JP2001058207A - Pusher of punching roller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steel tube free from any inner surface flaws without preworking a difficult-to-work material, in particular, a stock material inferior in the inner quality of the as-cast stock material by providing a back pressure applying means to push the stock material by the pressure until it is stably bit while applying the back pressure to the stock material. SOLUTION: The pusher preferably has a forward speed changing means to change the forward speed of the pusher according to the rolling condition, and a back pressure changing means to change the back pressure of the pusher. When a stock material 2 is carried before a pusher 10 at the retracted position, a sensor 5 detects the stock material 2, and the high-speed advancement to a drive control part of the pusher 10, and the pusher 10 carries the stock material 2 to a roll 3 side at high speed. When a sensor 4 provided immediately before the roll 3 detects the stock material 2, the sensor commands the low- speed advancement to the drive control part of the pusher 10, and the pusher 10 allows the stock material 2 to be bitten by the roll 3 at a low speed. The specified back pressure is applied to the stock material 2 until the biting is completed, and then, the pusher 10 is retracted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention perforates a poor-quality material in which porosity is present in the center of the material, because the material is still difficult to process or is unsuitable because of its poor hot workability. The present invention relates to a pusher device for a piercing mill capable of suppressing the occurrence of flaws during pipe production during rolling.

[0002]

2. Description of the Related Art In a piercing mill, a rolling force is applied to a billet by a pair of rolls, and a crack is generated in the center of the billet by a rotary forging effect. Piercing and rolling are possible between the plug and the plug. The pierced and rolled hollow shell is then elongated.
It is stretched by a rolling mill such as a mill, a plug mill or a mandrel mill, and is formed by a sizer or a stretch reducer.

[0003] A seamless pipe material can be relatively easily cast continuously into a round billet like a general low carbon steel having a small alloying component, and a material having a good hot workability is cast as it is. In the case of a cast alloy that is poor in hot workability, such as a high alloy, which tends to cause segregation at the center of the slab, a round slab may be formed by processing.

[0004] The main cause of workability deterioration is segregation and porosity in the center of a continuous slab, and the porosity generation mechanism that has a particularly great effect is generally that voids are formed in the final solidification stage of the slab, and molten steel is originally required. Where should be supplied,
In the case of a high alloy, the content of Cr and the like is high, so that the molten steel is not supplied to the shaft center portion because the viscosity of the molten steel increases. As described above, when a material that may include internal defects is used as cast, severe processing called Mannesmann drilling is performed at the beginning of the pipe making process, and internal surface flaws are generated due to porosity and segregation.

For this reason, high alloy materials having poor hot workability are:
After continuous casting, before the Mannesmann perforation, a process is performed in which the material is once heated and processed by blasting or the like to make the inside uniform. Producing a seamless pipe by adding pre-processing to this cast material leads to an increase in the number of steps and an increase in costs such as heating during pre-processing as compared with a material that can be used as a rolled material as cast.
For this reason, there has been a demand for a method of producing pipes without adding pre-processing as much as possible.

[0006] In order to solve this problem, it has been proposed to improve the casting method and to improve the tube rolling method.

As for the improvement of the casting method, there is a method of mechanically pressing a defect during continuous casting of a steel slab. this is,
JP-A-60-162563 and JP-A-63-242
As described in Japanese Patent Publication No. 452, it is often applied mainly to a steel slab or the like having a rectangular cross section. When this light reduction process is applied to a round billet, there is a problem that the billet shape goes away from a perfect circle. In addition, if the amount of reduction is increased in order to enhance the crimping effect, the above-described shape deterioration is promoted. A bad billet shape causes a problem of poor conveyance. Further, in order to reduce the amount of reduction and to obtain a sufficient pressure-bonding effect, the number of light reduction processes must be increased, and the equipment cost increases.

[0008] Regarding the improvement of pipe rolling, which is another method, there are many cases in which a technique for preventing inner surface flaws caused by Mannesmann cracking during piercing rolling has been studied. For example, as described in JP-A-55-106611,
In some cases, not only the inner surface flaw generation limit but also the biting conditions and the uneven thickness are specified. However, since the occurrence of inner surface flaws greatly depends on the material of the material, this technique cannot be applied to as-cast billets or difficult-to-machine materials.

Further, as described in Japanese Patent Application Laid-Open No. 04-147704, there is a method in which the temperature and strain rate of a material are specified to suppress inner surface flaws. However, when rolling is performed at a reduced temperature, the load on the piercing rolling mill and the subsequent process rolling mill increases, and therefore, there is a great limitation.
In addition, in the case of an as-cast billet, there is a porosity in advance, so that this method alone is not sufficient for suppressing the inner surface flaw.

