JP2011167765A - O-press die of uoe tube and method for producing uoe tube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an O-press die which attains reduction in the production cost of a UOE tube of an intermediate outside diameter and enlargement of a range of produceable diameter of the UOE tube under the conventional expansion condition without degrading work efficiency, in production of the UOE tube of an intermediate outside diameter in a production line of the UOE tube of which the produceable diameter is determined for each size of the O-press die step by step, and to provide a method for producing the UOE tube by using the O-press die. <P>SOLUTION: The O-press die for the UOE tube contains upper and lower dies 2A, 2B which are arranged on the upper and lower sides, wherein inner surfaces of the upper and lower dies have a shape formed by cutting a part of upper and lower halves of a transverse oval shape so that the inner surfaces of the upper and lower dies are transverse oval in shape when the gap Go between the upper and lower dies is set to be a predetermined value, and so that the inner surfaces of the upper and lower dies are connected to each other without any step when the upper and lower dies are tightly attached to each other. The UOE tube is produced by using the die. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention provides a UOE capable of expanding the range of manufacturable diameters when a single die is used in a UOE pipe production line whose manufacturable diameter is determined stepwise by the size of the O-press die. The present invention relates to a mold for O-press of a pipe and a method for manufacturing a UOE pipe using the same.

  As a typical example of the UOE pipe, a manufacturing process flow of the UOE steel pipe is shown in FIG. After cutting the plate material to a predetermined length (100), the width end cutting (110) is performed so as to obtain a predetermined width according to the outer diameter of the product, and then in the end bending press (120) and U press (130) processes After bending, an O tube is formed in an O press (140) process. Next, the opposing end surfaces of the O pipe are tack welded (150), joined by inner and outer surface welding (160), and then expanded (170) by an expander or the like to obtain a UOE steel pipe having a predetermined outer diameter. The obtained UOE steel pipe is subjected to a water pressure test (180) and an inspection (190) before shipment.

In the O-press (140) process, an O-press mold is used. Conventional O-press molds are shown in FIGS. Conventional O press mold, and mounted inside the master die 4 by stacking the insert liner 3 1 or more, on, when lower die 2A, the gap between 2B the predetermined value G _0, the inner surface (Dotted line imaginary) is a perfect circle, and the inner diameter D is adjusted by the number of stacked insert liners 3. 9A and 9B, D ₀ is the inner diameter of the master die 4, D is the inner diameter of the insert liner 3, and A in FIG. 9C is the center of a circle corresponding to the inner surface of the insert liner 3. It is.

In the O-press mold having such a structure, G ₀ is generally about 12.7 mm (1/2 inch), and the thickness of the insert liner 3 is set to 2 inches. Therefore, in general, in a UOE pipe production line, the outer diameter of a product that can be manufactured (hereinafter referred to as a “manufacturable range”) is determined step by step according to the number of insert liners as schematically shown in FIG. Therefore, there is a non-manufacturable range between the manufacturable ranges corresponding to the insert liners of each number of layers.

The horizontal axis in FIG. 10 is the type of O-press mold 1, 2, 3, 4,... (The number of insert liners decreases in ascending order), and the vertical axis in FIG. The upper limit and the lower limit of the outer diameter that can be manufactured are determined by the outer diameter, which will be described later. That is, as shown in FIG. 10, when the insert liner 3 corresponding to a specific outer diameter is used, the manufacturable range is d ′ _min (manufacturable minimum outer diameter) to d ′ _max ( The maximum outer diameter that can be manufactured) is regulated.

Here, as shown in FIG. 11 (a), the minimum manufacturable outer diameter d ′ _min is such that the upper and lower dies 2A and 2B are in close contact during O-pressing, and the O-tube 1 having a circumference less than this is attached. It depends on being unable to get. On the other hand, the maximum manufacturable outer diameter d ′ _max when using a conventional O-press mold is such that the gap G between the upper and lower dies exceeds G ₁ during the O-press, and the gap G between the upper and lower dies. Is excessively long, the material plate material jumps into the gap G between the upper and lower dies as shown in FIG. Even if the pipe is expanded at a predetermined expansion ratio, the accuracy of the shape and dimension such as the roundness of the product is deteriorated.

  By the way, in the manufacturing process of such a UOE steel pipe, for example, when an order of an intermediate outer diameter of a millimeter (mm) size enters and the necessity of the manufacturing arises, conventionally, it is often adapted to the intermediate size. Insert liners were created separately, but in such a case, expensive insert liners must be manufactured each time, and it takes time to replace the insert liner in terms of factory operation efficiency. Therefore, there is a problem that the manufacturing cost is increased and workability is deteriorated.

