JP2002066611A - Rolling method by use of barrel-type skew rolling roll - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rolling method by use of a barrel-type skew rolling roll capable of enhancing a pipe-spreading rate of a material or a pipe material on rolling, even if a skew rolling mill comprising a barrel-type roll is employed to a manufacturing process for a seamless steel pipe. SOLUTION: In the manufacturing process for the seamless steel pipe, a rolling material is surrounded and rolled by a plug that is pressed to the tip face of the horizontally traveling material, or inserted into the material from its tip, a pair of barrel-type skew rolling rolls consisting of an upper roll and a lower roll and a pair of roller shoes consisting of a right shoe and a left shoe. For piecing or spreading the material, the rolling is conducted by changing an intersecting angle of a vertical direction of each shaft of the barrel-type skew rolling rolls to the direction where a distance between the upper and lower rolls becomes longer at a point where the material gets apart from the rolls.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rolling method using a barrel-type inclined roll, and more particularly, to a method of manufacturing a seamless steel pipe in a manufacturing process of a seamless steel pipe, using a tilt-rolling machine equipped with a barrel-type roll. In rolling and drilling or expanding steel slabs (including from steel slabs to pipes), this is a technique for increasing the expansion ratio of the material to be rolled as compared with the prior art, thereby reducing material costs and tube making costs.

[0002]

2. Description of the Related Art An example of a process for manufacturing a seamless steel pipe (a plug,
The mill process is shown in FIG. There is a piercer mill 2 that pierces the steel slab that is the material 1,
A so-called "inclined rolling mill" having a roll with an inclined roll surface such as an elongator 4 for expanding the perforated tube 3 is arranged. These inclined rolling mills prevent the raw material 1 or the raw tube 3 from jumping out of a rolling region formed by an inclined rolling roll (hereinafter simply referred to as a roll 8) during rolling,
In order to control the deformation caused by the rolling, a guide member for a raw material 1 or a raw tube 3 which will be described later as a guide shoe is provided so as to surround the rolling region. Conventionally, a fixed shoe that does not operate is generally used as the guide shoe. However, since the fixed shoe comes into "sliding contact" with the material to be rolled, it receives a large amount of thermal stress and frictional force. At present, in order to solve this problem, most inclined rolling mills in the manufacturing process of small and medium diameter pipes use rotary disk shoes or roller shoes consisting of a rotating disk-shaped member mainly based on `` rolling friction ''. It has been adopted. The tentative pipe rolled by these inclined rolling mills is then stretched in the longitudinal direction by a plug mill 5, polished by a reeler 6 which is the same inclined rolling mill as described above, and the inner and outer diameters are reduced by a sizing mill 7. Is adjusted to a constant and the product becomes a seamless steel pipe.

[0003] When drilling with the piercer mill 2 or expanding the tube with the elongator 4, the outer diameter (symbol) of the steel slab 1 or the raw pipe 3 is usually adjusted toward the target outer diameter of the product. d _f ) is made larger than the outer diameter before rolling (called the original diameter, symbol d ₀ ). The degree of the expansion is represented by the expansion ratio (symbol P) in the following equation.

P = 100 × (d _f −d ₀ ) / d _{0 In} general, in the production of seamless steel pipes, from an economical point of view, the steel slab of the raw material 1 can be obtained when the product size is within a certain range.
This is because steel slabs of the same size are often used. Therefore, in the inclined rolling mill, it is desirable to perform rolling so that the pipe expansion ratio is as high as possible.

However, when the roll 8 of the inclined rolling mill is of a barrel type as shown in FIG.
About 10% for Pierce Mill 2 and 15 for Elongator 4
% Is the upper limit. This is because, if the expansion ratio is rolled higher than the above value, it becomes difficult to pull out the rear end when the rolled tube 9 is pulled out from the barrel-type roll 8, so that the degree of expansion is limited ( This is called poor butt slip). The reason why this deficient bottom defect occurs will be described below with reference to FIG. 1) The diameter (d _f ) of the rolled tube 9 is larger at the exit side of the roll 8 than at the entrance side (d ₀ ), and the tube 9 in contact with the roll 8 is separated from the roll 8. The position (referred to as a roll-off position) is shifted further downstream in the traveling direction of the tube 9. Normally, a distance between the maximum diameter position of the roll 8 (called a gorge position) and the roll-off position is called a lead distance, and the value is represented by L. That is, when the diameter of the rolled tube 9 is larger at the exit side of the roll 8 than at the entrance side, the length L increases. As a result, the difference between the maximum diameter (D ₁ ) of the roll 8 and the roll diameter (D ₂ ) at the roll-off position increases, and the circumference of the roll 8 changes at the maximum diameter position (called the gorge position) and the roll-off position. The speed difference increases, and a braking effect appears for the advance of the tubular body 9. 2) When the pipe expansion rate is increased, a pair of guides
The spacing between the shoes increases. When the roller shoe 10 is employed as the guide shoe, the distance between the roll 8 and the roller shoe 10 also increases. As a result, a flare-like bulge 11 is formed at the rear end of the tube 9, which makes it difficult for the tube 9 to come off the roll 8,
Uneven thickness also occurs.

