I-Beams
Structural sections on which the flanges are tapered and are typically not as long as the flanges on wide-flange beams. The flanges are thicker at the cross sections and thinner at the toes of the flanges. They are produced with depths of 3-24 inches.

ID
Inside diameter (of a coil).

Immersion Etching
Method in which a microstructure is dipped face up into etching solution and is moved around during etching. This is the most common etching method.

Impact Tests
Tests to determine the energy absorbed in fracturing a test specimen at high velocity. There are various kinds of impact tests, such as charpy, izod, drop weight, etc.

Inclusions (Non-metallic Inclusions)
Refers to a defect when particles of nonmetallic impurities, usually oxides, sulfides, silicates, refractories and such, which are the products of deoxidation, are insoluble in the matrix and are mechanically held in steel during solidification.

Inclusion Count
Determination of the number, kind, size, and distribution of non-metallic inclusions.

Induction Hardening
A surface-hardening process in which only the surface layer of a suitable ferrous workforce is heated by electrical induction to above the upper transformation temperature and immediately quenched.

Induction Process
A process in which the heating is done by eddy currents generated in the charge by the induction coil surrounding the charge. Depending upon the frequency used, the process is called low frequency, medium frequency and high frequency melting.

Ingot
A form of semi-finished steel. Liquid steel is teemed (poured) into vertical cast iron moulds, where it slowly solidifies. Once the steel is solid, the mould is stripped, and the 25- to 30-ton ingots are then ready for subsequent rolling or forging.

Ingot Corner Segregation
A longitudinal plane of relatively impure steel arising from segregation occurring in the region of a corner of an ingot.

Ingot Iron
Very low carbon steel generally made in the open hearth in which all the other elements are removed to the maximum extent possible. Some of the commercial products falling under this group have less than 0.1 percent of all elements put together.

Ingot Mould (Mould)
The container, usually made of cast iron, into which molten steel is poured and allowed to solidify.

Inmetco
What Inmetco is a coal-based process similar to FASTMET that uses iron oxide fines and pulverized coal to produce a scrap substitute. Mill scale and flue dust, inexpensive byproducts of steel making, can be mixed with the iron oxide fines. Inmetco, unlike other direct reduction products, is intended to be hot charged into an EAF, with attendant energy savings.
How The process includes three steps. First, iron oxide fines, pulverized coal and a binder are formed into pellets. Second, the pellets, two to three layers deep, are heated in a gas-fired rotary hearth furnace for 15-20 minutes to produce sponge iron. Subsequently, the iron must be desulfurized. The coal in the pellets provides much of the energy required in the second phase.

Insert
A piece of steel permanently fixed in the die, which may be used to fill a cavity or to replace a portion or the whole of the impression.

Integrated Mills
These facilities make steel by processing iron ore and other raw materials in blast furnaces. Technically, only the hot end differentiates integrated mills from mini-mills. However, the differing technological approaches to molten steel imply different scale efficiencies. See Mini Mills.

Integrated Steel Producer
A steel company which manufactures solid steel products; starts with raw materials such as iron ore, flux, etc, to make molten iron; converts the molten iron to liquid steel in the steel making furnaces and processes liquid to solid steel products.

Inter Annealed Wire
Wire drawn to an intermediate stage, annealed and drawn to the size required.

Inter-Chemical Gauge
Wet film thickness can also be measured using an Inter-chemical Gauge. A graduated circular cam is rolled against the plate between two parallel rollers. The wet film thickness is then read directly on cam at demarcation of coating wetting the cam.

Intermediate Annealing
Annealing wrought metal at one or more stages during manufacture and before final thermal treatment.

Intermediate Temper
A cold rolled hardness range specified with a 15-point Rockwell B spread. See Quarter Hard Temper and Half-Hard Temper.

Internal Cleanliness
Measure of number and types of non-metallic inclusions such as oxides, sulfides or silicates.

Interstitial Free Steel
A recently developed sheet steel product with very low carbon levels that is used primarily in automotive deep-drawing applications. Interstitial Free Steel's improved ductility (drawing ability) is made possible by vacuum degassing.

Interrupted Aging
Aging at two or more temperatures by steps and cooling to room temperature after each step. Compare with progressive aging and step aging.

Interrupted Quenching
Quenching in which the metal object being quenched is removed from the quenching medium while the object is at a temperature substantially higher than that of the quenching medium.

IPM (In-Process Material)
An identifiable piece of steel; can be a slab, coil, or a bundle of sheets, or several slit mults banded together.

Iron Carbide
One of several substitutes for high-quality, low-residual scrap for use in electric furnace steel making. Iron carbide producers use natural gas to reduce iron ore to iron carbide.

Iron Notch
The opening for removing the liquid iron from the blast furnace. The opening on the inside of the furnace is larger than that on the outside so that the tapping hole can be drilled horizontally or at different angles. Although most of the older furnaces had only one iron notch, modern large blast furnaces have two or three and a few very larger ones have four.

Iron Ore
Mineral containing enough iron to be a commercially viable source of the element for use in steel making. Except for fragments of meteorites found on Earth, iron is not a free element; instead, it is trapped in the earth's crust in its oxidized form. It is of two types : containing ferric oxide (Hematite) or ferro-ferric oxide (Magnetite).

Iron-Zinc Alloy Coating
See Galvanized Steel.

ISO Codes
The codes that designate the amount of contamination in the oil.

Isolate (Isolation)
To remove a boiler, or any particular part or system of a boiler, form service by closing the manual valves.

Isothermal Annealing
It is a type of full annealing in which the steel first is cooled to the temperature at which it is desired to have transformation occur, at a rate sufficiently rapid to prevent any structural change above that temperature. The steel then is held at the selected temperature for the time necessary to complete such transformation.

Isotropy
A term indicating equal physical or mechanical properties in all directions within a material.