Wrought iron, a metal building material, always contains less than 0.3 percent carbon, and it usually contains less than 0.1 percent. It also contains 1 to 2 percent slag, a mineral waste product produced during the metal smelting process. The low carbon content and slag present in wrought iron gives the material its distinctive characteristics, which include its tremendous elasticity and ductility. Wrought iron is also highly malleable, making it an effective working material. It usually only appears in outdoor furniture and items such as lamps in the 21st century, although, in the 18th century, it regularly appeared in fences, gates, railings, balconies, porches, verandas and more.
Metal manufacturers use a variety of measurements to indicate certain material properties of wrought iron and similar building materials. These measurements include tensile strength, elasticity, ductility, corrosion resistance, and toughness and impact resistance. Tensile strength describes the maximum weight a material can support before breaking. Elasticity describes the amount of weight a material can support before permanently bending or contorting, and ductility describes a material’s ability to change shape, rather than break, under pressure.
PSI is the abbreviated form of the term “pounds per square inch,” a common measurement used to test the strength of building materials. According to “Army Technical Manual TM 5-600,” a United States military publication, wrought iron usually exhibits a tensile strength of 50,000 pounds per square inch. Any pressure over 50,000 PSI causes this generic wrought iron to break. Elasticity measurements in wrought iron usually measure between 24,000 and 29,000 PSI, depending upon the manufacturing process of the particular metal.
The term “PSI Wrought Iron” indicates a strength measurement for a specific type of wrought iron. For instance, if you purchase wrought iron labeled by the manufacturer as 30,000-PSI Wrought Iron, your wrought iron exhibits a tensile strength of 30,000 PSI. Unless otherwise labeled, generic PSI measurements in metals always describe tensile strength. If you see the phrase “PSI Wrought Iron” preceded by a blank space on a form or some other printed literature, this probably indicates that a manufacturer or vendor will fill in PSI ratings for a particular material at some point in the future.