelling
  offers many advantages low cost, remarkable
  speed, simulation of real conditions, complete
  information, etc.
• Various types of mathematical models are applied
  in steelmaking process analysis, design,
  optimization, and control
• Computational fluid dynamics based models for
  simulation of reacting turbulent flows and
  transport
• Artificial intelligence based models (neural
  network models) for process control and
  optimization
• Thermodynamic models for equilibrium
  calculations
• Reduced order models for automation and control,
  which are already applied in practice.

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Process analysis and optimization involve
mathematical modelling primarily in an off-line
fashion. In contrast, process control requires
modelling and prediction in real time. Models in
category 1 are in general far too complex and
therefore, not suited for real time applications
in steelmaking process control. Online control
requires simpler models and in such context,
reduced order models have made in the
practice. Electric arc furnace A.B.S. Sisak
d.o.o. has the electric arc furnace with three
supplemental burners mounted in the sidewalls. In
addition to productivity improvements of 5 to
20, the burners provide economical energy for
melting scrap at low cost. An efficient oxy/fuel
practice typically supplies 25 of the total
energy required to melt the steel. This may be
higher or lower, depending on the desired results
and characteristics of the furnace and operation
in question. The many opportunities exists in
varying the power of electricity and burners
during the melting process in order to reduce the
overall fuel consumption (electricity and natural
gas), melting time, and consumption of refractory
and electrodes.
19

• Ladle preheating
• The ladle heating parameters significantly affect
  the metallurgical processes and there are four
  primary reasons for preheating ladles prior to
  pouring molten metal into them
• To minimize the cooling effect on the molten
  metal
• To minimize the thermal shock on the refractory
• To remove any moisture that may have accumulated
  in the vessel
• The benefits of ladle preheating include
  increased ladle lining life, lower refractory
  maintenance costs, and increased productivity and
  quality in casting due to more consistent melt
  temperatures.

The issue of proper conducting the process of
drying and heating the ladle lining has received
a special importance with the development of
ladle metallurgy and the dissemination of
continuous steel casting. Requirements of ladle
drying and heating are different, but these
processes have a major impact to its durability,
reliability and the quality of the castings. The
drying requires a very slow and uniform heating
with controlled velocity and dependent on the
lining and the capacity of the ladle. Usually a
ladle lining is composed of two layers -
insulation and operating. The appropriate
temperature conditions have to be required
depending on the type of lining.
20

• Todays refractories and steelmaking processes
  often require ladle preheated temperatures above
  1100C, which can be difficult to obtained with
  conventional air/fuel burners. There is a
  possibility to replace the existing system with
  advanced commercially available combustion
  technologies such as High Temperature Air
  Combustion (HiTAC) or Flameless Oxy-Fuel
  Combustion. This type of burner, equipped with
  full automation and flame detection, ensures safe
  operation and precise control of the temperature
  distribution during the heating process.
• In comparison with the existing conventional
  air/fuel burners, the ladle preheating with one
  of the advanced combustion technologies, for
  example with automatic self-recuperative burner,
  has the following benefits
• faster heating - depending only on the
  technology
• reducing the natural gas consumption up to 35
• possibility of increasing the ladle heating
  temperature of around 250 - 400C
• uniform surface temperature distribution
  (differences between the measured points not
  exceed 10C)
• radical reduction in CO and NOx emissions
• increasing the durability of the ladle linings

21
Environmental aspects were and have been a
serious challenge for steelmakers. Large volume
of gasses and dust are generated during various
stages of steelmaking. Efficient gas cleaning
plants or dedusitng system are required to clean
off-gases, to be practically free of dust and
sulphur. Dust and slag, etc. are valuable
by-products of the steel plants that can help
conserve energy and natural resources in an
effective manner and therefore require serious
considerations. Similarly, human involvement in
risk-prone area and hazardous environment should
be as little as possible. Apart from the
producers of steel, Metallurgical faculty have
cooperation with a number of metal processing
companies in Croatia, providing them various
technical and research services.