JP4615432B2 - Barrel type piercer roll to prevent the occurrence of internal flaws - Google Patents

Description

  The present invention relates to a barrel-type piercer roll that prevents the occurrence of internal flaws.

  In general, in piercing and rolling of seamless steel pipes, piercing and rolling are performed using a piercer mill. FIG. 2 is a top view of the barrel-type piercer mill, and FIG. 3 is a front sectional view of the barrel-type piercer mill. As shown in FIG. 2 or 3, 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 roll 1 has a linear shape with the gorge portion 8 at the top, and the billet 4 advances while rotating. For this reason, when the billet 4 is perforated by alternately pulling and compressing forces inside the billet 4, circumferential shear strain, which is one of the causes of the occurrence of internal flaws, is generated. Reference numeral 5 is a roll shaft, and 6 is a guide shoe.

Further, as disclosed in, for example, Japanese Patent Publication No. 60-59042 (Patent Document 1), by using a cone-type piercer roll and optimizing the combination of the inclination angle and the crossing angle, the outer surface twist of the shell. It has been proposed that circumferential shear deformation can be suppressed and generation of outer surface defects and inner surface defects can be prevented.
The barrel-type piercer roll has a barrel shape with a maximum diameter at the center of the roll, whereas the cone-type piercer roll has a conical shape with a diameter increasing from the roll entry side to the exit side.

Japanese Patent Publication No. 60-59042

On the other hand, FIG. 4 is a diagram showing a conventional barrel-type piercer roll profile. As shown in FIG. 4, the barrel type piercer roll 1 has a barrel shape, and the gorge portion 8 is the apex at the center of the roll, and the same or different angles on the entrance side 9 and the exit side 10 of the roll. θ _i and θ ₀ are given. If the angle θ _i on the roll entry side is increased, 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.

  The use of the conventional cone-type piercer roll as described above is very effective in 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. Further, the barrel-type piercer roll for preventing the occurrence of internal flaws has not been disclosed so far.

  In order to solve the above-mentioned problems, the inventors have intensively developed, and as a result, the outer diameter constraint of the shell near the gorge on the roll exit side can be strengthened by changing the roll profile from a straight line to a curved line. it can. As a result, by suppressing the outer diameter expansion of the shell and increasing the advanced speed of the shell, the flow of the metal in the circumferential direction can be suppressed, and the generation of inner surface flaws that can reduce the shear strain in the circumferential direction can be generated. A barrel-type piercer roll that can be prevented is provided.

The gist of the invention is that
(1) When drilling a billet using a barrel-type piercer roll, the profile of the barrel-type piercer roll is composed of curves with different radii on the roll entry side and the exit side, and the two curves have the same tangent at the gorge A barrel-type piercer roll that prevents the occurrence of internal flaws characterized by this.

(2) In the above (1), when drilling a billet using a barrel-type piercer roll, the curves on the inlet side and the outlet side of the profile of the barrel-type piercer roll are conditional expressions (1) to (3). A barrel-type piercer roll that prevents the occurrence of internal flaws characterized by satisfying
0.5DR ≦ Ri ≦ 3.0DR (1)
1.0DR ≦ Ro ≦ 4.0DR (2)
Ri ≦ Ro (3)
However, DR: Roll outer diameter
Ri: Roll entrance radius curve
Ro: roll exit curve radius

(3) The inner surface according to ( 2 ) above, wherein the roll profile is set to roll entry side curve radius Ri: 0.6DR to 2.0DR, and roll exit side curve radius Ro: 1.1DR to 3.0DR. It is in a barrel-type piercer roll that prevents wrinkles.

  As described above, according to the present invention, it is possible to prevent the occurrence of defects on the inner surface, and to produce extremely excellent effects that can contribute to quality improvement and yield improvement.

The present invention will be described in detail below with reference to the drawings.
FIG. 1 is a view showing a barrel type piercer roll profile according to the present invention. As shown in FIG. 1, the roll shape is barrel-shaped, and the roll entry side 9 and the roll exit side 10 have constant curves with the gorge portion 8 at the top in the center of the roll. That is, the roll entry side 9 and the roll exit side 10 are respectively curved with different radii, and the two curves are connected so as to have the same tangent at the gorge portion 8. When the roll outer diameter is DR, the roll entrance curve radius is Ri, and the roll exit curve radius is Ro, 0.5DR ≦ Ri ≦ 3.0DR (1)
1.0DR ≦ Ro ≦ 4.0DR (2)
Ri ≦ Ro (3)
, Ri and Ro are defined so as to satisfy the conditions (1) to (3) of this equation.

  If the roll entrance curve radius Ri is less than 0.5DR, billet biting failure occurs. Further, when Ri exceeds 3.0DR, the rotational forging effect becomes too large, and the number of inner surface flaws increases, so the range is set to 0.5 to 3.0DR. Desirably, it is set to 0.6 to 2.0DR.