[0006] In order to prevent such a defect,
Conventionally, there is an inclined rolling mill that employs a cone-shaped roll as shown in FIG. 3B and can expand the pipe at a rate of 30%. When this type of roll 8 is used, the roll diameter becomes larger toward the exit side, but since there is no large peripheral speed difference unlike the barrel type roll, the braking effect is eliminated. However, there has been a problem in that changing the existing barrel-type roll to a cone-type roll requires enormous costs.

[0007]

In view of the foregoing, the present invention has been made in consideration of the above circumstances, and even if an inclined rolling mill provided with a barrel-type roll is employed in the process of manufacturing a seamless steel pipe, the expansion rate of the material or raw pipe during rolling is reduced. It is an object of the present invention to provide a rolling method using a barrel-type inclined rolling roll, which is capable of significantly increasing the rolling resistance.

[0008]

Means for Solving the Problems The inventor has conducted intensive studies to achieve the above object and has embodied the results in the present invention.

That is, in the process of manufacturing a seamless steel pipe, the present invention provides a plug that is pressed against or inserted into the front end of a horizontally running material to be rolled, and a pair of barrel-type inclined rolling rolls at the top and bottom. A pair of rollers on the left and right
The material to be rolled is surrounded and rolled with a shoe, and a hole is formed in the material to be rolled,
Alternatively, when expanding the pipe, rolling is performed by changing the vertical crossing angle with respect to the axis of each barrel type inclined rolling roll in a direction in which the distance between the upper and lower rolls at a position where the material to be rolled is away from the roll is increased. This is a rolling method using a barrel-type inclined rolling roll.

[0010] The present invention also provides the roller shoe,
The center line between the left and right is previously displaced from the line connecting the center axis of the inclined rolling rolls vertically by 2.5 to 3.5 mm in the horizontal direction in advance, and the peripheral speed of the rolling rolls is set to 5.
This is a rolling method using a barrel-type inclined rolling roll, which differs by 0 to 7.6%.

Further, the present invention is a rolling method using a barrel-type inclined rolling roll, wherein the inclined rolling mill is one of a piercer and an elongator.

In the present invention, in the process of manufacturing a seamless steel pipe, the crossing angle of the pair of upper and lower barrel-type inclined rolls with respect to the axis is changed so that the distance between the upper and lower rolls at a position where the material to be rolled is separated from the rolls is increased. Since the lead distance for achieving the same expansion ratio is shorter than in the past using steel slabs or tubes of the same size, until the tube body fails to break through. The margin occurs. As a result, if such a state is maintained and the lead distance is extended to the limit of the occurrence of the deficient through-hole, the expansion ratio can be increased as compared with the conventional case. Further, in the present invention, the roller shoe is arranged such that the center line between the left and right thereof is horizontally shifted by 2.5 to 3.5 mm in advance from a line connecting the center axis of the inclined rolling roll in the vertical direction, and Since the peripheral speeds of the rolling rolls are made to differ from each other by 5.0 to 7.6%, the gap formed between them and the material to be rolled is reduced, and the flare-like bite at the rear end of the rolled tube is reduced. This can prevent the occurrence of unevenness and uneven thickness.

The rolling method may be carried out by any of the piercer mills and elongator rolling mills.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below along with the circumstances leading to the invention.

First, the inventor studied the conditions for preventing the tubular body 9 rolled at the same expansion ratio from causing a defect in the bottom of the elongator 4 having the existing barrel-type roll 8. As a result, it has been found that it is better to incline the axis of the roll 8 so as to cross the center line of the horizontal tube 9 in a vertical section. That is, in this case, as shown in the lower half of FIG. 1, the distance between the gorge position and the roll-off position of the material to be rolled is reduced, and the peripheral speed difference between those positions (specifically,
This is because, as will be described later, the evaluation is made based on the ratio of the peripheral speeds), and the braking effect on the progress of the tubular body 9 is reduced. This can be proved by a mathematical formula as described below.

