What Is Hot-rolled Precision Tube?

As an important type of tubing, precision tubes are gaining market favor for their high precision, excellent surface quality, and superior mechanical properties.

Among the many types of precision tubes, hot-rolled precision tubes have become a focus of industry attention due to their unique production process and wide range of applications.

Overview of Hot-Rolled Precision Tube

As the name suggests, hot-rolled precision tubes are precision tubes made through a hot rolling process. Compared to cold-rolled precision tubes, hot-rolled precision tubes utilize a heating process during production, deforming the metal material at high temperatures. Subsequently, through rolling, cutting, and heat treatment, the tubes achieve a certain level of dimensional accuracy and surface quality.

The key features of hot-rolled precision tubes are their high production efficiency, low manufacturing cost, and wide size range, making them suitable for mass production and application.

Hot-Rolled Precision Tube Process

1. Raw Material Preparation

Steel billets or bars that comply with standards such as DIN 2391 or ASTM A519 are selected as raw materials to ensure that the chemical composition and mechanical properties of the materials meet design requirements. Common steel grades include: 20#, Q345B, 16Mn, 42CrMo, 35CrMo, etc.

2. Heating

The raw material is heated to an appropriate temperature, typically around 1100°C, to achieve a plastic state, facilitating subsequent deformation.

3. Hot Rolling

The heated billet undergoes multiple rolls in the hot rolling mill, gradually deforming it into the desired pipe dimensions. This process allows for a wide range of dimensional adjustments and is highly efficient.

4. Cutting and Forming

After hot rolling, the pipe is cut into the desired length (e.g., 6m, 9m, 12m), and then formed and trimmed to ensure that the pipe's geometric dimensions meet standard standards.

5. Heat Treatment and Surface Treatment

Some hot-rolled precision pipes undergo heat treatment processes such as annealing and normalizing to improve internal structure and mechanical properties. Surface descaling and polishing are also used to enhance surface quality.

6. Inspection and Packaging

Dimensional inspection, surface inspection, and performance testing are performed to ensure that the tubes meet quality requirements. The tubes are then packaged and prepared for shipment.

Advantages of Hot-Rolled Precision Tubes

1. High Production Efficiency

Compared to cold rolling, the hot rolling process requires less equipment and offers faster production speeds, making it suitable for large-scale production.

2. Low Cost

Because the energy consumption and equipment investment required for hot processing are relatively low, the overall manufacturing cost is relatively low, achieving significant cost advantages while maintaining quality.

3. Wide Range of Applications

Hot-rolled precision tubes offer a wide range of sizes, meeting the needs of various applications, from larger diameters to finer gauges.

4. Excellent Mechanical Properties

Hot-rolled tubes exhibit excellent ductility and toughness, making them suitable for use in environments with high temperatures or high mechanical stress.

5. Stable Surface Quality

After proper heat treatment, the surface quality of hot-rolled precision tubes is relatively uniform, facilitating subsequent processing and assembly.

Disadvantages of Hot-Rolled Precision Tube

1. Slightly Lower Precision

Compared to cold-rolled precision tubes, hot-rolled tubes offer slightly lower dimensional accuracy and surface finish, requiring subsequent processing to compensate.

2. Inferior Internal Structure

During the hot-rolling process, the metal's internal structure may exhibit a high degree of coarse grains and defects, making it unsuitable for certain high-performance applications.

3. Surface Defects

During the production process, hot-rolled tubes may develop surface defects such as scale and scratches, requiring surface treatment.

4. Subsequent Processing Requirements

Due to limited dimensional accuracy, hot-rolled precision tubes may require cold working or other subsequent processing to meet performance requirements in certain precision machinery or demanding industries.

Common Size Ranges for Hot-Rolled Precision Tube

Hot-rolled precision tubes can be produced according to various standards (such as GB/T 8162-2018, DIN 2391, and ASTM A519), offering a wide range of sizes to meet diverse industrial needs:

1. Outer Diameter Range: Φ32mm to Φ630mm

2. Wall Thickness Range: 2mm to 60mm

3. Standard Lengths: 6m, 9m, and 12m, with custom lengths up to 16m available upon request.

4. Outer Diameter Tolerance: ±0.5% to ±1.0%

Comparison of Hot-Rolled Precision Tube with Other Tube Types

1. Hot-Rolled Precision Tubes vs. Cold-Rolled Precision Tubes

Cold-rolled tubes offer high dimensional accuracy (±0.2mm) and excellent surface finish, but are expensive and limited in production.

Hot-rolled tubes offer high efficiency and low cost, making them suitable for large-scale production, but they suffer from slightly lower precision.

2. Hot-Rolled Precision Tube vs. Seamless Tube

Seamless tubes are typically produced using hot or cold rolling processes. They offer high strength and excellent mechanical properties and are widely used in high-pressure fluid transportation applications, such as boiler tubes and oil pipelines.

Hot-rolled precision tubes rival seamless tubes in terms of dimensional control and surface quality, but with lower production costs, making them more suitable for general industrial applications.

3. Hot-Rolled Precision Tube vs. Welded Tube

Welded tubes are formed by welding tube billets or steel strips, resulting in lower costs and suitable for large-scale production. However, the weld seam of welded tubes can easily become a weak link, potentially affecting their mechanical properties.

Hot-Rolled precision tubes, on the other hand, offer better overall mechanical properties and fewer weld defects, making them suitable for applications requiring higher structural strength.

Applications of Hot-Rolled Precision Tube

1. Machinery Manufacturing

Hydraulic systems, machine tool spindles, and bearing rings.

2. Automotive Industry

Drive shafts, chassis components, and shock absorber cylinders.

3. Energy Industry

Oil casing pipe, boiler tube, and medium- and low-pressure oil and gas transmission systems.

4. Building Structures

Steel structural supports, bridge components, and scaffolding pipes.

5. Logistics and Transportation

Slurry pipelines and fluid transport pipelines.

Summary

Hot-rolled precision pipe, as a mature pipe production method, occupies a vital position in industrial production due to its high efficiency and economical nature. It offers a relatively reasonable cost solution while meeting basic mechanical performance and dimensional requirements, making it suitable for mass production and widespread application.