This standard specifies the nominal dimensions and masses per unit length of the welded steel pipes.
This standard is applicable to the nominal dimensions and masses per unit length for formulating the standards of round plain end welded steel pipes.
2 Normative References
The following standards contain provisions which, through reference in this text, constitute provisions of this national standard. For dated reference, subsequent correctionments to, or revisions of, any of these publications do not apply. However, all parties coming to an agreement according to this standard are encouraged to study whether the latest edition of these documents is applicable. For undated references, the latest edition of the normative document is applicable to these specifications.
GB/T 8170 "Rules for Rounding off of Numerical Values"
GB/T 20878-2007 "Stainless and Heat-resisting Steels—Designation and Chemical Composition"
3 Classification
Welded steel pipes given in this standard are divided into ordinary welded steel pipes, precision welded steel pipes and welded stainless steel pipes.
4 Nominal Dimensions
4.1 Dimension series
4.1.1 External diameter of the welded steel pipes is divided into three series: Series 1, Series 2 and Series 3, Series 1 is the universal series recommended to be adopted; Series 2 is non-universal series; and Series 3 refers to some few special and dedicated series.
The external diameter of ordinary weldable steel is divided into Series 1, Series 2 and Series 3, the external diameter of precision steel pipe is divided into Series 2 and Series 3, and that of the welded stainless steel pipe is divided into Series 1, Series and Series 3.
4.1.2 The wall thickness of ordinary welded steel pipe is divided into Series 1 and Series 2. Series 1 is the preferred series and Series 2 is not.
4.2 External diameter and wall thickness
4.2.1 See Table 1 for the external diameter and wall thickness of ordinary welded steel pipes.
4.2.2 See Table 2 for the external diameter and wall thickness of precision welded steel pipes.
4.2.3 See Table 3 for the external diameter and wall thickness of welded stainless steel pipes.
GB/T 21835-2008 The following standards are cited：
