Hollow Bar 280 Cold Drawn
280D refers to a hot-finished 280-tube which has been further processed by cold working, usually cold drawing. The cold working increases both yield and tensile strength but elongation is lowered. In comparison with the 280 hot-rolled product, dimensional tolerances are improved. 280D has equivalent weldability to hot-finished 280 while machinability is improved as a result of the cold working.
The standard which covers cold-drawn, seamless tubes is SS-EN 10305 - 1. The grade closest to 280 which is referred to in this standard is E410 +C. However, for the latter, the only stipulation is a minimum level for tensile strength whereas 280D has guaranteed minimum levels for both yield and tensile strength. Furthermore, the minimum elongation for 280D is considerably better than for E410 +C in SS-EN 10305 - 1.
The tolerances on outside diameter and wall are somewhat tighter for 280D than the levels stipulated in SS-EN 10305 - 1.