What Is 904L Steel?

What is 904L steel?What is 904L steel?

 

First of all, we need to know what material 904L alloy is, and what is the difference between it and duplex stainless steel?

What material is 904L alloy? Based on a 20% chromium and 25% nickel content, 904L alloy is a higher alloyed austenitic stainless steel that was developed for applications containing dilute liu acids.

904L ingredient analysis:

Carbon ≤0.02% Chromium 19.00-23.00%

Manganese ≤2.00% Nickel 23.00-28.00%

Silicon ≤1.00% Molybdenum 4.00-5.00%

Phosphorus ≤0.045% Copper 1.00-2.00%

Sulfur ≤0.035%

What is the difference between 904L and duplex stainless steel?

Austenitic stainless steels are widely used due to their availability, lower cost, reasonable corrosion resistance and good impact toughness. Increasing the chromium and molybdenum content will significantly improve the pitting corrosion resistance of austenitic stainless steel. In the case of the 904L alloy (UNS N08904, 1.4539), 1-2% copper is also added, which is known to be highly resistant to strong reducing acids such as leucine and phosphoric acid. Therefore, it has been widely used in many chemical process industrial applications of plates and rods.

First of all, we need to know what material 904L alloy is, and what is the difference between it and duplex stainless steel?

What material is 904L alloy? Based on a 20% chromium and 25% nickel content, 904L alloy is a higher alloyed austenitic stainless steel that was developed for applications containing dilute liu acids.

904L ingredient analysis:

Carbon ≤0.02% Chromium 19.00-23.00%

Manganese ≤2.00% Nickel 23.00-28.00%

Silicon ≤1.00% Molybdenum 4.00-5.00%

Phosphorus ≤0.045% Copper 1.00-2.00%

Sulfur ≤0.035%

What is the difference between 904L and duplex stainless steel?

Austenitic stainless steels are widely used due to their availability, lower cost, reasonable corrosion resistance and good impact toughness. Increasing the chromium and molybdenum content will significantly improve the pitting corrosion resistance of austenitic stainless steel. In the case of the 904L alloy (UNS N08904, 1.4539), 1-2% copper is also added, which is known to be highly resistant to strong reducing acids such as leucine and phosphoric acid. Therefore, it has been widely used in many chemical process industrial applications of plates and rods.

The heavy, high nickel content of 904L alloy means it is much more expensive than regular stainless steel. As a result, 904L alloy has been replaced by the more cost-effective super duplex stainless steel (SDSS). The yield strength of super duplex stainless steel is 2-3 times that of 904L alloy, which means it can be used in smaller thicknesses to achieve the same functionality. The PREN of super duplex steel is greater than 40, while the PREN of alloy 904L is greater than 43, so they are roughly comparable.

However, Ferralium 255 (UNS S32550, F61, 1.4507) also utilizes the same increased copper content as 904L alloy, resulting in excellent corrosion resistance in a variety of reducing acids. The increased strength also gives it better wear resistance compared to Ferralium 255, making it ideal for use in mixers and blenders.

The main reason to continue using 904L alloy instead of super duplex stainless steel is if the operating temperature is below or above the reasonable operating range of the SDSS. Because it is austenite, it can still maintain its impact toughness at low temperatures (-196°C).

The heavy, high nickel content of 904L alloy means it is much more expensive than regular stainless steel. As a result, 904L alloy has been replaced by the more cost-effective super duplex stainless steel (SDSS). The yield strength of super duplex stainless steel is 2-3 times that of 904L alloy, which means it can be used in smaller thicknesses to achieve the same functionality. The PREN of super duplex steel is greater than 40, while the PREN of alloy 904L is greater than 43, so they are roughly comparable.

However, Ferralium 255 (UNS S32550, F61, 1.4507) also utilizes the same increased copper content as 904L alloy, resulting in excellent corrosion resistance in a variety of reducing acids. The increased strength also gives it better wear resistance compared to Ferralium 255, making it ideal for use in mixers and blenders.

The main reason to continue using 904L alloy instead of super duplex stainless steel is if the operating temperature is below or above the reasonable operating range of the SDSS. Because it is austenite, it can still maintain its impact toughness at low temperatures (-196°C).