904L alloy steel has the following characteristics:

904L is a highly alloyed austenitic stainless steel with low carbon content. This steel is designed for environments with harsh corrosion conditions. Initially, this alloy was developed for corrosion resistance in dilute sulfuric acid. This feature has been proven to be very successful through years of practical application. 904L has been standardized in many countries and has been approved for use in the manufacture of pressure vessels. 904L alloy, like other commonly used CrNi austenitic steels, has good resistance to pitting and crevice corrosion, high resistance to stress corrosion cracking, good resistance to intergranular corrosion, good processability, and weldability. The maximum heating temperature during hot forging can reach 1180 degrees Celsius, and the minimum stop forging temperature is not less than 900 degrees Celsius. This steel can be hot formed at 1000-1150 degrees Celsius. The heat treatment process of this steel is 1100-1150 degrees Celsius, and it is rapidly cooled after heating. Although this steel can be welded using universal welding processes, the most appropriate welding methods are manual arc welding and tungsten inert gas arc welding. When using manual arc welding to weld plates with a diameter not exceeding 6mm, the diameter of the welding rod shall not exceed 2.5mm; When the plate thickness is greater than 6 millimeters, the diameter of the welding rod is less than 3.2 millimeters. When heat treatment is required after welding, it can be done by heating at 1075-1125 degrees Celsius and then rapidly cooling. When using tungsten inert gas arc welding, the filler metal can be used with the same welding rod. After welding, the weld seam must be pickled and passivated.

 

 

904L metallographic structure

904L is a completely austenitic structure, and compared to austenitic stainless steels with high molybdenum content, 904L is not sensitive to the precipitation of ferrite and alpha phase.

 

 

Corrosion resistance of 904L

Due to the low carbon content of 904L (maximum 0.020%), there will be no carbide precipitation under general heat treatment and welding conditions. This eliminates the risk of intergranular corrosion that occurs after general heat treatment and welding. Due to its 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 results in a lower corrosion rate even in the active state. In pure sulfuric acid with a concentration range of 0-98%, the usage temperature of 904L can reach up to 40 degrees Celsius. In pure phosphoric acid with a concentration range of 0-85%, its corrosion resistance is very good. Impurities have a strong impact on the corrosion resistance of industrial phosphoric acid produced by wet process technology. Among all types of phosphoric acid, 904L has better corrosion resistance than ordinary stainless steel. In highly oxidizing nitric acid, 904L has lower corrosion resistance compared to high alloyed steel grades without molybdenum. In hydrochloric acid, the use of 904L is limited to lower concentrations of 1-2%. Within this concentration range. The corrosion resistance of 904L is better than that of conventional stainless steel. 904L steel has high resistance to pitting corrosion. Its resistance to crevice corrosion is also very good in chloride solutions. The high nickel content of 904L reduces the corrosion rate in pits and crevices. Ordinary austenitic stainless steel may be sensitive to stress corrosion in an environment rich in chloride at temperatures above 60 degrees Celsius. By increasing the nickel content of the stainless steel, this sensitization can be reduced. Due to its high nickel content, 904L exhibits high resistance to stress corrosion cracking in chloride solutions, concentrated hydroxide solutions, and environments rich in hydrogen sulfide.

 

 

904L Tube sheet 

A 904L tube sheet is a component used in various industrial applications particularly in heat exchangers and condensers. The 904L stainless steel tube sheet is specifically chosen for its superior resistance to aggressive environments, such as those containing sulfuric acid, phosphoric acid, and chloride solutions. It offers exceptional resistance to pitting, crevice corrosion, and stress corrosion cracking, making it highly suitable for applications in the chemical, petrochemical, and offshore industries. The use of 904L stainless steel tube sheets ensures the long-term reliability and performance of heat transfer equipment. Its corrosion resistance properties allow for extended service life and reduced maintenance requirements, resulting in cost savings and enhanced operational efficiency. Choose 904L tube sheets for superior corrosion resistance and reliable performance in demanding environments. Experience the benefits of this high-quality stainless steel alloy for your heat exchangers and condensers.

 

 

904L flange

904L flanges are commonly used in industries such as chemical processing, petrochemical, pharmaceutical, and offshore applications. Their resistance to corrosion makes them suitable for handling corrosive fluids and gases. Additionally, 904L flanges offer excellent strength, durability, and weldability, making them a reliable choice for critical applications. The use of 904L flanges can help ensure the integrity and longevity of piping systems by providing a robust and corrosion-resistant connection. They are available in various types, including slip-on, weld neck, blind, and threaded flanges, to suit different installation requirements. In summary, 904L flanges are specifically made from 904L stainless steel, which offers superior corrosion resistance in demanding environments. Their use can enhance the reliability and performance of piping systems, making them ideal for applications where corrosion resistance is paramount.

