JPS63268504A - Cold rolling method for tube - Google Patents

Abstract

PURPOSE:To improve the dimensional accuracy and productivity of products by installing tilt rolling mills into tandem and rolling a stock by setting a roll tilt angle of the downstream side mill to be larger than that of the upstream side mill. CONSTITUTION:Tilt rolling mills 1, 2 are installed into tandem and tilt rolls 10, 20 are tilted by prescribed angles of beta1, beta2 to the pass line X-X of a tube P, respectively. Further, plugs 11, 21 are arranged so as to align their axial line with the pass-line X-X. At this time, the angle beta2 is set to be larger than the angle beta1 and the tilt angle of downstream side rolls is set to be sequentially larger than that of upstream side rolls. At the time of rolling a stock with the outside diameter and the number of rotations of the rolls 10, 20 are equal to each other, rolling speeds sequentially increase toward the downstream side, so that rolling with a large stretch ratio is performed. Hence, both the dimensional accuracy and productivity are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of cold elongation rolling of a pipe using an inclined rolling mill.

[Prior art] Seamless pipes are used in a wide range of applications such as mechanical structures, heat exchangers, and oil country tubular goods. Strict precision may be required. Seamless pipes used for such purposes are produced by forming pipes in a hot pipe-making process such as the Mannesmann pipe-making method, and then further performing cold finish forming.

Now, when forming a seamless pipe in the cold, a method using cold drawing is generally used, but this method may not be able to fully satisfy the above-mentioned requirements for accuracy. Therefore, in order to obtain a seamless pipe with excellent surface accuracy and dimensional accuracy and straightness, three inclined rolls that are inclined at a predetermined angle with respect to the pass line of the pipe that is the rolled material and the pass line between the rolls are used. Using an inclined rolling mill equipped with a plug arranged so that its axis coincides with the line, the tube is inserted into the inside of the tube while being spirally moved along the pass line by rotation of the inclined roll. A method has been put into practical use in which a predetermined reduction is applied between the plug and an inclined roll to elongate and roll the pipe (trade name: Fl).

-F 1nisher, USA Lodge & 5hi
play company 11).

(Problems to be Solved by the Invention) However, when performing cold elongation rolling of pipes using the above-mentioned inclined rolling mill, while there is a corresponding effect in improving each of the precisions mentioned above, Since the coefficient of friction between the tube and the inclined roll is small, there is a risk of slipping between the two and causing flaws on the outer circumferential surface of the tube, compared to when this is done hot. The stretching ratio (cross-sectional area of the pipe before rolling / cross-sectional area of the pipe after rolling) has to be set significantly smaller,
It is necessary to repeat multiple passes to obtain the required molding amount, and the setup for each pass takes a lot of time.
The rolling method has the disadvantage of low production efficiency.
The reality is that it has not been widely used.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for cold rolling a pipe that makes it possible to manufacture a pipe with excellent surface accuracy, dimensional accuracy, and straightness at high production efficiency. With the goal.

[Effect]

In the present invention, the rolled material tube is moved in the juxtaposed direction between a plurality of inclined rolling mills, each roll being set such that the angle of inclination increases as it reaches the downstream side in the juxtaposed direction. At the same time, a predetermined rolling reduction is sequentially applied in each inclined rolling mill to form a tube having predetermined dimensions.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on drawings showing embodiments thereof. FIG. 1 is a front view of an inclined rolling mill equipped with two stands used for carrying out the method of cold rolling pipes according to the present invention (hereinafter referred to as the method of the present invention) from the upstream side in the direction of movement of rolled material;
2 is a side sectional view taken along the line nn in FIG. 1, and FIG. 3 is a sectional view taken along the line ■-■ in FIG. 1 for explaining the inclination angle.

In the figure, reference numeral 1.2 denotes a stand, and the stand 1 has an approximately truncated conical inlet surface 10b and an outlet surface 1 on both sides of a gorge portion 10a, which is the maximum diameter portion, and whose diameter gradually decreases toward the end.
0c and three inclined rolls 10, 10, and 10 that are barrel-shaped as a whole, and a plug 11 that is cylindrical.
X-X indicated by a dashed line in the diagram
The line is the pass line of the pipe P, which is the rolled material, and is the intersection O (roll setting center) of the inclined roll 10. are located equidistantly on a circumference having a center on the pass line X-X and perpendicular thereto, and the pass line X-
It is arranged to be inclined by a predetermined inclination angle β1 (see FIG. 3) with respect to None. On the other hand, the plug 11 has its axis aligned with the pass line XX, and the inclined roll t
It is fixed to the plug rod R extending along the pass line XX in a state where it is positioned between o, to, and to, and rotates with the rotation of the rod R around its axis. There is no such thing.

