The second-largest class of stainless steel, constituting approximately 25% of stainless production.

Ferritic stainless steels are plain chromium steels with no significant nickel content; the lack of nickel results in lower corrosion resistance than the austenitics (chromium-nickel stainless steels). Ferritics are best suited for general and high-temperature corrosion applications rather than services requiring high strength. They are used in automotive trim and exhaust systems, interior architectural trim, and hot water tanks. Two of the most common grades are type 430 (general-purpose grade for many applications, including decorative ones) and type 409 (low-cost grade well suited to withstanding high temperatures).

Steel coated with a thin layer of zinc to provide corrosion resistance in underbody auto parts, garbage cans, storage tanks, or fencing wire. Sheet steel normally must be cold-rolled prior to the galvanizing stage.

Hot-Dipped
Steel is run through a molten zinc coating bath, followed by an air stream “wipe” that controls the thickness of the zinc finish.

Electrogalvanized
Zinc plating process whereby the molecules on the positively charged zinc anode attach to the negatively charged sheet steel. The thickness of the zinc coating is readily controlled. By increasing the electric charge or slowing the speed of the steel through the plating area, the coating will thicken.

Differences
Electrogalvanizing equipment is more expensive to build and to operate than hot dipped, but it gives the steelmaker more precise control over the weight of the zinc coating. The automotive manufacturers, because they need the superior welding, forming, and painting ability of electrogalvanized steel, purchase 90% of all tonnage produced.

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.

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

a. Stiffness or temper of wrought products
b. Machinability characteristics

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.

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.

Inconel is a family of austenitic nickel-chromium-based superalloys. Inconel alloys are oxidation-corrosion-resistant materials well suited for service in extreme environments subjected to pressure and heat. When heated, Inconel forms a thick, stable, passivating oxide layer protecting the surface from further attack. Inconel retains strength over a wide temperature range, attractive for high temperature applications where aluminum and steel would succumb to creep as a result of thermally induced crystal vacancies. Inconel’s high temperature strength is developed by solid solution strengthening or precipitation hardening, depending on the alloy.

Inconel alloys are typically used in high temperature applications. Common trade names for Inconel Alloy 625 include: Inconel 625, Chronin 625, Altemp 625, Haynes 625, Nickelvac 625 and Nicrofer 6020.

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 by-products of steelmaking, 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.