JPS58168405A - Rolling method of pipe in second piercer - Google Patents

Abstract

PURPOSE:To improve the inside surface shape of a metallic pipe and to improve the durability of a plug in the stage of producing the metallic pipe by a Mannesmann double piercing system by injecting cooling water from the forward end of the plug of the 2nd piercer. CONSTITUTION:The thick walled hollow blank pipe which is formed with the 1st piercer is expanded and rolled to a final metallic pipe product with the 2nd piercer in a pipe making process by Mannesmann plug mill by a double piercing system. The plug 4 to be used in this stage is connected to a mandrel 1 by means of an end fitting 3 to provide a cavity 4a in the inside. An ejection hole 4b for cooling water is provided obliquely forward in the forward end part thereof. In the stage of expanding and rolling the metallic blank pipe with the 2nd piercer, the cooling water supplied from the forward end of the plug 4 through the mandrel 1 is injected to cool the inside surface of the blank pipe and to increase the deformation resistance thereof. The generation of pit flaws on the inside surface by the plug and the seizure between the inside surface of the metallic blank pipe and the plug is eliminated and the durability of the plug is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a seamless pipe manufacturing method using a roll perforation method, and more particularly to a method for rolling a pipe using a second perforator of the so-called Mannesmann double perforation method.

In the so-called Mannesmann plug pipe manufacturing method, a double perforation method is usually adopted, and after obtaining a thick-walled hollow blank pipe (hereinafter referred to as perforation material) with a first piercer, a second piercer is used. A drilling machine (elongator) is used to expand the perforated material to a large diameter and roll it to a thick wall.

However, during rolling by the second punching machine during this secondary punching, annophthalm-shaped flaws occur on the inner surface of the perforated material, which has a large impact on the quality of the product.
Prevention of pit defects has been an issue.

In order to solve the above problem, the inventor of the present invention investigated the occurrence of pit flaws during rolling with a second punching machine, and found that the occurrence of internal bit flaws occurs when a part of the inner surface of the perforating material is eroded by the plug. We hypothesized that this is caused by printing on the inner surface of the perforated material again after it has been removed. and,
Really hard materials such as stainless steel, 'Cr-Mo
Focusing on the fact that pit defects are extremely rare in perforated materials such as steel, we have conducted research and found that even in the case of perforated materials made of materials other than those mentioned above, it is possible to cool the perforated materials before rolling with the second perforator. It has been found that by increasing the hardness, that is, increasing the deformation resistance, it is possible to similarly suppress the occurrence of bit flaws. A conceivable method for cooling the perforated material is to stop the perforated material during transfer from the first perforation machine to the second perforation machine and spray cooling liquid onto the inner surface of the perforated material. The second cold radius on the inner surface of the material
There is a lapse of time before rolling by the perforator, and the perforated material recuperates heat, making it not necessarily possible to obtain the desired effect.

Furthermore, there is a possibility that the cycle time will be worsened during the cooling process.

On the other hand, another problem in rolling with the second punching machine is the durability of the plug. In the second punching machine, a plurality of plugs are usually prepared, and after each plug is used (after rolling), it is immersed in a water tank to cool it, and these plugs are circulated and used. However, this method alone was not always sufficient and could not prevent the occurrence of seizure flaws, wrinkling flaws, etc. on the inner surface of the tube due to plug melting during rolling.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for rolling a tube in a second punching machine, which can improve the inner surface properties of the raw tube after rolling by the second punching machine and improve the durability of the plug.

That is, in the inclined roll double perforation system, the present invention is capable of rolling while cooling the inner surface of the perforated material and the plug immediately before rolling by jetting a cooling liquid from the tip of the plug during rolling by the second perforation machine. It is characterized by:

Next, the present invention will be explained based on the drawings.

The accompanying drawing is a schematic view showing an example of the configuration of the tip portion of the second drilling machine suitable for carrying out the method of the present invention.

1 shows the mandrel of the second drilling machine, and like a normal mandrel, a cooling liquid for cooling the mandrel is provided inside. A plug 4 is attached to the tip of the mandrel 1 via a mandrel tip fitting 3. Inside the mandrel tip fitting 3 and Hisolug 4, there is a mandrel 1.
Coolant inside? Cavities 3a and 4a communicating with the iso 2 are formed, respectively. The plug 4 is further formed with a plurality of coolant jet holes 4b at its tip, which communicate with the cavity 4a within the plug 4. The shape of the coolant jet hole 4b is inclined diagonally forward so that when the coolant is jetted from the coolant jet hole 4b, it hits the inner surface of the perforated material at a position forward in the direction of relative movement of the plug 4, as will be described later. Preferably. The dimensions, pressure, and ejection pressure of the coolant ejection holes 4b are appropriately selected depending on the dimensions, material, setup, etc. of the perforated material.

