904L seamless steel pipe

1. Simple Description:

904L super austenitic stainless steel is a low-carbon, high nickel, molybdenum austenitic stainless acid resistant steel.

GB grade: 00Cr20Ni25Mo4.5Cu

International Grade: 904L

American standard Grade: UNS：N08904

EN Grade: 1.4539

Size range: 10*2mm to 219*15mm or customized according client’s request

Length Range: 300mm to 20000mm

2. Chemical Composition:

3. Mechanical Properties:

4.904L Description：

1) Super austenitic stainless steel 904L (00Cr20Ni25Mo4.5Cu; UNS: N08904; EN: 1.4539) is

a high alloy austenitic stainless steel with low carbon content.

It has good corrosion resistance in dilute sulfuric acid and is specially designed for environments

with severe corrosion conditions. It has high chromium content and sufficient nickel content. The addition of copper makes it have

strong acid resistance, especially high resistance to chloride interstitial corrosion and stress corrosion cracking. It is not easy to appear

corrosion spots and cracks. Its resistance to pitting corrosion is slightly better than that of other steels. It has good processability and

weldability, and can be used for pressure vessels.

2) Metallographic structure of 904L stainless steel:

904L is a completely austenitic structure. Compared with ordinary austenitic stainless steel with high molybdenum content,

904L has a significant effect on ferrite and α The precipitation of phase is not sensitive.

a. Physical and mechanical properties:

Density: 8.0g/cm3. Tensile strength: σ b≥520Mpa。 Elongation: δ ≥35%。 Corrosion resistance of 904L stainless steel:

Because the carbon content of 904L is very low (maximum 0.020%), there will be no carbide precipitation under general

heat treatment and welding conditions. This eliminates the risk of intergranular corrosion after general heat treatment and welding.

Because of the high content of chromium, nickel and molybdenum and the addition of copper, the 904L can be passivated even in reducing

environments, such as sulfuric acid and formic acid.

The high nickel content makes it have a low corrosion rate in the active state. In the concentration range of 0~98% of pure sulfuric acid,

the use temperature of 904L can be as high as 40 ℃. The corrosion resistance of pure phosphoric acid in the concentration range of 0~85% is

very good.

In the industrial phosphoric acid produced by wet process, impurities have a strong impact on the corrosion resistance. Among all kinds

of phosphoric acid, 904L has better corrosion resistance than ordinary stainless steel. In strong oxidizing nitric acid, the corrosion resistance of 904L

is lower than that of high alloyed steel without molybdenum. In hydrochloric acid, the use of 904L is limited to 1-2% of the lower concentration.

In this concentration range. The corrosion resistance of 904L is better than that of conventional stainless steel. 904L steel has high resistance to

spot corrosion.

In chloride solution, its crevice corrosion resistance is also very good. The high nickel content of 904L reduces the corrosion rate in pits and crevices.

When the temperature of ordinary austenitic stainless steel is higher than 60 ℃, it may be sensitive to stress corrosion in a chloride rich

environment.

This sensitivity can be reduced by increasing the nickel content of stainless steel. Due to the high nickel content, 904L has high resistance to

stress corrosion cracking in chloride solution, concentrated hydroxide solution and hydrogen sulfide rich environment.

Supporting welding materials: welding rod (E385-16/17), welding wire (ER385).

b. Precautions for application of 904L:

1. Processability

1.1 Welding performance

Like ordinary stainless steel, 904L can be welded by various welding methods. The most common welding method is manual arc welding or

inert gas shielded welding.

The electrode or wire metal is based on the composition of the base metal and has higher purity. The molybdenum content is required to be

higher than the base metal.

Preheating is generally not required before welding, but in cold outdoor operation, to avoid condensation of water vapor, joints or adjacent

areas can be heated evenly.

The local temperature shall not exceed 100 ℃ to avoid carbon accumulation and intergranular corrosion. Small linear energy, continuous

and fast welding rate should be adopted during welding.

Generally, heat treatment is not required after welding. If heat treatment is required, it must be heated to 11000 ～ 1150 ℃ and then cooled quickly.

1.2 Machining performance

The machining characteristics of 904L are similar to those of other austenitic stainless steels. There is a tendency of tool sticking and work hardening during the processing.

Carbide tools with positive rake angle must be used, and sulfurized and chlorinated oil shall be used as cutting coolant. The equipment and process shall be on the premise of

reducing work hardening. Slow cutting speed and feed rate shall be avoided during cutting.

5. Related production:

6. Further treatment

1) Polish

2) Marking:

7 . Packing and Loading:

8. Application:

The 904L is used in the following fields:

*Petroleum and petrochemical equipment, such as reactors in petrochemical equipment.

*Storage and transportation equipment of sulfuric acid, such as heat exchanger.

*The flue gas desulfurization device of the power plant is mainly used in the absorber body, flue, shutter, internals, spraying system, etc.

*Scrubber and fan in organic acid treatment system.

*Sea water treatment plant, sea water heat exchanger, paper industry equipment, sulfuric acid and nitric acid equipment, acid making,

pharmaceutical industry and other chemical equipment, pressure vessels, food equipment.

*Pharmaceutical factory: centrifuge, reactor, etc.

*Vegetable food: soy sauce pot, cooking wine, salt pot, equipment and dressings.

*904L is a matching steel for dilute sulfuric acid strong corrosive medium.