Therefore, a method of manufacturing an intermediate size UOE pipe using a stepped inch size O-press mold has been proposed. FIG. 11 (b) shows the production of an intermediate outer shape UOE steel pipe in an extension line method of the conventional step-wise inch-size UOE steel pipe manufacturing technique, and the gap between the upper and lower dies. A good-shaped O-tube 1 having no bent portion formed by setting G to G ₁ (G ₀ <G ₁ but not excessive) is shown. By the way, the O pipe 1 is expanded at a predetermined expansion ratio (usually 0.5 to 1.5%) in the expansion process after the O press, whereby a predetermined outer diameter and desired mechanical properties are obtained. It is formed as follows. However, this UOE pipe manufacturing method is used for manufacturing a product having an intermediate outer diameter dm (d _K <dm <d _{K + 1} ) with respect to the general size of the final product outer diameters d _K and d _{K + 1.} , using O pressing mold for corresponding to the general size d _K inside diameter D _K, by increasing the gap between the upper and lower dies at O pressing lowermost, molding the O pipe portrait, then as usual The tube is expanded at a tube expansion rate to make it an intermediate product outer diameter. As shown in FIG. 15 (b), the material plate material protrudes outside in the gap between the upper and lower dies due to the force during O-pressing. And the bending due to the buckling also remains in the expanded replica O-tube, and the dimensional accuracy deteriorates.

  Therefore, a method for manufacturing a UOE pipe which prevents such a shape defect is disclosed in Japanese Patent Laid-Open No. 58-41619. As shown in FIGS. 12 (a) and 12 (b), this UOE tube manufacturing method prevents buckling that occurs in the O tube 1 during O pressing by a buckling prevention stopper 50 provided between the upper and lower dies. It is preventing. However, when this buckling prevention stopper 50 is mounted, for example, an O press in which six master dies 4 and six insert liners 3 each having a length of about 3 m are arranged so that an O pipe 1 having a length of 18 m can be formed. There was a problem that workability deteriorated because 2 × 6 buckling prevention stoppers 50 were attached to each mold (see FIGS. 12C and 12D).

Japanese Patent Application Laid-Open No. 9-29339 discloses a UOE pipe manufactured by using an O-press mold configured such that one is an existing mold and the other is a new mold, and the mold manufacturing cost can be halved. A method is disclosed. The O press mold, as shown in FIG. 13, the upper and lower dies 2A, the radius of curvature R _A of the circle corresponding to the inner surface of 2B, along with the R _B differ, the radius of the center position A, different A ', and When the horizontal dimensions L _A and L _B of the upper and lower dies 2A and 2B are set to L _A = L _B and the upper and lower dies 2A and 2B are brought into close contact with each other, no step is formed on the inner surface.

However, even in the case of an O-press mold having a semicircular inner surface with different radii, the buckling prevention stopper 50 does not need to be attached and the workability is not deteriorated. There was a problem that it was difficult to expand the range of manufacturable outer diameters compared to conventional O-press molds. That is, when the inner surface is a semicircular shape having different radii of curvature, the gap G between the upper and lower dies is set to 0 during O-pressing, as shown in FIG. When a product is to be obtained, the bent portion 1A shown in FIG. 14B is generated in the O tube 1, and even if the tube is expanded at a predetermined tube expansion rate, the roundness is poor. As shown in FIG. 15A, even if the gap G between the upper and lower dies is set to a value G ₂ smaller than the aforementioned G ₁ , when trying to obtain a product having the same maximum outer diameter as in the case of a conventional true circle, FIG. ) Is formed in the O-tube 1, and thereafter, even if the tube is expanded at a predetermined expansion rate, the roundness is still poor, so the range of manufacturable outer diameters can be expanded. There was no.

  Furthermore, in Japanese Patent Laid-Open No. 9-1234, an existing O-press mold is used to form an O-tube having an outer diameter that is slightly smaller than the target, and the tube expansion rate is increased in the tube-expansion process after the O-press. Although it has been proposed to manufacture a UOE pipe having an intermediate outer diameter, there is a problem that the mechanical properties of the UOE pipe product, particularly the elongation characteristics, are deteriorated. Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art, and in the UOE pipe production line in which the manufacturable range of the UOE pipe is determined step by step for each size of the O-press mold. When manufacturing an outer diameter UOE pipe, the manufacturing cost can be reduced, and the UOE pipe can be manufactured without degrading workability and using a single mold that is the same pipe expansion condition as before. An object of the present invention is to propose a mold for an O press capable of expanding the range and a method for manufacturing a UOE pipe using the same.

