JP2643369B2 - Inclined roll elongation rolling method of metal tube and inclined roll - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is adopted in a Mannesmann pipe manufacturing method which is a typical method for manufacturing a seamless metal pipe, and is an inclined roll type elongation rolling using a mandrel bar as an inner surface regulating tool. The present invention relates to an elongation rolling method using a mill and an inclined roll thereof.

[Conventional technology]

In general, a seamless metal pipe made by a plug mill rolling method in the Mannesmann pipe manufacturing method first passes a heated round steel slab through a piercer, drills a hole in the center thereof to obtain a hollow shell, and expands the hollow shell through an elongator as necessary. It is manufactured by diameter rolling and elongation rolling by a plug mill in order to obtain a certain wall thickness and outer diameter, followed by polishing, shape correction and sizing by a reeler and a sizer, and a refinement process.

By the way, as an elongation rolling mill instead of the plug mill for performing the above elongation rolling, a barrel-shaped rolling roll similar to the piercer or elongator in which the axis is inclined with respect to the hollow shell pass line (hereinafter referred to as an inclined roll)
And a mandrel bar in combination with an inclined roll type elongation mill. As shown in FIG. 7, the inclined rolls of this elongation mill have a frustoconical entry side T whose diameter is reduced in the upstream direction of the pass line P, and are reduced in diameter in the downstream direction of the pass line P. It is formed of an outlet side S having a truncated cone shape, and a substantially cylindrical reeling portion R between the inlet side T and the outlet side S.

The conventional skew rolls A, B are those surface angle alpha _R for pass line P of the reeling portion R becomes 0 °, and the side portion S out with the reeling portion R are flush Or the surface angle α _R of the reeling portion _R and the surface angle α _{L of the} exit side portion S
There was no limitation on the relationship between the angle and the angle. For example, the reference “Iron and Steel Engineer” 1986.6 P
36-42 `` ACCU-ROLL: A new type of seamless tube m
ill ”, α _R = 0 °, 1.5 ° ≦ α _L ≦ 2.5 °.

[Problems to be solved by the invention]

However, the conventional inclined rolls A as described above, the B, so that the surface angle alpha _L side S out to the surface angle alpha _R reeling portion R, as it is, the inclined rolls A, stretched rolled by B Reflected in the thickness distribution of the metal tube (hollow shell H), since the metal tube is rotated and fed, the outer peripheral surface of the reeling portion R of the inclined rolls A and B is uniformly formed on the outer peripheral surface of the metal tube. 6, the inner peripheral surface of the metal tube whose outer periphery is rolled at the outlet side portion S has a spiral thickness distribution in which an acute-angled uneven shape is generated as shown in FIG. there were.

In order to solve this problem, for example, those disclosed in Japanese Patent Application Laid-Open No. 60-206514, Japanese Patent Application No. 62-175745, and Japanese Patent Application No. 30
There is one described in No. 1096. Japanese Unexamined Patent Publication No. 60-206514 discloses an inclined roll rolling method using a plug as an inner surface tool, in which a material thickness after rolling is measured to obtain a thickness unevenness ratio, and a target thickness unevenness ratio is obtained. In this manner, the crossing angle and the inclination angle of the inclined roll with respect to the pass line are adjusted.

In addition, what is described in Japanese Patent Application No. 62-175745 is a spiral mark on the inner peripheral surface of a metal tube caused by a spiral wall thickness distribution of a metal tube after rolling in an inclined roll elongation rolling method using a mandrel bar as an inner tool. By changing the crossing angle of the inclined roll with respect to the pass line so as to minimize the height (SM in FIG. 7), the surface angle of the reeling portion is adjusted to obtain a seamless metal pipe having a small uneven thickness. is there.

Further, the one described in Japanese Patent Application No. 62-301096 discloses a method in which a plate guide shoe type two-roll oblique stretching rolling method using a mandrel bar as an internal tool is used to adjust the height of the spiral mark of the material after rolling. Measure and adjust the surface angle of the plate and guide shoe (the angle of inclination of the plate and guide shoe with respect to the pass line) and the interval so that the height of the spiral mark is minimized, and bias the spiral mark to a minimum. It is a method to obtain a seamless metal tube with small meat.

