Stainless steel grades & finishes
Stainless steel is a popular material for sheet metal production. It is an iron-based alloy that contains at least 10% chromium and brings unique benefits such as high resistance to corrosion, heat and oxidisation.
Stainless steel sheet can vary in grades and finishes, all of which will affect the properties of the metal and so, to fabricate highly precise, durable components that use the material's advantages, many factors need to be considered.
Grades of stainless steel
The grades of metal most used in fabrication include 304, 316 & 430.
304-grade contains 18% chromium and 8% nickel and offers low-cost corrosion resistance to oxidisation, versatility and ease of fabrication. Grade 304 is austenitic and is often used to fabricate indoor products such as electrical enclosures, kitchen equipment and stainless hardware.
316-grade contains 2% molybdenum, which strengthens its resistance to chlorides, seawater, acidic chemicals and heat. Grade 316 is therefore favoured for the manufacture of outdoor products and those placed in testing environments such as marine applications or oil equipment.
430-grade is a ferritic metal with good corrosion resistance (however less than 304) and particularly strong resistance to nitric acid. The grade is readily weldable, ferromagnetic, has high machinability and is less expensive than the austenitic grade 304. 430 is commonly used for domestic appliances, automotive trim products and metal fabrications for chemical applications.
Stainless steel finishes
When selecting a finish, it's important to consider the application of the product and understand that each finish will provide a different cosmetic appearance, a varying level of corrosion resistance and require different levels of manufacturing which may impact the cost.
The benefits of each finish and the suitability for application are discussed below.
Brushed finish
Brushed: A brushed finish offers a non-reflective directional surface, produced by polishing the metal surface with a grit belt and then softening with adhesive. The process can roughen the surface and reduce corrosion resistance. However, its appealing matte cosmetic appearance makes it commonplace for many household applications such as kitchen sinks.
Bead blasted finish
Glass Bead Blasting: This involves blasting fine glass beads (on their own or mixed with other non-abrasive materials) onto the surface at high pressure. It eliminates any impurities or deposits and provides a soft a smooth, low-reflective finish. Although susceptible to fingerprint staining, it is a relatively cost-effective finishing method. Manufacturers of medical equipment, food distribution and packaging conveyors often favour this hygienic, matte finish to metal fabricated products.
Passivated finish
Passivated: Passivation uses an acid solution to remove any contamination from the surface of the steel that may encourage rust or corrosion, for example, dirt iron particles. It can also enhance the natural corrosion resistance. Passivation results in a bright, smooth finish and is used in metal products for the medical and dental industries.
Mirror steel finish
Mirror Polished: Polished finishes are highly reflective, mirror-like and easy to clean. Common applications are commercial products such as forecourt equipment, catering dispensers and handrails. The finishing method is achieved from polishing with fine abrasives and comprehensive buffing.
With dedicated facilities, including on-site shot bead blasting and electro-mechanical assembly, KMF Precision Sheet Metal is the UK's leading sheet metal fabricator. Contact one of our experts today to discuss your fabrication project.