Carbon Steel Pipe Wall Thickness Standards and Heat Treatment Requirements

The Importance and Application of Carbon Steel Pipe Wall Thickness Standards:

The development and implementation of carbon steel pipe wall thickness standards are crucial for ensuring industrial production and construction safety. Appropriate wall thickness ensures sufficient structural strength when withstanding pressure, loads, and impact, thereby preventing safety accidents caused by thin walls.

At the same time, unified wall thickness standards also help standardize the production process and enhance quality control. By adhering to national standards, manufacturers can ensure that their carbon steel pipe products meet quality requirements and improve market competitiveness. Furthermore, clear wall thickness specifications provide engineering designers with a convenient selection basis, simplifying the design process and improving work efficiency.

Carbon Steel Pipe Wall Thickness Range:

Carbon Steel Pipe wall thickness ranges vary depending on the production process:

Wall Thickness Range:
Hot-rolled Steel Pipe: Typically has an outer diameter greater than 32mm and a wall thickness of 2.5-75mm.

Cold-rolled steel pipe: The minimum outer diameter can be 6mm, and the wall thickness can be as thin as 0.25mm. Thin-walled pipes below 0.25mm can even have an outer diameter of 5mm.

High-precision cold-drawn pipe:
The wall thickness can be controlled within ±0.02-0.05mm, with a minimum wall thickness of 0.25mm. These pipes are often used in high-precision applications such as pneumatic and hydraulic components.

What wall thickness of carbon steel pipe requires heat treatment?

When the wall thickness of carbon steel pipes reaches or exceeds 26mm, preheating is required before welding to ensure weld quality. This can be achieved using electrical heating methods. The optimal preheating temperature range is 100-200°C to prevent thermal stress and crack formation in the material during welding.

During the preheating process, special attention should be paid to controlling the temperature between weld layers, ensuring it does not fall below the preheating temperature. This ensures uniform heating of the weld area and improves the performance of the weld joint. Setting the preheating range is also crucial. For butt welds of carbon steel pipes, the preheating range should be no less than three times the wall thickness on both sides of the groove to ensure uniform heating inside and outside, avoiding local overheating that could degrade material properties.

It is important to note that the area 100 mm outside the heated area should be kept insulated to prevent localized low temperatures that could affect weld quality. In practice, the temperature should be uniform across the entire weld area to avoid weld defects caused by localized temperature inconsistencies, thereby ensuring the strength and durability of the welded joint.

Preheating not only reduces thermal stress in the material during welding but also improves the microstructure of the welded joint, enhancing its plasticity and toughness. For thick-walled carbon steel pipes, the correct preheating method and temperature range are crucial, helping to improve the quality and reliability of the welded joint.

National Standard Specification for Wall Thickness of Carbon Steel Pipe Pressure Grades:

In addition to determining wall thickness based on the outer diameter, the wall thickness of carbon steel pipes should also be selected based on the pressure grade to which they are subjected. Carbon steel pipes of different pressure grades require different wall thicknesses to ensure pressure resistance and safety.

National standards specify specific wall thickness requirements for carbon steel pipes at different pressure levels. For example, GB/T 8163-2008, "Seamless Steel Pipes for Liquid Transportation," details reference wall thickness values for carbon steel pipes of varying diameters at different pressure levels. These values are derived based on a comprehensive consideration of factors such as the pipe's intended use, operating pressure, and allowable material stress, providing an important basis for engineering design and practical application.

Read more: Schedule 80 Carbon Steel Pipe or SCH 40 Pipe vs. SCH 80 Pipe