JPS6167511A - Rolling method of seamless pipe - Google Patents

Abstract

PURPOSE:To elevate the dimensional accuracy of a product and pipe making efficiency by making the number of rolling reduction times for diameter shrinkage within the specified range in the rolling stage equipping a thickness deviation correcting function as well to a piercing and extension function. CONSTITUTION:The number of rolling reduction times for diameter shrinkage is set within the range of 1-15 times in case of rolling a seamless pipe with placing a diameter shrinkage rolling reduction by the rear half part of a roll 11 on the stock 13 to be rolled by plural inclined rolls 11 and a plug 12. Since it is the case of the number of the diameter shrinkage rolling reduction times N being >=1 that the thickness deviation correcting effect is realized on the practical level by the diameter shrinkage rolling reduction work, the low limit value of the number of times N is taken as one. On the other hand the more the number of times N is increased the more the thickness deviation improvement rate is increased and for instance it is necessary to elongate the body length of the roll part III of the roll II so as to make the number of times N in twenty or more in order to secure the thickness deviation improvement rate of >=90%. Also since there is a fear of the reduction in the roll strength against the rolling load it is practical to set an upper limit value on the number of times N and the upper limit value is taken as fifteen based on the fact that the product of high accuracy of never been before can be offered.

Description

[Detailed description of the invention] C technical field] The present invention relates to a method for rolling S-shaped pipes.

[Background technology] As a method of manufacturing seamless pipes using the pressure feeding method.

Typical examples are the Mannesmann mandrel mill system mainly for small-diameter sizes and the Mannesmann plug mill system mainly for medium-diameter sizes.

The dimensional accuracy of the pipe is greatly influenced by the settings of rolling conditions in each process in those methods, centering of tools, wear management, heat uniformity of the material, etc. - For example, a pair of barrel-shaped rolls 1 are arranged left and right or above and below, and a piercing plug 2 is set at an intermediate position of the barrel-shaped rolls 1, as shown in FIGS. 2 and 3. 3 is a guide shoe, 4 is a perforated raw pipe, 5
is a round billet before drilling, 6 is a mandrel that supports the plug 2, <-, the mandrel par 6 has one end tied to the thrust block 7 side, and the other end supports the plug 2, It is a kind of cantilever beam. Therefore, the drilling plug 2 tends to deviate from the center position l between the rolls during drilling, resulting in uneven wall thickness of the rolled blank pipe 4. O.T.
Although this is an inevitable phenomenon, if the amount of uneven thickness exceeds a predetermined standard value, the quality of the pipe material will be degraded, and the yield of the product will be significantly impaired. On the other hand, recently, hollow reducers
Alternatively, a rolling method called an eco-alyzer has been proposed in which a rolling IA process is added for the purpose of correcting uneven thickness in the next step of the drilling process (for example, JP-A-57-88207).
Although this method plays a role in improving dimensional accuracy, it has the disadvantage of increasing the number of steps compared to the conventional pipe manufacturing process.

On the other hand, the hollow reducer is installed in one inclined rolling mill.
For example, on page 128 of ``Mounted Plastic Working'' (edited by Hiroshi Suzuki, published by Shokabo in July 1929), there is a rolling method that includes a rolling process similar to that of Mannesmann type. It is clearly stated that one of the perforation methods is a pipe-making method in which another conical portion is provided on the exit side of a barrel-shaped roll to reduce the outer diameter. Further, as a recent patent application example, Japanese Patent Laid-Open No. 57-81908 also proposes an inclined rolling method equivalent to the above-mentioned pipe manufacturing method. The rolling methods shown in the two examples cited above have the following problems in their specific implementation. In other words, (a) selection of an appropriate amount of reduction in the outer diameter of the pipe material, (b) appropriate setting of the number of machining operations to be applied when reducing the outer diameter of the pipe material as it moves forward while rotating in a spiral pattern, and (C) selection of the appropriate amount of reduction in the outer diameter of the pipe material. The proper shape of the roll part, etc. is not clear, making it difficult to obtain more stable operational improvement effects.

In other words, in the inclined rolling method, the pipe material is not rotated but is subjected to crimping. Even under the external pressure iIt, the improvement effect targeted in U) differs depending on the coal shape, rolling settings, etc. The inventor has discovered an appropriate range of implementation in which the rough reduction in diameter at the rear end of the inclined roll as described above brings about significant effects such as improvement in dimensional accuracy and improvement in rolling efficiency. I have discovered something.