However, in the above-mentioned rolling methods, all require a measuring device for the thickness of the material after rolling or the height of the spiral mark, and these devices are precise devices obtained by the advancement of measuring technology in recent years. However, there has been a problem that costs and personnel are required to maintain the stable operation.

Also, in order to change the crossing angle or the inclination angle of the inclined roll with respect to the pass line, means such as a hydraulic device such as a roll chock must be installed. Higher machine prices,
There was a problem that increased production costs such as maintenance and repair costs and an increase in personnel. Further, there is a similar problem in adjusting the surface angle and the interval of the plate and the guide shoe.

The present invention has been made in view of the above problems,
Limiting the surface angle of the reeling portion and the exit side surface angle with respect to the pass line of the inclined roll, and further providing an auxiliary reeling portion in which the roll radius changes smoothly between the reeling portion and the exit side portion, By limiting the length of the auxiliary reeling part, a metal pipe with good dimensional accuracy can be obtained without the occurrence of a spiral thickness distribution with sharp irregularities in the drawn and rolled metal pipe when the hollow shell is drawn and rolled. Is obtained by the slight change of the roll shape of the inclined roll, and the above-described good results are obtained. It is intended to provide.

[Means for solving the problem]

In order to achieve the above object, the present invention provides an inclined roll elongation method for a metal tube, in which a mandrel bar is penetrated into the hollow shell while screwing the hollow shell using a plurality of inclined rolls. In the method of elongation rolling, a surface angle α _R 0 ゜ <α _{R of a} reeling portion with respect to a pass line of the plurality of inclined rolls is used.
≦ 0.5 °, and elongation rolling is performed such that the surface angle α _L of the exit side with respect to the pass line is set to be in the range of 2.0 ° ≦ α _L ≦ 3.0 °.

The surface angle α _R of the reeling portion with respect to the pass line as the inclined roll is in the range of 0 ° <α _R ≦ 0.5 °, and the surface angle α _L of the exit side portion with respect to the pass line is 2.0 ° ≦ α _L ≦ 3.0 °. It is characterized in that it can be a range.

In addition, an auxiliary reeling portion whose radius smoothly changes in the axial direction is provided between the reeling portion and the outlet side portion.

An auxiliary reeling portion having a length L in the axial direction is provided between the reeling portion and the delivery side portion, and the length L, the inclination angle β of the inclined roll with respect to the pass line, L ≧ 0.5 · KVDt between the outer diameter D of the metal tube and the forward efficiency kV
The relationship of the expression of tanβ is established.

[Action]

According to the present invention, as described above, the surface angle α _R of the reeling portion with respect to the pass line of the inclined roll is in the range of 0 ° <α _R ≦ 0.5 °, and the surface angle α _L of the exit side portion is 2.0 ° ≦ α. _Since the outer peripheral surface of the hollow shell is always brought into contact with the reeling portion at least once at least by setting _L ≦ 3.0 °, the metal tube drawn and rolled using the inclined rolls has an acute angle. A metal pipe having good dimensional accuracy can be obtained without occurrence of a defective wall thickness having a rough uneven shape.

In addition, since a portion where the radius of the inclined roll changes smoothly in the axial direction of the inclined roll is provided between the reeling portion and the delivery side of the inclined roll, a metal tube stretch-rolled using the inclined roll is provided. In this case, the edge mark thickness step on the outer and inner surfaces, which has conventionally occurred, becomes smooth and unclear.

The conditions at this time are, as described above, the inclination angle β of the inclined roll with respect to the pass line of the inclined roll, the outer diameter D of the metal tube after rolling, the forward efficiency kV, the reeling portion, and the delivery side portion. Between the axial length L of the connecting portion,
If the relationship of L ≧ 0.5 · KV Dπ tanβ is satisfied, any part of the outer peripheral surface of the hollow shell always passes through this connection part, so that a step is formed on the outer peripheral surface of the metal tube after elongation rolling. Never be.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the drawings showing an embodiment in which a method for elongating and rolling a metal tube according to the present invention and an inclined roll are applied to an inclined roll type elongation rolling mill having no crossing angle.

