The language of steel

This glossary provides an introduction to the world of steel.


Steel is an alloy (a mixture of chemical elements of which at least one is a metal) of iron and carbon.


The heat treatment process by which steel products are reheated to a suitable temperature to remove stresses from previous processing and to soften them and/or improve their machinability and cold-forming properties.

Apparent steel use (ASU)

ASU is obtained by adding up deliveries (defined as what comes out of the steel producer’s facility gate) and net direct imports. As a unit of measurement worldsteel uses the metric tonne.


A finished steel product, commonly in flat, square, round or hexagonal shapes. Rolled from billets, bars are produced in two major types: merchant and special.

Basic oxygen steelmaking

Making steel through oxidation by injecting oxygen through a lance above a molten mixture of pig iron and scrap steel.

Bessemer process

A process for making steel by blowing air into molten pig iron through the bottom of a converter.


A semi-finished steel product with a square cross-section up to 155mm x 155mm. This product is either rolled or continuously cast and is then transformed by rolling to obtain finished products like wire rod, merchant bars and other sections. The range of semi-finished products above 155 mm x 155 mm are called blooms.


Steel sheet of high dimensional precision, in simple or complex form, sometimes multi-thickness, constituting principally automobile body parts.

Blast furnace

A furnace used for smelting iron from iron ore.


See billet

Breakthrough technology

Breakthrough technology produces low-carbon steel in a radically different way to the conventional blast furnace, DRI or EAF technology. Examples of breakthrough technology being developed include hydrogen reduction, the application of CCS, the electrolysis of iron ore, a suite of carbon capture usage and storage (CCUS) technologies and new smelting reduction processes.


Carbon-free is a difficult expression to relate to steel as steel without carbon is iron, and the carbon content of steel is precisely controlled to achieve the properties demanded in a specific batch. Carbon will need to be added to hydrogen reduced iron in order to turn it into steel through the refining process.

Carbon-neutral steel (or net-zero steel)

If a balance can be achieved between the greenhouse gases put into the atmosphere when producing steel and emissions taken out of the atmosphere by sinks, the resulting steel can be referred to as carbon-neutral steel (or net-zero steel). The production of carbon-neutral steel may require offsets in other sectors to achieve true neutrality, and it is important that if claims of carbon neutrality are made producers are transparent about boundaries, their accounting methodologies, and the quality and credibility of any offsets used.

Carbon steel

A type of steel of which the main alloying element is carbon.


Increasing the carbon content of steel by diffusing carbon into the surface, allowing the surface to be heat-treated to become a hard, wear-resistant layer.


An object formed by using a mould.

Clean steel

Clean steel is a technical expression used in the steel sector to refer to steels containing low levels of impurities, oxides, inclusions, or low or ultra-low level of carbon dissolved in the metal. The phrase is in common use, including by worldsteel in our 2004 ‘Study on Clean Steel’, and means something specific. As such worldsteel does not refer to “clean steel” in the context of climate change.


The primary fuel used by integrated iron and steel producers.


Applying a protective layer to the outside of material using various methods such as galvanising.


A finished steel product such as sheet or strip which has been wound or coiled after rolling.


A form of carbonised coal burned in blast furnaces to reduce iron ore pellets or other iron-bearing materials iron.

Coke ovens

Ovens where coke is produced. Coal is usually dropped into the ovens through openings in the roof, and heated by gas burning in flues in the walls within the coke oven battery. After heating for about 18 hours, the end doors are removed and a ram pushes the coke into a quenching car for cooling before delivery to the blast furnace.

Cold rolling

Passing a sheet or strip that has previously been hot rolled and picked through cold rolls (below the softening temperature of the metal). Cold rolling makes a product that is thinner, smoother and stronger than can be made by hot rolling alone.

Compact strip production

A continuous process developed in the 1980s that significantly reduces the production workflow from liquid-phase steel to the finished hot-rolled strip.

Continuous casting

A process for solidifying steel in the form of a continuous strand rather than individual ingots. Molten steel is poured into open-bottomed, water-cooled moulds. As the molten steel passes through the mould, the outer shell solidifies.


Cold rolled coil (see cold rolling)

Crude steel

Steel in the first solid state after melting, suitable for further processing or for sale. Synonymous with raw steel.

Direct reduction

A group of processes for making iron from ore without exceeding the melting temperature. No blast furnace is needed.

Electric arc furnace

A furnace that melts steel scrap using the heat generated by a high power electric arc. During the melting process, elements are added to achieve the correct chemistry and oxygen is blown into the furnace to purify the steel.

Electrical steels

Specially manufactured cold-rolled sheet and strip containing silicon, processed to develop definite magnetic characteristics for use by the electrical industry.

Green steel

Green steel is being used and interpreted by many different parties to mean different things, often in the context of marketing new more environmentally conscious products. It has been used to refer to steel manufactured using breakthrough technology, steel produced from scrap, reused and remanufactured steel, and conventional steel with emissions offset through the retirement of carbon units or allowances. Given this inherent lack of clarity and diversity of meanings ‘green steel’ is not an expression worldsteel uses.

