Steel

lastmod 2025-02-14created 2023-02-1615 edits

Steel is iron with a carbon content of 0.035–1.7%. Its properties can be changed greatly by heat treatment, so it is used as a material for many kinds of machines and tools. It is a metal alloy with iron as its main component, in which the performance of iron (strength, toughness, magnetism, heat resistance, etc.) has been artificially enhanced. In terms of composition, it refers to iron with a carbon content from 0.3% up to 2%. However, highly alloyed steels below 0.3%, such as stainless steel and heat-resistant steel, are also included in the scope of steel. Together with wrought iron and cast iron, it is also called iron and steel; material finished from steel is called steel material, and plate-shaped steel material is called steel plate.

Categories

• Ferrous metallurgy
• Steelmaking

Structure of the Korean steel industry

Comparison of ironmaking methods

• Iron production methods and processes (blast furnace / electric arc furnace / FINEX)

Terms

• Steel Terms DB - POSCO Research Institute - POSCO Research Institute

Other Deoxidation reaction (C-Injection)

Refers to the operation, in the steelmaking and refining process, of removing the excess oxygen added to the molten steel after impurities such as carbon, silicon, and phosphorus have been oxidized into gas or slag.

Equipment term Guide

A very important operation that accurately guides the rolled material as it enters the roll pass. Product quality, yield, and productivity depend on how this guiding device is installed, and although guiding devices differ by usage, the following requirements must be met.

Guide requirements

1. Must be easy to assemble and disassemble.
2. Must have a long service life.
3. Must not deform from thermal shock.

Other Slag foaming (Slag Foaming)

The process of blowing oxygen into molten steel so that the iron oxidizes, creating slag foam.

Equipment term Pin diameter (Pin Dia)

Roll-like equipment used in the bending step when processing rebar.

Equipment term Rolling mill (Roll Stand)

Refers to the machine tool used for rolling metal.

Other Slag (Slag)

The residue left after extracting metal from ore; refers to a mixture of acidic oxides and basic oxides.

Equipment term Mould (Mould / Mold)

Refers to the form into which molten metal (molten iron) is poured to make castings.

Equipment term Burner (Burner)

A device that ejects gaseous, liquid, and powdered fuels such as gas, oil, and pulverized solids at high speed. As a combustion device for gas or liquid fuel, it refers to one that mixes fuel and air in suitable proportions and ignites it at the outlet.

Process term Steelmaking

Pig iron made in the blast furnace contains many impurities such as silicon, phosphorus, and sulfur in addition to carbon; refers to the process carried out to adjust these and increase mechanical strength.

Process term Tapping

The operation of taking molten steel out of an electric furnace, blast furnace, etc.

Equipment term Electrode rod

Refers to a highly conductive stainless steel rod used for cutting and welding metal, as electrodes of electric furnaces, and so on.

Steel product Standard

Refers to the technical standards set mainly for industrial products to make production and use convenient.

Steel product Steel grade

The type of steel material. Classified mainly by mechanical properties such as yield point and tensile strength, or by chemical composition.

Equipment term Tundish (Tundish)

In continuous casting, the primary vessel into which molten steel is poured from the ladle holding it.

Equipment term Ladle (Laddle)

A ladle is a vessel that holds molten steel after blowing in the converter is complete.

Other Refractory

A material that withstands high temperatures: it does not soften at high temperatures of at least 1,000 ℃, maintains its strength sufficiently, and can also withstand chemical action and the like.

Other Bubbling (Bubbling)

The phenomenon in which gas in a liquid forms bubbles and rises.

Steel product Billet (Square Billet)

Steel material with a square cross-section before being rolled into sections; long pieces are called billets and short ones slabs.

Equipment term Electric furnace (Electric

rc Furnace)AEquipment that heats steel scrap using electric heat.

Process term Cutting

The process of cutting to the specifications the customer wants.

Process term Rolling (plastic working)

The stage of making products in the specifications and shapes the customer wants. The product is formed by passing it through about 22 stands (rolls), divided into roughing, intermediate rolling, and finishing rolling.

Process term Reheating furnace

Used to reheat billets at 800 degrees up to a temperature of 1,200 degrees Celsius, making rolling easier.

Process term Continuous casting (CCM)

The process of turning molten steel that has undergone secondary refining in the refining furnace into billets for use in the rolling process.

Process term Refining (LF)

The process of adjusting the required components (Si, Mn, P, S, V, Nb) to meet specifications.

Process term Melting

The process of heating steel scrap using electric heat.

Process term Charging

The process of putting the main raw material, steel scrap, into the electric furnace.

Steel product Bar In Coil (BIC)

'Coil rebar', rebar produced in hoop form rather than bar form.

Steel product Deformed bar

SD (Steel Deformed) Refers to rebar with lug and rib projections on its surface.

Steel product Round bar

SR (Steel Round) Refers to rebar without lug and rib projections on its surface.

Other Sulfur (Sulfur)

Forms the compound FeS with iron, causing hot shortness and steel embrittlement (reduced tensile strength, elongation, and impact value), and becomes a cause of fracture during processing. Embrittlement prevention: add Mn to form high-melting-point MnS (keep Mn/S≥10). Combines with Mn, Zr, Ti, Mo, etc. to improve machinability, and worsens weldability and forge weldability.