Further, in order to pierce an alloy material having poor hot workability without flaws, it is effective to perform piercing under light pressure. As shown in FIG. 7, the perforation under light pressure can be realized by advancing the perforation plug 1 toward the material 2 and increasing the interval between the rolls 3 and 3. This is because the rotational forging effect can be suppressed as much as possible and the Mannesmann crack can be minimized, so that the quality of the inner surface can be improved. Incidentally, material 2 and B during soft reduction perforation - contact length l ₂ of Le 3 is less than the contact length l ₁ of at conventional drilling without soft reduction (see Fig. 6).

However, in order to perform the drilling under light pressure,
When the material driven by the frictional force between the roll and the material comes into contact with the piercing plug, a drag is generated, and this exceeds the driving force applied to the material from the roll, resulting in poor biting. In addition to the resistance of the drilled plug,
Insufficient frictional force between the roll and the material is conceivable, but there are irregularities called knurling on the surface of the perforated roll, and the influence on poor biting is small except for the fluctuation of the roll surface due to aging. .

[0012]

As described above, in order to obtain a product having good inner surface quality without changing the conventional material manufacturing and canning processes, it is necessary to pre-process the material. This leads to an increase in capital investment or an increase in the number of processes for pre-processing, resulting in an increase in cost. Also, in order to make a pipe while accepting the part where the quality of the material is inferior, it was necessary to carry out a major equipment modification.

According to the present invention, there is provided a conventional pipe making process which does not require any major equipment remodeling, does not require pre-working on difficult-to-machine materials, especially materials having inferior quality as cast, and has no internal flaws. An object of the present invention is to provide a pusher device of a piercing mill capable of manufacturing a steel pipe.

[0014]

According to the present invention, the above object is achieved by the following apparatus.

According to a first aspect of the present invention, there is provided a pusher for a piercing mill having a back pressure applying means for applying a back pressure to a material while pushing the material stably until the material is stuck when the material does not bite during inclined drilling. -A device.

In this device, the material can be pushed into the roll by the back pressure applying means until the material is bitten into the roll, so that the difficult-to-machine material can be bitten into the roll in light pressure drilling. Then, it is possible to prevent the occurrence of inner surface flaws due to light pressure perforation.

According to a second aspect of the present invention, in the first aspect, a forward speed changing means for changing the forward speed of the pusher in accordance with the rolling conditions, and a back pressure for changing the back pressure of the pusher. And a change unit.

According to this apparatus, it is possible to change the advancing speed of the raw material with respect to the roll and the back pressure for pushing the raw material in accordance with the rolling conditions of the raw material. If the material is conveyed at a high speed, the cycle time can be reduced.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The apparatus of the present invention will be described below with reference to the drawings. Conventionally, a pusher device has been designed to transport a material to a piercing mill. In order to cause the difficult-to-machine material to bite into the roll under light pressure piercing conditions, it is necessary to apply a back pressure to the pusher that can overcome the resistance of the plug. As shown in FIG. 5, the back pressure (pressing force) increases as the rolling reduction (roll interval at plug tip position / material billet diameter) increases.

The biting ability of the material is greatly affected by the pushing speed of the material. In order to improve the biting property of the material, it is necessary to match the pushing speed of the material with the speed at which the billet advances during piercing and rolling. The advance speed v of the billet is roughly obtained by the following equation (1). v = (2t / d) · Dnπsinθ (1) where t is the thickness after piercing and rolling, d is the outer diameter of the billet,
D is the body diameter at the roll gouge position, n is the roll rotation speed, and θ is the roll tilt angle.

As shown in the equation (1), the speed v varies greatly depending on the roll body diameter D, the wall thickness t after piercing and rolling, and the billet outer diameter d. Needs to be changed according to the rolling conditions. However, the advance speed v of the billet is much lower than the advance speed of the pusher normally used as a transfer device. If the pusher is advanced at the speed of advance of the billet during transport, the rolling cycle time will increase and the rolling efficiency will decrease. Therefore, in order to shorten the rolling cycle time and increase the rolling efficiency, it is necessary to control the pusher forward at a high speed immediately before the piercing mill and then at a low speed.

The device of the present invention has been developed to satisfy the above requirements. FIG. 1 is a conceptual diagram of the apparatus of the present invention, and FIG.
FIG. 3 is a hydraulic circuit diagram according to the device of the present invention.

In FIG. 1, 1 is a piercing plug, 2 is a material to be pierced and rolled, 3 is a roll of a piercing mill, and 10 is a pusher. Here, the rod of the pusher cylinder 11 is a pusher 10. A hydraulic unit 20 controls the operation of the rod of the pusher cylinder 11, that is, the operation of the pusher 10. The pusher cylinder 11 is used as back pressure applying means for stably biting difficult-to-machine materials into the rolls 3 of the inclined drilling machine. Sensor for detecting material 2 immediately before roll 3
4 are provided. In addition to the sensor-4, a sensor-5 is provided near the pusher at the limit of retreat as shown in FIG. This sensor-5 is
This is to detect the presence of a material in front of the pusher at the retreat limit.