Flat products

A type of finished rolled steel product like steel strip and plate.

Fossil-free steel

Fossil-free steel is steel manufactured without using any fossil fuels such as coal or natural gas, nor any fossil fuel-derived energy.

Fossil hydrogen

Fossil fuel hydrogen is made from unabated fossil fuels, chiefly:

  • Grey hydrogen is made from natural gas through the process of steam methane reforming, without CCS so CO2 is emitted to atmosphere.
  • Brown, or black hydrogen is manufactured through coal gasification and leads to significantly higher GHG emissions than other hues.

Hydrogen is a key vector that will allow GHG emissions from the iron and steel sector to be significantly reduced, and many of worldsteel’s members are exploring this technology option. Hydrogen is often attributed to a colour, depending on its low-carbon credentials.

When worldsteel talks about low carbon hydrogen, we mean:

  • Green hydrogen is produced through the electrolysis of water, powered by renewable electricity.
  • Blue hydrogen is made from natural gas through the process of steam methane reforming combined with CCS.
  • Hydrogen can also be produced using electrolysis using other sources of low-carbon electricity, such as nuclear or CCS. We also consider this to be low-carbon.
Hot dip galvanisation

A process by which steel is given long-term corrosion protection by coating it with molten zinc.

Hot and cold rolling mill

Hot-rolling mill: Equipment on which solidified steel preheated to a high temperature is continuously rolled between two rotating cylinders.
Cold rolling mill: Equipment that reduces the thickness of flat steel products by rolling the metal between alloy steel cylinders at room temperature.

Hot metal

Molten iron produced in the blast furnace.


Hot-rolled coil (see hot rolling)

Indirect steel

Indirect trade in steel takes place through exports and imports of steel containing goods and is expressed in finished steel equivalent of products used.


A metal block cast in a particular shape for convenient further processing.

In-line strip production (ISP)

ISP produces hot-rolled coil down to finished gauges of 1mm, and has its origins in joint development work by Arvedi with German plant maker Mannesmann Demag in the late 1980s.

Integrated mill

Large-scale plant combining iron smelting and steelmaking facilities, usually based on basic oxygen furnace. May also include systems for turning steel into finished products.

Iron ore

The primary raw material in the manufacture of steel.

Ladle metallurgy

The process whereby conditions (temperature, pressure and chemistry) are controlled within the ladle of the steelmaking furnace to improve productivity in preceding and subsequent steps, as well as the quality of the final product.


Used by the steel industry to remove impurities from the iron made in blast furnaces. Limestone containing magnesium, called dolomite, is also sometimes used in the purifying process.

Line pipe

Used for transportation of gas, oil or water generally in a pipeline or utility distribution system.

Long products

A type of finished rolled steel product like rail and steel bars.

Lost time injury

Any work-related injury, resulting in the company, contractor or third party contractor employee not being able to return to work for their next scheduled work period. Returning to work with work restrictions does not constitute a lost time injury status, no matter how minimal or severe the restrictions, provided it is at the employee’s next scheduled shift. Lost Time Injury Frequency Rate (LTIFR) is calculated as number of Lost Time Injuries per million man hours.

Low-carbon steel

Low-carbon steel is manufactured using technologies and practices that result in the emission of significantly lower emissions than conventional production.

Mechanical tubing

Welded or seamless tubing produced in a large number of shapes to closer tolerances than other pipes.

Mini mill

A small-scale steelmaking plant based on the EAF, making new steel from mostly steel scrap. May also include facilities for producing finished steel products.

Net ton

See ton

Net-zero steel

See carbon-neutral steel

Oil country tubular goods (OCTG)

Pipe used in wells in oil and gas industries, consisting of casing, tubing and drill pipe. Casing is the structural retainer for the walls; tubing is used within casing oil wells to convey oil to ground level; drill pipe is used to transmit power to a rotary drilling tool below ground level.

Open hearth process

A process for making steel from molten iron and scrap. The open hearth furnace has a shallow hearth and roof that help to remove impurities from the molten iron. The flame and gases pass across the top of the enclosed hearth, heat being reflected down onto the material in the hearth. This process has been replaced by the basic oxygen process in most modern facilities.


An enriched form of iron ore shaped into small balls.


Using chemicals to remove the scale from finished steel.

Pig Iron

The product that results from smelting iron ore with a high-carbon fuel such as coke


A flat-rolled product from slabs or ingots of greater thickness than sheet or strip.

Rebar steel

A reinforcing steel bar

Refining stand

A stage in the process of making crude steel, during which the crude steel is further refined (i.e. most residual impurities are removed) and additions of other metals may be made before it is cast.


The initial stages in the process of reducing the thickness of steel slabs.

