Aluminum and stainless steel alloys come in a variety of standard product forms, strip and sheet being among them. For those less familiar with the industry vernacular of aluminum and stainless steel, there is a difference between strip and sheet.
What is aluminum and stainless steel sheet?
Sheet is among the most common metal products, normally defined as any aluminum or stainless steel that is less than a quarter of an inch thick. Anything below one thousandth of an inch is considered foil, while anything .25” and greater is considered a plate product.
Sheet is formed by passing a pre-heated metal slab or billet through rollers until it has achieved the desired thickness. The process is commonly known as hot rolling.
Stainless and carbon steel products are often pickled following the hot rolling process. This is done by passing the metal through an acid bath. Traditional carbon steel is quite susceptible to rusting after the pickling process, so a thin film of oil is applied to protect the surface. For most stainless steels this is unnecessary.
Stainless steel usually goes through an annealing process to improve ductility and corrosion resistance. Depending on the grade, aluminum sheet can be thermally treated, strain hardened or annealed. This is usually determined by the fabrication method for a particular product.
The coils may go through additional cold rolling processes to further reduce the thickness of the material. The edges of the coils are trimmed to produce a finished standard width, such as 48”, 60” or 72”. The coils may get further processed on a leveling line and cut to standard lengths, such as 96”, 120” or 144”.
What is aluminum and stainless steel strip?
Both strip and sheet start out as a flat rolled coil product at the mill. Again, the process begins with a slab or billet that gets reduced through successive passes through rolling mills in the hot rolling process. The coiled stock may also achieve its final thickness by direct cold-rolling.
The greatest difference between strip and sheet is the width of the coiled product. Any coiled product 24” and wider is considered sheet, while anything under 24” is described as strip. Today’s precision slitters can produce widths as small as .035”, but many applications below .25” wide may realize more benefit from a drawn or rolled wire product.
To produce strip, the coil is then cut to its finished width through a process known as roll slitting. Multiple widths are slit from a single master coil. Standard widths are generally between three quarters of an inch and eight inches. A traditional ribbon, or pancake, coil consists of a single strip that is wound on top of itself until the maximum OD tolerance is reached. Oscillate, or traverse, wound coils take pancake coils, weld them together, and wind the strip back and forth on a traversing rewind drum, like that of a spool of thread or garden hose.
What applications are common for sheet and strip?
As their size indicates, sheet products are used for larger metal fabrications and strip coil is used to produce smaller parts. Strip is commonly employed in progressive stamping and deep drawing processes, or roll-forming operations for tube manufacturing. Standard sheet sizes are often sheared into lesser sheets that are formed, welded or drawn into various fabricated parts, or used in their entirety depending on the operation and project involved.