FIG. 1 is an explanatory view showing a relationship between a mandrel bar and an inclined roll used in the method of the present invention, in which H is a hollow shell, 1A and 1B are inclined rolls, M is a mandrel bar,
P indicates a pass line. The hollow shell H is heated to a predetermined temperature, is transferred from the upstream side (left side in the figure) to the downstream side (right side in the figure), is fed between the inclined rolls 1A and 1B, and is in contact with the outer peripheral surface. The mandrel bar M is caused to move in the axial direction while being rotated around the axis by 1A and 1B, and is stretched and rolled in a state where the mandrel bar M penetrates the center hole.

Each of the inclined rolls 1A and 1B has a frusto-conical entrance side 11 whose diameter decreases toward the upstream direction of the pass line P and a frusto-conical exit side (sizing portion) whose diameter decreases toward the downstream direction of the pass line P. ) 13 and a reeling portion 12 between the entrance side portion 11 and the exit side portion 13.

In the present invention, the surface angle α _R of the reeling portion 12 with respect to the pass line P of the inclined rolls 1A, 1B is 0 ° <α.
_R ≦ 0.5 °, and the surface angle α _L of the exit side portion 13 is
It is set to be in the range of 2.0 ° ≦ α _L ≦ 3.0 °.

Next, the surface angle α _R of the reeling portion 12 and the surface angle α _{L of the} outlet side portion 13
The reason for setting as described above will be described. In the inclined roll type elongation rolling mill, the hollow shell H is screwed in the axial direction along the reeling portion 12 in which the gap between the inclined rolls 1A and 1B and the inner surface tool (mandrel bar M) is a substantially constant portion. It is a rule that the metal tube after elongation rolling is made uniform in thickness by contacting at least once with all portions of the outer peripheral surface of the metal tube. However, since the roll body lengths of the inclined rolls 1A and 1B are generally limited, it is difficult to bring all the outer peripheral surfaces of the hollow shell H into contact with the reeling portion 12 at least once or more. It can be said that there occurs a reeling residue (a portion of w ₁ and w ₂ in FIG. 7) which does not pass through the reeling portion 12. And this reeling residue remains as a defective wall thickness distribution of the metal tube. From this, it was found that the thickness distribution can be improved by improving the roll shape of the reeling portion 12.

Therefore, when the surface angle α _R1 = 0 of the reeling portion 12, a portion that does not pass through the reeling portion 12 is formed on the outer peripheral surface of the metal pipe, and it is not possible to eliminate the remaining reeling. To minimize the ring remainder, for example, Japanese Patent Application No. Sho 62
In -175745, the crossing angle is changed and adjusted. Changing the cross angle becomes possible to adjust the surface angle alpha _R reeling unit 12 for pass line P, this time, the angle adjustment range of the surface angle alpha _R reeling section 12 is 0
It has been found from the results of implementation that {<α _R ≦ 0.5}.

That is, when the surface angle α _R <0 ° of the reeling portion 12, the roll gap decreases toward the downstream side in the axial direction in the reeling portion 12, so that the outer diameter restraining force on the hollow shell H increases, and the buttocks become jammed. And the like. On the other hand, when α _R > 0.5 °, the gap between the reeling portion 12 of the inclined rolls 1A and 1B and the mandrel bar M greatly increases toward the downstream side in the axial direction, and the reeling effect is lost.

On the other hand, since the cross-sectional shape of the hollow shell H is not circular but rather an elliptical shape at the reeling end portion, the hollow shell H is emptied to correct the elliptical shape so as to have a shape close to a perfect circle. An exit side portion 13 is provided. The surface angle α _L of the protruding side portion 13 has no effect of emptying when α _L > 3 °. On the other hand, when α _L <2 °, the outer diameter restraining force on the hollow shell H for correcting the ellipse is too large and the bottom angle α _L is small. An unstable phenomenon such as clogging occurs.