[Object of the Invention] The present invention provides a rolling process in which the perforation and stretching machine parts have a thickness correction function. It is an object of the present invention to provide a method for rolling a meshless tube with excellent rolling strength and W-response efficiency.

[Structure of the Invention] In order to achieve the above object, the present invention provides a method for rolling a wireless pipe in which a material to be rolled that is rolled by a plurality of inclined rolls and plugs is subjected to diameter reduction in the latter half of the inclined rolls. , the number of reductions in diameter is set within the range of 1 to 15 times.

[Detailed Description of the Invention] FIG. 1 is a partially cutaway side view showing the rolling state according to the present invention. This makes it possible to apply diameter reduction reduction. 14 is a mandrel bar, and the inclined roll 11 is a conventional barrel-shaped piercer.
Unlike Elongator Roll and Elongator Roll, mainly the roll part (
It consists of four parts: 1) to the roll part ([V').

The rolling mill to which the present invention is applied is equipped with n inclined rolls 11 of two or three or more. Further, the material to be rolled 13 may be either a solid round billet or a hollow round billet.

The crushing method using the #4 protection roll 11 and the plug 12 will be explained below. First, the material to be rolled 13 (solid round billet 7) 13A or hollow round billet 13B) is bitten between the roll portions CI) of the inclined rolls 11, and at the same time rotates in a spiral manner. Hollowing begins at billet ) 13B, hollow round fin, and thinning begins at ) 13B 0
Next, the rolled material 13 is rolled at the roll portion ([
1) and the plug 12, the pipe is stretched to reduce its thickness and at the same time undergo a diameter-increasing (tube expansion) process. Conventional piercers or elongators (both 20-1 type and 30-1 type) finish rolling during these two perforation and stretching processes. In the latter half of the process, it is possible to further perform WJI return outer diameter reduction. That is, the tube material that has undergone perforation and stretching is reduced in outer diameter (1ii diameter reduction) at the call part (III) of the #lI oblique roll 11.
receive. This 1■ Roll part (III) of the oblique roll 11
To explain the deformation behavior of the material, the rolled material 15 that has been perforated and/or thinned by the rolls and plugs rotates forward in a spiral, so that a type of deformation occurs n times per rotation of the rolled material 15. While being pressurized, the outer diameter is reduced according to the gap between the rolls (that is, the diameter is reduced). Here, n is the number of rolls constituting a set of multiple rolls, and in the case of a 20-hole type piercer, n=2. Through this diameter reduction process, the rolled material 1
5 has a tendency to increase, but if there is an uneven thickness in the circumferential cross section of the rolled material 15, the thinner part will yield preferentially, and this thinner part will be separated from the thicker part. Plastic flow of the material occurs. As a result, 1 rolled material 1
The thickness of the parts 5 and 5 can be made equal.

As described above, the mechanism of uneven thickness rolling 1 by the inclined roll 11 and the plug 12 is that the rolled material 15 is rotated during rotation.
In the process of reducing the diameter while being repeatedly compressed during rolling, the thin wall portion of the rolled material 15 with uneven thickness increases preferentially. As a result of studying the appropriate rolling conditions for achieving sufficient effectiveness, it was found that the following factors play an important role. That is, (1) Dimensions of the rolled material before and after diameter reduction (outer diameter or diameter is D) (2) Taper angle of diameter reduction roll part (III) (roll inclination angle α) (3) For diameter reduction IH length (X) of roll part (III) (4)
Smaller roll spacing (E) at the exit roll portion (rV) after diameter reduction (5) Inclination angle (β) of 1lii diameter processing rolls (1)
) are naturally considered as the dimensions of the rolled material 15, (2) and (3) determine the roll shape of the diameter-reduced part, and (4) is directly related to the amount of diameter reduction. It is something to do. (5) is related to the pressure tUff of the rolled material per degree, particularly the forward distance per rotation of the rolled material, and is included in the mill setting along with (4).

