1.Introduction:

Stainless steel pipes are an integral part of modern infrastructure, offering exceptional durability, strength, and resistance to corrosion. From construction and transportation to food processing and medical industries, stainless steel pipes are essential for numerous applications. In this guide, we’ll explore the various types of stainless steel pipes,In this guide, we will explore the various types of stainless steel pipes and some key aspects about them.

2.Types of Stainless Steel Pipes

2.1 Seamless Pipes

Seamless stainless steel pipes are formed by extruding the material into a tube without welding the edges. This results in a continuous, uniform structure that offers superior strength, especially in high-pressure applications. Seamless pipes are typically used where high levels of pressure, temperature, and fluid flow are involved. They are stronger than welded pipes and are ideal for high-stress environments.

Uses:

• Oil & gas pipelines

• Power plants

• Aerospace and defense

• Chemical processing industries

  
  

2.2 Welded Pipes

Welded stainless steel pipes are made by rolling stainless steel sheets or strips into a tubular shape and then welding the edges together. These pipes can be more cost-effective than seamless pipes but may not perform as well under extreme conditions. The welding process could introduce weak spots, making these pipes less suitable for applications that demand higher pressure or stress.

Uses:

• Low to medium-pressure systems

• Plumbing systems

• HVAC applications

• Industrial processing

2.3 Spiral-Welded Pipes

Spiral-welded pipes are created by winding a stainless steel strip into a spiral shape and then welding it along the length of the pipe. This method is often used to create large-diameter pipes. Spiral-welded pipes are often used for projects requiring long lengths and large diameters, as well as situations where a higher degree of flexibility and strength is needed.

Uses:

• Large diameter pipelines

• Water and sewage systems

• Structural applications

• Large industrial pipelines

3. Key Stainless Steel Grades for Pipe Manufacturing

Common stainless steel pipe materials mainly include the following：

3.1 201 Stainless Steel Pipe

• Composition: Contains lower chromium content, typically between 13.5% and 15%, making it less corrosion-resistant than 304 and other similar steels.

• Characteristics: More cost-effective but has poor corrosion resistance.

• Applications: Commonly used for low-end decorative applications and non-corrosive environments, such as in home decoration and low-corrosion piping systems.

3.2 304 Stainless Steel Pipe

• Composition: Contains 18% chromium and 8% nickel, and belongs to austenitic stainless steel.

• Characteristics: Offers good corrosion resistance and mechanical properties, making it suitable for general industrial, construction, and decorative applications.

• Applications: Widely used in construction, machinery, chemical industries, and medical fields, such as for indoor and outdoor decoration, steam, air, food-grade media, water treatment, and other pipeline connections.

3.3 316 Stainless Steel Pipe

• Composition: Contains higher nickel content and a small amount of molybdenum, offering stronger corrosion resistance than 304.

• Characteristics: Particularly suitable for the chemical, marine, and pharmaceutical industries due to its excellent resistance to corrosive media.

• Applications: Used in marine environments, chemical plants, pharmaceutical industries, medical equipment, food processing, and other environments requiring strong corrosion resistance.

3.4 321 Stainless Steel Pipe

• Composition: Similar to 304, but with the addition of titanium to prevent intergranular corrosion at high temperatures.

• Characteristics: Offers better high-temperature performance compared to 304, and it is easier to machine due to the addition of small amounts of sulfur and phosphorus.

• Applications: Used in high-temperature environments, such as in aerospace equipment, chemical plants, and high-temperature steam pipelines.

3.5 400 Series Stainless Steel Pipe

• Composition: Primarily consists of ferritic and martensitic stainless steels, with around 11% chromium and lower nickel content.

• Characteristics: Good heat resistance but weaker corrosion resistance. Typically used in applications where high corrosion resistance is not a critical requirement.

• Applications: Used in high-heat environments, such as heat exchangers, boilers, and automotive exhaust systems.

  
  

3.6 410 Stainless Steel Pipe

• Composition: Martensitic stainless steel with high-strength chromium.

• Characteristics: Offers good wear resistance but poor corrosion resistance.

• Applications: Used in cutting tools, valves, pumps, and other industrial equipment requiring high strength and wear resistance.

3.7 430 Stainless Steel Pipe

• Composition: Ferritic stainless steel with a higher chromium content and lower nickel content.

• Characteristics: Offers good formability but has poor temperature and corrosion resistance. It is mainly used for decorative purposes.

• Applications: Commonly used in kitchen equipment, household appliances, and automotive exhaust systems.

3.8 440 Stainless Steel Pipe

• Composition: High-strength tool steel with a slightly higher carbon content. It can achieve high yield strength and hardness (up to 58HRC) after appropriate heat treatment.

• Characteristics: After heat treatment, 440 stainless steel pipes have very high hardness, making them suitable for cutting tools.

• Applications: Used in cutting tools, knives, scissors, and other tools requiring high hardness and wear resistance.

tips：In terms of usage, stainless steel pipes are divided into stainless steel industrial pipes and stainless steel decorative pipes; according to the production process, there are stainless steel seamless pipes and welded pipes. There are many materials, but in terms of commonly used materials, industrial pipes are mostly made of 304 or 304L materials, and there are also 321, 310, 316L, etc. The main materials of decorative pipes are 201 and 304, and a small amount of 202, 301 or 316L is used.

