Continuous rolling process of straight seam steel pipe

The continuous rolling process of straight seam steel pipes is a key manufacturing method used in the production of steel pipes. This process involves the continuous deformation of steel billets or slabs into thin steel sheets or plates, which are then welded into pipes. The process is efficient and allows for the production of high-quality pipes with precise dimensions and consistent material properties.

Key Steps in the Continuous Rolling Process for Straight Seam Steel Pipes:

1. Billet or Slab Preparation

The process starts with heating steel billets or slabs in a furnace to a high temperature, typically between 1100°C to 1300°C, to make them malleable for rolling.

The heated billets or slabs are then passed through the rolling mill to be reduced into thinner strips or plates.

2. Continuous Rolling in the Mill

The heated billets or slabs are fed into a continuous rolling mill, where they pass through a series of roll stands (sets of rolls) that progressively reduce the thickness of the steel.

Rollers apply pressure to elongate and reduce the thickness of the steel, shaping it into a thin, flat strip or plate.

This continuous process ensures the material moves through the mill without interruption, maintaining consistent production speeds.

3. Forming the Steel Strip

Once the desired thickness is achieved, the steel strip is formed into a tube shape using continuous forming mills. The strip is bent into a cylindrical shape.

This process often involves edge preparation to ensure that the edges of the strip are aligned for welding.

4. Welding the Seam

The edges of the formed strip are then welded together using high-frequency electric resistance welding (ERW) or laser welding.

In the ERW process, an electric current is passed through the edges of the strip, heating the metal to the point where it fuses together, forming a continuous weld seam.

The welded seam is cooled and subjected to quality checks to ensure the integrity of the weld.

5. Sizing and Finishing

After welding, the pipe undergoes sizing mills where it is passed through a set of rollers to adjust its diameter to the desired size.

The pipe is then cut to the required lengths, depending on the specifications or customer requirements.

6. Heat Treatment

In some cases, the pipe may undergo heat treatment to improve its mechanical properties, such as hardness and tensile strength. This treatment is done in a controlled furnace or through cooling processes to achieve specific material properties.

7. Coating and Inspection

Once the pipe is formed and sized, it may be coated with protective layers (such as galvanizing or epoxy coating) to improve its corrosion resistance, particularly for use in harsh environments.

Non-destructive testing (NDT) such as ultrasonic testing or eddy current testing is performed to ensure that there are no defects in the weld or the pipe body.