Next, we will explain the use of parameters that encompass various factors and can uniformly control the degree of each effect. In FIG. 1, the contact length in the longitudinal direction of the rolled material 15 in contact with the inclined roll 11 for diameter reduction processing is defined as L, and this is defined as the outer diameter of the rolled material 15, the roll spacing E, and the roll surface. When associated with the angle α, equations (1) and (2
) is as follows.

D-E ÷ 2 Ltan a
-(1)L'=D (1-E/D)/[2
tan a] - - (2) Next, the distance #xL that the rolled material 15 advances in one rotation is given by equation (3) where the roll inclination angle β and the rolling (pre-a) efficiency η (%) are given.

XI = (η/100) πDsinβ−(3)
Here, D is the exit outer diameter of the rolled material 15.

From equations (2) and (3), the range of roll contact &L for diameter reduction is determined by the number of rotations Nta when the rolled material 15 is rotated. As mentioned above, In inclined rolling consisting of n roll groups, the number of rolling reductions is one per revolution of the material to be rolled 15, so from the above equation (4), the total number of reductions N that the material to be rolled 15 undergoes is ( 4) n-8 in formula, that is, the following (5)
It is expressed by the formula.

...(5) Note that the roll portion ([II) of the inclined roll 11 is the same as the above (1)
Even in the general case of a curved roll shape that does not have the roll face angle α of the formula ), the roll contact length can be calculated from the geometric relationship between the outer diameter of the rolled material 15 before diameter reduction and the roll shape. Since it is possible to obtain the above apparent roll face angle α from the predetermined outer diameter diaphragm ψ, i.e. diameter reduction pressure j, j, (t − E/D) and equation (2), , the above handling can be applied as is.

Next, the thickness unevenness rate or thickness unevenness improvement rate in the following examples will be explained. First, the thickness unevenness ratio is the average value of the thickness unevenness ratio (cross-sectional thickness unevenness ratio) in each cross section in the longitudinal direction of the rolled material.

Thickness unevenness rate (%) Here, the value in parentheses is the cross-sectional thickness unevenness rate, and the maximum value of wall thickness t (1I
ax) and the minimum value (tn) divided by the average cross-sectional wall thickness ta. j is the number of cross-sectional thickness unevenness ratios determined by 411 in the longitudinal direction of the rolled material. Thirdly, the thickness unevenness improvement rate is the roll portion (I) of the inclined roll 11.

The uneven thickness of the rolled material 15 rolled only by (II) is before improvement, and the uneven thickness of the rolled material subjected to diameter reduction processing in roll parts (m) and (IV) is after improvement. is defined by the following equation (7).

Improving rate of thickness unevenness (%) = - is half in = O, SX in. If so, the uneven thickness improvement rate will be 50% from equation (7).

The results of implementation using the 20-1 method will be explained below.

Figure 4 shows the shadow of the set draft ratio (1-E/D) x 100 (%) for outer diameter drawing, that is, diameter reduction reduction, and the larger the draft ratio, the greater the improvement in uneven thickness.
FIG. 5 shows the influence of the roll surface angle α and the roll inclination angle β, and it can be seen that reducing both angles has the effect of improving uneven thickness. Note that the thickness unevenness rate when the draft rate is 0 is the [raw pipe thickness unevenness rate]. The effects of draft rate, roll face angle, and roll inclination angle are
), and when the data in Figures 4 and 5 are rearranged according to Formula (5), the results are as shown by the symbols in Figure 6, which shows a fairly uniform trend. It is allowed to show.

The shaded part in Fig. 6 (■) is the roll part (m) of the inclined roll 11.
Roll inclination angle (rV) with a sufficiently smooth curve at the end of
In this case, the roll part (II
The bending between I) and (IV) is eliminated, and the rolled material 1
Prevents the occurrence of steps and differences in spiral marks on the surface of 5.
By doing so, the deviation of uneven thickness -V becomes even better. Note that even when the roll arrangement of the inclined rolls 11 is set to 20 mm or more and rolling is performed using a 30 mm method or a 40 mm method, the uneven thickness correction effect is exactly the same as described above.
It has been found that when sorted using the uniform parameter N, the values are displayed within the range ``■'' inside the solid line in FIG.

