What is the difference between hot finished and cold finished tube?

The terms "hot finished" and "cold finished" refer to the processes by which steel tubes or pipes are shaped and finished. The difference between the two primarily lies in the temperature at which the tubes are processed, which affects their mechanical properties and surface finish.

Hot Finished Tubes:

1. Manufacturing Process: Hot finished tubes are produced by heating steel to a high temperature (typically above 1000°C) and then shaping it through processes like extrusion, piercing, or rotary forging. The tube is then cooled to room temperature.

2. Surface Finish: The surface finish of hot finished tubes is typically rougher compared to cold finished tubes because of the high-temperature manufacturing process. This may require additional surface treatments for specific applications.

3. Mechanical Properties: Hot finishing generally results in a tube with good internal structure but with a slightly lower precision in terms of dimensions. The material tends to be more ductile, but it might also exhibit residual stresses.

4. Applications: Hot finished tubes are often used for applications where high precision isn't the primary concern but strength and durability are. These tubes are commonly used in structural, automotive, and heavy-duty applications.

5. Cost: Typically, hot finished tubes are less expensive due to the simpler manufacturing process.

Cold Finished Tubes:

1. Manufacturing Process: Cold finished tubes are processed at or near room temperature, following processes like cold drawing or pilgering. In these processes, the steel tube is pulled through a die to reduce its diameter and increase its length.

2. Surface Finish: Cold finished tubes have a much smoother surface finish compared to hot finished ones, as they undergo additional work-hardening during the drawing process. This results in a more polished, clean, and uniform surface.

3. Mechanical Properties: Cold finishing imparts higher strength and improved dimensional precision to the tube. Cold finished tubes also tend to have better surface hardness and are more dimensionally accurate.

4. Applications: Cold finished tubes are ideal for applications that require high dimensional tolerance, smooth surface finish, and superior mechanical properties. These are commonly used in hydraulic, aerospace, and precision machinery.

5. Cost: Cold finished tubes are generally more expensive due to the additional processing steps required to achieve higher precision and surface finish.

Summary of Key Differences: