We manufacture four steel grades (J55, K55,N80, L80 and P110), six sizes (1. ... ", 3-1/2", 4", 4-1/2") of tube. welded round tube There are four steel grades (J55, K55,N80, L80 and P110), two ... of which is in the leading level at home. Two steel grades (J55 and N80)and three specifications of workover casings ...