1.4404 vs. 1.4408

Attribute	1.4404	1.4408
Chemical Composition	Contains 16-18% Chromium, 10-13% Nickel, 2% Manganese, 1% Silicon, 0.03% Sulfur, 0.03% Phosphorus	Contains 16-18% Chromium, 10-13% Nickel, 2% Manganese, 1% Silicon, 0.04-0.10% Carbon, 0.03% Sulfur, 0.03% Phosphorus
Corrosion Resistance	Good corrosion resistance in many environments	Improved corrosion resistance compared to 1.4404 due to higher carbon content
Strength	Good strength and toughness	Higher strength compared to 1.4404 due to higher carbon content
Applications	Commonly used in food processing, chemical, and pharmaceutical industries	Used in applications where higher strength and corrosion resistance are required

Introduction

Stainless steel is a popular material in various industries due to its corrosion resistance, durability, and aesthetic appeal. Two common grades of stainless steel are 1.4404 and 1.4408. While they may seem similar at first glance, there are key differences between the two that make them suitable for different applications.

Chemical Composition

1.4404, also known as 316L, is a low carbon version of 1.4401 (316) stainless steel. It contains around 17% chromium, 10% nickel, and 2% molybdenum. On the other hand, 1.4408, also known as 316H, has a higher carbon content compared to 1.4404. It contains around 17% chromium, 10% nickel, and 2% molybdenum, similar to 1.4404, but with added carbon for increased strength.

Corrosion Resistance

Both 1.4404 and 1.4408 stainless steel grades offer excellent corrosion resistance, making them suitable for use in harsh environments. The presence of chromium in the alloy forms a protective oxide layer on the surface of the material, preventing corrosion from occurring. Additionally, the molybdenum content in both grades enhances their resistance to pitting and crevice corrosion.

Strength and Hardness

1.4408 stainless steel, with its higher carbon content, offers greater strength and hardness compared to 1.4404. The increased carbon content allows for improved mechanical properties, making 1.4408 a preferred choice for applications that require higher tensile strength and hardness. On the other hand, 1.4404, with its lower carbon content, may be more suitable for applications where formability and weldability are important factors.

Heat Resistance

Both 1.4404 and 1.4408 stainless steel grades exhibit good heat resistance, allowing them to be used in high-temperature applications. The presence of molybdenum in the alloy enhances their resistance to oxidation at elevated temperatures. However, it is important to note that 1.4408, with its higher carbon content, may have slightly lower thermal conductivity compared to 1.4404.

Weldability

Weldability is an important factor to consider when choosing a stainless steel grade for fabrication purposes. Both 1.4404 and 1.4408 are readily weldable using common welding techniques such as TIG, MIG, and stick welding. However, due to its lower carbon content, 1.4404 may offer better weldability and reduced risk of sensitization compared to 1.4408, which has a higher carbon content.

Applications

1.4404 stainless steel is commonly used in industries such as food processing, pharmaceuticals, and marine applications due to its excellent corrosion resistance and formability. Its low carbon content makes it suitable for welding and fabrication processes. On the other hand, 1.4408 stainless steel is often used in high-temperature applications such as heat exchangers, furnace parts, and exhaust systems, where strength and hardness are critical factors.

Conclusion

In conclusion, while both 1.4404 and 1.4408 stainless steel grades offer excellent corrosion resistance and durability, they have distinct differences in terms of chemical composition, strength, and applications. The choice between the two grades will depend on the specific requirements of the application, such as strength, weldability, and heat resistance. Understanding these differences is crucial in selecting the right stainless steel grade for a particular project.