JP2007229795A - Barrel-shaped piercer roll for reducing shearing strain in circumferential direction - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide barrel-shaped piercer rolls with which shearing strain in the circumferential direction is reduced. <P>SOLUTION: In these barrel-shaped piercer rolls for reducing shearing strain in the circumferential direction, when piercing a billet by using the barrel-shaped piercer roll, by setting gorge positions so that deviated width from the mill center is ≤10% of the roll length, expanding action to a material to be pierced is increased and the material to be pierced is expanded, the shearing strain is reduced. Furthermore, in the barrel-shaped piercer rolls for reducing the shearing strain in the circumferential direction, a profile is made so as to have strong shell restrain on the outlet of the roll. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a barrel type piercer roll capable of reducing circumferential shear strain.

  Conventionally, one of the quality defects of seamless steel pipes manufactured by the Mannesmann drilling method is internal flaws, and the generation factors can be broadly divided into two types: pipe material quality and piercer drilling conditions. Thus, as a result of investigating the influence of the piercer drilling conditions on the inner surface flaw occurrence rate, it was found that the inner surface flaw occurrence rate increases as the rotary forging effect increases. Therefore, in order to reduce the plug tip draft rate, which is an evaluation index of the rotary forging effect, lead and gorge setting criteria have been established and managed.

  However, as a result of measures against billet biting defects, the plug tip draft rate may increase, and even if the plug tip draft rate is low, internal flaws often occur, which is not a definitive measure. On the other hand, a cross-angle drilling method using a cone-type roll has been developed, and a method for preventing inner surface flaws by suppressing the rotary forging effect that causes inner surface flaws and the circumferential shear strain that causes inner surface flaw propagation has been proposed. Yes. On the other hand, in the case of a barrel-type piercer roll, if the rotary forging effect is suppressed by changing the profile, the billet biting property deteriorates. In addition, the relationship with the profile of the circumferential shear strain has not been reported so far.

Conventionally, when a barrel type piercer roll is used, the occurrence of circumferential shear strain cannot be completely prevented. Further, when a cone type piercer roll is used, for example, as disclosed in Japanese Patent Publication No. 60-59042 (Patent Document 1), the combination of the inclination angle and the crossing angle is optimized, so that the outside of the shell is removed. A method has been proposed that can suppress surface twisting and circumferential shear deformation and prevent the occurrence of outer surface defects and inner surface defects.
The barrel-type piercer roll has a barrel shape having a maximum diameter at the center of the roll, whereas the cone-type piercer roll has a conical shape whose diameter increases from the roll entry side to the exit side. .

On the other hand, FIG. 6 is a diagram showing a conventional barrel-type piercer roll profile. As shown in FIG. 6, the barrel-type piercer roll 1 has a barrel shape, and has the same or different radii on the entrance side 9 and the exit side 10 of the roll with the gorge portion 8 at the center of the roll. R _i and R _o arcs are provided. When the radius R _i of the roll entry side arc is reduced, the rotary forging effect is reduced and the generation of inner surface flaws is suppressed. However, the resistance to the advanced billet becomes large, and biting defects frequently occur.

Japanese Patent Publication No. 60-59042

  As described above, the use of the conventional cone-type piercer roll is very effective for preventing the occurrence of internal flaws. However, in order to employ a cone-type piercer roll in a rolling line that has used a barrel-type piercer roll, there is a problem that a large-scale facility modification is required and a large amount of cost is required. Therefore, it is a big problem to reduce the circumferential shear strain when the barrel type piercer roll is used.

  In order to solve the above-mentioned problems, the inventors have made extensive developments. As a result, the gorge position, which has not been clearly defined in the past, has a deviation width from the mill center of 10% or less of the roll length. With this setting, the pipe expansion action on the material to be drilled is increased, and by expanding the shell during drilling, the circumferential flow of the metal can be relaxed, resulting in a reduction in circumferential shear strain. As a result, it is possible to provide a barrel type piercer roll that can reduce the incidence of internal flaws.

The gist of the invention is that
(1) When drilling a billet using a barrel-type piercer roll, the deviation width from the mill center at the gorge position is set to 10% or less of the roll length to reduce the circumferential shear strain. Type piercer roll.
(2) The barrel-type piercer roll according to (1), which reduces the shear stress in the circumferential direction, has a strong shell restraint on the roll exit side.

  As described above, according to the present invention, it is possible to reduce the occurrence rate of inner surface flaws, and to achieve an industrially excellent effect that can improve quality and yield.

Hereinafter, the present invention will be described in detail with reference to the drawings.
Generally, in piercing and rolling of seamless steel pipes, piercing and rolling are performed using a piercer mill. FIG. 1 is a top sectional view of a barrel-type piercer mill, and FIG. 2 is a front sectional view of the barrel-type piercer mill. . As shown in FIG. 1 or 2, in the piercer, the tip of the piercer mandrel 3 inserted from the opposite side is pressed while the billet 4 is pushed by the pusher 7 during the drilling and the billet 4 is rotated using the pair of piercer rolls 1. The plug 2 is used for drilling at the center of the billet 4 using the rotary forging effect. The piercer roll 1 has a barrel shape with the gorge portion 8 at the top, and the billet 4 advances while rotating. For this reason, the billet 4 can alternately be pulled and compressed in the billet 4 to drill the billet 4, and the circle that causes the propagation of the inner surface flaw due to the difference in the peripheral speed of the metal flow between the shell outer surface and the inner surface during drilling. Circumferential shear strain occurs. Reference numeral 5 is a roll shaft, and 6 is a guide shoe.

