Hot rolling and cold rolling are two different processing methods for steel pipes

Hot rolling and cold rolling are two common processing methods in steel pipe production. They have certain differences in the processing process, the characteristics of the finished products, and the applicable fields.

First, hot rolling
Hot rolling refers to the processing method of heating the steel billet to a high temperature and then rolling it. During the hot rolling process, the steel billet is preheated to a temperature close to or exceeding its recrystallization temperature and then rolled by the rolling mill rollers. The main characteristics of hot-rolled steel pipes are as follows:
1. Process characteristics
- High heating temperature: Hot rolling requires the steel billet to be heated to a high temperature, usually above 1100°C. High temperature helps to reduce the deformation resistance of steel and improve rolling efficiency.
- High rolling force: Since hot-rolled steel has good plasticity at high temperatures, a large rolling force can be applied, making the cross-sectional shape and size easier to adjust.
- Relatively poor surface quality: The surface of hot-rolled steel pipes is prone to defects such as scale, rust, and rolling marks, which require subsequent surface treatment.
2. Product characteristics
- Roughness is large: Due to the high temperature and high rolling force during hot rolling, the surface of the steel pipe will have a certain degree of roughness and is not smooth enough.
- High internal stress: The cooling speed of hot-rolled steel pipes is fast, and there are stress differences in the formation of internal structures, which make it easy to form internal stress and annealing treatment is required to eliminate internal stress.
- Good mechanical properties: Hot-rolled steel pipes have high yield strength and elongation, and are suitable for fields requiring high strength and plasticity.

Second, cold rolling
Cold rolling refers to the processing method of rolling steel billets at room temperature. Compared with hot rolling, the processing technology of cold rolling has some unique characteristics, which determine the characteristics and uses of cold-rolled steel pipes. Let's take a look at the characteristics of cold rolling:
1. Process characteristics
- Low heating temperature: The processing temperature of cold-rolled steel is usually carried out at room temperature, and high-temperature heating treatment is not required.
- Low rolling force: Due to the poor plasticity of cold-rolled steel, the rolling force is relatively small, and it is easy to control the dimensional accuracy and shape of the plate.
- Good surface quality: The surface quality of cold-rolled steel pipes is good, without obvious defects such as scale and rust, and no surface treatment is required.
2. Product characteristics
- High dimensional accuracy: The dimensional accuracy of cold-rolled steel pipes is high, which can meet more stringent requirements. Especially for steel pipes with thin wall thickness and small diameter, the cold rolling process is more advantageous.
- High surface finish: The surface of cold-rolled steel pipes is smoother than that of hot-rolled steel pipes, which can meet some application scenarios with high surface requirements.
- Mechanical properties are slightly inferior to hot rolling: Due to the poor plasticity of steel during cold rolling, the yield strength and elongation of cold-rolled steel pipes are slightly lower than those of hot-rolled steel pipes.

In summary, hot rolling and cold rolling are two common methods in steel pipe processing, and they have obvious differences in process characteristics, product characteristics, and applicable fields. The hot rolling process is suitable for scenarios with high requirements for mechanical properties, while cold rolling is more suitable for applications requiring high dimensional accuracy and surface quality. In actual selection, it is necessary to determine which processing method to use according to specific needs to obtain ideal steel pipe products.

In summary, hot rolling and cold rolling are the two main ways of steel pipe processing. They are processed at high temperature and room temperature respectively, producing steel pipe products with different characteristics. By understanding and mastering the characteristics of these two processing methods, we can better select and apply steel pipes to meet the needs of various projects and industries.