904L (N08904,14539) Super Austenitic Stainless Steel contains 14.0-18.0% chromium, 24.0-26.0% nickel and 4.5% molybdenum.904L super Austenitic stainless steel belongs to low carbon high nickel, molybdenum austenitic stainless acid resistant steel, which is the proprietary material of France H. S company.It has good activation-passivation transformation ability, excellent corrosion resistance, good corrosion resistance in non-oxidizing acids such as sulfuric acid, acetic acid, formic acid and phosphoric acid, good pitting resistance in neutral medium containing chloride ion, and good anti-crevice corrosion [TJC STEEL]and anti-stress corrosion performance.It is suitable for sulfuric acid of various concentration below 70℃. It is resistant to acetic acid of any concentration and temperature under atmospheric pressure. It is also corrosion-resistant in mixed acid of formic acid and acetic acid.

 

Introduction for 904L Super Austenitic Stainless Steel:

Super Austenitic stainless steel 904L (00CR20NI25MO4.5Cu;UNS: N08904;EN: 1.4539) is a high alloy austenitic stainless steel with low carbon content. It is highly resistant to corrosion in dilute sulfuric acid and is designed for environments with harsh corrosion conditions.Has the high chromium content and plenty of nickel content, the addition of copper makes it have strong ability to resist acid, especially for chloride clearance[TJC STEEL] corrosion and stress corrosion cracking are highly resistant, not easy to appear, erosion and fracture pitting resistance slightly better than other steel grade, good machinability and weldability, can be used for pressure vessels.

 

Brands and standards:

UNS N08904 (A standard jointly designed by the American Society of Motor Vehicle Engineers and the American Society of Materials and Testing in[TJC STEEL] 1967), DIN1.4539 (German standard), ASTM A240 (American Society of Materials and Testing Standard);The new standard will be classified as stainless steel series, while the original standard ASME SB-625 will be classified as nickel base alloy series), SUS890L.

 

Metallographic Structure Of 904l Stainless Steel:

The 904L is a complete austenitic structure, which is insensitive to ferrite and precipitation compared with austenitic stainless steel with high molybdenum content.

Physical and mechanical properties:

Density: 8.0g/cm3.Tensile strength: B ≥520Mpa.Elongation: ≥35%.

 

Corrosion Resistance of 904L Stainless Steel:

Since the carbon content of 904L is very low (up to 0.020%), there will be no carbide precipitation under the general heat treatment and welding conditions.This eliminates the risk of intercrystalline corrosion that usually occurs after [TJC STEEL]heat treatment and welding.Because of the high cr-Ni-Mo 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 makes it have a lower corrosion rate in the active state.In the concentration range of 0~98% pure sulfuric acid, 904L can be used at temperatures up to 40 degrees Celsius.The corrosion resistance of pure phosphoric acid is very good in the range of 0~85% concentration.In industrial phosphoric acid produced by wet process, impurities have a strong effect on corrosion resistance.Among all kinds of phosphoric acids, 904L has better corrosion resistance than ordinary stainless steel.In strongly oxidizing nitric acid, 904L is less corrosion resistant than high alloyed steel without molybdenum.In hydrochloric acid, the use of 904L is limited to lower concentrations of 1-2%.In this concentration range.The corrosion resistance of 904L is better than that of conventional stainless steel.The 904L steel has high corrosion resistance.In chloride solution, the corrosion resistance of cracks is also very good.The high nickel content of 904L reduces the corrosion rate in pits and crevices.Ordinary austenitic stainless [TJC STEEL]steels may be sensitive to stress corrosion in a chlorine-rich environment at temperatures above 60 ° C. This sensitization can be reduced by increasing the nickel content of the stainless steels.Due to the high nickel content, 904L is highly resistant to stress corrosion cracking in chloride solution, concentrated hydroxide solution and hydrogen sulfide rich environment.

 

Supporting Welding Material: Electrode (e385-16/17), Welding Wire (ER385).

904L Application Notes:

1. Machining Performance

1.1 Welding Performance

As with ordinary stainless steel, the 90 4L can be welded in a variety of ways.The most commonly used welding methods are manual arc welding or inert gas shielded metal arc welding. The electrode or wire metal is based on the composition of the base material and has higher purity. The content of molybdenum is higher than that of the base material.Preheating is generally not necessary before welding, but in cold outdoor work, in order to avoid moisture condensation, joint or adjacent areas can be evenly heated.Note [TJC STEEL]that the local temperature should not exceed 100 ℃ to avoid carbon accumulation and intercrystalline corrosion.Small wire energy, continuous and fast welding rate is suitable for welding.Generally, there is no need for heat treatment after welding. If heat treatment is needed, it should be heated to 110 0 ~ 1150℃ and then cooled quickly.

1.2 Machining Performance

The machining characteristics of the 90 4 L stainless steel are similar to other austenitic stainless steel.The cutting coolant should be vulcanized and chlorinated oil. The equipment and process should be based on the premise of reducing [TJC STEEL]working hardening.Slow cutting speed and feed quantity should be avoided in the cutting process.

 

Chemical Composition(%):

MATERIAL	%	Cr	Ni	Mo	Cu	Fe	C	Mn	Si	P	S
904L	Min	19	23	4	1	REST
904L	Max	23	28	5	2		0.02	2	1	0.045	0.035

Mechanical Property:

Min	Tensile Strength	Yield Strength RP0.2N/mm2	Elongation
	Rm N/mm2		A5 %
904L[TJC STEEL]	490	216	35

Density for 904L Stainless Steel: 8.0 g/cm3

Melting Point for 904L Stainless Steel: 1300-1390 ℃

 

 

Others:

904L Purpose, Application Scope, Application Field:

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

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

* The flue gas desulfurization unit of power plant mainly uses the tower body of absorber, flue, door panel, interior parts, spray system, etc.

* Scrubbers and fans in organic acid [TJC STEEL]treatment systems.

* Seawater treatment plant, seawater heat exchanger, papermaking industry equipment, sulfuric acid, nitric acid equipment, acid making, pharmaceutical industry and other chemical equipment, pressure vessel, food equipment.

* Pharmaceutical factory: centrifuge, reactor, etc.

* Plant foods: soy sauce cans, cooking wine, salt shakers, equipment and dressings.

* 904L is a suitable type of steel for dilute sulfuric acid.