Unit 2
What is steel
There have been various definitions as to what steel is, but it can be
generally defined as a material that consists mainly of iron, with a
carbon content of less than 2%. Other elements may also be present, but
of all the alloy elements, carbon has the most distinct effect on the
steel properties.
Carbon
Pure iron has neither the strength, nor the hardness required for most
applications, but when combined with small amounts of carbon, it becomes
steel. Changing the carbon content and adding other elements affects
the steel properties. If the amount of added alloy elements exceeds
0.5%, the material is called alloy steel. With the present alloy
elements below 0.5%, the material is called non-alloy steel.
Carbon also plays an important role during steel making. Its content
depends on the production process, but usually excess carbon has to be
removed during the liquid phase.
Exercise 1:
Translate the following text into Czech:
Pure iron has neither
the strength, nor the hardness required for most applications, but when
combined with small amounts of carbon, it becomes steel. Changing the
carbon content and adding other elements affects the steel properties.
If the amount of added alloy elements exceeds 0.5%, the material is
called alloy steel. With the present alloy elements below 0.5%, the
material is called non-alloy steel.
Carbon also plays an important role during steel making. Its content
depends on the production process, but usually excess carbon has to be
removed during the liquid phase.
Answer Key: Exercise 1
Diverse product
Steel is thus a collective noun for a product that varies according to
methods of production, shape, dimensions, chemical composition,
properties and applications. The chemical properties and the mechanical
properties are specified in standards and various steel grades are
produced via different production processes. The broad range of
properties that can be implemented, the many forms, in which steel is
supplied, together with its ability to be easily recycled, make this
product suitable for the most diverse fields of application.
Besides the quality of the final product, other aspects such as cost
price, energy saving and a low environmental aspect are equally
important.
Stages of steel production
Steel is produced in integrated steel works which comprise all
production units needed to convert the raw materials into the final
product. Steel works are divided into “hot” sections and “cold”
sections.
The following two subchapters include many – as yet - unfamiliar words
which will be dealt with in a greater detail in the follow up chapters.
Exercise 2:
Please select technical terms from the text below and translate them:
Diverse product
Steel is thus a collective noun for a product that varies according to
methods of production, shape, dimensions, chemical composition,
properties and applications. The chemical properties and the mechanical
properties are specified in standards and various steel grades are
produced via different production processes. The broad range of
properties that can be implemented, the many forms, in which steel is
supplied, together with its ability to be easily recycled, make this
product suitable for the most diverse fields of application.
Besides the quality of the final product, other aspects such as cost
price, energy saving and a low environmental aspect are equally
important.
Stages of steel production
Steel is produced in integrated steel works which comprise all
production units needed to convert the raw materials into the final
product. Steel works are divided into “hot” sections and “cold”
sections.
The following two subchapters include many – as yet - unfamiliar words
which will be dealt with in a greater detail in the follow up chapters.
Answer Key: Exercise 2
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Hot sections that start with raw materials and produce hot rolled coils include the following stages:
- Preparation of the raw materials – iron ore and coal
- Production of pig iron in the blast furnace
- Desulphurization of the pig iron and transport to the steel plant
- Converting the pig iron into steel in the converter
- Ladle metallurgy: degassing for certain steel grades, alloying and temperature adjustment
- Continuous slab casting
- Slab inspection and slab scarfing where necessary
- Reheating of the slabs and subsequent hot rolling
A hot rolled coil can be used either as a semi-finished product or as a final product. Hot rolled material is used as such for construction, making pipes, etc. but it can also undergo further processing in the cold rolling section or a coating line. Hot rolled coated products are used mainly for applications in the building industry. Cold rolled final products are used in car bodies, domestic appliances, packaging, etc.
Exercise 3:
Cold section of integrated steel works generally consists of the following stages:
- Pickling and cold rolling
- Continuous or batch annealing to attain the required mechanical properties
- Skin pass milling to generate roughness, improve flatness and optimize the mechanical properties
- Metallic and / or organic coating if required
- Inspection and packaging
In the case of thermal or hot dip galvanizing, the last four stages are combined in the coating line.
As a result of economic and ecological developments, more stringent criteria regarding thickness and flatness tolerance as well as surface quality demand new technology with highly automated equipment and built-in control systems.