By configuring the tip portion of the second drilling machine as described above, a part of the cooling liquid for cooling the mandrel flowing through the cooling liquid nozzle 2 in the mandrel l is transferred to the spout hole 4b at the tip of the plug 4. It can be ejected from. If it is necessary to increase the amount of coolant to be ejected, the coolant pipe 2 may be removed and all of the coolant flowing through the mandrel 1 may be ejected from the tip of the plug 4.

Now, in accordance with the present invention, when the thick-walled hollow perforated material obtained by the first drilling is subsequently rolled and expanded, the tip part of the second perforation machine is inserted into the hollow part of the perforated material, and the coolant is poured into the perforated material. When supplied, the cooling liquid that has passed through the mandrel 1 passes through the cavity 3a in the mandrel tip fitting 3 and the cavity 4a in the plug 4, as shown by the arrow in the figure, and flows into the cooling liquid at the tip of the plug 4. It is injected from the ejection hole 4b onto the inner surface of the perforated material in front of the plug 4. In this way, the inner surface of the perforated material is cooled immediately before rolling by the plug 4 of the second perforator, and the deformation resistance near the inner surface is instantaneously increased. the result,
It is possible to prevent the perforated material from undergoing rapid deformation during rolling. In addition, since the vicinity of the inner surface of the perforated material becomes instantly hard just before rolling, it is possible to prevent the occurrence of inner surface pit defects due to gouging and re-cylindrication of the inner surface of the perforated material. Furthermore, the cooling liquid that has been supplied through the mandrel 1 further flows through the mandrel tip fitting 3 and the plug 4.

Since the plug is injected from the tip of the plug, the plug is constantly cooled by the internal cooling liquid during rolling, which effectively prevents seizure of the perforated material and melting of the plug during rolling. It is possible to improve the durability of the plug and prevent the occurrence of seizure defects and wrinkle defects on the inner surface of the tube.

The effectiveness of the method of the present invention in preventing the occurrence of internal pit defects is that the incidence of internal pit defects with a depth of 0.3 wm or more is suppressed to 1/3 or less compared to the conventional method that does not cool the internal surface of the perforated material immediately before rolling. It is something that can be done. In addition, a method in which the tip device of the second drilling machine described above is used and air is blown onto the inner surface of the drilling material instead of a cooling liquid such as water does not substantially improve the effect compared to the conventional method. It can be seen from Σ that cooling the inner surface of the perforated material immediately before rolling with a cooling liquid is effective in preventing the occurrence of bit defects.

In addition, in the present invention, not only the cooling liquid, such as water, is spouted from the spout hole 4b at the tip of the plug 4, but also a mixture with a substance such as a lubricant is spouted to further improve the inner surface properties of the product. You can also try it out.

The method of the present invention is also effective as a method for descaling the inner surface of a perforated material. That is, in general, during rolling by the second punching machine, a state of hollow kneading occurs after the punching material is bitten by the roll of the second punching machine until it hits the plug 4.
The scale built inside the perforation material will be peeled off to some extent.

When cooling liquid is injected from the tip of the plug 4 in this state, the scale is washed away with the cooling liquid and descaling is performed.

In order to enhance this effect, it is more effective to increase the injection pressure of the coolant.

Furthermore, according to the present invention, the inner surface of the perforated material is only instantaneously cooled immediately before rolling, which often causes problems in cycle time.

Further, the present invention can be implemented using a conventional mandrel cooling liquid system as is by only partially changing the shapes of the plug and the mandrel end fitting, and is therefore extremely simple and highly practical in terms of equipment.

[Brief explanation of the drawing]

The drawing is a schematic diagram showing an example of the configuration of the tip portion of the second drilling machine used in the present invention. 1... Mandrel 2... Coolant pipe 3.
・・Mandrel tip fitting

Claims (1)

[Claims] (1) The inclined roll double perforation method is characterized by cooling the inner surface of the perforated material and the plug immediately before rolling by spouting a cooling liquid from the tip of the plug during rolling by the second perforation machine. A method of rolling a tube in a second punching machine.