Mar. 24, 2025
Stainless steel is a flexible material known for its great resistance to rust and long-lasting quality. It comes in various forms, including austenitic, ferritic, martensitic, duplex, and precipitation-hardened stainless steel.
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Ferritic stainless steel is different from austenitic steel. It has a body-centered cubic (BCC) arrangement and has less nickel. Ferritic stainless steel is also attracted to magnets and is used in situations where these characteristics are advantageous.
This article will focus on ferritic stainless steel, covering its definition, composition, key properties, processing methods, and common grades. Our goal is to give you a clear overview of when and why ferritic stainless steel might be the right choice for your needs.
Ferritic stainless steel is a stainless steel with a body-centered cubic (BCC) crystal arrangement that is similar to pure iron at room temperature. The composition typically contains 10.5% to 18% chromium (but a specific grade can be as high as 30%) with little or no nickel and low carbon content.
It is one of the five stainless steel classes, which is widely used in automotive exhaust systems, household appliances, and industrial equipment. Common grades include 430, 409, and 439. It is magnetic and cannot be hardened through heat treatment.
Ferritic stainless steel is mainly composed of iron, chromium, and carbon. Iron is the main element, constituting the largest portion of the composition. Chromium, making up 10.5-30%, is the main additive that gives corrosion resistance. The carbon content is low, typically less than 0.1%, which keeps the steel soft and malleable. Other elements like molybdenum, aluminum, and titanium might be present in smaller amounts to improve specific properties.
The following 3 features are the most prominent characteristics of ferritic stainless steel.
These characteristics are tied to ferritic stainless steel's chemical, physical, and mechanical properties, which ensure its reliability and effectiveness. Let's explore these in detail.
Ferritic stainless steel's chemical properties involve its behavior in chemical environments, most notably corrosion, and oxidation resistance, with the main properties being:
Ferritic stainless steel's physical properties are key to selecting it for engineering and industrial uses, particularly in heat exchange and magnetic applications. Next, please review the important physical characteristics in the table below:
Ferritic stainless steel's physical traits determine its strength and durability in building applications. Please read the table below for key mechanical properties:
Want to know about the characteristics of austenitic steels? Please read thisaustenitic overview article.
Unlike austenitic, martensitic, duplex, and precipitation-hardening stainless steel, ferritic stainless steel requires specific handling during production. Below, we'll explore these unique processing methods and the issues that require attention.
Ferritic stainless steel starts with a straightforward melting and casting process. It is then easily formed, much like carbon steel. Unlike austenitic stainless steel, ferritic steel doesn't harden significantly during forming, so it doesn't require frequent annealing.
Ferritic stainless steel typically undergoes solution treatment and annealing to relieve stress and improve ductility. Unlike martensitic steel, it is air-cooled rather than quenched. It cannot be strengthened by heating like precipitation-hardening steels.
Care is necessary to avoid 475°C embrittlement, which can occur with prolonged exposure, leading to reduced toughness.
Cold-rolling ferritic stainless steel helps maintain its magnetic properties, unlike austenitic steel, which may lose magnetism during this process. The strength and hardness of ferritic steel increase significantly after cold rolling.
However, its formability is relatively poor, making it prone to wrinkling and deformation during the process. To ensure good forming quality, rolling parameters such as reduction and rolling speed must be carefully controlled.
Working with ferritic stainless steel is usually easier than working with austenitic stainless steel. It experiences less galling, making it more manageable for various machining operations. Its stable microstructure contributes to consistent machining performance.
Welding ferritic stainless steel requires care to prevent grain growth and brittleness. Common methods include TIG, MIG, and spot welding. Unlike austenitic steel, ferritic steel may need post-weld heat treatment to restore toughness.
Its lower thermal expansion helps reduce welding distortion. To prevent sensitization, it's important to weld at lower temperatures and minimize heat input.
Phase transformation in ferritic stainless steel, vital in welding and heat treatment, is mainly driven by its alloy composition, especially chromium and other elements. This section covers the key aspects of these transformations.
Ferritic stainless steel primarily remains in the body-centered cubic (BCC) ferrite phase. This phase is stable from room temperature up to about 912°C.
Sensitization happens when ferritic stainless steel is exposed to 450°C to 850°C. In this range, chromium carbides form at grain boundaries, reducing chromium and leading to lower corrosion resistance. This makes the steel more prone to intergranular corrosion. Preventing this requires careful heat control during welding and heat treatment.
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Although ferritic stainless steel has unique advantages that make it suitable for specific applications, it also has certain drawbacks due to its inherent properties. These disadvantages can be addressed through various methods. Understanding these pros and cons is crucial for choosing the right material for your needs.
Ferritic stainless steel includes various grades, each with particular qualities for different applications. Knowing these grades and their applications helps in choosing the right material for various needs.
Here, we cover other important aspects and frequent questions to help you make informed choices about ferritic stainless steel.
Ferritic stainless steel can be recognized by its magnetic traits and its body-centered cubic (BCC) crystal arrangement. It usually contains chromium and has less nickel compared to austenitic stainless steel.