Other Phosphorus (Phosphorus)

Somewhat increases hardness and tensile strength but reduces reduction of area, and the formation of the Fe3P compound lowers impact resistance and causes cold shortness. P segregates severely during solidification, solidifying as Fe3P and segregating at grain boundaries; it is hard to diffuse even with high-temperature heating, so it remains as a BAND STRUCTURE, is elongated in that direction during processing, reduces impact value, and becomes the center of rupture.

Other Manganese (Manganese)

Mn raises hardenability and strength without reducing the elongation of steel, increases plasticity at high temperatures, and improves castability; steel alloyed with Mn is not sensitive to heat treatment, so it is suitable as weldable structural steel.

Other Silicon (Silicon)

Increases hardness, elastic modulus, and tensile strength, and reduces elongation, impact value, and weldability; it is the most effective deoxidizer in steelmaking, and its oxides in molten steel combine with Mn oxides to form SiO2 or silicate inclusions that separate and float up easily.

Rebar quality Carbon (Carbon)

Known to form carbides with Fe, Cr, Mo, V, etc. and increase strength; as carbides increase, strength improves but ductility and toughness decrease.

Rebar quality Carbon equivalent (Carbon Equivalent)

In steel, alloying elements can be added to increase hardenability, corrosion resistance, and heat resistance. Because they lower the critical cooling rate and transformation temperature, they make transformation to martensite easier and thus raise hardenability. Carbon equivalent converts the hardenability of these elements (which causes cracking when high) into the effect of carbon content; since cracking can be avoided through the preheating and interpass temperature when welding steel, the carbon equivalent serves as the basis for setting this preheating and interpass temperature.

Steel product Lugs & ribs

Lug (transverse rib): Refers to the band formed around the circumference, perpendicular to the straight line of the rebar. Rib (longitudinal rib): Refers to the band forming a straight line parallel to the straight direction of the rebar.

Rebar quality Nominal perimeter

Refers to the perimeter when converted to an equivalent round steel bar.

Rebar quality Unit weight

Unit weight = weight per unit = refers to the unit weight (Kg/m) when converted to an equivalent round steel bar.

Rebar quality Nominal cross-sectional area[S]

Refers to the cross-sectional area when converted to an equivalent round steel bar.

Rebar quality Nominal diameter[d]

Refers to the diameter when converted to an equivalent round steel bar.

Rebar quality Grip distance

Refers to the length of the test piece between the testing machine's grips when the test piece is mounted in the machine.

Rebar quality Grip section

The end part of the test piece that is held in the testing machine's grips.

Rebar quality Gauge length

The distance between two gauge marks made on the parallel section; the reference length for measuring elongation.

Rebar quality Yield point elongation

During a tensile test, the change in length between the gauge marks from when the parallel section of the test piece begins to yield, through deformation increasing under nearly constant stress, until stress next begins to increase smoothly, expressed as a percentage of the gauge length.

Rebar quality Elongation at break

Permanent elongation after the test piece breaks. (Written as “elongation” when there is no risk of confusion.) Expressed as the initial gauge length as a percentage of the gauge length after fracture; the KS standard sets minimum values by steel grade and SIZE.

Rebar quality Yield strength

During a tensile test, the maximum load before the parallel section of the test piece yields, divided by the nominal cross-sectional area of the parallel section. Yielding means the rebar has received a load beyond the elastic deformation load and passes into the stage of permanent deformation; the KS standard sets minimum values by steel grade. SD300 (mild steel): 300 N/㎟, SD400 (high-strength steel): 400 N/㎟, SD500 (ultra-high-strength steel): 500 N/㎟

Rebar quality Tensile strength

The maximum tensile load divided by the nominal cross-sectional area of the parallel section; the KS standard sets minimum tensile strength values by steel grade.

Other Scale

The oxide layer formed on the surface when metals such as steel and copper alloys are heated to high temperatures. Rebar likewise forms an oxide layer (scale) on its surface as the product, heated to high temperature for rolling, cools and reacts with air. When the rebar surface is struck with a metal object, it peels off like a shell; this does not mean the product is defective — rather, the oxide layer on the surface prevents the rebar from oxidizing (corroding).

Rebar quality Maximum tensile load

Refers to the maximum load the test piece withstood during a tensile test. Rebar is tensile tested with a universal testing machine, and the maximum load the rebar withstood before breaking is called the maximum tensile load. (Unit: N)

Heat number (Heat Number)

Based on the blast furnace. Products made from the molten iron of one blast furnace have the same Heat no.

Conversely, the same Heat number means they come from the same blast furnace.

The same initial molten iron means the same chemical composition (Chemical composition).

Lot number (Lot Number)

Based on heat treatment.

Products heat-treated in the same heat treatment furnace get the same Lot no.

Conversely, the same Lot no means they come from the same heat treatment furnace.

Being heat-treated together means the same physical properties (Physical properties).

Steel Industry

See also

• Manufacturing
• Heavy industry
• Iron
• Furnace

Favorite site

• Steel - Wikipedia