As a result, in FIGS. 1 and 2, the surface angle α _R of the reeling portion 12 with respect to the pass line P in the inclined rolls 1A and 1B is in the range of 0 ° <α _R ≦ 0.5 °, and 13 has a surface angle α _L of 2.0 ° ≦ α _L ≦ 3.0 °,
It was found that a metal tube with good dimensional accuracy could be obtained without the occurrence of a thick wall with sharp irregularities in the drawn and rolled metal tube.

Further, as shown in FIG. 3, when the roll axes 1a, 1b of the inclined rolls 1A, 1B have an intersection angle γ with respect to the pass line P, the roll axes 1a, 1B are aligned with the roll axes 1a, 1b of the inclined rolls 1A, 1B. The plane angles α _R ′ and α _L ′ are obtained by the following equations.

α _R ′ = γ−α _R , α _L ′ = γ = α _L Therefore, when manufacturing the inclined rolls 1A and 1B, it is preferable to manufacture the inclined rolls 1A and 1B so that the surface angles become α _R ′ and α _L ′.

FIG. 4 shows a second embodiment of the present invention. In this embodiment, the radius of the inclined rolls 1A and 1B is set between the reeling portion 12 and the exit side portion 13 of the inclined rolls 1A and 1B. Is provided with an auxiliary reeling portion 14 that smoothly changes in the direction of the axis of the inclined roll.

Explaining the reason, with the inclined roll in which the surface angle changes suddenly from the normal reeling section 12 to the exit side section 13, an edge mark is easily attached to the outer surface of the metal tube, and the air filing action at the exit side section 13 causes In some cases, the edge mark cannot be sufficiently eliminated. In this case, an edge mark formed between the reeling portion 12 and the outlet side portion 13 clearly remains on the inner surface of the pipe even after the end of rolling.

Therefore, by providing the auxiliary reeling portion 14 that smoothly connects the outer peripheral surfaces of the reeling portion 12 and the outlet side portion 13, the edge mark and the thickness step on the outer peripheral surface of the metal tube as described above become smooth. It turned out to be ambiguous.

In order to obtain such an effect, the reeling part
The length L of the auxiliary reeling portion 14 between the 12 and the outlet side portion 13 is
If the hollow pitch H is equal to or more than half of the rolling pitch RP (the length that the hollow shell H advances in one rotation) shown in FIG. Therefore,
Assuming the inclination angle β with respect to the pass line, the outer diameter D of the metal tube after rolling, and the forward efficiency kV, the rolling pitch RP is RP = kV · π
D · tanβ, the reeling part 12 and the outlet part 1
3 and the length L of the auxiliary reeling portion 14 in the axial direction of the auxiliary reeling portion 14 so as to have the relationship of L ≧ 0.5 · KV Dπ tanβ in the axial direction of the auxiliary reeling portion 14. The length L may be set. The radius RL of the generatrix of the auxiliary reeling portion 14 is the radius of the normal arc of the end point X on the exit side of the reeling portion 12 and the starting point Y on the reeling portion side of the exit side portion 13. The value RL is a value obtained by the equation of L / (sin α _L −sin α _R ). That is, as shown in FIG.
The intersection point of the normal line of the end point X on the exit side and the starting point Y on the reeling side of the exit side 13 is Z, and from this Z, the axis 1a (1b)
A straight line m is drawn in parallel to the outlet side, and a straight line n is drawn from the starting point Y on the reeling portion side of the outlet side portion 13 toward the straight line m and perpendicular to the straight line m. , n is V. △ YZV formed by connecting each point of Y, Z, V
Focusing on ▲ ▼ = RL · sin α _R + L (1) Holds.

From the above equations (1) and (2) Holds.

Then, by transforming the above equation (3), Becomes

As shown in FIG. 5, when the roll axes 1a and 1b of the inclined rolls 1A and 1B have an intersection angle γ with respect to the pass line P, the length L ′ of the auxiliary reeling portion 14 is L / L. cosγ (L
Is the value of the auxiliary length of the reeling portion 14) in the absence of a cross angle, radius RL 'is L' / a determined value at _{(sinα L '-sinα R')} .

Next, the results of the inclined rolling according to the method of the present invention and the inclined rolling according to the conventional method, and the results of the inclined rolling according to the reference example,
This will be described with reference to Table 1 and FIG.