Exercise 4:
Pickling -
Cold rolling -
Annealing -
Organic coating -
Hot dip galvanizing -
Skin pass milling -
Integrated steel works include a blast furnace and a converter to produce liquid steel. This is also called blast furnace steel making or primary steel making. In addition to iron ore, about 20% scrap iron is also used in this process. The energy required to melt this iron is provided by fossil fuels. Before the raw materials (iron ore and coal) are suitable for use in the blast furnace, they have to undergo intensive preparation.
Electric furnaces on the other hand are charged with 100% scrap iron or with iron ore or direct reduced iron (DRI). These materials melt by putting in large amounts of electrical energy by means of an electric arc. Hence their name: Electric Arc Furnace (EAF) also called secondary steel making. Steel production in electric furnaces no longer requires intensive preparation of raw material. Because the charges of an electric furnace are smaller, they can meet the demand more flexibly. But the process also has its limitations: quality and price of scrap metal are of overriding importance. Besides, some elements present in the scrap metal are retained in the liquid steel.
Exercise 5:
Please answer the following questions:
What falls under the primary steel making?
What falls under the secondary steel making?
Because of the huge investment entailed in building a new steel works, new technologies that require less capital have been developed. The mini mill is one of these. These are compact steel works using electric furnaces and thin slab casters. This greatly simplifies downstream processing in that a simple hot rolling treatment usually suffices to produce the final product.
A further simplification of this process could be achieved by casting the slabs directly in the thickness required for the final product, bypassing thus the rolling stage completely. This process is called strip casting.
Mini mill applications tend to be used for production of rather simpler grades due to possible quality problems such as surface defects.
Exercise 6:
Please answer the following questions:
What constitutes the simplification of a mini mill?
What is called strip casting?
What is the disadvantage of mini mills?
Exercise 7:
Slab caster -
Strip casting -
Exercise 3:
- Preparation of the raw materials – iron and coal
- Production of iron in the furnace
- Desulphurization of the iron and transport to the steel plant
- Converting the iron into steel in the
- Ladle metallurgy: for certain steel grades, alloying and temperature adjustment
- slab casting
- Slab inspection and slab where necessary
- Reheating of the slabs and subsequent hot
Points to remember:
- Carbon plays a very important role during steel making. It is the most common alloying material for iron, but various other alloying elements are also used.
- Integrated steel works are divided into a “hot” section and a “cold” section.
- Primary steel making uses blast furnace and converter.
- Secondary steel making uses electric furnace.
- Mini mill requires less capital, but is mostly used for simpler steel grades
Glossary:
| English | Czech |
| Alloy | Slitina |
| Alloy elements | Legující prvky |
| Alloy steel | Legovaná ocel |
| Annealing | Žíhání |
| Blast furnace | Vysoká pec |
| Carbon | Uhlík |
| Casting | Odlévání |
| Coil | Svitek |
| Cold rolled | Válcováno za studena |
| Continuous casting | Kontilití |
| Degassing | Odplynování |
| Hot dip galvanizing | Žárové zinkování |
| Hot rolled | Válcováno za tepla |
| Charge | Vsázka |
| Ladle | Pánev |
| Mini mill | Mini huť |
| Pickling | Moření |
| Pig Iron | Surové železo |
| Scarfing | Čištění plamenem |
| Scrap metal | Kovový šrot |
| Skin pass | Válcovat povrchově za studena |
| Slab | Brama |
| Slag | Struska |
| Steel grade | Jakost oceli |
Gallery:
Skin Pass Mill
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Schematic Diagram of Steel Production
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Integrated Steelworks Flow Chart
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Electric Arc Furnace
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Carbon
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Coal
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Cold Rolled Coil
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Hot Rolled Coil
|
|
Iron Ore
|
Pig Iron
|
Slab
|
Steel
|
Sources:
Applebaum, M, Everything You Always Wanted to Know About Steel. A Glossary of Terms and Concepts, Summer 1998, Solomon Smith Barney Inc., 2000
Meseure, K., Product range - Flat carbon steel for
industry, ArcelorMittal R&D Gent, ArcelorMittal University -
Understanding Steel, 2009
Meseure, K., Steel Making, ArcelorMittal R&D Gent, ArcelorMittal University - Understanding Steel, 2009
Velzeboer, M., Mining, ArcelorMittal University - Understanding Steel, 2009
PC Translator. CD-ROM. Korytná:LangSoft & SOFTEX Software, 2007
http://www.onesteel.com/
http://www.steel.org/
http://www.steel-training.co.uk