Unit 3
What are the properties of steel?
Each grade of steel has a number of typical properties that determine the difference between the various steel grades. The most important properties can be divided into three groups:
- physical properties
- chemical properties
- mechanical properties
The mechanical properties are determined by the chemical composition and the microstructure. The chemical composition and the processing during the various production stages determine the microstructure and the properties of the final product. Together they constitute the intrinsic properties of the steel. These intrinsic properties are laid down according to international standards. However, some customers may impose their own specifications based on their own experience, and these are often more stringent than the standard.
In addition to the intrinsic properties of the material, a customer may also require it to be suitable for certain applications or demand certain performance properties. After all, there is little point in producing a material that meets the standards or the customer’s specifications if it still causes problems in practice. These are called the technological properties.
The final choice for a specific steel grade depends upon its price and the possibility to obtain a combination of the properties desired.
Exercise 1:
Please select technical terms from the text below and translate them:
Mechanical properties
The mechanical properties describe how steel grades behave when
subjected to a mechanical load. They are listed in all specifications.
The mechanical properties are strongly affected by the chemical
composition and the microstructure.
Mechanical properties change with temperature and environmental
conditions. Consequently, the conditions during the test must always be
mentioned when reporting mechanical properties. The most important
mechanical properties are: yield point, tensile strength, elongation,
hardness, toughness, fatigue, etc.
In most instances, the mechanical properties are the decisive factor in
the choice a steel grade for a given application. The best way to
specify a steel grade is to refer to an internationally recognized
standard. These standards assist both the customer and the steel
producer when describing the required mechanical properties and
technological properties in practice.
Answer Key: Exercise 1
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Exercise 2:
Translate into Czech:
What are the properties of steel?
Each grade of steel has
a number of typical properties that determine the difference between
the various steel grades. The most important properties can be divided
into three groups:
- physical properties
- chemical properties
- mechanical properties
The mechanical properties are determined by the chemical composition and
the microstructure. The chemical composition and the processing during
the various production stages determine the microstructure and the
properties of the final product. Together they constitute the intrinsic
properties of the steel. These intrinsic properties are laid down
according to international standards. However, some customers may impose
their own specifications based on their own experience, and these are
often more stringent than the standard.
In addition to the intrinsic properties of the material, a customer may
also require it to be suitable for certain applications or demand
certain performance properties. After all, there is little point in
producing a material that meets the standards or the customer’s
specifications if it still causes problems in practice. These are called
the technological properties.
The final choice for a specific steel grade depends upon its price and
the possibility to obtain a combination of the properties desired.
Answer Key: Exercise 2
The most important element in all steel grades is iron. Carbon steel contains at least 98% iron. Steel alloys such as stainless steel usually contain over 70% iron.
Therefore, most physical properties of steel are governed by the presence of iron:
- melting point
- density
- thermal conductivity
- thermal expansion
- electric and magnetic behavior
In many instances, the specifications and standards refer only to the mechanical properties and chemical composition, since the physical properties cannot be changed just like that. For example, the density of non-alloyed steel and steel alloys is about the same: 7.85 g/cm3. The microstructure hardly affects the density or other physical properties.
The magnetic properties are an exception here. For certain applications such as steel in transformers or permanent magnets, the magnetic properties are very important. Non-alloyed steel grades are usually magnetic at room temperature, but non-magnetic at elevated temperatures. Magnetic properties are strongly influenced by the microstructure and the chemical composition, and some steel alloy grades such as high grade stainless steel, are non-magnetic.
Exercise 3:
By its very nature, iron reacts very readily with oxygen present in air to form iron oxide. In combination with humidity we call this rusting or corrosion. At elevated temperatures, such as during hot rolling, a thick oxide layer is rapidly formed.
The chemical composition of steel largely determines its resistance to oxidation or the pernicious influence of other elements. Thus the presence of chromium in steel causes a thin, corrosion resistant layer of chromium oxide to be formed on the steel surface. When damaged, this layer regenerates itself. Steel grades alloyed with large amounts of chromium and nickel are corrosion resistant in most environments and are therefore called stainless steel.
The microstructure can affect the chemical properties. Impurities in the steel or a change in its microstructure, for instance as a result of thermal treatment, can change the resistance against corrosion.
