What is Sheet Metal?
Sheet metal is metal formed by an industrial process into thin, flat pieces. Sheet metal is one of the fundamental forms used in metalworking, and it can be cut and bent into a variety of shapes. Countless everyday objects are fabricated from sheet metal.
Thicknesses can vary significantly; extremely thin sheet metal is considered foil or sheet, and pieces thicker than 6 mm (0.25 inch) are considered plate steel or “structural steel”.
Sheet metal is available in flat pieces or coiled strips. The coils are formed by passing a continuous sheet of metal through a slitter.
In most parts of the world, the sheet thickness is given in millimeters. In the United States, sheet metal thickness is commonly specified by a traditional, non-linear measure known as thickness. The larger the number, the thinner the metal.
Commonly used sheet steel ranges from 30 gauge to about 7 gauge. Thickness distinguishes between ferrous metals (iron-based) and non-ferrous metals such as aluminum or copper. For example, copper thickness is measured in ounces, which represents the weight of copper contained in a one-square-foot area. Parts made from sheet metal must maintain a consistent thickness for best results.
Many different metals can be used in sheet metal manufacturing such as aluminum, brass, copper, steel, tin, nickel, and titanium. Some important sheets for decorative purposes include silver, gold, and platinum (platinum sheet is also used as a catalyst).
Related: What are the different types of metal?
Sheet metal is used in car and truck bodies, airplane fuselages and wings, medical tables, roofs for buildings (architecture), and many other applications. Sheets of iron and other materials with high magnetic permeability, also known as laminated steel cores, find applications in transformers and electrical machinery.
Historically, an important use of sheet metal was in plate armor worn by cavalry, and sheet metal continues to have many decorative uses, including in harnesses. Sheet metal workers are also known as “tin beaters” (or “tin knockers”), a name derived from the hammering of sheet metal seams when installing sheet metal roofing.
Types of Sheet Metal
There are six major types of sheet metal material, each with its own unique advantages:
- Alloy steel
- Carbon steel
- Tool steel
- Galvanized steel
- Stainless steel
For applications that require a more lightweight material, aluminum is an excellent option. This type of sheet metal offers significant corrosion resistance even without a finish. Aluminum is also strong and can undergo laser cutting, welding, and machining.
A moderately-priced material, aluminum has a range of characteristics across several grades to meet application requirements. Grade 1100 offers relatively low strength but is chemical and weather-resistant, weldable, and ductile, allowing deep drawing.
Grade 3003 is stronger and formable, weldable, corrosion-resistant, and affordable. Grade 5052 is significantly stronger while still formable, weldable, and corrosion-resistant. Grade 6061 is a structural alloy that is corrosion-resistant and strong, but not formable. It is weldable, though it sacrifices some strength when welded.
2. Alloy Steel
As the name suggests, alloy steel combines multiple elements to enable a customizable set of properties. The main component of this material is carbon steel. Common additions include tungsten, chromium, and manganese, for rigidity, or vanadium and nickel, for strength. In addition to its versatility, alloy steel is also highly affordable.
3. Carbon Steel
Iron is alloyed with carbon in this sheet metal material, providing an option with high amounts of strength. Depending on the desired application, a manufacturer can choose from steel with low, medium, or high levels of carbon content.
Low amounts of carbon result in a highly versatile material, most commonly found in everyday objects like fences and gates. Medium carbon steel is a popular choice for automotive vehicles and appliances. Higher levels of carbon result in a slightly more fragile product, ideal for delicate items, such as wires.
3. Tool Steel
Immensely versatile, tool steel is a rigid alloy containing about one percent carbon. As with alloy steel, the elements contained within tool steel vary in type and ratio depending on the desired application. Tool steel is resistant to abrasion and functions well in extreme temperatures.
Its properties make this type of sheet metal ideal for the construction of tools, such as punches, dies, blades, and hammers.
4. Galvanized Steel
Galvanized steel is available in two varieties: electro-galvanized sheets and hot-dipped metallic-coated sheets. The former is composed of cold-rolled annealed steel. It has a pure zinc coating with no zinc spangle.
The latter is composed of cold-rolled hard steel plates coated with a mixture of pure zinc and an iron-zinc alloy. This type of galvanized steel offers more corrosion resistance and is slightly more affordable than electro-galvanized sheets.
Related: What is Galvanized Steel?
5. Stainless Steel
This type of sheet metal is ideal for products that will be exposed to frequent moisture. It contains chromium, an element that significantly reduces corrosion caused by harsh or damp environments. Components made from stainless steel sheet metal fabrication can increase the lifespan of a product or structure, from kitchen sinks to office buildings.
Related: What is Stainless Steel?
Stand and spring-like stainless steel are the two categories used in sheet metal fabrication.
- Standard stainless can be non-magnetic; any of the 300 series steels are the most commonly used type of stainless. It does not require hot work or other stress relief during manufacturing. Grade 316 is the most corrosion-resistant of the stainless-steel grades and maintains its strength at high temperatures. Grade 304 is the most widely used and, while it is somewhat less corrosion-resistant, offers good formability and weldability.
- Standard type magnetic stainless for sheet metal fabrication is the 400 series. Grade 410 offers less corrosion resistance but is heat treatable. Grade 430 is an inexpensive alternative to the other stainless-steel options and is used in applications where corrosion resistance is not a major requirement such as brush-finished appliance surfaces. Because these materials tend toward elastic rather than plastic deformation, they must be over bent to achieve the final form.
- Spring-like steels will work-harden quickly and must be heated to relieve stresses when being formed. Grades include 301, 17-4, 1095, and 1075. Spring-like stainless typically requires specialized equipment and processes and must be over bent to achieve the final form.
6. Cold rolled steel (CRS)
The process of cold rolling steel is used to smooth the finish of hot rolled steel as well as to hold a tighter tolerance when forming. CRS is available in 1008 and 1018 alloys.
7. Pre plated steel
This sheet metal material is either hot-dip galvanized steel or galvannealed steel, which is galvanized and then annealed.
Uses of Sheet Metal
Sheet metal is used in automobile and truck (lorry) bodies, airplane fuselages and wings, medical tables, roofs for buildings (architecture), and many other applications.
Sheet metal of iron and other materials with high magnetic permeability, also known as laminated steel cores, has applications in transformers and electric machines.
Historically, an important use of sheet metal was in plate armor worn by cavalry, and sheet metal continues to have many decorative uses, including in horse tack.
Sheet metal workers are also known as “tin bashers” (or “tin knockers”), a name derived from the hammering of panel seams when installing tin roofs.