Plain Steel - (also know as carbon steel)
 
Steel is an alloy of iron, carbon, and other materials, such as chromium, manganese, nickel, and molybdenum. Carbon is the principal hardening element in steel and as the carbon content increases, the hardness increases; ductility and weldability decreases. In general, steel is considered to be plain or carbon steel when no minimum content is specified, or when any element is added to obtain a desired effect. Carbon steel is more susceptible to corrosion than galvanized, aluminum, or stainless steel.

Steel is classified as:
 Sheets, Coils or Cut Lengths for 7 Gauge or lighter thickness
 Plate for 3/16 inch or heavier thickness
 High Carbon Steel
 
High-carbon steels are extremely strong but more brittle. This composition allows better responses to heat treatment and longer service life than medium-carbon steels. High-carbon steels have superior surface hardness resulting in high wear resistance. The AISI designations for High-carbon steel are: AISI 1055-1095, 1137-1151, and 1561-1572 

Aluminum combines a unique set of properties (lightweight and resistant to corrosion). It is also nontoxic which makes it an excellent material in cooking utensils. Most aluminum types are an alloy of aluminum, which includes a small quantity of silicon, iron, copper, magnesium, or nickel. These alloys differ in hardness, tensile strength, and other properties.
Stainless steel is an alloy of iron, chromium, nickel, carbon, and other materials. The principal benefit of this product is its resistance to corrosion and/or oxidation. Series 300 stainless steels are chrome-nickel, non-hardening, and austenitic (nonmagnetic). Series 400 steels can be chrome, hardenable martensitic or non-hardenable ferritic (both magnetic). The appearance of stainless steel products with a mill finish may not be suitable for some applications. The appearance can be improved by sand blasting.