F904L

Time:2019-08-14

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GB/T

UNS

AISI/ASTM

ID

W.Nr

015Cr21Ni26Mo5Cu2

N08904

904L

F904L

1.4539


 

chemical composition:

alloy

%

Ni

Cr

Mo

Cu

Fe

C

Mo

P

S

904L

min

24

19

4

1

margin





max

26

21

5

2

0.02

2

0.03

0.015


Physical properties:

Density

8.0 g/cm3

Melting point

1300-1390 


The minimum mechanical properties of the alloy at 904L at room temperature:

Static

Tensile Strength 
Rm N/mm2

Yield StrengthRP0.2N/mm2

Elongation 

A5 %

904L

490

215

35

 

The 904L alloy has the following characteristics:

904L is a high-alloy austenitic stainless steel with a very low carbon content. The steel is designed for harsh environments. The alloy was originally developed for corrosion resistance in dilute sulfuric acid. This feature has been proven to be very successful after many years of practical application. The 904L is now standardized in many countries and has been approved for the manufacture of pressure vessels. Like other commonly used CrNi austenitic steels, 904L alloy has good resistance to pitting corrosion and crevice corrosion, high resistance to stress corrosion cracking, good resistance to intergranular corrosion, good processability and Weldability. The maximum heating temperature for hot forging can reach 1180 degrees Celsius, and the minimum stop forging temperature is not less than 900 degrees Celsius. This steel thermoforming can be carried out at 1000--1150 degrees Celsius. The heat treatment process of the steel is 1100--1150 degrees Celsius, and is quickly cooled after heating. Although this steel can be welded by a common welding process, the most suitable welding methods are manual arc welding and tungsten argon arc welding. When the manual arc welding is used to weld a sheet of not more than 6 mm, the diameter of the electrode is not more than 2.5 mm; when the thickness is more than 6 mm, the diameter of the electrode is less than 3.2 mm. When heat treatment is required after welding, it can be treated quickly after heating at 1075--1125 degrees Celsius. The filler metal used in tungsten argon arc welding can be made of the same material, and the weld after welding must be pickled and passivated.


904L metallographic structure

904L is a completely austenitic structure, and 904L is insensitive to precipitation of ferrite and α phase, compared to austenitic stainless steel, which generally contains a high amount of molybdenum.

904L corrosion resistance

Since the 904L carbon content is very low (maximum 0.020%), there is no carbide precipitation in the case of general heat treatment and welding. This eliminates the risk of intergranular corrosion that occurs after general heat treatment and soldering. Due to the high chromium-nickel-molybdenum content and the addition of copper, 904L can be passivated even in reducing environments such as sulfuric acid and formic acid. The high nickel content gives it a lower corrosion rate in the active state. In pure sulfuric acid in the concentration range of 0~98%, 904L can be used up to 40 degrees Celsius. The corrosion resistance is very good in pure phosphoric acid in the range of 0-85%. In industrial phosphoric acid produced by the wet process, impurities have a strong influence on corrosion resistance. Among all the various phosphoric acids, 904L is superior in corrosion resistance to ordinary stainless steel. In the highly oxidizing nitric acid, 904L has lower corrosion resistance than the highly alloyed steel without molybdenum. In hydrochloric acid, the use of 904L is limited to a lower concentration of 1-2%. In this concentration range. 904L has better corrosion resistance than conventional stainless steel. 904L steel has a high resistance to pitting corrosion. Its resistance to crevice corrosion in chloride solutions is also good. The high nickel content of the 904L reduces the rate of corrosion at the pits and gaps. Ordinary austenitic stainless steels may be sensitive to stress corrosion in a chloride-rich environment at temperatures above 60 degrees Celsius, which can be reduced by increasing the nickel content of the stainless steel. Due to its high nickel content, 904L has high resistance to stress corrosion cracking in chloride solutions, concentrated hydroxide solutions and hydrogen sulfide-rich environments.


904L application area:

904L alloy is a versatile material that can be used in many industries:

1. Petroleum, petrochemical equipment, such as reactors in petrochemical equipment.

2. Storage and transportation equipment for sulfuric acid, such as heat exchangers.

3. Power plant flue gas desulfurization device, the main use parts are: tower body of the absorption tower, flue, door panel, internal parts, sprinkler system, etc.

4. Washers and fans in organic acid treatment systems.



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