Abstract: It is pointed out that like the barrel type piercer process,the control of the cone type piercer roll speed is also very important.The major quality defect as occurring in the cone type piercer process with highdeforming steel and alloy steel is the lamination.The critical measure as taken to eliminate the said defect is to reduce the roll speed.It is emphasized that the lamination defect of certain alloy steel shells can not be eliminated just by "big toe angle",and that the common explanation for the development of the shell lamination is not true that the "continuous" uneven metal deformation,i.e.,the rotary piercing-caused torsional deformation of the metal is responsible for the said defect.