The finishing conditions of cold-drawn seamless steel tubes are as follows:




Cold out (hard)
BK(+C)
The tube does not undergo heat treatment after final cold forming, so it has considerable deformation resistance.


Cold out (soft)
BKW(+LC)
The final heat treatment is followed by cold stretching, involving limited deformation. Appropriate further processing allows a certain degree of cold forming (e.g. bending, expansion)


Cold out, relieve pressure
BKS (+SR)


annealing
GBK(+A)
The final cold forming process is followed by annealing in a controlled atmosphere.


return
NBK(+N)
The final cold forming process is followed by annealing above the upper deformation point in a controlled atmosphere.