904L Center Baffle Thk: 20MM OD: 935MM

• Type: 904L Center Baffle
• Material: 1.4539 (Alloy 904L/UNS N08904)
• Standard: ASME, etc
• Size: OD: 935 MM
• THK: 20 MM

What is 904L?

904L super austenitic stainless steel contains 14.0-18.0% chromium, 24.0-26.0% nickel, and 4.5% molybdenum. 904L super austenitic stainless steel is a low carbon, high nickel, molybdenum austenitic stainless acid resistant steel. 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, phosphoric acid, good pitting resistance in neutral chloride ion-containing media, and good resistance to crevice corrosion and stress corrosion resistance. It is suitable for various concentrations of sulfuric acid below 70℃, and has good corrosion resistance in acetic acid of any concentration and any temperature at atmospheric pressure, and in mixed acids of formic acid and acetic acid.
Super austenitic stainless steel 904L (00Cr20Ni25Mo4.5Cu; UNS: N08904; EN: 1.4539) is a highly alloyed austenitic stainless steel with low carbon content and good corrosion resistance in dilute sulfuric acid, designed for environments with harsh corrosive conditions. With a high chromium content and sufficient nickel content, the addition of copper makes it a strong acid resistance, especially for chloride interstitial corrosion and stress corrosion cracking with high resistance, not easy to appear corrosion spots and cracks, pitting resistance is slightly better than other steel grades, with good workability and weldability, can be used for pressure vessels.

• Tensile strength, Rm = 530 – 570 MPa
• Yield point, Rp0,2: >230 MPa
• Elongation, A: >35%
• Modulus of elasticity,E: 195 GPa
• Heat capacity, cp20℃= 450 J * kg-1 * K-1
• Heat conductivity, λ: 12 W * m-1 * K-1
• Linear Expansion Factor, α20℃=15,8 * 10-6 K-1
• Specific resistance: 1 Ω * mm2/m
• Hardness: <230 HB

Grades and standards.
UNS N08904 (American Society of Motor Vehicle Engineers and the American Society for Testing and Materials in 1967 jointly designed the standard), DIN1.4539 (German standard), ASTM A240 (American Society for Testing and Materials standard; the new standard will be classified as stainless steel series, the original standard ASME SB-625 will be classified as nickel-based alloy series), SUS890L.
The metallographic structure of 904L stainless steel:
904L is completely austenitic organization, compared with the general austenitic stainless steel with high molybdenum content, 904L is not sensitive to the precipitation of ferrite and alpha phase.
Physical and mechanical properties.
Density: 8.0g/cm3.

SS 904L Equivalent Grade

The datasheet below summarizes Rolex 904L stainless steel equivalent grade such as European EN (German DIN EN, British BS EN, French NF EN…), Chinese GB, ISO, Japanese JIS standard.

AISI 904L equivalent material	US	Standard	AISI SAE; ASTM
		Type	904L (UNS N08904)
	European Union	Standard	EN 10088-2; EN 10088-3
		Grade (Steel Number)	X1NiCrMoCu25-20-5 (1.4539)
	ISO	Standard	ISO 15510
		ISO Name (ISO Number)	X1NiCrMoCu25-20-5 (4539-089-04-I)
	Japan	Standard	JIS G4303
		Grade	SUS 890L
	China	Standard	GB/T 20878; GB/T 4237; GB/T 3280
		Grade	015Cr21Ni26Mo5Cu2

Datasheet and Specification of 904L

The following data sheet summarizes the chemical composition, properties, heat treatment and equivalent grade of 904L stainless steel (SS904L).

Chemical Composition of 904L

The following data sheet gives SS 904L stainless steel chemical composition.

Mechanical Properties of 904L

The following table lists Rolex 904L stainless steel (SS904L) mechanical properties such as yield strength, tensile strength, elongation and hardness.

AISI ASTM 904L Steel Mechanical Properties
ASTM	AISI Type	Tensile Strength, MPa (ksi), ≥	0.2% Yield Strength, MPa (ksi), ≥	Elongation in 50 mm (2 in.), %, ≥	Rockwell Hardness (HRBW), ≤	Product forms	Conditions
ASTM A276/A276M	904L (UNS N08904)	490 (71)	220 (31)	35	–	Bars and Shapes	Annealed, Hot-finished or cold-finished
ASTM A240/A240M		490 (71)	220 (31)	35	90	Plate, Sheet, and Strip

Heat Treatment of 904L

Annealing: The recommended annealing temperatures for 904L wrought steel is 1095 °C (2000 °F).