 

904L application areas:

904L alloy is a versatile material that can be applied in many industrial fields:

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

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

3. The flue gas desulfurization device in power plants is mainly used in the tower body, flue, door panels, internal components, spray systems, etc. of the absorption tower.

4. Scrubbers and fans in organic acid treatment systems.

 

 

Similar grades

GB/T	UNS	AISI/ASTM	ID	W.Nr
00Cr20Ni25Mo4.5Cu	N08904	904L	F904L	1.4539

 

 

904L chemical composition

C	Si	Mn	P	S	Cr	Ni	Mo	Cu	Fe
0.02	1	2	0.045	0.035	19-23	23-28	4-5	1-2

 

 

Mechanical properties

Tensile strength	Yield Strength	Elongation	Density	Melting point
RmN/mm	Rp0.2N/mm	A5％	8.0g/cm3	1300-1390℃

 

 

 

Wuxi Changrun has provided high-quality tube sheets, nozzles, flanges, and customized forgings for heat exchangers, boilers, pressure vessels, etc. to many well-known petrochemical enterprises at home and abroad. Our customers include PetroChina, Sinopec, Chevron, Bayer, Shell, BASF, etc. Send your drawings to sales@wuxichangrun.com We will provide you with the best quotation and the highest quality products.

 

What is the function of overlay welded tube sheets?

 

In industrial applications, corrosion resistance and structural integrity are very important, and welded overlay tube sheets have become essential components. Overlay welding also known as cladding, is a process of coating a corrosion-resistant alloy on the surface of a based materials. This technology provides an effective solution to protect the tube sheet from the impact of corrosive environments and extends its service life. And it can greatly reduce costs.

 

The main purpose of overlay welding tube sheets is to improve the performance and durability of heat exchangers, boilers, and other equipment using tube sheets. The following are some main advantages and precautions related to overlay welded tube sheets:

 

Corrosion Resistance:

By cladding a layer of corrosion-resistant alloy to the tube sheet's surface, the weld overlay layer protects against corrosion caused by corrosive fluids, high temperatures, or harsh operating conditions. This corrosion resistance helps to minimize maintenance requirements and maximizes the service life of the equipment. Common corrosion-resistant overlay metals include copper, titanium, nickel, cobalt based alloys, and austenitic stainless steel. For example, stainless steel overlay welding is used on the inner walls of petrochemical containers. When welding, workers should pay attention to the dilution rate of the based plate on the welding layer to ensure the alloy content required for corrosion resistance of the welding layer.

 

Material Compatibility:

Weld overlay tube sheets allow for the selection of different materials for the base material and the cladding layer. This flexibility enables the use of cost-effective base materials while ensuring optimal corrosion resistance and compatibility with the process fluids or gases. The chemical composition of the welding material should be similar as the base materials to ensure that the welding layer has good corrosion resistance and wear resistance. The welding material should have sufficient strength and toughness to ensure the structural performance and durability of the welding layer. The overlay welding material should have good welding performance, including melting point, fluidity, wettability, etc. The welding material should have good crack resistance to ensure that the welding layer will not crack due to vibration and deformation during operation. The welding material should have a certain degree of wear resistance to ensure that the welding layer does not excessively wear during operation.

 

Enhanced Strength and Integrity:

Weld overlay also improves the mechanical properties of forged tube sheet, including strength and toughness. It has higher hardness and wear resistance, and can withstand longer periods of wear and impact. The cladding layer adds an extra level of protection and reinforcement to the base material, reducing the risk of failure or leakage during operation.

 

Customization and Precision:

Weld overlay tube sheets can be tailored to specific project requirements, such as the size and pattern of the tube holes, the thickness and composition of the cladding layer, and the welding techniques used. This customization allows for precise fitting and dependable performance in various applications.

 

When selecting weld overlay tube sheets, several factors should be considered:

 

1.Corrosion Environment: Assess the nature of the operating environment, including the temperature, pressure, and the types of fluids or gases being processed. This information helps determine the appropriate corrosion-resistant alloy for the cladding layer.

 

2. Base Material Compatibility: Consider the compatibility between the base material and the cladding layer to ensure optimal bonding and long-term performance. 

 

3. Cladding Thickness: Determine the appropriate thickness of the cladding layer based on the severity of the corrosion environment and the desired service life of the equipment.

 

4. Manufacturing Standards: Verify that the weld overlay tube sheets comply with relevant industry standards and quality assurance processes to ensure their reliability and performance.

 

In summary, weld overlay tube sheets play a crucial role in enhancing the corrosion resistance and durability of heat exchangers, boilers, and other equipment. The careful selection of materials, customization options, and adherence to manufacturing standards are key considerations when choosing weld overlay tube sheets for optimal performance and long-term reliability. https://www.wuxichangrun.com/