When the axis of the conventional roll 8 is horizontal: V ₁ = D ₁ · π · N (1) Equation V ₂ = D ₂ · π · N (2) Equation L = (D ₁ -D ₂ ) / 2tanα (3) When the axis of the roll 8 is tilted from the horizontal; V ₁ = D ₁ · π · N (4) V ₂ ′ = D ₂ ′ · π · N (5) L = (D ₁ − D ₂ ′) / ₂ tan (α + γ) (6) where V ₁ is the roll peripheral speed at the gorge position D ₁ is the roll diameter at the gorge position N is the roll rotation speed V ₂ is the roll-off position Is the roll peripheral speed D ₂ , the roll diameter at the roll-off position L, the lead distance α, the roll surface angle γ is the cross angle of the roll axis, and the dash is a value obtained by adding the cross angle to the roll axis. . Comparing the above equations (3) and (6), it is clear that D ₂ ′ is always larger than D ₂ and γ is also positive, so that the lead distance is smaller in equation (6) than in equation (3). is there.
The peripheral speed ratio is as follows: V ₂ / V ₁ = D ₂ / D ₁ in the conventional case, and V ₂ ′ / V ₁ = D ₂ ′ / D ₁ in the case where the crossing angle is given. In both formulas, the former is apparently smaller, and the value when the latter crossing angle is given is larger. However, D ₁ is always D ₂
Since the value is larger, the value of the peripheral speed ratio is closer to 1 and the peripheral speed difference between the roll positions is smaller.

As described above, if the crossing angle of the roll 8 with respect to the axis is changed in a direction in which the distance between the upper and lower rolls at the roll-off position of the pipe 9 increases, the lead distance is reduced at the same expansion ratio and the peripheral speed is reduced. As the ratio approaches 1, the braking effect on the tube 9 is significantly reduced. Therefore, if the value of the crossing angle is changed and the lead distance is increased to the limit where the defect occurs, the pipe expansion rate can be increased as compared with the conventional case. Incidentally, when an existing barrel-type roll was provided with a crossing angle of 1.5 °, the lead distance could be reduced by 35% as compared with the conventional case as shown in FIG. 5 at the same expansion ratio. As a result, it was confirmed that the peripheral speed ratio at the gorge position and the roll-off position was reduced by 28% as shown in FIG.

Next, in order to make the tube 9 come off from the roll 8 more smoothly, it is necessary to prevent the flare-like biting 11 occurring at the rear end of the tube 9 during rolling. . For this reason, the present inventor has found that the start-up 1 shown in FIG.
The cause of 1 was determined, and it was found that as the diameter of the tube increased, the distance between the top and bottom of the roll 8 and the distance between the right and left of the roller shoe 10 increased, and the gap 12 around the tube increased. 7 (b), the center line between the left and right rollers / shoes 10 is previously shifted horizontally by ΔH from the line connecting the center axes of the rolls 8 as shown in FIG. 7 (b). In addition, it was considered that the problem could be solved by making the peripheral speed of the roll 8 slightly (ΔV) slightly different between the upper and lower sides. The reason for providing the offset of ΔH (referred to as offset) at the center of the roller-shoe distance beforehand is that the gap between the roll on the offset side and the roller-shu becomes large in order to identify the flare-like biting position. This is because the biting occurs in the larger gap, and the difference of ΔV in the peripheral speed of the upper and lower rolls 8 is that tension is applied to the biting portion by the peripheral speed difference to prevent flare. To do that.

In order to confirm the effect of this countermeasure, a test operation was performed in which ΔH and ΔV were changed, and an example of the results is shown in FIG. From FIG. 8, when ΔH is in the range of 2.5 to 3.5 mm, there is an optimum ΔV in the bottom of the tubular body 9, and the peripheral speed difference between the upper and lower rolls is 5 to 7.6%. It is clear that it is good to do. In addition, ΔH is set to 2.5 to 3.5.
If the value is less than 2.5, the flare occurrence position cannot be specified, and if the value exceeds 3.5, the displacement of the shear center with respect to the path center is too large, and the shape of the outlet tube deteriorates (the wavy on the outer surface increases). This causes inconvenience. Further, the reason why ΔV is set to 5 to 7.6% is that, as shown in FIG. 8, if less than 5%, a bite 11 occurs on the upper side of the tube during rolling, and if it exceeds 7.6%, the tube Began downward 1
This is because 1 occurs.

[0020]

Example 1 A seamless steel pipe was manufactured from a round steel slab (round billet) made of austenitic stainless steel SUS304 by using a plug mill process shown in FIG. . First, material 1 with Piasa Mill 2
Piercing and rolling is performed to obtain a raw tube 3. Subsequently, the raw tube 3 is expanded by an elongator 4, and a temporary pipe (referred to as hollow) is formed.
I made it. At the time of the pipe expansion, the rolling method according to the present invention was adopted, and the results were compared with those obtained by the conventional method. In addition, the rolling conditions of the elongator are collectively shown in Table 1.

