Unit 4
Technological properties, Microstructure, Analyses
Technological properties
These properties are explicitly linked to the subsequent use or
treatment of the material. They can be seen as a result of a combination
of intrinsic properties. We mainly distinguish between:
- formability
- weldability
- resistance to fatigue
- suitability for cutting and punching
- suitability for enameling
- coatability
- suitability for thermal treatment
Exercise 1:
Formability
Weldability
Resistance to fafigue
Suitability for enameling
Coatability
Suitability for thermal treatment
Suitability for cutting and punching
Microstructure
To understand the behavior and properties of the various steel grades, we have to look at the microstructure of steel. The microstructure comprises information about the crystal lattice, a description of lattice imperfections and the texture. The microstructure is determined by the chemical composition and the thermo-mechanical treatment during the process.
The microstructure contains the following information:
- crystallographic type (e.g. the unit cell of ferrite or austenite)
- complete description of the lattice imperfections (e.g. vacancy, dislocations, grain boundaries, etc.)
- texture or crystallographic orientations
The microstructure greatly affects the mechanical and technological properties of steel
Exercise 2:
Translate into Czech:
Microstructure
To understand the behavior and properties of the various steel grades,
we have to look at the microstructure of steel. The microstructure
comprises information about the crystal lattice, a description of
lattice imperfections and the texture. The microstructure is determined
by the chemical composition and the thermo-mechanical treatment during
the process.
The microstructure contains the following information:
- crystallographic type (e.g. the unit cell of ferrite or austenite)
- complete description of the lattice imperfections (e.g. vacancy, dislocations, grain boundaries, etc.)
- texture or crystallographic orientations
The microstructure greatly affects the mechanical and technological properties of steel.
Answer Key: Exercise 2
Chemical composition
The chemical composition of the steel is determined by analysis in the steel plant. The chemical composition is determined online while the steel is still liquid. Samples are taken at various stages (the blast furnace, desulphurising, the converter and the ladle treatment). These samples are dispatched immediately to the laboratories adjacent to the steel plant. There, the chemical composition is determined by various analytical techniques according to the element to be measured. Within a few minutes, the composition is known.
The strength and hardness of the steel is determined to a large extent by its chemical composition. The more alloy elements added, the harder the steel. The chemical composition also affects the microstructure of the steel: the grain size, the preferred texture etc.
Exercise 3:
Use Internet for the following task:
Find a testing laboratory in the Czech Republic, where you can have any steel properties examined.
Mechanical properties
In order to measure the mechanical properties of a steel grade, a number of standardized physical tests are carried out.
Tensile test
During a tensile test, a standardized sample is clamped in a tensile
testing machine, after its initial length and cross section have been
measured. By moving one of the jaws, the sample is submitted to a load.
As a result, the sample elongates and thins until it eventually breaks.
During the test, the force and the elongation of the sample are
measured.
Hardness test
Hardness is important because it gives us an idea of the resistance a
material offers to abrasion. There are a number of different methods of
measuring hardness but they are all based upon the same principle.
Hardness is the resistance offered by the material to permanent
indentation caused by a body of a certain shape to which a certain force
is applied. The various methods differ from each other according to the
indenter (a ball, a pyramid, a cone) and the force applied.
In all cases the depth of the indentation is measured. This is a measure
of the hardness, since the harder the material, the shallower the
indentation will be.
Because the hardness also expresses the resistance to plastic
deformation, there is a good correlation between hardness and ultimate
tensile stress.
Exercise 4:
Translate into Czech:
Tensile test
During a tensile test, a standardized sample is clamped in a tensile
testing machine, after its initial length and cross section have been
measured. By moving one of the jaws, the sample is submitted to a load.
As a result, the sample elongates and thins until it eventually breaks.
During the test, the force and the elongation of the sample are
measured.
Answer Key: Exercise 4
Exercise 5:
Exercise 6:
The depth of the indentation is measured. .
The toughness of a material is not so easy to express as a number as a tensile strength, since the toughness depends not only on the material itself, but also on the conditions under which it is measured. For this reason, the notched impact strength test is carried out under deliberately unfavorable conditions. During the test, a notched test bar is broken in a single blow. The energy needed to break the sample is a measure of its toughness.
The test result is highly temperature dependent. For this reason, the test is usually carried out at various temperatures. The lower the temperature, the less tough the sample is and thus the lower the impact strength.
Exercise 7:
The energy needed to break the sample is measured. .
Exercise 8:
As already mentioned in Unit 1, the terminology may differ at times. Let us illustrate this with the notched impact strength test.
Look at Czech resources on the Internet, mentioning the notched impact strength test. What are the translations into Czech there? Find two or three different ones.
Answer Key: Exercise 8
http://ebookbrowse.com/2-4-1-vrubova-zkouska-houzevnatosti-razem-v-doc-d71927067
- Czech translation #1
http://www.quido.cz/mereni/vrub.htm
- Czech translation #2
http://jaja.kn.vutbr.cz/~janirek2/dok/materialy/5tRaz.doc
- Czech translation #3
Exercise 5:
is the resistance offered by the material to permanent caused by a body of a certain to which a certain force is applied. The various methods differ from each other according to the (a ball, a pyramid, a cone) and the force applied.
Points to remember:
- The microstructure comprises information about the crystal lattice, a description of lattice imperfections and the texture.
- Chemical composition of steel is determined online while the steel is still liquid.
- Mechanical properties are measured by standardized tests: tensile test, hardness test and notched impact strength test.
Glossary:
| English | Czech |
| Austenite | Austenit |
| Cross section | Příčný řez |
| Enameling | Smaltování |
| Ferrite | Ferit |
| Hardness test | Zkouška tvrdosti |
| Lattice | Krystalová mřížka |
| Notched impact strength test | Zkouška vrubové houževnatosti |
| Tensile test | Tahová zkouška |
| Texture | Textura |
| Weldability | Svařitelnost |
Gallery:
Weldability
|
Welding
|
Thermo Scientific ARL 4460 Metals Analyzer
|
Tensile Test
|
Hardness Test
|
Hardness Test 2
|
Notched Impact Strength Test
|
Notched Impact Strength Test 2
|
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 properties, ArcelorMittal R&D Gent, ArcelorMittal University - Understanding Steel, 2008
PC Translator. CD-ROM. Korytná:LangSoft & SOFTEX Software, 2007
http://alloytech.com/Default.asp
http://www.arcelormittal.com/fce
http://www.bchistory.org/beavercounty/SteelMakingEtc/SteelMaking.html
http://www.onesteel.com/
http://www.pdmsteel.com/index.html
http://www.steel.org/
http://www.steel-training.co.uk