Differences between Seamless Steel Pipe and Hot-Expanded Pipe

Different Production Processes:

The production processes of seamless steel pipe and hot-expanded pipe are significantly different. Base pipe refers to the primary seamless steel pipe produced from various steel billets as raw materials, after processing and heat treatment. The production of base pipe requires multiple processing steps, including billet pretreatment, piercing, hot rolling, or cold drawing. The production process of base pipe is relatively complex and difficult, but the resulting seamless steel pipe has high quality and strength, making it an important material widely used in various machinery and structural equipment.

Pipe expansion, on the other hand, is a process of enlarging the size of an existing seamless steel pipe as a base pipe. Its production process is relatively simple, mainly using two methods: one is rolling or stretching; the other is heated expansion and extrusion. The production process of pipe expansion requires specialized processing equipment and molds. During the expansion process, the steel pipe is subjected to greater pressure and force. Although the processing difficulty is not as high as that of base pipe, the processing precision requirements are higher because the expanded product needs to ensure surface smoothness and dimensional accuracy to guarantee its application performance.

Features Comparison:

1. Compared to the original seamless pipe wall thickness, thermally expanded seamless pipes have the following characteristics:

- Increased pipe inner diameter, resulting in increased flow rate.
- More economical than replacing existing pipes, and requires no major modifications to the existing system.
- Can be expanded for pipes of different diameters and materials, offering greater flexibility.

2. Original pipe wall thickness has the following characteristics:

- Stable pipe wall thickness, eliminating deformation due to heating expansion and simplifying construction.
- Unlike thermally expanded pipes, the pipe inner diameter cannot be changed, limiting the increase in flow rate.

Application Scenarios:

1. Applicable Scenarios for Thermally Expanded Pipes:

Generally, expanded pipes are suitable for low-pressure and medium-low-pressure transmission, such as water supply and drainage, and gas supply.

- When increased flow rate is required, or when the pipe inner diameter is too small for convenient replacement.
- When the existing pipe wall thickness no longer meets the requirements.
- When pipes require maintenance and upgrades based on actual conditions.
- Suitable for critical pipelines such as those for gas and oil, ensuring pipeline stability and safety.

2. Seamless Pipe Original Wall Thickness Application Scenarios:

- Compared to hot-expanded pipes, seamless pipes are suitable for high-pressure and special environments, such as petroleum, chemical, and nuclear power.
- For some time-tested pipelines, a constant wall thickness ensures the pipeline's normal service life.

However, in some environments, both can be used; the choice depends on the specific application requirements and economic viability.

In general, seamless pipes have superior pressure-bearing capacity. Hot-expanded pipes supplement and extend the specification range of hot-rolled seamless pipes, mainly used for large and extra-large diameter applications. When the required specifications are within the range of ordinary hot-rolled seamless pipes, always choose ordinary hot-rolled pipes because they are more economical and have more stable quality. Only when the required diameter is very large and welded pipes cannot be accepted (such as when pressure and reliability requirements are extremely high) should hot-expanded seamless pipes be chosen.

Hot-expanded seamless pipes are made by further processing ordinary hot-rolled seamless pipes as the "mother pipe." This means it includes the entire production cost of a regular seamless tube, plus the cost of subsequent processes. Therefore, in practical use, the choice needs to be made based on specific circumstances.

Read more: Seam pipe and Seamless pipe