In Table 1, the column A-1 shows various conditions in the case of tilt rolling by the conventional method, and the column A-2 shows the reference example, that is, the reeling surface angle exceeds the claims of the present invention. Values in the case of inclined rolling at the time of the value, B-1 is various conditions of inclined rolling in the case where the auxiliary roll is not provided on the inclined roll in the present invention, and B-2 is auxiliary reeling in the inclined roll in the present invention. Each condition of inclined rolling in the case where a portion is provided is shown.

FIG. 6 shows a change in wall thickness (uneven thickness state) in the pipe axis direction in the metal pipes manufactured by the above A-1, A-2, B-1, and B-2. FIG. 6A shows the above A-1.
6 (b) shows the case of the above A-2, FIG. 6 (c) shows the case of B-1, and FIG. 6 (d) shows the case of B-2.

As is clear from FIG. 6, the method of the present invention (B-1, B-2) is compared with the metal pipe which has been subjected to the inclined rolling by the conventional method (A-1) and the reference example (A-2). It can be seen that the change in the thickness of the metal pipe in the pipe axis direction is small. Therefore, according to the present invention, it is possible to obtain a metal tube having good dimensional accuracy without generating a thick wall having a sharp unevenness in the inclined-rolled metal tube.

〔The invention's effect〕

Since the present invention employs the above-described method and forms a structure, a metal pipe that is drawn and rolled at the time of drawing and rolling of a hollow shell does not have a thick wall with an acute unevenness and a good dimensional accuracy. Simplification because the above-mentioned good results can be obtained only by a slight change in the roll shape of the inclined roll without the need for a hydraulic device or the like required in the conventional device. In addition, effects such as high industrial use value such as cost reduction can be exhibited.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example in which the present invention is applied to an inclined roll type elongation rolling mill having no crossing angle, and FIGS. 2 and 4 (a) show respective inclinations used in the inclined roll type elongation rolling mill. FIG. 4 (b) is a schematic view of the main part of the roll, FIG. 4 (b) is an explanatory view for obtaining the diameter of the auxiliary reeling part, and FIG. 3 and FIG. FIG. 6 is a schematic view of a main part of each inclined roll used in the case of a roll type elongating rolling mill,
FIG. 7 is a graph showing a change in wall thickness in the axial direction of a metal tube in each of the conventional method, a reference example not claimed in the present invention, and the result of the inclined rolling according to the method of the present invention. FIG. It is a schematic diagram which shows the state which extended and rolled the hollow shell with the rolling mill. H: Hollow shell, M: Mandrel bar P: Pass line, 12: Reeling part, 13: Outgoing side part 14: Auxiliary reeling part, 1A, 1B: Inclined roll

Claims (4)

(57) [Claims] 1. A method of elongating and rolling a hollow shell by screwing a hollow shell using a plurality of inclined rolls and penetrating a mandrel bar into the hollow shell. The surface angle α _R of the ring portion is set in the range of 0 ° <αR ≦ 0.5 °, and the surface angle α _L of the exit side portion with respect to the pass line is set in the range of 2.0 ° ≦ α _L ≦ 3.0 °. An inclined roll elongation rolling method for a metal tube, which comprises elongation rolling. 2. The inclined roll used in the inclined roll elongation rolling method for a metal tube according to claim 1, wherein the face angle α _R of the reeling portion with respect to the pass line is in the range of 0 ° <α _R ≦ 0.5 °. , The surface angle α _L of the exit side with respect to the pass line is
An inclined roll, which can be in the range of 2.0 ° ≦ α _L ≦ 3.0 °. 3. The inclined roll according to claim 2, further comprising an auxiliary reeling portion whose radius smoothly changes in the axial direction between the reeling portion and the outlet side portion. 4. An auxiliary reeling portion having a length L in the axial direction is provided between the reeling portion and the outlet side portion.
Between the inclination angle β of the inclined roll with respect to the pass line, the outer diameter D of the metal tube after rolling, and the forward efficiency kV, L ≧ 0.5
The inclined roll according to claim 3, wherein the relationship of KV Dπ tanβ is satisfied.