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Stainless Steel Fabrication: Everything you Need to Know

What is Stainless Steel?

Stainless steel is a versatile raw material with many applications in both home and industrial settings. It is used for everything from cookware to surgical instruments to aerospace applications and heavy fabrications for the oil and gas industry. Unlike mild steel, stainless steel has high corrosion resistance properties, making it the perfect material for certain metal fabrications.

To make the most of this valuable material, it’s essential to understand how it is fabricated. This article will explain the process of stainless steel fabrication, including the types of available stainless steel and their associated applications.

What is Stainless Steel fabrication?

Stainless steel fabrication is creating finished products from stainless steel sheets, coils, or bars. The fabrication process begins by cutting the metal to size and then shaping it into the desired form. This can be done through various methods, including CNC machining, laser cutting, CNC punching, CNC bending, and welding. Once the fabrication is complete, the product is polished, or a powder coating is applied as needed.

What are the five types of stainless steel and their applications?

There are five main types of stainless steel: austenitic, ferritic, martensitic, duplex, and precipitation hardened. Each type has a different chemical composition and properties, making them suited for various applications.

Austenitic Stainless Steel

Austenitic stainless steel is the most common type and comprises 18% chromium and 8% nickel. It is non-magnetic and highly corrosion-resistant. This type is used extensively in food processing machinery, chemical processing, and pharmaceuticals. AISI grade 304 and 304L are the standard grades used in many applications. However, if more corrosion resistance is required, we recommend AISI grade 316 or 321 for marine applications.

Ferritic Stainless Steels

Ferritic stainless steel comprises 17% chromium and 0.15% carbon. It is magnetic and less corrosion-resistant than austenitic stainless steel, but it is still more resistant to corrosion than other types of steel. In addition, ferritic stainless steel is more ductile, resistant to corrosion, and cost-effective than austenitic and duplex grades. Ferritic Stainless Steel is mainly utilised in manufacturing automotive components, industrial machinery, and kitchenware since they readily endure cold working and deep drawing procedures.

Martensitic Stainless Steels

Martensitic stainless steel is used in applications where increased strength or hardness is needed, such as machine parts and vehicle components. Martensitic stainless steel comprises at least 10% chromium and 0.5% carbon, but some varieties include nickel, manganese, molybdenum, or titanium. Martensitic stainless steels have a higher carbon content which gives them increased hardness and good wear resistance. Typical applications for martensitic stainless steels are medical tools such as scalpels, razor blades, and cutlery.

Duplex Stainless Steels

Duplex stainless steel is a type of stainless steel that contains both ferritic and austenitic stainless steel. This alloy is characterised by its high resistance to corrosion and its high strength. Duplex stainless steel is often used in applications where strength and corrosion resistance are required. Some of the most common applications for duplex stainless steel include architecture, pipelines, chemical process plant, pumps, tanks, and pressure vessels.

Precipitation Hardened Stainless Steels

Precipitation hardening is a heat treatment process that leads to very tough material. The process involves heating the stainless steel to a suitable temperature, followed by rapid cooling or quenching. This heat treatment is often used on martensitic steels and results in increased hardness and strength without affecting its ductility. The composition of precipitation-hardened stainless steel typically contains 8% chromium, 17% nickel, and 10% manganese. Typical applications for these stainless steels are gears, turbines, shafts, and containers for nuclear materials.

Why it’s essential to know the type of stainless steel you’re using

When fabricating with stainless steel, it’s important to understand the different types and their applications. Each type of stainless steel has unique properties making it well suited for various applications. If you choose the wrong kind of stainless steel for your application, you may not get your desired results.

For example, if you need a highly corrosion-resistant material, you should use austenitic stainless steel. On the other hand, if you need a material with high strength and toughness, you should use martensitic stainless steel. By understanding the different types of stainless steel and their properties, you can make sure you’re using the correct material for your application.

What are the different methods of surface finish for stainless steel fabrications?

When fabricating with stainless steel, you can choose many different surface finishes. The finish you choose will depend on the application and the desired look. Some of the most common surface finishes for stainless steel are broadly categorised as:

  • Mill finishes
  • Acid finishes
  • Polished finishes

Mill finishes are the most common type of finish for stainless steel. They are achieved by rolling the sheet metal to the desired thickness and passing it through a series of rollers that give it a smooth, matte finish. One of the most used finishes we use is called 2B and looks like a uniformly steamed mirror.

Acid finishes are created by treating the sheet metal with a corrosive acid that etches the surface, leaving a rough, pitted finish. The three most used acid finishes are descaling, passivation, and wet etching. Acid finishes are often used in applications where durability is more important than appearance, such as industrial process plant or unseen parts.

Polished finishes vary from a standard “brushed” finish, known as DP (dull polished), and increase in intensity up to a mirror finish. Polished stainless steel sheet is typically used in high-end beauty applications, architecture, and sheet metal components exposed to view or where a reflective appearance is desirable.

Summary

There are many types of stainless steel available, and each has its own strengths and weaknesses. To choose the right kind of stainless steel for your project, you need to understand the applications that each type is best suited.

As we noted earlier, the most common types of stainless steel are 304, 316, and 430. 304 stainless steel is the most versatile type and is suitable for a wide range of applications. It has excellent corrosion resistance and can be used in indoor and outdoor settings. 316 stainless steel is also corrosion-resistant, but it is more expensive than 304 stainless steel. It is often used in marine applications and other environments where high corrosion resistance is required. 430 stainless steel is the least expensive type of stainless steel, but it has lower corrosion resistance and is only suitable for indoor applications.

Pegasus Precision provides stainless steel fabrication services to the instrumentation industry. Our engineers are experts in all forms of metal fabrication using ferrous and non-ferrous metals and can advise you on the most appropriate materials for your application.