Glossary

A

Alloying

Alloying elements are added to steel, individually or in combination, in order to bring forth desired properties. The alloying elements that are used in our steels are silicon (Si), manganese (Mn), chromium (Cr), nickel (Ni), molybdenum (Mo), vanadium (V) and boron (B). It can be said that C, Si, Mn, Cr and B are inexpensive, while Ni, Mo and V are expensive.

Alloyed steel

Steel which contains substantial amounts of alloying elements (other elements are carbon and smaller amounts of silicon and manganese) to change its properties.

Annealing

Heating up to, and holding at a suitable temperature, followed by cooling down at a suitable speed in order to:

• lower hardness
• improve cutting ability (machinability)
• improve cold forming ability
• achieve a desired structure
• release inner stresses

ASTM

American Society for Testing of Materials.

Austenite

Structure of pure iron (ferrite) over 910ºC. Austenite can, unlike ferrite, dissolve considerable amounts of carbon, up to 1.7%.

Austenitizing

Heating up of steel to a temperature where the structure is 100% austenite.

B

Bainite

A product of transformation from austenite which is obtained at a temperature lower than that at which fine lamellar pearlite is formed but higher than the temperature at which martensite forms.

Billet

An intermediate section of round or square that is produced from the rolling of ingots.

Brinell hardness

Hardness measured when a steel or hard metal ball is pressed against a material and the deformation is recorded.

Brittleness

The opposite of toughness; a brittle material has poor ductility.

C

Carbon steel

A non-alloyed steel in which the amount of carbon present is the major factor in determining its mechanical properties.

Carbide

Carbides are chemical compounds comprising carbon and one or more metallic elements, such as chromium carbide.

Casting gate

Common tapping pipe for ingot teeming into moulds.

CCT diagram

A diagram which describes transformations in steel during continual cooling for various cooling rates.

Cemented Carbide

A material, usually sinter, which consists of a carbide phase (tungsten, titanium or tantalum carbide or a compound of these) in a basic matrix of common cobalt.

Cementite

A combination between carbon and iron with the compound symbol Fe₃C.

Charge

A steel melt. Every melting (pouring) gets an individual number = charge number (or heat number).

Charging

A term used for, as an example, loading scrap into a melting furnace or loading material into a heat-treating furnace.

Contraction

Measurement of how much the cross-sectional area of a tensile test has reduced at the breaking point.

D

Decarbization

Loss of carbon to the atmosphere from the surface of a steel.

Deoxidation

To reduce the oxygen content in liquid steel. Aluminium is used as a deoxidation additive, since it bonds with the oxygen to form aluminium oxide (Al203). Due to inductive stirring in the ladle arc furnace, the aluminium oxide ends up in the slag surface of the steel. This process is called deoxidation.

Diffusion

The process when atoms are moving in the matrix from a higher concentration to become more uniformly distributed. That process is enhanced by higher temperatures.

Which has given the name to the heat treatment, where the aim is to get a more uniform alloying, or eg getting hydrogen out of the steel, by diffusion.

See also Soaking.

E

Eddy current testing

A method for steel grade check or detecting the presence of cracks through the introduction of eddy currents into the material.

Elongation

How much a tensile test is able to lengthen before it breaks.

Eutectoid

Pearlite is a eutectoid compound of iron and carbon and contains 0.8% C.

Excite

An atom is excited when it takes up/stores energy by transferring its electrons to a more energy-rich state (generally further away from the nucleus). It is said then that the atom is excited. When the electron then returns, it releases energy by sending out (emitting) a photon (light particle). The energy of the photon is exactly equal to the energy that the atom puts out. Most atomic sorts have a light emission wavelength that is equal to visible light or in its proximity.

F

Ferrite

The base structure of pure iron.

Ferro-alloys

Most of the alloying elements added to the ladle furnace are in the form of alloys between iron and the element in question. The most common are FeMn, FeSi and FeCr.

Flakes

Inner defect that can occur in steel if the hydrogen level is too high.

G

Grain

An individual crystal in a multicrystalline material.

Grain boundary cementite

The cementite which separates in the austenite grain boundaries during the slow cooling of a steel with a carbon content less than 0.8%.

Grain boundary ferrite

The ferrite that separates in the austenite grain boundaries during the slow cooling of a steel with a carbon content less than 0.8%.

Grain size

The average size of the grains in a polycrystalline material. Measured under a microscope.

H

Hardenability

A term applied to steels to describe the relative ease with which martensite can be formed in the steel.

Hardening

Cooling in air, oil or water in order to build martensite.

Hardness

A materials ability to withstand plastic deformation, when indented by a loaded indenter.

Heat

A steel melt. Every melting (pouring) gets an individual number = heat number (or charge number).

Hydrogen annealing

Heat treatment aimed at the removal of residual hydrogen in a material.

I

Impact testing

A method for testing the toughness of a material.

Inductive stirring

Mixing of the molten steel in a ladle with help of electromagnetic forces.

Ingot teeming

Casting of molten steel in moulds. The solidified steel piece is called an ingot.

Isothermal annealing

Heat-treating with two different temperatures in order to create a grainy, course lamella pearlite-ferritic structure, suitable for machining.

J

Jominy testing

A test used to assess the hardenability of a steel, that is to say its ability during hardening to build martensite.

Jominy curve

Hardness measured as a function of depth under a cooled surface during hardening in controlled conditions.

L

Ladle

A container for transporting molten steel.

