Stainless Steel Classification: 300 and 400 Series

Stainless steels are key materials in various industries thanks to their corrosion resistance, durability and versatility. At Serviacero Especiales, we offer a specialized selection of stainless steels classified in two main series: 300 and 400, designed to meet the specific needs of our customers. In this article we explore the characteristics, applications and differences of these series.

300 Series: Austenitic Stainless Steels 

300 series steels are austenitic, meaning they have a crystalline structure that provides high corrosion resistance and excellent malleability. These properties make them ideal for applications in aggressive environments. At Serviacero Especiales, we have grades 303, 304 and 316, each with particular characteristics.

AISI 303 

303 stainless steel is known as an “easy machining steel” due to the addition of sulfur and phosphorus, which improve its machinability:

Main features of AISI 303: 

Good corrosion resistance in moderately oxidizing environments.

• Excellent for high precision machining.
• It is not magnetic in the annealed state.
• Typical applications:
• Mechanical components such as screws, bushings and couplings.
• Parts exposed to moderate corrosive environments.

AISI 304 

304 stainless steel is one of the most versatile and used on the market:

Main features of AISI 304: 

• Excellent resistance to oxidation and corrosion.
• High weldability and malleability.
• It is non-magnetic in the annealed condition, although it may become slightly magnetized by deformation.

Typical AISI 304 applications: 

• Food, chemical and petrochemical industry.
• Architectural components such as hinges and handles.
• Fastening and transmission elements.

AISI 316 

316 is noted for its superior resistance to corrosion, especially in marine or harsh chemical environments:

Main features AISI 316: 

• Superior corrosion resistance due to the presence of molybdenum (Mo).
• Excellent performance in high temperatures and aggressive environments.
• High weldability and malleability.

Typical AISI 316 applications: 

• Pharmaceutical, medical and food industry.
• Components in contact with salt water or aggressive chemicals.
• Oil & gas systems.

400 Series: Martensitic Stainless Steels 

400 series steels, such as 416, are martensitic, allowing them to be hardened by heat treatment. They are highly recommended for applications where mechanical strength and machinability are key.

AISI 416 

416 stainless steel is recognized for its easy machinability and hardenability:

Main features of AISI 416: 

• "Free machining" steel due to the addition of sulfur.
• Corrosion resistance suitable for moderately corrosive environments.
• Magnetic in all conditions.

Typical AISI 416 applications: 

• Screws, shafts and pump components.
• Mechanical parts in the agricultural sector and hydraulic systems.

Key differences between the 300 and 400 series 

Composition and structure: 

• Series 300: Austenitic, not hardenable by heat treatment.
• 400 Series: Martensitic, hardenable by quenching.

corrosion resistance: 

• 300 Series: Greater resistance, ideal for highly corrosive environments.
• 400 Series: Moderate strength, suitable for less demanding conditions.

Magnetism: 

• 300 Series: Non-magnetic in the annealed condition.
• 400 Series: Magnetic in all conditions.

Applications: 

• 300 Series: Uses in chemical, food and architectural industries.
• 400 Series: Mechanical applications and components subject to high machining requirements.

Why choose Serviacero Especiales? 

At Serviacero Especiales, we are committed to offering quality solutions that support the success of your projects. Our 300 and 400 series stainless steels are available in different presentations. Seek technical advice from us to make the best selection of the stainless steel you require.

Do you have questions or need more information? Contact us and discover how our products can transform your processes.

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