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PM 2.5
The moniker for the Environmental Protection Agency's new Particulate Matter standards. The EPA is revising current PM standards and establishing a new PM 2.5 standard regarding the release of particulate matter down to 2.5 micrometers in diameter (less than one-third the width of a human hair).

Peak Earnings
The ultimate earnings level of a company at the top of the business cycle. This is the expected profit during the time of the highest commodity demand and the strongest product pricing.

Pellets
(See Agglomerating Processes )

Pickling
WHAT Process that cleans a steel coil of its rust, dirt and oil so that further work can be done to the metal.

WHY When hot-rolled coils cool, rust forms on the unprotected metal; often coils are stored or transported while exposed to outside air and water.

HOW Through a continuous process, the steel is uncoiled and sent through a series of hydrochloric acid baths that remove the oxides (rust). The steel sheet is then rinsed and dried.

Pig Iron
The name for the melted iron produced in a blast furnace, containing a large quantity of carbon (above 1.5%). Named long ago when molten iron was poured through a trench in the ground to flow into shallow earthen holes, the arrangement looked like newborn pigs suckling. The central channel became known as the "sow," and the molds were "pigs."

Piling (Sheet Piling)
A structural steel product with edges designed to interlock; used in the construction of cofferdams or riverbank reinforcement.

Pipe
Technically a tube used to transport fluids or gases. However, pipe and tube are often used interchangeably in steel lexicon, with a given label applied primarily as a matter of historical use.

Plate
Sheet steel with a width of more than eight inches, with a thickness ranging from one quarter of an inch to more than one foot (see Sheet Steel ).

Powder Metals
Fabrication technology in which fine metallic powder is compacted under high pressure and then heated at a temperature slightly below the melting point to solidify the material. Primary users of powder metal parts are auto, electronics and aerospace industries.

Precipitation Hardening (PH)
A small group of stainless steels with high chromium and nickel content, with the most common types having characteristics close to those of martensitic (plain chromium stainless class with exceptional strength) steels. Heat treatment provides this class with its very high strength and hardness. Applications for PH stainless steels include shafts for pumps and valves as well as aircraft parts.

Pulverized Coal Injection System (PCI)
A blast furnace enhancement to reduce an integrated mill's reliance on coke (because of environmental problems with its production). Up to 30% of the coke charged into the blast furnace can be replaced by this talcum-like coal powder, which is injected through nozzles at the bottom of the furnace.