Seamless tube ovality standards and influencing factors

Definition and measurement method of ovality:

Ovality refers to the ratio of the maximum distance to the minimum distance between the center line of the seamless tube & tubing section and the axis, usually expressed as D/d, where D is the maximum diameter and d is the minimum diameter. The three-point method or the auxiliary circle method is generally used to measure ovality.

Factors affecting the quality of seamless steel tubes due to ovality:

1. Steel pipe rolling process and equipment: Different rolling processes and equipment will directly affect the roundness and ovality of the steel pipe. If there are insufficient rolling passes or too many rolling passes during the production process, it will easily lead to an increase in ovality.
2. Material quality: The internal quality, composition, structure and other factors of the steel will also affect the ovality. For example, defects such as pores or inclusions inside the steel will cause bulges or depressions on the surface of the steel pipe, thus affecting the ovality of the steel pipe.

3. Wear of the pressure roller: The wear of the pressure roller used to adjust the ovality of the steel pipe during rolling will also affect the geometry and ovality of the steel pipe.

Domestic and foreign ovality standards:
1. International standards: The relevant standards formulated by the International Seamless Pipe Manufacturing Standards Organization (ISO) require that the ovality of steel pipes should be within 10% of the sum of the pipe diameter and wall thickness.
2. American standard: The American ASTM standard stipulates that the ovality of steel pipe is 1% of the difference between the outer diameter and the inner diameter.
3. Japanese standard: Japan's JIS standard stipulates that the ovality should not exceed 0.5% of the diameter.
4. Domestic standards: The maximum ovality error allowed by Chinese national standards is ±8% on the sum of pipe diameter and wall thickness.

Summarize:
The ovality of seamless tubes is one of the important factors affecting their quality and is very important for steel pipe production and quality control. Various countries have corresponding standards for ovality. Relevant standards should be followed during production, and various factors that affect ovality should be eliminated as much as possible to ensure the production of high-quality seamless tubes.