[0021]

[Table 1]

FIG. 9 shows the results of tube expansion by the elongator 4. According to FIG. 9, according to the present invention, even in the elongator 4 having the barrel-type roll 8 instead of the cone-type roll, the expansion ratio of the tube 9 from the roll 8 can be reduced without causing the tube 9 to come off from the roll 8. It can be seen that this can be increased from 15% to 34%. And, by achieving the improvement of the pipe expansion rate, the billet size as the raw material 1 can be consolidated, and the productivity is improved by reducing the time required for changing the mill due to the size change. In addition, the above-mentioned pipe expansion rate is such that the intersection angle given to the roll 8 is 1.
It is a value of the elongator 4 up to 5 °, but if the crossing angle can be further increased, a larger expansion ratio can be achieved. (Example 2) SU which is an austenitic stainless steel
The round steel slab (round billet) made of S304 is used as the material 1,
A seamless steel pipe was manufactured using the plug mill process shown in FIG. First, the raw material 1 was pierced and rolled by a piercer mill 2 to obtain a raw tube 3. Subsequently, the raw tube 3 was expanded by an elongator 4 to form a temporary tube (referred to as hollow). At the time of the perforation, the rolling method according to the present invention was adopted, and the results were compared with those obtained by the conventional method. Table 2 shows the rolling conditions of the piercer mill 2 collectively.

[0023]

[Table 2]

As a result of expanding the pipe with the piercer mill 2, the pipe 9 can be prevented from failing to come off from the roll 8 without fail.
The expansion rate was increased from 10% to 17%. And, by achieving the improvement of the hole expansion rate, the billet size as the material 1 can be consolidated, and the productivity is improved by reducing the time required for changing the mill due to the size change.

In the above embodiment, the rolling method according to the present invention is applied to the elongator 4 for expanding the raw tube 3 and the piercer mill 2 for piercing the blank 1, but the present invention does not cause any problem. .

[0026]

As described above, according to the present invention, in an inclined rolling mill provided with a barrel-type roll for producing a seamless steel pipe, not only can the expansion rate of the material to be rolled be significantly improved, but also the pipe end can be improved. No so-called flare (enlargement of the end diameter) is generated in the portion, and poor bottom-out, poor pipe end, poor bite, etc. are greatly reduced, and the productivity and yield of the seamless steel pipe are improved.

[Brief description of the drawings]

FIG. 1 is a view for explaining a pipe expanding method according to the present invention, in which an upper half shows a relationship between a conventional roll and a tubular body, and a lower half shows a relationship between a roll and a tubular body when the present invention is applied.

FIG. 2 is a flow diagram illustrating a plug mill process for producing a seamless steel pipe.

FIG. 3 is a view showing the shape of an inclined roll, and FIG.
Is a barrel type, and (b) is a cone type.

FIG. 4 is a diagram illustrating a problem that occurs at the time of pipe expansion.

FIG. 5 is a diagram showing a result of a reduction in a lead distance by applying the present invention.

FIG. 6 is a diagram showing a result of a reduction in a peripheral speed difference depending on a roll position by applying the present invention.

FIGS. 7A and 7B are diagrams for explaining the cause (a) of the occurrence of biting of the tube in the gap between the roll and the roller shoe, and a countermeasure (b).

FIG. 8 is a diagram showing a relationship between a difference in peripheral speed between upper and lower rolls and a rate of occurrence of a defect in a tubular body.

FIG. 9 is a diagram showing an improvement state of a pipe expansion rate by implementing the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 material (steel slab, billet) 2 piercer mill 3 raw tube 4 elongator 5 plug mill 6 reeler 7 sizing mill 8 roll 9 tube (hollow) 10 roller shoe 11 biting 12 gap 13 plug 14 heating furnace

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takeshi Takeshi 1-1-1 Kawasaki-cho, Handa-shi, Aichi Prefecture Kawasaki Steel Corporation Chita Works

Claims (3)

[Claims] In a manufacturing process of a seamless steel pipe, a plug which is pressed against a front end surface of a material to be rolled traveling horizontally or inserted into the inside from the front end, a pair of barrel type inclined rolling rolls at the top and bottom, and a pair of left and right at the left and right. Rolling and surrounding the material to be rolled with a roller shoe, and when piercing or expanding the material to be rolled, the vertical crossing angle with respect to the axis of each barrel-type inclined rolling roll is determined at a position where the material to be rolled is separated from the roll. Rolling in a direction in which the distance between the upper and lower rolls is increased. 2. The roller shoe according to claim 1, wherein a center line between the left and right sides of the roller shoe is horizontally shifted by 2.5 to 3.5 mm in advance from a line connecting the center axis of the inclined roll vertically. Set the peripheral speed of the rolling rolls up and down to 5.0 to 7.6%
The rolling method according to claim 1, wherein the rolling method is different from the rolling method. 3. The rolling method using a barrel-type inclined rolling roll according to claim 1, wherein the inclined rolling mill is one of a piercer and an elongator.