The hydraulic circuit of the hydraulic unit 20 will be described with reference to FIG. A pump side pipe 24 for sending the pressure oil of the hydraulic pump is connected to respective pump ports of the direction control valve 21 and the direction control valve 22. An oil tank return pipe 27 is connected to the respective tank ports of the direction control valve 21 and the direction control valve 22. The direction control valve 21 is
The directional control valve 22 controls the forward or backward movement of the pusher 10, and is used to select a differential circuit. The differential circuit is used at the time of high-speed transport of a round billet which needs to supply a large amount of oil to the piston side chamber 11a of the pusher cylinder.

Directional control valve 21 and pusher cylinder-1
A flow regulating valve 23 as a means for changing the forward speed of the pusher is mounted in the middle of a pipe 25 communicating with the first piston side chamber 11a, whereby the amount of oil supplied to the piston side chamber 11a of the pusher cylinder is reduced. Can be changed. The pump side pipe 24 is provided with a pressure control valve 28 as a back pressure changing means of the pusher, whereby the pressure of the hydraulic oil supplied to the pusher cylinder can be changed. 26 is a pipe connecting the B port of the direction control valve 22 and the rod side chamber 11b of the pusher cylinder.

In the above example, the hydraulic cylinder and the hydraulic circuit are used as the back pressure applying means, the forward speed changing means of the pusher, and the back pressure changing means of the pusher. Alternatively, a chain drive system using a DC motor or a rack and pinion drive system may be employed.

Next, a method of rolling a difficult-to-process material by the above-described apparatus will be described. FIG. 3 is an explanatory view conceptually showing a process until a difficult-to-work material is bitten into a roll of an inclined piercing mill. Before the pusher 10 in the retreat limit position,
When the round billet 2 is transported, the sensor (HMD: Hot
Metal Detector 5 detects round billet and pusher
High speed forward control (eg: 1000 mm / sec;
(See (d)): (a). Pusher-10,
The round billet 2 is conveyed to the roll 3 at a high speed. Sensor-4 provided immediately before the roll detects the round billet,
The pusher's drive control unit moves forward at low speed (example: 200 mm /
sec; (d)): (b).

The pusher 10 causes the round billet 2 to bite into the roll 3 at a low speed. The pusher applies a constant back pressure to the round billet from the start of biting to the completion of biting: (c).

FIG. 4 is an example of a velocity diagram of a pusher when piercing-rolling a difficult-to-machine material.

The pusher moves forward at a high speed according to a forward command from the sensor 5, and moves forward at a low speed according to a command from the sensor 4.
The pusher is pushed until the round billet bites into the rolls 3, 3 and the round billet begins to be forged by the roll.
Moves forward at low speed while applying back pressure to the round billet. The time from the start of rolling of the round billet to the start of rotary forging (completion of biting) is short. When the start of the rotary forging of the round billet is confirmed, a backward command is issued to the pusher. The pusher then retreats at a high speed, and stops at the retreat limit in response to a stop command.

[0031]

According to the first aspect of the present invention, it is possible to bite a difficult-to-machine material into a roll in drilling under light pressure, thereby preventing the occurrence of an inner surface flaw.

According to the apparatus of the second aspect, it is possible to perform piercing rolling appropriate for rolling conditions, and to shorten the rolling cycle time.

Further, the apparatus of the present invention can be realized by a small remodeling of the existing equipment, so that the remodeling cost is low.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of the device of the present invention.

FIG. 2 is a hydraulic circuit diagram according to the device of the present invention.

FIG. 3 is a conceptual diagram showing a process until a difficult-to-process material is bitten into a roll.

FIG. 4 is a velocity diagram of a pusher when piercing-rolling a difficult-to-machine material.

FIG. 5 is a diagram showing a relationship between a draft and a pushing force of a pusher.

FIG. 6 is a conceptual diagram of conventional piercing and rolling without light reduction.

FIG. 7 is a conceptual diagram of perforation under light pressure.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 drilling plug 2 material 3 roll 4, 5 sensor 10 pusher 11 pusher cylinder 20 hydraulic unit 21, 22 directional control valve 23 flow control valve 24 pump side pipe 25, 26 communication pipe 27 oil tank return pipe 28 Pressure control valve

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Motoi Hashizume, 1-2-1, Marunouchi, Chiyoda-ku, Tokyo, Japan Inside Nihon Kokan Co., Ltd. (72) Masahiko Yasukawa 1-2-1, Marunouchi, Chiyoda-ku, Tokyo, Japan (72) Inventor Tatsuharu Oda 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd.

Claims (2)

[Claims] 1. A piercing and rolling facility for seamless pipe production,
A pusher device for a piercing mill, comprising a back pressure applying means for pushing the material stably while applying a back pressure to the material by a pusher. 2. The piercing rolling device according to claim 1, further comprising a forward speed changing means for changing the forward speed of the pusher according to the rolling conditions, and a back pressure changing means for changing the back pressure of the pusher. Machine pusher device.