As is clear from FIG. 6, the effect of correcting uneven thickness by the outer diameter drawing process, that is, the diameter reduction process, is achieved at a practical level when the number N of diameter reduction reductions is 1 or more.
The lower limit of the diameter reduction reduction number in the present invention was set to 1. On the other hand, the rate of improvement in thickness unevenness increases as the number of m-diameter reductions increases. For example, in order to secure an improvement rate of thickness unevenness of 90% or more, the number of reductions in diameter should be approximately 20 or more. The body length of the roll portion (DI) of the inclined roll 11 must also be made longer, and there is a concern that the roll strength against the rolling load will decrease, so it is practical to set an upper limit on the number of reductions in diameter. In the present invention, due to the problem of the strength of the roll,
Also, with reference to information on the dimensional accuracy of rolled materials in rolling with current piercers and elongators, if it is possible to achieve an 80% improvement in thickness unevenness, it is possible to achieve unprecedented high precision in various current pipe manufacturing processes. Based on the ability to provide the product, the upper limit of the number of reductions in diameter was set at 15 times.

Therefore, according to the present invention, since the wall thickness unevenness rate is about 20% at most at the end of the pipe, which is said to have a significant history of wall thickness unevenness, it is possible to improve the wall thickness unevenness by 80%. It is now possible to send the rolled material, which has been improved to a full-body thickness unevenness level of approximately 4% or less, to the next rolling process, making it possible to significantly improve dimensional accuracy, and at the same time, it is possible to improve the dimensional accuracy of the rolled material by reducing the conventional tube end cropping. II) It has the effect of significantly shortening the length and significantly improving the yield.

Further, according to the present invention, in addition to the above effects, the following effects (a), (b), and (C) can be obtained.

(a) Two-point support significantly improves stability against runout of the rolled material during rolling. i.e. conventional drilling,
In the stretching process, the material to be rolled was gripped only at one point near the bone section (maximum roll diameter section) from the roll section (I) to the roll section (■); From (II[) to (IT), the material to be rolled is also subject to grinding, and it is important to reduce the run-out of the material to be rolled and thereby to obtain the effect of preventing uneven thickness.

(b) +iii direction tension EE due to enlargement of exit roll diameter
E), embodying the situation in 4. That is, since the roll diameter is increased over the roll portions (m) to (rV) of the inclined roll 11, the roll circumferential speed is greater than the roll portion (1) (I
I) Become faster. This is equivalent to applying a tensile force to the rolled material from the exit side, and is effective in improving rolling speed and efficiency. Note that, for this purpose, it is advantageous to make the roll shape cone-shaped rather than the conventional barrel-shaped roll because the exit roll diameter can be increased and the roll circumferential speed can be increased.

(C) #4 oblique el-ru lL noel el-ru The roll surface formed by the joint between (II) and (m) has a slight clearance with the rolled material, and the rolled material after thinning drawing It functions as a kind of louver that adjusts the mass balance between the material and the material to be rolled after diameter reduction.

[Effects of the Invention] As described above, the present invention provides a seamless pipe rolling method in which a material to be rolled that is rolled by a plurality of inclined rolls and a plug is subjected to diameter reduction in the latter half of the inclined rolls. The number of times is set within the range of 1 to 15 times. Therefore, it is possible to improve dimensional accuracy and pipe-making efficiency in a rolling process that has a punching and stretching function as well as a thickness correction function.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway side view showing an example of a rolling state according to the present invention, FIG. 2 is a side view showing a conventional rolling state, and FIG.
The figure is a cross-sectional view taken along line m-m in Figure 2, Figure 4 is a line diagram showing the relationship between draft rate and thickness unevenness rate, and Figure 5 is a diagram showing the relationship between draft rate and thickness unevenness rate. FIG. 6 is a diagram showing the relationship between the uneven thickness correction rate and the number of diameter reduction reductions. 11... Inclined roll, 12... Plug, 13...
Rolled material. Agent Patent Attorney Osamu Shiokawa Figure 1 □-112 Figure 2 Figure 3 Figure 4 Draft rate, (1-E/D) x 100 ('/,
) Figure 5

Claims (1)

[Claims] (1) In a seamless pipe rolling method in which the material to be rolled is rolled by a plurality of inclined rolls and plugs, the diameter reduction is applied in the latter half of the inclined rolls, and the number of diameter reduction reductions is 1 to 15 times.
A method for rolling a seamless pipe, characterized in that the rolling method is set within a range of times.