Conventional barrel-shaped (or MAN) perforators are widely used in the production of hot-rolled seamless steel tubes. However, since the double-supported conical piercing machine appeared in 1980, the conical piercing machine has developed faster. Compared to the barrel roller puncher, the tapered punching unit has the following features.
(1) The roller diameter of the tapered roller gradually increases from the inlet to the outlet, so that the circumferential speed of the roller increases gradually from the inlet to the outlet with the increase of the roller diameter, which is beneficial to the axial deformation of the metal and reduces the twist of the seamless steel pipe capillary. And the additional deformation, which has the effect of delaying the “horizontal forging effect” (Mann effect), can improve the inner surface quality of the seamless steel pipe capillary. Therefore, it is more advantageous for the perforated continuous casting billet and the alloy steel.
(2) The axial velocity of the outlet is high and the perforation efficiency is high.
(3) The extension coefficient is large, up to 6.
(4) The expansion amount can be as large as 30%~40%.
(5) The weight of the equipment and the installed capacity are both large and the investment is high.
The deformation process of the barrel roller and the tapered roller punch is the same.
The puncher consists of a roll, a guide (guide) and a plug that form a deformed hole.
The perforation deformation is divided into four stages: the biting section (I zone), the perforation section (II zone), the uniform section (III zone), and the gauge section (IV zone).
(l) bite into section (I zone)
The main function of the bite-in section is to realize a bite of the seamless steel pipe blank, and to prepare for the secondary biting of the seamless steel pipe blank contact head and to perform the piercing.
After the seamless steel tube blank is bitten, the roll inlet cone surface is tapered, and when it is advanced in the perforation direction (longitudinal direction), it is gradually compressed in diameter. A part of the metal of the compressed portion flows in the lateral direction, so that the cross section of the blank is rounded and elliptical, and a part of the metal (mainly the surface metal) extends in the longitudinal direction, and a “bell”-shaped depression is formed on the front end surface of the blank. This depression and centering hole (if necessary) center the head and the blank.
(2) Perforated section (II zone)
The main function of the perforated section is to convert the solid billet into a hollow seamless steel tube capillary from the nose of the head to the conical strip of the head.
The deformation feature of this section is that the distance between the surface of the roll and the surface of the head is gradually reduced. The seamless steel tube is rotated forward and the wall thickness is compressed, which is a spiral continuous rolling process. The metal whose wall thickness is pressed can flow (expanded) and longitudinally (extends) in the lateral direction. However, the lateral flow deformation is limited by the guide disc, and the longitudinal extension deformation is dominant. Due to the active rotation of the guide disc, the longitudinal friction of the metal is applied to strengthen the longitudinal extension of the metal, and the elongation coefficient can reach more than 6.
(3) The entire section (Zone III)
The main function of the uniform section is to uniform the pipe wall to improve the wall thickness dimensional accuracy and the quality of the inner and outer surfaces. This length starts from the conical band and the inner wall of the seamless steel tube leaves the head.
Since the top bus bar and the roller bus bar are approximately parallel, the wall thickness is small, and the main effect is to equalize. The cross section of the seamless steel tube is also elliptical in this section.
(4) Rules section (section IV)
The main function of the gauge section is to round the elliptical seamless steel tube capillary. This length starts from the inner wall of the seamless steel tube and ends when the seamless steel tube leaves the roll.