Hafnium

An exotic alloy usually obtained as a by-product of zirconium production with outstanding corrosion resistance and good mechanical properties. It is added to specialty alloys for use in jet engine parts and as control rod material in nuclear reactors.

Hardening

What?

Process that increases the hardness of steel, i.e., the degree to which steel will resist cutting, abrasion, penetration, bending, and stretching.

Why?

The increased endurance provided by hardening makes steel suitable for additional applications.

How?

Hardening can be achieved through various methods, including 1) heat treatment, where the properties of steel are altered by subjecting the steel to a series of temperature changes; and 2) cold working, in which changes in the structure and shape of steel are achieved through rolling, hammering, or stretching the steel at a relatively low temperature.

Hardness

Defined in terms of the method of measurement. Usually the resistance to indentation

Stiffness or temper of wrought products

Machinability characteristics

Heat Treatment

What?

Altering the properties of steel by subjecting it to a series of temperature changes.

Why?

To increase the hardness, strength, or ductility of steel so that it is suitable for additional applications.

How?

The steel is heated and then cooled as necessary to provide changes in the structural form that will impart the desired characteristics. The time spent at each temperature and the rates of cooling have significant impact on the effect of the treatment.

Heavy Structural Shapes

A general term given to rolled flanged sections that have at least one dimension of their cross sections three inches or greater. The category includes beams, channels, tees and zees if the depth dimension is three inches or greater, and angles if the length of the leg is three inches or greater.

High-Carbon Steel

Steel with more than 0.3% carbon. The more carbon that is dissolved in the iron, the less formable and the tougher the steel becomes. High-carbon steel’s hardness makes it suitable for plow blades, shovels, bedsprings, cutting edges, or other high-wear applications.

High Strength Low Alloy (HSLA) 1

A specific group of steel in which higher strength, and in some cases additional resistance to atmospheric corrosion or improved formability, are obtained by moderate amounts of one or more alloying elements such as columbium, vanadium, titanium, used alone or in combination.

Hot Band (Hot-Rolled Steel)

A coil of steel rolled on a hot-strip mill (hot-rolled steel). It can be sold in this form to customers or further processed into other finished products.

Hot Briquetted Iron (HBI)

Direct reduced iron that has been processed into briquettes. Instead of using a blast furnace, the oxygen is removed from the ore using natural gas and results in a substance that is 90%–92% iron. Because DRI may spontaneously combust during transportation, HBI is preferred when the metallic material must be stored or moved.

Hot End

The section of a steelmaking complex from the furnace up to, but not including, the hot-strip mill.

Hot Metal

The name for the molten iron produced in a blast furnace. It proceeds to the basic oxygen furnace in molten form or is cast as pig iron.

Hot Mill 1

The rolling mill that reduces a hot slab into a coil of specified thickness; the processing is done at a relatively high temperature (when the steel is still “red”).

Hot Roll 1

Product that is sold in its “as produced state” off the Hot Mill with no further reduction or processing steps aside from being pickled and oiled (if specified).

Hot-Strip Mill

A rolling mill of several stands of rolls that converts slabs into hot-rolled coils. The hot-strip mill squeezes slabs, which can range in thickness from two to ten inches, depending on the type of continuous caster, between horizontal rolls with a progressively smaller space between them (while vertical rolls govern the width) to produce a coil of flat-rolled steel about a quarter-inch in thickness and a quarter mile in length.

HYL I, HYL III

Processes for producing DRI and HBI developed by Hylsa. The processes reduce iron ore lump or pellets with reformed natural gas in a vertical shaft furnace. The HYL I process uses four fixed-bed reactors; HYL III uses a single-shaft furnace.

Hydrate

An aluminum oxide with three molecules of chemically combined water.

Hydroforming

A forming process in which a tube is placed into a forming die. The tube is then formed to the shape of the die through the application of internal water pressure.

The hydroforming process allows for severe shape deformation, making it ideal for automotive structural parts such as engine cradles, radiator supports, and body rails. Various shaped and sized holes can be punched in the tube almost anywhere during the process.