Stretch Reducing Mill

– Key Equipment for Seamless Tube Production

The Stretch Reducing Mill (SRM) is a critical piece of equipment in the hot rolling line for seamless tube production. Positioned typically after the heating furnace and piercing mill, the stretch reducing mill plays a crucial role in further processing the centerless bars, ensuring that the steel tubes meet the required specifications. Through the process of hot rolling, the mill reduces the diameter, adjusts the wall thickness, equalizes wall thickness, and can even increase wall thickness when necessary. This mill enables seamless pipe production with high precision and smooth surface quality, making it an indispensable tool in modern steel tube manufacturing.

Functionality and Design of the Stretch Reducing Mill:

The primary function of the Stretch Reducing Mill is to perform further rolling on the waste pipe after the initial processing stage in the mill. The centerless bar is fed into the stretch reducing mill, where tension is applied to the material, and it undergoes hot rolling to adjust its diameter and wall thickness. The mill typically consists of several pairs of rollers, each with specialized grooves, that gradually reduce the size of the billet as it passes through the rolls.

In the design of the mill, the center of the pass formed by each group of rolls should align in a straight line, ensuring consistent and uniform reduction of the billet. The reduction occurs incrementally as the billet passes through each successive pair of rollers, eventually reducing the original diameter to the desired size. This process allows for precise control over the finished dimensions of the seamless tube.

The result of the stretch reducing process is a smooth, round, and straight tube with a minimal diameter deviation, making it ideal for applications that require high-dimensional accuracy and surface quality.

Applications of the Stretch Reducing Mill:

1. Diameter and Wall Thickness Control: The SRM ensures that the diameter and wall thickness of the seamless steel tube are within tight tolerances. This is critical for applications in industries such as oil and gas, automotive, aerospace, and construction, where precision is essential.

2. Eliminating Defects: By reducing the wall thickness and controlling the shape, the stretch reducing mill helps eliminate any defects such as ovality, irregular surface finishes, and thickness variations in the tube. It ensures that the final product meets the strictest quality standards.

3. Special Pipe Shapes: The stretch reducing mill can also be used to shape special profiles for welded round pipes. It reshapes the pipe into various non-circular or special cross-sectional shapes, expanding the range of products that can be manufactured.

4. Surface Smoothing: As the pipe passes through the mill, the process smoothens the surface, eliminating any knife marks or external burrs that may remain from previous steps in the production process. This ensures the final pipe has a smooth, clean surface, ready for further processing or immediate use.

5. Straightening: The SRM also helps in roughly straightening the steel pipe, reducing any bending or distortion that may have occurred during previous stages. This is especially important to ensure that the tube enters the final cutting stage (flying saw) in a flat and straight condition.

   

Key Features of Stretch Reducing Mills:

1. High Precision: The Stretch Reducing Mill is designed to achieve precise control over the diameter and wall thickness of seamless tubes. With high single-stand reduction rates and more than 50% total reduction, it provides excellent dimensional accuracy for the final product.

2. Wide Product Specifications: The stretch reducing mill is capable of producing a wide range of tube sizes, making it a versatile option for manufacturers producing tubes for various applications. The mill can be adapted to meet different production requirements, whether producing smaller diameter tubes or larger, thicker-walled tubes.

3. High Rolling Speed: The stretch reducing mill operates at high speeds, allowing for increased production rates. This is crucial for high-volume manufacturing environments where efficiency and throughput are critical.

4. Uniform Wall Thickness: One of the key advantages of the SRM is its ability to reduce wall thickness variation. The finished pipe typically exhibits a maximum thickness difference of 0.4mm in the same section, ensuring uniformity and quality in the final product.

5. Durable and Efficient: Made from high-quality materials, the stretch reducing mill is designed for durability and long service life. Its robust construction ensures consistent performance, even under harsh operating conditions.

6. Customization Options: Our Stretch Reducing Mills are available in various configurations, including 6 to 24 stands, depending on the production line’s needs. This flexibility allows manufacturers to select the best setup for their production capacity and specifications.

Technical Specifications:

The Stretch Reducing Mill is typically used after the piercing mill and heating furnace and includes the following features:

• High Single Stand Reduction Rate: More than 50% total reduction.

• Finished Steel Pipe Thickness: Maximum thickness increase of 0.5mm.

• Wall Thickness Difference: No more than 0.4mm variation in the same section.

• Rolling Speed: High-speed rolling for improved production efficiency.

• Stand Configurations: 6 to 24 stands available, customizable based on production requirements.

Advantages of Using a Stretch Reducing Mill:

1. Improved Productivity: With its high-speed operation and precision control, the stretch reducing mill significantly boosts productivity by increasing throughput and reducing the need for additional finishing processes.

2. Higher Yield: By reducing defects and achieving uniform wall thickness, the SRM improves the overall yield of the production process, ensuring that a higher percentage of produced tubes meet the required specifications.

3. Cost-Effectiveness: The stretch reducing mill reduces the need for multiple rolling stages, which lowers production costs and minimizes material wastage.

4. Enhanced Pipe Quality: The finished pipes produced by the SRM are of superior quality, with smooth surfaces, precise dimensions, and minimal variation in wall thickness. This makes them suitable for high-performance applications in various industries.

Applications in Industries:

The Stretch Reducing Mill is widely used in industries that require high-quality, precision seamless steel pipes, including:

• Oil and Gas: For drilling and transportation of oil and gas.

• Automotive: For manufacturing components such as exhaust pipes, chassis, and more.

• Aerospace: For producing lightweight yet durable pipes for aircraft and spacecraft.

• Construction: For producing steel pipes used in structural applications.

• Water and Wastewater: For producing pipes used in water supply and sewage systems.

The Stretch Reducing Mill is an essential piece of equipment for the production of high-quality seamless steel pipes. Its ability to reduce diameter, adjust wall thickness, and improve pipe shape and surface quality makes it a vital tool in modern pipe manufacturing lines. With customizable configurations, high precision, and increased production efficiency, the stretch reducing mill plays a key role in meeting the stringent demands of industries worldwide.