1 Scope
This national standard specifies seamless steel tube size, shape, masses and tolerances.
This standard is applicable to selection of size, shape, masses and tolerances in formulating all kinds of flat-end seamless steel tube.
2 Outside diameter and wall thickness
2.1 Classification
Outside diameter and wall thickness of steel tube can be divided three classes: outside diameter and wall thickness of common steel tube (refer to Table 1); outside diameter and wall thickness of precision tube (refer to Table 2) and outside diameter and wall thickness of stainless steel tube (refer to Table 3).
2.2 Outside diameter
Outside diameter of steel tube can be divided into three series: series 1, series 2 and series 3. Series 1 is the common series, belonging to the recommended adopted series; series 2 is not the common series; series 3 is the special series.
Outside diameter of common steel tube can be divided into series 1, series 2 and series; outside diameter of precision tube can be divided into series 2 and series 3; outside diameter of stainless steel tube can be divided into series 1, series 2 and series 3.
2.3 Permissible variation
2.3.1 Outside diameter and wall thickness tolerances selection
2.3.1.1 Steel tube application and technological equipments shall be taken into consideration.
2.3.1.2 Tolerances of outside diameter and wall thickness adopted in product standard shall be superior to standardized tolerances. According to customer requirements and product, Nonstandardized or other tolerances can be adopted.
2.3.2 Outside diameter tolerances
2.3.2.1 Refer to table 4 for the preferred standardized outside diameter tolerances.
2.3.2.2 Refer to table 5 for the recommended Nonstandardized outside diameter tolerances.