  FIG. 3 is a diagram illustrating a piercer setup state. 3A is a front cross-sectional view, FIG. 3B is a cross-sectional view, and FIG. 3C is a view showing the inclination angle θ of the piercer roll. As shown in this figure, the symbol X represents the billet diameter, Y represents the gorge interval, and Z represents the plug diameter.

FIG. 4 is a diagram showing the influence of the roll outlet profile on the circumferential shear strain. 4A shows profile A (R _i = 1000 mm, R _o = 1200 mm), FIG. 4B shows profile B (R _i = 1000 mm, R _o = 2100 mm), and FIG. 4C shows profile C (R _i = 1000 mm, shows the R _o = 3000 mm), the current street, set the gorge position from the mill center position of 70mm inlet side, the same the entry side arc radius R _i, to change the delivery side arc radius R _o As a result of changing the shell restraint level on the roll exit side and testing the influence of the exit profile on the circumferential shear strain, when the gorge was set at a position 70 mm inward from the mill center, the roll exit side It was found that changing the profile did not reduce the circumferential shear strain.

  FIG. 5 is a diagram showing the influence of the gorge position on the circumferential shear strain. This figure shows the circumferential shear strain when the gorge is set at the mill center. FIG. 5A shows the profile A, FIG. 5B shows the profile B, and FIG. c) shows the relationship between the perforation ratio and the circumferential shear strain in the case of profile C when the tilt angles are 7 °, 9 °, 11 °, and 13 °. The shear shear strain in the circumferential direction was reduced in all profiles as compared with the case where the position was set at the 70 mm entry side from the mill center.

  Further, as the shell restraint on the roll exit side is stronger, the reduction rate of the circumferential shear strain is larger, about 4 to 12% for profile A, about 9 to 23% for profile B, and about 19 to 36% for profile C. It has become. Therefore, it was found that the absolute value of the circumferential shear strain is smaller as the profile of the shell restraint on the roll exit side is stronger.

  As described above, when the gorge position is set so that the deviation width from the mill center is 10% or less of the roll length, the circumferential shear strain is smaller than when the gorge position is set to the position on the entry side from the mill center. Decrease. Moreover, when the gorge position is set so that the deviation width from the mill center is 10% or less of the roll length, the circumferential shear strain becomes smaller as the profile of the shell restraint on the outlet side is stronger.

  Furthermore, when the gorge position is set so that the deviation width from the mill center is 10% or less of the roll length, the outer diameter of the shell perforated under the same conditions as compared with the case where the gorge position is set to the entry side position from the mill center. And the wall thickness is reduced, and as a result, the value of D (outer diameter) / T (wall thickness) with respect to the perforation ratio is increased. Therefore, when changing the gorge position, it is necessary to set appropriate drilling conditions in consideration of the rolling conditions of the rolling mill after the piercer mill.

  The reason why the shear strain in the circumferential direction is reduced when the gorge position is set so that the deviation from the mill center is 10% or less of the roll length as compared with the case where the gorge position is set at the entry position from the mill center. Although it is not clear, by reducing the deviation width of the gorge from the mill center, the compressive horizontal component force received from the roll on the cross section of the drilled material decreases, and the tensile horizontal component force increases. Since the pipe expanding action to the perforated material is increased and the outer diameter of the shell is increased, there is a possibility that the circumferential flow of the metal could be alleviated.

Hereinafter, the present invention will be specifically described with reference to examples.
When drilling SUJ2 billet using barrel type piercer roll with outer diameter of 1000mm, length of 700mm, inlet side radius of 1000mm, outlet side radius of 3000mm, the gorge position of the roll is conventionally mill center as shown in Table 1 To 70 mm inward. Therefore, the conventional gorge position was set to 90 mm, 80 mm, 70 mm, 60 mm, 50 mm entry side, mill center, 50 mm, 60 mm, 70 mm, 80 mm, 90 mm exit side from the mill center, and the roll inclination angle and perforation ratio were changed. Billets were perforated under conditions. As a result of investigating the circumferential shear strain, when the deviation width of the roll gorge from the mill center is set to 10% or less of the roll length, the circumferential shear strain is reduced by about 15% compared to the conventional case. I understood.
In addition, the circumferential shear strain is

  As described above, as can be seen from Table 1, by setting the gorge position so that the deviation width from the mill center is 10% or less of the roll length, the tube expansion action on the drilled material is increased. By expanding the material to be drilled, the circumferential flow of the metal can be reduced. In particular, it becomes prominent by making the profile of the shell restraint on the roll exit side strong, and as a result, it is possible to reduce the circumferential shear strain, to reduce the rate of inner surface flaws, and to improve quality and yield. It is possible to provide a barrel-type piercer roll that is extremely advantageous in industry.

It is an upper surface sectional view of a barrel type piercer mill. It is front sectional drawing of a barrel type piercer mill. It is a figure which shows a piercer setup state. It is a figure which shows the influence of the roll exit side profile which acts on the circumferential direction shear strain. It is a figure which shows the influence of the gorge position which acts on the circumferential direction shear strain. It is a figure which shows the conventional barrel type piercer roll profile.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Piercer roll 2 Plug 3 Piercer mandrel 4 Billet 5 Roll shaft 6 Guide shoe 7 Pusher 8 Gorge part 9 Roll entrance side 10 Roll exit side X Billet diameter Y Gorge interval Z Plug diameter


Patent Applicant Sanyo Special Steel Co., Ltd.
Attorney: Attorney Shiina

Claims (2)

Barrel type piercer roll for reducing circumferential shear strain, characterized in that when piercing a billet using a barrel type piercer roll, the deviation width from the mill center at the gorge position is 10% or less of the roll length. . The barrel type piercer roll for reducing circumferential shear strain according to claim 1, wherein the profile of the shell on the roll exit side is strong.

Images