What Is Sheet Metal?- Definition, Types, and Uses

What is Sheet Metal?

Sheet metal is metal formed into thin, flat pieces, usually by an industrial process.

Thicknesses can vary significantly; extremely thin sheets are considered foil or leaf, and pieces thicker than 6 mm (0.25 in) are considered plate, such as plate steel, a class of structural steel.

Sheet metal is available in flat pieces or coiled strips. The coils are formed by running a continuous sheet of metal through a roll slitter.

In most of the world, sheet metal thickness is consistently specified in millimeters. In the U.S., the thickness of sheet metal is commonly specified by a traditional, non-linear measure known as its gauge.

The larger the gauge number, the thinner the metal. Commonly used steel sheet metal ranges from 30 gauge to about 7 gauge. Gauge differs between ferrous (iron-based) metals and nonferrous metals such as aluminum or copper.

Many different metals can be made into sheet metal, such as aluminium, brass, copper, steel, tin, nickel and titanium.

For decorative uses, some important sheet metals include silver, gold, and platinum (platinum sheet metal is also utilized as a catalyst). These metal sheets are processed through different processing technologies, mainly including cold rolling and hot rolling.

Sometimes hot-dip galvanizing process is adopted as needed to prevent it from rusting due to constant exposure to the outdoors. Sometimes a layer of color coating is applied to the surface of the cold-rolled sheet to obtain a decorative and protective metal sheet, generally called a color-coated metal sheet.

Sheet metal is used in automobile and truck (lorry) bodies, major appliances, airplane fuselages and wings, tinplate for tin cans, roofing for buildings (architecture), and many other applications.

What is Sheet Metal

Types of Sheet Metal

There are six major types of sheet metal material, each with its own unique advantages:

  • Aluminum
  • Alloy Steel
  • Carbon Steel
  • Tool steel
  • Galvanized steel
  • Stainless steel

1. Aluminum

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?

There are a number of grades to choose from, for the purpose of this white paper we will focus on the top three found in precision sheet metal fabrication:

  • Austenitic stainless is a non-magnetic – any of the 300 series steel – that contains high levels of chromium and nickel and low levels of carbon. Known for their formability and resistance to corrosion, these are the most widely used grade of stainless steel.
  • Ferritic – Stainless steels that are magnetic, non-heat-treatable steels that contain 11-30% chromium but with little or no nickel. Typically employed for non-structural uses where either good corrosion resistance is needed such as with seawater applications or decorative applications where aesthetics are the main concern.  These metals are most commonly found in the 400 series stainless steel.
  • Martensitic – A group of chromium steels ordinarily containing no nickel developed to provide steel grades that are both corrosion resistant and hardenable via heat-treating to a wide range of hardness and strength levels.

6. Cold rolled steel (CRS)

Use cold rolled sheet (CRS) to get better material strength with a good surface finish. Parts made from cold rolled sheet must be painted or otherwise protected immediately to prevent surface rust.

Cold rolled sheet metal can be laser cut, punched, and formed with excellent results similarly to the HRPO sheet mentioned above. The surface finish of painted parts is usually very good with CRS.

7. Pre plated steel

Sheet metal material that is either hot-dipped galvanized steel or galvanealed steel, which is galvanized then annealed.

Galvanization is the process of applying a protective zinc coating to steel in order to prevent rust and corrosion. 

Annealing is a heat treatment process that alters the microstructure of a material to change its mechanical or electrical properties, typically reducing the hardness and increasing the ductility for easier fabrication.

What Is Sheet Metal Used For?

The uses of sheet metal will vary based on the type of metal being used. Certain types of sheet metal will only be able to meet performance standards for specific applications. The type of material often dictates what a sheet metal is used for:

Carbon steel sheet

Carbon steel sheet is often used for general fabrication purposes, especially when corrosion is not a concern or if there will be a coating process following fabrication to protect the steel from the elements.

It can be used for anything from car bodies to store signs. The reason for its versatility is because it is relatively affordable and typically has superior tensile strength when compared with copper and aluminium.

Galvanized steel sheet

Galvanized steel sheet is a form of carbon steel sheet metal that has gone through a galvanising process where zinc oxide is coated on the outside surface of the steel to protect it from rusting. \

Galvanized steel is frequently used in automotive parts and objects exposed to water such as greenhouse equipment, buckets, irrigation pipe and marine vessels.

Stainless steel sheet

Stainless steel sheet is typically more expensive than galvanised or carbon steel because of the additional alloying elements in its composition. However, these alloying elements give stainless steel sheet enhanced corrosion resistance.

This ability to resist corrosion makes it widely used in critical applications such as aerospace engine components, high-performance marine structures and vessels, pharmaceutical processing equipment and food handling equipment.

Stainless steel sheet also has good aesthetic appeal that makes it popular for signage and appliances.

Aluminum sheet

Aluminum sheet is roughly ⅓ the density of steel, making it a frequently used metal for applications when weight is a concern. It is also quite resistant to corrosion.

The combination of lightweight and corrosion resistance make Aluminium sheet a great choice for boat components, marine structures, cookware, automotive parts, and aerospace parts.

Copper sheet

Copper sheet is known for its electrical conductivity, aesthetic appeal, and malleability. It is used in equipment where electricity must be easily transferred to a workpiece like in some resistance welding equipment or certain types of battery systems.

Because of its malleability and superior aesthetic qualities, it is also commonly used in home decor and other forms of artwork.