Rolling mill

Equipment that reduces and transforms the shape of semi-finished or intermediate steel products by passing the material through a gap between rolls that is smaller than the entering materials.


The heavy rust that forms on the surface of steel while it is kept hot during rolling, forging, etc.


Steel scrap is one of the steel industry’s most important raw materials. It comes from all steel-containing products that reach the end of their life (post-consumer scrap), from demolished structures to end of life vehicles, packaging, white goods and machinery, and the yield losses in the steelmaking and manufacturing processes (pre-consumer scrap). It can also include iron scrap. All steel can be recycled into new steel. All new steel contains some steel scrap.

Semi-finished products

Steel products such as billet, blooms and slabs. These products can be made by direct continuous casting of hot steel or by pouring the liquid steel into ingots, which are then hot rolled into semi-finished products.


A flat-rolled product over 12 inches in width and of less thickness than plate.

Sheet piling

Rolled sections with interlocking joints (continuous throughout the entire length of the piece) on each edge to permit being driven edge-to-edge to form continuous walls for retaining earth or water.

Sinter plant

A plant in which iron ore is crushed, homogenised and mixed with limestone and coke breeze and then cooked (“sintered”) to form sinter which is the main ferrous component of blast furnace burden.


A process that combines ores too fine for efficient blast furnace use with flux stone. The mixture is heated to form clumps, which allow better draft in the blast furnace.


A semi-finished steel product obtained by rolling ingots on a rolling mill or processed through a continuous caster and cut into various lengths. The slab has a rectangular cross section and is used as a starting material in the production process of flat products, i.e. hot rolled coils or plates.


A co-product, containing inert materials from the ‘burden’ (the materials put into the blast furnace at the beginning of the steelmaking process), that is produced during the melting process.


Smelting is a metallurgical term meaning to extract a metal from its ore by melting the ore. Melting is simply the process of changing from a solid to a liquid state due to the application of high heat.

Sponge iron

The product of the direct reduction process. Also known as direct reduced iron (DRI).

Standard pipe

Used for low-pressure conveyance of air, steam, gas, water, oil or other fluids and for mechanical applications. Used primarily in machinery, buildings, sprinkler systems, irrigation systems, and water wells rather than in pipelines or distribution systems.

Stainless steels

Stainless steels are distinguished from carbon steel by their chromium (ferritic steel) content and, in certain cases, nickel (austenitic steel). Adding chromium to carbon steel makes it more rust and stain-resistant, and when nickel is added to chromium stainless steel it enhances its mechanical properties, for example its density, heat capacity and strength.

Step Up

Step Up is worldsteel’s 4-stage efficiency review process. Step Up aims to improve the efficiency of steel production now, to support our members in operating their sites at a level of performance commensurate with the world’s most efficient sites. Step Up is a transitional programme and should not be seen as providing a solution to the steel industry’s climate change challenges.


A continuous length of steel produced in a mill, prior to cutting and/or shaping into finished or semi-finished products.


Flat steel coil products, with widths of less than 600mm for hot rolled products and less than 500mm for cold-rolled products. The wider flat products are called wide strips.

Structural pipe and tubing

Welded or seamless pipe and tubing generally used for structural or load-bearing purposes above-ground by the construction industry, as well as for structural members in ships, trucks, and farm equipment.

Structural shapes

Rolled flange sections, sections welded from plates, and special sections with at least one dimension of their cross-section three inches or greater. Included are angles, beams, channels, tees and zeds.

Structural steel

Steel shaped for use in construction.


To make something harder through heating.

Thin strip continuous casting

Casting technology that takes liquid steel and casts it into solid strip in one step, thereby eliminating the need for a continuous slab caster and hot strip mill.

Tin coated steel

Cold rolled sheet, strip or plate coated with tin or chromium.

Ton (t)
  1. A unit of weight in the US Customary System equal to 2,240 pounds. Also known as long ton.
  2. A unit of weight in the US Customary System equal to 2,000 pounds. Also known as short ton. Also known as net ton.
Tonne (T)

A metric tonne, equivalent to 1,000 kilograms or 2,204.6 pounds or 1.1023 short ton.

True Steel Use

True steel use (TSU) is obtained by subtracting net indirect exports of steel from apparent steel use (ASU). Total TSU is not equal to ASU because of differences in country coverage and methodological specifics of indirect trade in steel calculations. Further details can be found at

Wire rods

Coiled bars of up to 18.5 millimetres in diameter, used mainly in the production of wire.

Wire: drawn and/or rolled

The broad range of products produced by cold reducing hot-rolled steel through a die, series of dies, or through rolls to improve surface finish, dimensional accuracy and physical properties.


Joining two pieces of metal together using heat and pressure to soften the materials.

Wrought iron

Low-carbon content iron that is tough and malleable for forging and welding.

Zero-carbon steel

To be truly zero-carbonsteel would need to be produced without any CO2 emissions at all. This is a very high bar to reach, and it is difficult to conceive of a production technology that could achieve this in the short term.