4. What are the specifications?

Nominal Diameter:

Common nominal diameters for stainless steel water pipes include DN15, DN20, DN25, DN32, DN40, DN50, DN65, DN80, DN100, DN125, DN150, DN200, etc. These diameters refer to the internal diameter of the pipe and are standardized to ensure compatibility with fittings and connectors.

Wall Thickness:

The wall thickness of stainless steel water pipes varies depending on the nominal diameter. For example, a DN15 pipe might have a wall thickness of around 0.8mm, whereas a DN200 pipe could have a wall thickness of 3.0mm or even thicker. The wall thickness is an important factor that influences the strength, pressure resistance, and overall durability of the pipe.

Length:

Stainless steel water pipes are typically available in standard lengths, such as 4 meters or 6 meters. However, they can also be customized according to the specific requirements of users. Custom lengths can be ordered for projects where the standard sizes do not meet the needs of the installation.

Connection Methods:

There are several types of connection methods used for stainless steel water pipes, including:

• Press-fit (Crimping): This method involves compressing the pipe and fitting together using a special tool. It’s quick and doesn't require welding, making it ideal for installations where ease of assembly is important.

• Welding: Stainless steel pipes can be welded together to form a permanent, leak-proof connection. This is commonly used in high-pressure or high-temperature applications where strength is essential.

• Grooved (Threaded or Coupled): This connection involves grooving the ends of the pipes and connecting them with couplings. It is often used for ease of disassembly and repair.

Tips：Each connection method influences the specifications of the pipe, such as its compatibility with fittings and the type of seals required.

5. Applications

5.1 Decoration Industry

For stainless steel pipes, the first reaction is that they are mostly used in industry. With the development of economy, they are more and more widely used in decoration industry, such as stair handrails, window guards, railings, furniture, etc. The most common materials are 201 and 304.

Compared with industrial use, decorative stainless steel pipes can be customized in surface, such as polishing, brushing, PVD plating (gold, champagne gold, rose gold, blue, bronze, etc.)

5.2 industry

Stainless steel pipes are widely used in the steel industry: chemical industry, construction industry, machinery industry, aircraft and automobile manufacturing, boilers, medical equipment, furniture and bicycle manufacturing, etc. A large number of various steel pipes are also needed. With the development of new technologies such as atomic energy, rockets, missiles and aerospace industries, stainless steel pipes are becoming more and more important in national defense industry, science and technology and economic construction.

Water &Oil & Gas: Stainless steel pipes are crucial in pipelines, especially in offshore drilling and extraction due to their high corrosion resistance.

Chemical Industry: Due to their resistance to a wide range of chemicals, they are used in transporting corrosive substances.Mainly use stainless steel seamless pipes, specifications include: 304, 321, 316, 316L, 347, 317L, etc., the outer diameter is about ￠18-￠610, the wall thickness is about 6mm-50mm.

Food & Beverage: Stainless steel pipes are widely used for food processing and water supply systems.

Pharmaceuticals: For sanitary applications where hygiene is critical, such as in cleanrooms and pharmaceutical manufacturing.The sanitary seamless pipes made of imported SUS304 and 316L can meet the special requirements of various media in the food and biopharmaceutical fields.

Water & Wastewater Treatment: They’re employed in systems dealing with high-pressure water flow and in harsh environments.The best choice for water industry, such as water preparation, storage, transportation, purification, regeneration, desalination, etc. The annual demand is about 25,000 tons.

6.Production Process

6.1 Raw Material Preparation

Choose high-quality stainless steel raw materials, typically using stainless steel coils or plates of grade 304 or 316. These materials offer excellent corrosion resistance and mechanical properties, making them ideal for producing stainless steel pipes.

6.2 Cutting

According to the required length and size of the stainless steel pipe, cut the stainless steel coil or plate to the appropriate length for manufacturing pipes and fittings. This step can be automated or semi-automated using cutting machines and other equipment.

6.3 Rolling

The cut stainless steel plates are then rolled into the desired shape to form a tubular structure. This process is typically carried out using forming machines or hydraulic presses. During the rolling process, it is essential to control temperature and pressure strictly to ensure the accuracy and strength of the pipes.

6.4 Welding

For seamless stainless steel pipes, the formed tubes need to be welded. Common welding methods include TIG (Tungsten Inert Gas) welding or high-frequency welding techniques. The welding process requires strict control over temperature and welding speed to ensure the quality and stability of the weld. The welds should be smooth, free of cracks, and devoid of inclusions or other defects. After welding, the seamless stainless steel pipe undergoes additional processes, such as hot rolling or cold rolling, to eliminate stress concentration and changes in the structure that may have occurred during welding, thereby improving the overall performance of the pipe.

6.5 Shaping

The welded pipes are then further shaped, such as by bending, flaring, reducing, or expanding, to achieve the required pipe fittings. These operations are typically performed using specialized forming equipment.

6.6 Surface Treatment

If necessary, the pipes undergo surface treatments like polishing, brushing, or sandblasting. Surface treatment not only enhances the aesthetic appearance of the pipes and fittings but also improves their corrosion resistance and wear resistance.