Corrosion resistance of 904L stainless steel

Since the carbon content of 904L is very low (max. 0.020%), there is no carbide precipitation under general heat treatment and welding. This eliminates the risk of intergranular corrosion that occurs after general heat treatment and welding. Due to the high chromium-nickel-molybdenum content and the addition of copper elements, 904L can be passivated even in reducing environments such as sulfuric acid and formic acid. The high nickel content gives it a low corrosion rate even 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. In pure phosphoric acid in the concentration range of 0-85%, its corrosion resistance is very good. In industrial phosphoric acid produced by the wet process, impurities have a strong influence on the corrosion resistance. In all kinds of phosphoric acid, 904L corrosion resistance is better than ordinary stainless steel. In strongly oxidizing nitric acid, 904L has lower corrosion resistance compared to highly alloyed steel grades 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 steels. 904L steel has a high resistance to pitting corrosion. Its resistance to crevice corrosion is also good in chloride solutions. 904L’s high nickel content reduces the rate of corrosion at pits and crevices. Ordinary austenitic stainless steels may be sensitive to stress corrosion in a chloride-rich environment at temperatures above 60 degrees C. This sensitization can be reduced by increasing the nickel content of the stainless steel. Due to the high nickel content, 904L has a high resistance to stress corrosion rupture in chloride solutions, concentrated hydroxide solutions and hydrogen sulfide-rich environments.

Processing performance of 904L

Welding performance of 904L

As with general stainless steel, 904L can be welded using a variety of welding methods. The most commonly used welding method for manual arc welding or inert gas shielded welding, welding rod or wire metal based on the composition of the base metal material and higher purity, molybdenum content requirements than the base material. Preheating is generally not necessary before welding, but in cold outdoor work, to avoid condensation of water vapor, the joint or the adjacent area can be uniformly heated. Note that the local temperature should not exceed 100 ℃, so as not to lead to carbon agglomeration, causing intergranular corrosion. Welding should use a small linear energy, continuous and fast welding rate. After welding generally do not need heat treatment, if heat treatment, must be heated to 1100-1150 ℃ after rapid cooling.

Matching welding consumables: welding rod (E385-16/17), welding wire (ER385).

Machinability of 904L
904L machining characteristics similar to other austenitic stainless steel, the process has a tendency to sticky tool and work hardening. Must use positive front angle carbide tools, sulfide and chlorinated oil as cutting coolant, equipment and process should be to reduce the premise of machining hardening. Slow cutting speed and tool feed should be avoided in the cutting process.

What is a baffle?

A baffle is an arched or disc-ring shaped flat plate installed inside the shell perpendicular to the tube bundle. Installing a baffle plate forces the shell-side fluid to cross the tube bundle multiple times along the specified path, increasing the flow rate and turbulence velocity and improving the heat transfer effect. In horizontal heat exchangers, the baffle plate can also play a supporting role in the tube bundle. The fixation of the baffle plate is achieved through a pull rod and a distance tube.

Typical Baffle Geometries

• Single Segmented Baffles
• Double Segmented Baffles
• Disc and Donut Baffles

The processing method of baffle

Baffles are a high-tech material used for fluid mechanics experiments and engineering applications, whose main function is to limit fluid motion within a plane for easy experimentation and testing. The processing methods for baffles include the following categories:

• 1. Laser cutting: Laser cutting is a high-precision, high-efficiency method for processing baffles. When using a laser beam to cut a baffle, precise positioning and depth processing can achieve the desired shape and size.
• 2. CNC machining: CNC machining is a high-precision machining method based on CAD/CAM software, which can automatically generate CNC codes and perform machining. This processing method can ensure that the size and shape accuracy of the baffle meet the requirements.
• 3. Plasma cutting: Plasma cutting is a method of cutting a baffle using high-temperature plasma gas. This method can produce high-strength and high-hardness cutting surfaces, but it is necessary to pay attention to the safety issues of plasma gas.
• 4. Flame cutting: Flame cutting is a method of cutting a baffle by mixing oxygen and gas. This method has a fast-cutting speed, but attention needs to be paid to the safety of the flame, and the control of gas and flame needs to be more precise.

It should be noted that the applicable conditions and costs of different processing methods for baffles also vary. Hence, the selection of processing methods must be based on specific circumstances.

China Center Baffles Manufacturer www.epowermetals.com offers 904L Center Baffle Thk: 20MM OD: 935MM.