There are more than 250 types of stainless steel. Due to its beauty and performance, it has economic value and is used in many industries.
Stainless steel is mainly divided into five categories. Each category combines specific chemical elements and unique mechanical properties, such as austenitic stainless steel in the 300 series and ferritic and martensitic stainless steel in the 400 series.
This article will explain the differences between 300 and 400 series stainless steel.
The 300 series stainless steel is austenitic. It is a combination of carbon, chromium, nickel, and molybdenum. Because of its high nickel content, it is non-magnetic, has strong corrosion resistance, and performs well at high temperatures. It has many different characteristics and is widely used. It is excellent in high-temperature environments but cannot be heat treated.
304 and 316 are the most popular grades of 300 series stainless steel in the market.
The 400 series stainless steel is a mix of martensitic and ferritic stainless steel. It is made of carbon, chromium, and manganese. Compared to the 300 series, it has very little or no nickel. It has excellent toughness, wear resistance, and strength. It is magnetic, can be heat treated, and is durable. However, it does not resist rust as well as the 300 series.
410 is a popular grade in the 400 series stainless steel.
Differences Between 300 VS 400 Series Stainless Steel
Chemical Composition
300 Series: Contains 18% – 30% chromium, 6% – 20% nickel, and molybdenum. Chromium forms a protective layer, nickel stabilizes the austenite structure and increases toughness, and molybdenum helps resist pitting corrosion. This makes 300 series stainless steel suitable for corrosive environments, such as 316 stainless steel, which has excellent corrosion resistance in marine facilities.
400 Series: Contains 11% – 12% chromium and manganese, with little or no nickel and a higher carbon content. Chromium provides basic corrosion resistance, manganese increases strength, and high carbon enhances hardness and wear resistance. For example, 430 stainless steel is used in indoor decorations, balancing cost and performance.
Corrosion Resistance
300 Series: Due to its high nickel and chromium content, it forms a stable passive film that provides excellent resistance to many types of corrosion. It is widely used in food processing, medical, and chemical equipment. For example, 304 stainless steel is used in food processing equipment and does not easily rust when exposed to acidic or alkaline ingredients, ensuring hygiene and safety.
400 Series: Has weaker corrosion resistance. It may rust in highly corrosive environments. However, 430 stainless steel can be used in weaker corrosive environments. The high carbon content gives it excellent wear resistance, making it ideal for tool edges and mechanical friction surfaces, reducing wear and extending life.
Mechanical Properties
300 Series: The austenitic structure gives it excellent ductility, allowing it to undergo large deformations. It is easy to form by cold working, but its strength decreases at high temperatures. For example, automotive body parts maintain their shape well after stamping, but high-temperature components need special treatments.
400 Series: The higher carbon content gives it high hardness and strength. For example, martensitic 440 stainless steel, after heat treatment, becomes very hard, making it suitable for tools and wear-resistant parts. However, its ductility is limited, and care is needed during processing to avoid cracks.
Processing Performance
300 Series: Has excellent processing properties. It is easy to form by cold processing, such as stamping, bending, and stretching. It also performs well in hot processing and can be forged or rolled within a suitable temperature range to produce various forms like plates, pipes, and bars.
400 Series: Ferritic stainless steel in the 400 series has good hot working properties, but its cold working performance is slightly worse than the 300 series. Martensitic stainless steels, due to their higher hardness and strength, are more challenging to process, but easier-to-process grades (like 416) have sulfur added to improve machinability.
Weldability
300 Series: Has good weldability with excellent joint performance. The heat-affected zone is small, and distortion is minimal. Various welding methods can be used, such as TIG welding for stainless steel pipes, ensuring high-quality welds. It is widely used in structural component manufacturing.
400 Series: Especially martensitic stainless steels, have poor weldability. They are prone to cracking and require preheating, post-heating, and careful control of process parameters. For example, when welding 410 stainless steel, preheating reduces stress, and tempering improves toughness, ensuring good weld quality.
Cost
400 Series: Due to its low or no nickel content, it is more cost-effective. It is used in applications where cost is a concern, such as architectural decoration, general industrial equipment, and household appliances. For example, 400 series is used in building railings, providing basic performance at a lower cost.
300 Series: The price of nickel is high and fluctuates, which affects the cost. 300 series stainless steels are used in critical applications that require high corrosion resistance and performance, such as chemical pipelines and medical equipment. Although they are more expensive, they ensure long-term, reliable performance.
Microstructure
300 Series: Has a face-centered cubic (FCC) structure, with tightly packed and regular atomic arrangements. This gives it good toughness and formability, and its crystals are not easily broken during processing, making it ideal for cold working. For example, 304 stainless steel can be shaped into fine designs for cutlery.
400 Series: Has a body-centered cubic (BCC) structure, with a relatively larger atomic spacing, which gives it higher strength and hardness. After appropriate heat treatment, its strength significantly increases. For example, 440 stainless steel is used for tools, where it can maintain a sharp edge.
Magnetism:
300 Series: Due to its austenitic structure, the electron spins are disordered, so it is usually non-magnetic or weakly magnetic. It is widely used in electronic devices and areas sensitive to magnetic fields, such as medical MRI equipment, to avoid interference with sensitive instruments and ensure smooth operation.
400 Series: Ferritic and martensitic stainless steels contain more unpaired electrons and are magnetic. They are commonly used in motors, generators, and magnetic clamps. The magnetic properties help improve electromagnetic conversion efficiency and meet the needs for adsorption and fixation.
Hardenability
300 Series: The austenitic structure is stable, so it does not harden well with heating. However, it can be strengthened through cold working, as dislocations increase. For example, 304 stainless steel becomes stronger after cold drawing, making it suitable for structural parts that require moderate strength and complex shapes.
400 Series: Can undergo martensitic transformation through heating and cooling, significantly increasing its hardness. For example, 410 stainless steel, after quenching, becomes very hard and is suitable for manufacturing wear-resistant parts, meeting the high hardness requirements of tools and mechanical components.
Applications
300 Series: Due to its excellent corrosion resistance, non-magnetic properties, and good formability, it is commonly used in food processing (e.g., cutlery), medical (e.g., instruments), architectural decoration, and chemical corrosion-resistant components.
400 Series: With high strength, wear resistance, and magnetic properties, it is suitable for tools, mechanical wear parts, automotive components (e.g., exhaust pipes, interiors), and magnetic-related applications.
If you would like to learn more about 300 and 400 stainless steel, feel free to contact us.
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