Rotary Rolling-continuous Rolling Process——An Approach to Eliminating Interior Surface Spiral-line Marks of Rotary-rolled Steel Tube

To solve the problem that serious inner surface spiral line marks stay with the light wall shells and tubes with rather big D/S values as rolled by rotary-rolling pipe mills like the Assel mill,a proposal as conceived on the basis of relevant experiences of others is put forward.The proposal involves such a solution,i.e.,setting up a so-called“the second mill stand”at the run-out side of the rotary piercing mill or the rotary rolling mill proper so as to eliminate the interior surface spiral line marks of the tube,and thus get the inner surface quality improved by means of rotary rolling-continuous rolling process.“The second mill stand”may be designed with use of the rotary sizing technique.Another way is using the rotary pressing circular mill or the extracting mill as“the second stand”.