Ladle furnace

A workstation for the ladle with an inductive stirrer, a valve (lid) with graphite electrodes for heating, and a vacuum valve. Alloy addition, deoxidation, sulphur refinement, degassing and temperature adjusting take place here.

 

 

 

M

Macro-inclusions

Larger, non-metallic inclusions that originate from help material during steel production (furnace lining, runners, casting powder, etc.).

Martensite

The main structure of hardenable steel. The structure is built when the steel has been heated up to hardening temperature and then cooled quickly to a low temperature.

Martempering

Martensite hardening in which the cooling is temporarily discontinued just above the Ms temperature in order to reduce hardening strains.

Mechanical strength

Properties which are determined by mechanical tests that measure the response of the material to loading - for example, modulus of elasticity, tensile strength, elongation, hardness and impact strength.

Micro-inclusions

Small non-metallic inclusions that are created during steel production, mainly oxides and sulphides.

Muffle furnace

A conventional heating furnace.

Mould

Casting form for molten steel.

N

Nitriding

Surface hardening through the supply of nitrogen to the surface zone.

Normalization

Heating of steel to a suitable temperature above the transformation temperature, followed by air-cooling. Grain size becomes smaller and the structure becomes more even.

O

Out of roundness

The difference between a cross-section’s largest and smallest diameters.

Oxides

A bond between oxygen and other elements, for example aluminium, silicon and calcium.

P

Patenting

A heat treatment to create a pearlitic structure suitable for large reductions during wire drawing.

Pearlite

A lamella form of ferrite and cementite.

Pipe

The cavity that comes up in the upper part of an ingot during solidification.

Q

Quenching

Cooling in air, oil or water in order to build martensite.

Quenching and tempering

Heat treatment that consists of heating up to hardening temperature (austenitizing), cooling in air, oil or water (hardening or quenching), followed by another heating up to 150-675°C (tempering). The result is a material with high strength in combination with good toughness. Summary: The hardening makes the material hard, the tempering adjusts the hardness. Even our bearing steel goes through a sort of hardening and tempering with our clients. The tempering temperature is quite low, which makes for a high hardness and a low toughness.

R

Recrystallization

This restores the crystal structure of deformed material. Performed at 650°C.

Reduction

Lowering of the oxygen content in, for example, iron ore or the oxide content in the top slag.

Reduction in area

The difference between starting cross-sectional area and final cross-sectional area. Expressed as a percentage of the starting area.

Refining (1)

Reducing the carbon and phosphorus levels in the molten steel with the help of the addition of oxygen. The oxygen bonds with carbon and phosphorus to create carbon monoxide and phosphorus oxide.

Refining (2)

The collective term used for the processes that take place in the ladle furnace that are aimed towards the production of high quality, clean steel; alloying, deoxidation, sulphur refinement, degassing and temperature adjusting.

Runner

Casting channel.

Runner bricks

The bricks located in the casting channels.

S

Scrap basket

Container used for loading scrap into the electric arc furnace

Segregation

An uneven distribution of alloying elements or inclusions.

Soaking

Holding the ingots at high temperature in pit furnaces before rolling. This is done to even out the uneven distribution of alloying elements that occurs in connection with the solidification of the molten steel in the ingots.

Soft annealing

Material is held at a certain temperature for a certain amount of time so that the structure can obtain a round carbide form, in order to:

• improve cutting ability (machinability)
• reduce hardness
• improve cold formability

Because the carbides achieve a round form, this process is also called spheroidizing.

Spectrotest

Short for optical emissions spectrometry. A method for steel grade check by measuring the intensity of excited and emitted atoms that comes from respective elements in the material.

Steel grade

Steel with precisely defined and reproducible properties.

Stress Relieving Annealing

Reduces the stresses in material. Performed at 500 to 600°C.

Straightness

The deviation of a bar from an ideal straight line. Measured using the rise of the bar over a defined length, usually 1 meter, when the bar is resting on a horizontal base.

Stray flux testing

A method of detecting the presence of cracks by using a magnetic flow.

Strength

The ability of a material to withstand stress, before permanent form damage is done and before it breaks.

Stress relieve annealing

Heat treatment aimed at the removal of inner stresses in the material.

Sulphides

A compound between sulphur and other elements, such as manganese.

Surface hardening

Heat treatment in which only the surface area of the material is hardened.

Surface roughness

A measurement of the surface deviation compared to an ideal geometrical surface. We use the notation Ra to indicate mean roughness and the notation Rt to indicate maximum roughness.

T

Tempering

In order to achieve the right hardness (and toughness) in a steel after hardening, tempering takes place by warming up the material to a temperature of 150-675°C. Tempering time depends on the total mass of the material.

Tensile strength

The relationship between breaking load and the original cross-sectional area in breaking strain testing.

Tolerance

Actually – tolerance width. The difference between the greatest and smallest permissible size.

Torr

A non-SI measurement unit for pressure.

Tough-hardening

Another word for hardening (quenching) and tempering.

Toughness

A material’s ability to be plastic deformed before it breaks.

U

Ultimate tensile strength

Measurement of the load that a material can tolerate before it breaks.

Ultrasonic testing

An inspection technique in which high frequency sound waves are introduced into material in order to detect any inner defects that may be present.

Uphill teeming

Casting method in which ingot moulds are filled with molten steel from the bottom up.

V

Vacuum degassing

A secondary refining process for liquid steel in which it is exposed to a low pressure environment with the aim of achieving a reduction of not only hydrogen in the steel, but oxygen and sulphur levels as well.

Y

Yield strength

The load a material can handle before a permanent change of form.