The stand 2 is disposed at an appropriate distance downstream in the rolling direction from the stand 1 having the above-mentioned configuration, and is spaced apart from the stand 1 by an appropriate length in the rolling progress direction.
Inclined rolls 2G, 20.2 each having substantially the same shape as 1;
0 and a plug 21. Inclined roll 2G
, 20.20 is inclined at a predetermined inclination angle β2 with respect to the pass line XX, as shown in FIG.
10. The inclined rolls 1 are positioned between 10 and 10, respectively.
0.10.10, and the plug 21 is
It is fixed to the tip of the plug rod R in the same way as the plug 11.

The pipe P, which is the rolled material, is fed from the stand l side with its axis aligned with the pass line XX, and is passed through the entrance surface 10b of the inclined roll 10.
After being caught between 10b and 10b, due to the friction between the three inclined rolls 10, 10, and 10 that rotate at an angle of inclination β1, it moves in the direction shown by the white arrow in FIG. A predetermined amount of force is applied between the plug 11 and the inclined roll 10.10゜O, which is screwed along the pass line XX and penetrated into the axial center position of the plug 11. The inclined rolls 20, 20, 20, 20, 20, 20.
A predetermined reduction is applied between the tube 20 and the plug 21, and the tube is further stretched and then taken out as a tube having a predetermined size.

Now, the rolling speed of the pipe P in the stand 1 or the stand 2, that is, the component v1 or vl in the pass line XX direction of the speed of the forward movement of the pipe P is the inclined roll 10.10.
．． 10 or the inclined roll 20, 20, or 20 from the component v1 or vl of the circumferential velocity in the pass line XX direction, respectively, by the following formula.

Vl = CI ・vl - (1) V2 = C2
-V2 - (21 However, C is a constant determined within the range of 0.8 to 1.2 depending on the surface condition of the inclined roll IO or the inclined roll 20 and the stretching ratio in the stand 1 or stand 2. Also, the above v1 or vl is calculated from the geometric relationship in the inclined roll lO or the inclined roll 20 by the following equations.

Vl=π・DI ・N1 ・sin β1− (3
) vl ; π・D2 ・N2 +sin β2 −
(4) However, Dl: Maximum outer diameter D2 of inclined roll lO
: pJ Maximum outer diameter N1 of the inclined roll 20 : Number of rotations N2 of the inclined roll 10 : Number of rotations of the inclined roll 20 From equations (1) and (3), or from equations (2) and (4), stand The rolling speed v1 in stand 1 or the rolling speed v2 in stand 2 is the following (5) 2 or (6), respectively.
Calculated by the formula.

-VI-(g ・g ・Dl −N1 ・sinβ
, ・(51V2 = C2・fE ・D2 ・N2
・sin β2 ・+61 On the other hand, as a result of stretching and rolling performed at a predetermined stretching ratio in the stand 1, the length in the axial direction of the pipe P on the exit side of the stand 1 is larger than that on the input side. When the rolling speed v2 in the stand 2 is made equal to the rolling speed v1 in the stand 1, the inclined rolls 2o in the stand 2 act to prevent the tube P from advancing. Therefore, the rolling speed v2 is vl
It needs to be larger than. By the way, from the above formulas (5) and (6), the rolling speed V2 is V.

As a means to make the outer diameter D2 of the inclined roll 20 larger than
A first means for making the outer diameter of the inclined roll 10 larger than the outer diameter of the inclined roll 10, a second means for making the rotation speed N2 of the inclined roll 20 larger than the rotation speed N of the inclined roll 10, and the inclined roll 20.
The inclination angle β2 at the inclination roll lO is the inclination angle β2 at the inclination roll lO
It is clear that there is a third way to make it greater than 1. However, when the first means or the second means is used, the component u2 of the circumferential velocity of the inclined roll 20 in the direction orthogonal to the pass line XX is also the same component u of the inclined roll lO.
As a result, a force that twists the pipe P between the stand 1 and the stand 2 about its axis acts on the pipe P and the inclined roll to, to, to or incline. There is a possibility that slippage may occur between the rolls 20, 20, and 20, and scratches may occur on the outer peripheral surface of the pipe P obtained as a product. Therefore, in the method of the present invention, the inclination angle β2 is made larger than the inclination angle β1 while the outer diameter D2 and rotation speed N2 of the inclination roll 20 are kept equal to the outer diameter D1 and the rotation speed N1 of the inclination roll 10, respectively. In other words, by the third method, the rolling speed v2 is set higher than the rolling speed v1.

Now, the speeds ul and ul can be determined by the following equations, respectively, based on the geometrical relationship between the inclined rolls 10 and 20.

ul xg I Dl -N1 ・
cos β 1 − (71u2 = t
t-D2 -N2 -cos β2 (8) For example, if the inclination angle β1 is set to the minimum 5° under normal working conditions, and the inclination angle β2 is set to the maximum 15°, the explanation will be simplified. Therefore, if CI = 02 in the above equations (5) and (6), the rolling speed v2 in stand 2 and the rolling speed v1 in stand 1 are calculated by these two equations.
The ratio is V2 /Vl -5in 15°/sin
5°I=I2.97, whereas the ratio of the speed u2 to ul is ul /ut −cog 15@/co
s5' = 0.97, and even when the rolling speed v2 in stand 2 is approximately three times the rolling speed v1 in stand l, there is almost no difference between ul and ul, and the present invention According to the method, it is clear that there is no risk of the above-mentioned flaws occurring.

