Fine particles of limestone (flux) and iron ore are difficult to handle and transport because of dusting and decomposition. The powdery material is therefore usually processed into larger pieces. The raw material’s properties determine the technique that is used by mills.

Sinter
Baked particles that stick together in roughly one-inch chunks. Normally used for iron ore dust collected from the blast furnaces.

Pellets
Iron ore or limestone particles are rolled into little balls in a balling drum and hardened by heat.

Briquettes
Small lumps are formed by pressing material together. Hot Briquetted Iron (HBI) is a concentrated iron ore substitute for scrap for use in electric furnaces.

What?
A heat or thermal treatment process by which a previously cold-rolled steel coil is made more suitable for forming and bending. The steel sheet is heated to a designated temperature for a sufficient amount of time and then cooled.

Why?
The bonds between the grains of the metal are stretched when a coil is cold-rolled, leaving the steel brittle and breakable. Annealing “recrystallizes” the grain structure of steel by allowing for new bonds to be formed at the higher temperature.

How?
There are two ways to anneal cold-rolled steel coils: batch and continuous.

a. Batch (Box) Three to four coils are stacked on top of each other, and a cover is placed on top for up to 3 days, then b. heated in a non-oxygen atmosphere (to prevent rust) and slowly cooled.
Continuous. Normally part of a coating line, the steel is uncoiled and run through a series of vertical loops within a heater. The temperature and cooling rates are controlled to obtain the desired mechanical properties for the steel.

What?
A process for further refinement of stainless steel through reduction of carbon content.

Why?
The amount of carbon in stainless steel must be lower than that in carbon steel or lower alloy steel (i.e., steel with alloying element content below 5%). While electric arc furnaces (EAF) are the conventional means of melting and refining stainless steel, AOD is an economical supplement, as operating time is shorter and temperatures are lower than in EAF steelmaking. In addition, using AOD for refining stainless steel increases the availability of the EAF for melting purposes.

How?
Molten, unrefined steel is transferred from the EAF into a separate vessel. A mixture of argon and oxygen is blown from the bottom of the vessel through the melted steel. Cleaning agents are added to the vessel along with these gases to eliminate impurities, while the oxygen combines with carbon in the unrefined steel to reduce the carbon level. The presence of argon enhances the affinity of carbon for oxygen and thus facilitates the removal of carbon.

What?
A natural reduction in work force as a result of resignations, retirements, or death.

Why?
Most unionized companies cannot unilaterally reduce their employment levels to cut costs, so management must rely on attrition to provide openings that it, in turn, does not fill. Because the median ages of work forces at the integrated mills may be more than 50, an increasing number of retirements may provide these companies with added flexibility to improve their competitiveness.

The largest category of stainless steel, accounting for about 70% of all production. The austenitic class offers the most resistance to corrosion in the stainless group, owing to its substantial nickel content and higher levels of chromium. Austenitic stainless steels are hardened and strengthened through cold working (changing the structure and shape of steel by applying stress at low temperature) instead of by heat treatment. Ductility (ability to change shape without fracture) is exceptional for the austenitic stainless steels. Excellent weldability and superior performance in very low-temperature services are additional features of this class.

Applications include cooking utensils, food processing equipment, exterior architecture, equipment for the chemical industry, truck trailers, and kitchen sinks.

The two most common grades are type 304 (the most widely specified stainless steel, providing corrosion resistance in numerous standard services) and type 316 (similar to 304, with molybdenum added, to increase opposition to various forms of deterioration).

What?
A pear-shaped furnace, lined with refractory bricks, that refines molten iron from the blast furnace and scrap into steel. Up to 30% of the charge into the BOF can be scrap, with hot metal accounting for the rest.

Why?
BOFs, which can refine a heat (batch) of steel in less than 45 minutes, replaced open-hearth furnaces in the 1950s; the latter required five to six hours to process the metal. The BOF’s rapid operation, lower cost, and ease of control give it a distinct advantage over previous methods.

How?
Scrap is dumped into the furnace vessel, followed by the hot metal from the blast furnace. A lance is lowered from above, through which blows a high-pressure stream of oxygen to cause chemical reactions that separate impurities as fumes or slag. Once refined, the liquid steel and slag are poured into separate containers.

Normal ability to produce metals in a given time period. This rating should include maintenance requirements, but because such service is scheduled to match the needs of the machinery (not those of the calendar), a mill might run at more than 100% of capacity one month and then fall well below rated capacity as maintenance is performed.

Engineered Capacity
The theoretical volume of a mill or smelter, given its constraints of raw material supply and normal working speed.

“True” Capacity
Volume at full utilization, allowing for the maintenance of equipment and reflecting current material constraints. (Bottlenecks of supply and distribution can change over time — capacity will expand or reduce.)

What?
Method of applying a stainless steel coating to carbon steel or lower alloy steel (i.e., steel with alloying element content below 5%).

Why?
To increase corrosion resistance at lower initial cost than exclusive use of stainless steel.

How?
By 1) welding stainless steel onto carbon steel; 2) pouring melted stainless steel around a solid carbon steel slab in a mold; or 3) placing a slab of carbon steel between two plates of stainless steel and bonding them by rolling at high temperature on a plate mill.