If the roll exit curve radius Ro is less than 1.0DR, the outer diameter constraint of the shell in the vicinity of the gorge on the roll exit side is not sufficient, and the rate of occurrence of inner surface flaws is not improved. Moreover, if it exceeds 4.0DR, the outer diameter restraint of the shell in the vicinity of the gorge on the roll exit side is too strong, and conversely hinders the advancement of the shell, and the rotational forging effect on the roll entry side increases, generating internal flaws. Since the number ratio increases, the range is set to 1.0 to 4.0 DR. Desirably, it is 1.1-3.0DR.
Furthermore, Ri ≦ Ro is set because when Ri is larger than Ro, the advanced speed of the shell becomes larger on the roll entry side than on the roll exit side, and the advance of the shell stagnates on the gorge exit side. Since the effect is increased, internal flaws occur, so Ri ≦ Ro.

  As described above, by changing the roll profile from a straight line to a curved line, the outer diameter constraint of the shell near the gorge on the roll exit side is strengthened. As a result, by suppressing the outer diameter expansion of the shell and increasing the advanced speed of the shell, the circumferential flow of the metal can be suppressed and the shear strain in the circumferential direction can be reduced.

Hereinafter, the present invention will be specifically described with reference to examples.
Using a barrel type piercer roll having an outer diameter DR: φ1000 mm and a length of 700 mm, the roll entry side curve radius Ri and the roll exit side curve radius Ro are variously changed, and the perforation ratio is 1.4, 1.8,2. Table 1 shows the rate of occurrence of inner surface flaws when 20000 SUJ2 billets with a diameter of 120 mm, which were changed to 2 and 2.6, were drilled. As a result, looking at the rate of occurrence of inner surface flaws for each perforation ratio, in the case of a perforation ratio of 1.4, a pass of 0.23% or less was accepted, and a product exceeding 0.23% was rejected. Displayed with ×. Similarly, in the case of a perforation ratio of 1.8, a case where 0.24% or less is passed is indicated as ◯, and a case where the ratio exceeds 0.24% is indicated as a failure X, and in the case of a perforation ratio of 2.2, 0 is displayed. .26% or less is accepted as ◯, and those exceeding 0.26% are indicated as unacceptable ×, and in the case of a perforation ratio of 2.6, 0.30% or less is accepted as ○, 0.30 Those exceeding% were judged as rejected x.

  As shown in Table 1, no. Nos. 1 to 5 are examples of the present invention. 6 to 10 are comparative examples. Comparative Example No. 6 is a case where the roll exit curve radius Ro is less than 1.0DR. In this case, the outer diameter constraint of the shell in the vicinity of the roll exit gorge is not sufficient, and the inner surface flaw occurrence rate was not improved. Comparative Example No. No. 7 is a case where the roll entrance curve radius Ri exceeds 3.0DR and Ri is larger than Ro. In this case, the rotational forging effect becomes too great, and the number of inner surface flaws increased.

Comparative Example No. 8 is a case where the roll exit curve radius Ro exceeds 4.0DR. In this case, the outer diameter restraint of the shell in the vicinity of the gorge on the roll exit side is too strong, and on the contrary, the advance of the shell is hindered. The rotational forging effect on the entry side increased, and the number of inner surface flaws increased. Comparative Example No. No. 9 is a case where the roll entrance curve radius Ri is less than 0.5DR, and in this case, a billet biting failure occurred. Comparative Example No. 10 is a case where the roll profile is a straight surface angle of θ _i = θ ₀ = 3.5 °, and in this case, the rate of occurrence of inner surface flaws is not improved.

  On the other hand, the present invention example No. Nos. 1 to 5 satisfy all the conditions of the present invention. Compared with 6 to 10, good results were obtained with a smaller number of inner surface flaws. As described above, according to the present invention, it is possible to prevent the occurrence of defects on the inner surface as compared with the prior art, and as a result, it is extremely useful industrially that can improve the quality and the yield. .

It is a figure which shows the barrel type piercer roll profile which concerns on this invention. It is a top view of a barrel type piercer mill. It is front sectional drawing of a barrel type piercer mill. It is a figure which shows the conventional barrel type piercer roll profile.

Explanation 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 entry side 10 Roll exit side


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

Claims (3)

When drilling a billet using a barrel-type piercer roll, the profile of the barrel-type piercer roll is composed of curves with different radii on the roll entry side and the exit side, and the two curves have the same tangent at the gorge A barrel-type piercer roll that prevents the occurrence of internal flaws. In Claim 1, in drilling a billet using a barrel-type piercer roll, the curves on the roll entry side and the exit side of the profile of the barrel-type piercer roll satisfy the conditional expressions (1) to (3). A barrel-type piercer roll that prevents the occurrence of internal flaws.
0.5DR ≦ Ri ≦ 3.0DR (1)
1.0DR ≦ Ro ≦ 4.0DR (2)
Ri ≦ Ro (3)
However, DR: Roll outer diameter
Ri: Roll entrance radius curve
Ro: Roll exit curve radius The occurrence of inner surface flaws according to claim 2 , wherein the roll profile is set to roll entrance curve radius Ri: 0.6DR to 2.0DR and roll exit curve radius Ro: 1.1DR to 3.0DR. Barrel type piercer roll to prevent.

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