Application Technology

Stainless steel is a metal used in various applications – due to its durability, heat and corrosion resistance. Here, APM Hexseal explores what stainless steel is and the different types available, whilst also describing the advantages of its use in various applications.

Stainless steel is an alloy composed of varying amounts of manganese, silicon, chromium and low carbon steel. The chromium content in stainless steel provides lasting corrosion resistance in oxygenated environments, and extreme temperatures, and can deliver exceptional durability when hardened. While stainless steel is typically an alloy composed of the four components above, select grades add molybdenum and nickel to improve the corrosion resistance. 

While there are several compositions, for a steel alloy to be considered stainless steel, it must contain at least 10.5% chromium or more. Various grades of stainless steel exist to deliver performance in a broad spectrum of applications. 

There are five primary types of stainless steel – austenitic, ferritic, duplex, martensitic, Precipitation Hardening (PH) – as well as various grades to choose from, with the 300 and 400 series being the most popular.  Austenitic is the most popular stainless steel type that improves formability and weldability with nitrogen, manganese and nickel additives. Another type, ferritic, is a chromium-based, magnetic stainless steel used in limited applications – with a carbon content of 0.10%. Duplex is a 50/50 combination of austenitic and ferritic stainless steel that offers resistance and strength but does not withstand welding well.

As well as these, martensitic is a stainless steel type similar to ferritic steel that offers higher strength than ferritic but less resistance than austenitic steel – due to its higher carbon content. Lastly, Precipitation Hardening (PH) is a stainless steel type with aluminium, niobium, copper additives, and exceptional strength, due to an aging heat treatment.

Benefits of stainless steel

Stainless steel offers various advantages that make it a preferred choice in many applications including strength, cleanliness, aesthetics, corrosion resistance, recyclability, as well as durability. It is also a high strength alloy that can maintain strength at extremely low and high temperatures, making it desirable for many applications. Stainless steel also prohibits pathogen and bacterial growth – meaning it can be easily cleaned and maintained. It can be cleaned to a shiny finish with a swabbing and all purpose cleaner, followed by polishing. It’s low maintenance and ease of cleaning also make it ideal for sanitary applications.

Stainless steel also has excellent resistance to water staining, rust and corrosion. It can handle various environmental conditions with extreme temperatures and pressures. The corrosion resistance of stainless steel comes from the chromium content that creates a self repairing barrier over the surface of the metal to resist corrosion, rust and damage. Grades of stainless steel with increased molybdenum, titanium, and nickel content, can enhance the alloy’s properties, including corrosion resistance. After a stainless steel product has exceeded its lifespan, it can be recycled to make other stainless steel products. 

Stainless steel is one of the most durable metals used and can be made lightweight and maintain a high toughness to reduce buckling under heavy loads. It can also hold heavy weights in extreme environmental conditions, including high and low temperatures.

These benefits enable stainless steel to be relied on in a number of applications in a variety of industries, including marine infrastructure,  aviation, railway and bridge construction.

It is for these reasons that APM Hexseal uses stainless steel as standard for its sealing screws, sealing nuts and sealing washers, as well as having stainless steel inserts in many of its switch boots. “We only use the best raw materials in our products,” comments the company. “Using our 75 year experience, we can also make any of our products stainless, on request, confirming our position as a leader in this technology.”