Exercise 4:
Use Internet for the following tasks:
1) What international organization governs the chemical nomenclature? What is its Czech translation?
2) What organization provides the Czech translation of chemical nomenclature?
3) Find a website describing the English chemical nomenclature.
Answer Key: Exercise 4
1) Chemical nomenclature is governed by: http://www.iupac.org
Czech translation is:
2) Czech translation is governed by http://www.imc.cas.cz/cz/umch/iupaccentre.htm http://www.csch.cz
3) For more information, visit the following website: http://www.websters-online-dictionary.org/definitions/IUPAC%20nomenclature%20of%20inorganic%20chemistry?cx=partner-pub-0939450753529744%3Av0qd01-tdlq=FORID%3A9=UTF-8=IUPAC%20nomenclature%20of%20inorganic%20chemistry
The mechanical properties describe how steel grades behave when subjected to a mechanical load. They are listed in all specifications. The mechanical properties are strongly affected by the chemical composition and the microstructure.
Mechanical properties change with temperature and environmental conditions. Consequently, the conditions during the test must always be mentioned when reporting mechanical properties. The most important mechanical properties are: yield point, tensile strength, elongation, hardness, toughness, fatigue, etc.
In most instances, the mechanical properties are the decisive factor in the choice a steel grade for a given application. The best way to specify a steel grade is to refer to an internationally recognized standard. These standards assist both the customer and the steel producer when describing the required mechanical properties and technological properties in practice.
Chemical composition
The chemical composition is also a very important aspect of steel. In addition to iron, steel also contains other elements such as alloying elements that have been added for a purpose or unwanted impurities. The most important elements are: carbon, manganese, silicon, phosphorus, sulphur, aluminum, nitrogen, titanium, niobium, vanadium, copper, chromium, nickel and boron.
The chemical composition has an important effect upon the microstructure, the physical and mechanical properties as well as the technological properties of steel.
Exercise 5:
Carbon
Manganese
Silicon
Phosphorus
Sulphur
Aluminum
Nitrogen
Titanium
Niobium
Vanadium
Copper
Chromium
Nickel
Boron
Oxygen
Iron Oxide
Chromium Oxide
Exercise 3:
The most important element in all steel grades is . Carbon steel contains at least 98% . Steel alloys such as stainless steel usually contain over 70% .
Therefore, most physical properties of steel are governed by the presence of :
- melting
- density
- thermal
- thermal
- electric and behavior
In many instances, the specifications and standards refer only to the mechanical and chemical , since the physical properties cannot be changed just like that. For example, the density of steel and steel alloys is about the same: 7.85 g/cm3. The microstructure hardly affects the or other physical properties.
Points to remember:
- Physical properties are governed by the presence of iron: melting point, density, thermal expansion, conductivity, electrical and magnetic behavior.
- The chemical composition of steel largely determines its resistance to oxidation or the pernicious influence of other elements.
- Mechanical properties describe how steel grades behave when subjected to a mechanical load. They change with temperature and environmental conditions.
Glossary:
| English | Czech |
| Elongation | Elongace, poměrné prodloužení |
| Fatigue | Únava materiálu |
| Intrinsic properties | Vnitřní vlastnosti |
| Melting point | Bod tavení |
| Stainless steel | Nerezová ocel |
| Tensile strength | Pevnost v tahu |
| Thermal conductivity | Tepelná vodivost |
| Thermal expansion | Tepelná roztažnost |
| Yield point | Mez kluzu |
Gallery:
Illustrative Graph 1
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Illustrative Graph 2
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Physical Properties
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Corrosion 1
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Corrosion 2
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Corrosion 3
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Mechanical Properties
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Chemical Composition
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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., Steel Making, ArcelorMittal R&D Gent, ArcelorMittal University - Understanding Steel, 2009
Meseure, K., Steel properties, ArcelorMittal R&D Gent, ArcelorMittal University - Understanding Steel, 2008
PC Translator. CD-ROM. Korytná:LangSoft & SOFTEX Software, 2007
http://www.eef.org.uk/default.htm
http://www.onesteel.com/
http://www.steel.org/
http://www.steel-training.co.uk