What Are the Advantages of Galvannealed Steel Sheet?
Galvannealed steel is produced in a similar process to galvanized metal but takes a different manufacturing step that gives it an additional benefit. After the sheet leaves the galvanizing bath, it undergoes heat treatment in an annealing furnace that diffuses iron into the zinc coating.
This provides many benefits for your application, especially in terms of rust resistance. Some applications that use galvannealed sheet include:
Corrosion Resistance
The coating of zinc on galvannealed steel is an excellent barrier against corrosion. The galvannealing process removes the contaminants that might be present on the metal surface, and this enables the zinc to bond tightly with it. This resulting zinc-iron alloy coating protects the steel from oxidation and promotes long service life.
The corrosive resistance of painted galvannealed steel can help to reduce maintenance galvannealed steel sheet and replacement costs. It is often used for structures that must withstand prolonged exposure to the elements, such as busses and other vehicles, garage doors, highway signs, and computer chassis.
Galvannealed steel’s matte finish facilitates superior paint adhesion. This attribute is crucial for products that require a visually appealing and durable finish. It also makes it ideal for use in architectural elements like fixtures and railings, as well as household appliances and HVAC systems.
In addition to its corrosion-resistance, galvannealed steel is readily formable and weldable. The zinc-iron alloy layer formed during the annealing process contributes to its weldability, making it an effective material for industrial applications with significant welding operations. The alloy layer also helps to prevent weld spatter, and it provides an electrically conductive surface for making strong and reliable welds. The ductility of galvannealed steel also allows it to be used for structural components in manufacturing.
Aesthetics
Galvanized steel has a shiny, spangled appearance that can be desirable for certain applications. However, it can also be a hindrance if you need to paint the material, especially if you’re working in an environment that’s damp or salty. The surface of galvannealed metal has a slight matte texturing, which makes it easier for paint to bond mechanically with the surface. This is why many manufacturers choose to use galvannealed sheet metal for projects that require painted finishes.
The extra step of annealing Q235 steel plate that follows the hot-dip process is responsible for this aesthetic difference. The annealing process allows the zinc to react with the iron in the steel, resulting in an iron-zinc alloy layer on the surface of the galvanized steel. This eliminates the spangled appearance and leaves the metal with a more uniform matte grey finish.
The matte finish also provides better visual appeal and durability compared to galvanized steel. While the spangled appearance of galvanized steel can be attractive, it can cause problems with paint adhesion and rust resistance in some environments. While it’s possible to work with unpainted galvannealed steel, this type of surface won’t provide the same level of corrosion resistance or visual appeal as painted materials. If you need to work with unpainted galvannealed metal, make sure to take steps to prepare the surface for painting, including sanding, cleaning, and applying a primer. DATAMYTE, our low-code workflow automation platform, can help you create custom workflows and smart forms to guide your employees through these tasks.
Weldability
Galvannealed steel sheet has a less spangled appearance than traditional galvanized metal, which is critical in applications like signage and building construction that require a non-reflective surface. Additionally, it has excellent weldability thanks to its zinc-iron alloy coating that provides greater resistance to corrosion than standard galvanized steel.
Its ductility means that it can be formed into different shapes without damaging its protective coating, making it ideal for use in automotive panels and household appliances where it is often required to bend and shape components. It can also be used in electrical systems to make conduits and enclosures.
The underlying iron element in galvannealed steel makes it harder than standard galvanized steel, which improves its weldability and resistance to manufacturing damage such as chipping and scratching. This improved weldability also makes it easier to create strong, reliable welds, as it is less likely to degrade or disperse its zinc coating during the welding process.
It is important to note that you should take care when welding galvannealed steel, as there is a small amount of lead in the coating that can vaporise during welding, producing dangerous lead oxide fumes. These fumes can cause long-term health problems, so it is important to always wear appropriate safety equipment when working with this type of metal. This includes breathing masks and gloves to avoid exposure.
Formability
For automobile manufacturers to produce exterior components of cars, they need both accurate shapes and high strength. Formability is an essential property for achieving these requirements. A galvannealed steel sheet is used for making these exterior components. It has excellent press formability and high BH properties, making it possible to shape the steel sheet into desired parts with ease. The material also has superior paint adhesion and resists corrosion, making it an ideal choice for manufacturing automobile bodies and other vehicle parts.
During the hot-dip galvanizing process, a steel sheet is coated with zinc. Immediately after the coating, it undergoes an in-line heat treatment that converts the zinc into a zinc-iron alloy. This eliminates the spangled appearance of galvanized steel and gives the material a dull gray finish that is easier to paint than standard galvanized metal. The matte surface of the zinc-iron coating is also more durable than that of standard galvanized steel, providing extra scratch resistance.
Adding Si and P, which are effective alloying elements, increases the tensile strength of the base metal without impairing its formability. However, if these materials are added in excessive quantities, the low temperature chipping resistance tends to be degraded and bake hardenability is inhibited. The present invention provides a galvannealed steel sheet with superior low temperature chipping resistance, bake hardenability, and powdering resistance by controlling the amount of these alloying elements.