Yes, the 400 series stainless steels are usually ferritic. Grades like 409 and 430 are common examples of ferritic stainless steel.
No, the 300 series stainless steels are mainly austenitic. They contain higher amounts of nickel and chromium, which result in an austenitic structure rather than ferritic.
Ferritic stainless steels have a body-centered cubic (BCC) structure, are magnetic, and have lower nickel content. Austenitic stainless steels have a face-centered cubic (FCC) structure, are non-magnetic, and contain more nickel and chromium.
Ferritic stainless steels are generally less strong than austenitic steels but offer better resistance to stress corrosion cracking. Austenitic stainless steels usually provide higher strength and toughness.
This article briefly explains the definition, composition, properties, grades, applications, and other important aspects of ferritic stainless steel. To learn more about stainless steel or other steel types, check out our blog or contact our metal experts.
Stainless steel is the name of a family of iron-based alloys known for their corrosion and heat resistance. One of the leading stainless steel characteristics is its minimum chromium content of 10.5%, which gives it superior corrosion resistance compared to other types of steel. Like other steels, stainless steel is composed primarily of iron and carbon, but with the addition of several other alloying elements, the most prominent being chromium. Other common alloys in stainless steel are nickel, magnesium, molybdenum, and nitrogen.
Stainless steel has many desirable properties that contribute significantly to its widespread application in making parts and components across many industrial sectors. Above all, its chromium content makes it highly resistant to corrosion. The 10.5% minimum content makes steel approximately 200 times more corrosion-resistant than steel without chromium. Other favorable stainless steel characteristics for consumers are its high strength and durability, high and low-temperature resistance, increased formability and easy fabrication, low maintenance, long-lasting, attractive appearance, and environmentally friendly and recyclable. Once stainless steel is serviced, it must not be treated, coated, or painted.
There are many numerical grading systems for stainless steel, designated according to their composition, physical properties, and applications. Each type of stainless steel is classified by its series number and then assigned a numerical grade. The most popular series numbers are 200, 300, 400, 600, and . The most common grades are type 304 and 316, consisting of austenitic chromium-nickel alloys. Cutlery-grade stainless steels are found in the 400 Series, derived from ferritic and martensitic chromium alloys. Type 420 is known as surgical steel, and type 440 is known as razor blade steel.
For more information, see our page on stainless steel types.
The family of stainless steels is primarily classified into four main categories based on their crystal microstructure.
Ferritic steels are 400-grade stainless steels noted for their high chromium content, ranging from 10.5% to 27%. They have magnetic properties, too, and offer good ductility, tensile-property stability, and resistance to corrosion, thermal fatigue, and stress-corrosion cracking.
Typical applications for ferritic stainless steels include automotive components and parts, the petrochemical industry, heat exchangers, furnaces, and durable goods like appliances and food equipment.
Perhaps the most common category of stainless steel, austenitic grade steels are high in chromium, with varying amounts of nickel, manganese, nitrogen, and some carbon. Austenitic steels are divided into the 300 series and 200 series subcategories, which determine which alloys are used. The austenitic structure of the 300 series is distinguished via the addition of nickel. The 200 series primarily uses the addition of manganese and nitrogen. Grade 304 is the most common stainless steel.
Sometimes referred to as 18/8 because of its 18% chromium and 8% nickel, it is used in kitchen equipment, cutlery, food processing equipment, and structural components in the automotive and aerospace industries. Grade 316 is another common stainless steel. It makes a wide range of products, such as food preparation equipment, laboratory benches, medical and surgical equipment, boat fittings, and pharmaceutical, textile, and chemical processing equipment.
Read more about 304 vs 316 stainless steel
Martensitic stainless steels are in the 400 Grade series of stainless steels. They have a low to high carbon content, and contain 12% to 15% chromium and up to 1% molybdenum. It's used whenever corrosion resistance and-or oxidation resistance are required along with either high strength at low temperatures or creep resistance at elevated temperatures. Martensitic steels are also magnetic and possess relatively high ductility and toughness, which make them easier to form.
Applications for martensitic stainless steels include a wide range of parts and components, from compressor blades and turbine parts, kitchen utensils, bolts, nuts and screws, pump and valve parts, dental and surgical instruments, to electric motors, pumps, valves, machine parts sharp surgical instruments, cutlery, knife blades, and other cutting hand tools.
As the name implies, duplex stainless steels possess a mixed microstructure of ferrite and austenite. The chromium and molybdenum content is high, with 22% to 25% and up to 5%, respectively, with very low nickel content. The duplex structure gives the stainless steel many desirable properties. For starters, it offers double the strength of ordinary austenitic or ferritic stainless steels, with excellent corrosion resistance and toughness.
Designated in the Grade series, duplex stainless steel is ideal for applications in demanding environments such as in chemical, oil, and gas processing and equipment, marine, high chloride environments, pulp and paper industry, cargo tanks for ships and truck, and bio-fuels plants, chloride containment or pressure vessels, transportation, heat exchanger tubes, construction, the food industry, desalination plants, and components for FGD systems.
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