DIN 2391-81 Part 2 defines the technical delivery conditions for seamless precision steel tubes according to DIN 2391 Part 1 which are made from the steel grades listed in section 5.

Precision tubes

Tubes according to this Standard are mainly used where accuracy to dimension and, possibly, small wall thicknesses and good surface condition are required.

Mechanical and technological properties

8.1. The mechanical properties depend on the condition on delivery as defined in table 3.

8.2. In technological testing (drift expandig test and flattening test) the samples must comply with the requirements of sections 11.2.3.2. and 11.2.3.3.

8.3. In the case of other steel grades and/or other conditions on delivery then those specified in tables 2, 3 and 8, the mechanical and technological properties must be mutually agreed. In these cases, the tubes are supplied according to quality grade C.

8.4. The steels listed in table 2 are deemed to be suitable for welding because of their chemical composition and metal lurgical treatment.

In the BK or BKW conditions on delivery, the mechanical properties are modified in the zone which has been subjectes to heating. This should be taken into account (see DIN 8528 Part 1) in assessing the weldability of a component.