The inclination angle β2 of the stand 2 is determined by the following formula based on the inclination angle β1 of the stand 1 and the stretching ratio E1 of the stand 1.

β2≧E1 ・β1 ...(9) As mentioned above, C
1-02, the inclination angle β2 determined by the above equation (9) is the inclination roll 20, 20.20 of the stand 2.
By setting respectively, stand 1 and stand 2
A tensile force is applied to the pipe P between the two in the axial direction, or rolling proceeds in a state where the tensile force becomes zero. - In this example, the case where elongation rolling is carried out using two stands has been explained, but it goes without saying that the method of the present invention can be applied even when two or more stands are provided, and in that case, The second section of inclination angle in the i-th stand from the most upstream side in the rolling direction is:
It may be determined by the following equation 00, which is similar to equation (9) above.

β1≧Ei−1”β, −, −(II In addition, the shape of the inclined roll 10.20 is not limited to the barrel shape shown in this embodiment, but may be other shapes such as a cone shape. .

Finally, an example in which a tube was elongated and rolled according to the method of the present invention using a rolling mill equipped with two stands shown in FIGS. 1 to 3 will be described.

In the following example, the inclination angle β1 in the stand 1
5°, and the stretching ratio E, is the inclined roll 10.10.1
0 and the pipe P, the inclination angle β2 of the stand 2 was set variously within the range of 5° to 7.5°, and the stretching ratio was variously set at each set angle. The working degree (the value obtained by subtracting the reciprocal of the stretching ratio from 1) when slipping occurs in stand 1 or stand 2 during rolling by carrying out stretch rolling is set as the limit working degree and corresponds to each of the above-mentioned set angles. I compared it.

(Example 1) Material of rolled material JIS 5US304 Dimensions of rolled material
Outer diameter 195g + Wall thickness 2.0ms + Stretching ratio at stand 1 1.37 (Example 2) Material of rolled material JIS 5US316 Dimensions of rolled material
Outer diameter: 25.4+n+ Wall thickness: 1.8mm Stretching ratio in stand 1: 1.27 Figures 4 and 5 show:
This is a graph showing the results of Examples 1 and 2, respectively, with the horizontal axis representing the inclination angle β2 of the stand 2, and the vertical axis representing the limit machining degree as a percentage. These figures are from Example 1. In any of the second embodiments, the limit machining rate increases as the inclination angle β2 increases, and the inclination angle β2 is approximately 6.7 in the first embodiment.
°, and in Example 2 approximately 6.3 °
It is shown that the increase in the limit machining rate is saturated when .

On the other hand, when calculating the inclination angle β2 to be set in Example 1 or Example 2 using the above formula (9), in the case of Example 1, β2≧1.37X5'6.85', and Example 2 In the case of β2≧1.27X 5' −6,35, the inclination angle β2 calculated by the above equation (9)
It can be seen that a sufficient degree of machining can be obtained by setting .

(Effects) As described in detail above, the method of the present invention involves arranging a plurality of stands of an inclined rolling mill in tandem, each having an inclined roll and a plug, and setting the inclination angle of the inclined roll in each stand in the direction of rolling progress. By making the inclination angle larger than that of the upstream stand, under a large draw ratio,
Since it is possible to stretch-roll a pipe in the cold, the method of the present invention makes it possible to manufacture a pipe with excellent surface accuracy, dimensional accuracy, and straightness at high production efficiency. It has a great effect.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention, and FIG. 1 is a schematic front view showing the implementation state of the method of the present invention, and FIG.
FIG. 3 is a cross-sectional view taken along the line mm in FIG. 1, FIG. 3 is a view taken along the line mm in FIG. 1, and FIGS. 4 and 5 are graphs showing the results of implementing the method of the present invention. 1.2... Stand 10.20... Inclined roll 11.21... Plug P... Pipe β1. β2
...Tilt angle patent Applicant Sumitomo Metal Industries Co., Ltd. Agent Patent Attorney Norio Kono No. 1 Argument 4 Σ β2 (Je5) No. 51! l

Claims (1)

[Scope of Claims] A method for cold elongation rolling of a pipe using an inclined rolling mill equipped with one, two or three rolls and a plug, the inclined rolling mills being arranged in tandem, 1. A method for cold rolling a tube, characterized in that rolling is performed with the inclination angle of the rolls in each incline rolling mill being larger than the inclination angle of the rolls in the respective upstream inclination rolling mills.