  The mold for O press of the UOE tube of the present invention is composed of upper and lower dies arranged above and below, and when the gap between the upper and lower dies is a predetermined value, As shown in the figure, the inner surfaces of the upper and lower dies are shaped by cutting out only the upper half and the lower half of the horizontally long circular shape, and when the upper and lower dies are in close contact, the inner surfaces of the upper and lower dies have no step. It is configured to be connected. In the O-press mold according to the present invention, when the gap between the upper and lower dies is set to a predetermined value, the lateral dimension b / vertical dimension a of the laterally oblong circle is more than 1.00 and 1.05 or less. Is preferred.

  Here, it is desirable that the oblong shape in the present invention is an ellipse having a minor axis of the vertical dimension a and a major axis of the lateral dimension b. In the UOE pipe manufacturing method of the present invention, a plate material having a predetermined width is bent into a U shape, and then formed into an O pipe by using an O-press mold, and then the opposite ends of the O pipe are joined. And in the manufacturing method of the UOE pipe | tube which expands by a predetermined pipe expansion ratio and manufactures a UOE pipe | tube, the metal mold | die for O press of this invention is used as said metal mold | die for O press.

  According to the present invention, in the production line of UOE pipe in which the range of the outer diameter of the UOE pipe that is manufacturable is determined for each O-press mold, The range of diameter can be expanded. As a result, it is possible to reduce the number of insert liners that can be produced to manufacture intermediate outer diameter UOE pipes, and to reduce the number of insert liner replacements. Can be shortened.

  Further, according to the present invention, it is not necessary to attach a new member such as a buckling prevention stopper to the O-press mold, and an intermediate outer diameter UOE tube can be efficiently manufactured under the conventional tube expansion conditions. become.

It is a front view of an example metallic mold concerning the present invention. It is a side view of an example metallic mold concerning the present invention. It is a front view explaining the effect | action of an example metal mold | die which concerns on this invention, and is a schematic diagram which shows the manufacture process of the UOE steel pipe of the minimum outer diameter. (A) (b) (c) is a front view explaining the effect | action of an example metal mold | die which concerns on this invention, and is a schematic diagram which shows the manufacturing process of the UOE steel pipe of the largest outer diameter. (D) is a figure explaining the problem of a prior art. (A) is a front view of an example metal mold | die which concerns on a reference example, (b), (c) is a front view explaining the effect | action. (A), (b) is a front view which shows the other metal mold | die structure which concerns on this invention. It is a graph which shows the roundness of the UOE steel pipe of the example of an invention compared with a prior art example. It is a flowchart which shows the manufacturing process of a UOE steel pipe. It is a figure which shows the conventional metal mold | die, Comprising: (a) is a master die, (b) is an insert liner, (c) is a front view of upper and lower dies. It is a graph explaining the product outer diameter of the UOE pipe | tube at the time of using the conventional metal mold | die. It is a front view explaining the effect | action at the time of using the conventional metal mold | die. It is a figure which shows the other conventional mold structure, Comprising: (a), (b) is a front view which shows the mounting condition of the buckling prevention stopper, (c), (d) is a top view of an upper die, a front view It is. It is a front view which shows the other conventional metal mold | die. It is a front view which shows the shape defect of O pipe at the time of using the conventional metal mold | die. It is a front view which shows the other shape defect of O tube at the time of using the conventional metal mold | die.

  First, referring to FIG. 1 and FIG. 2, an O-press mold for an example UOE pipe according to the present invention will be described. FIG. 1 is a front view of an example O-press mold according to the present invention, FIG. 2 is a side view thereof, and the left-right direction of FIG. 2 is a length direction. In FIGS. 1 and 2, 2A and 2B are upper and lower dies, and a UOE pipe O-press mold (hereinafter also simply referred to as a mold) includes an upper die 2A and a lower die 2B. A mold composed of upper and lower dies 2 </ b> A and 2 </ b> B includes a master die 4 and an insert liner 3 attached to the master die 4. Further, as shown in FIG. 2, a plurality of upper and lower dies 2A and 2B are overlapped in the length direction.

In one example mold according to the present invention, the inner surface of the insert liner 3 and the master die 4 which constitute the upper die 2A is located a lower side of the upper half of the oblong circular as shape notched by G _0/2, Further, the inner surface of the insert liner 3 and the master die 4 which constitutes the lower die 2B is an upper horizontal circular lower half of Examples shape notched by G _0/2.
In this case, the horizontally long circle is an ellipse whose short axis is the vertical dimension a and whose long axis is the horizontal dimension b, and a <b. The vertical dimension a is the distance between the inner surfaces of the upper and lower dies 2A and 2B when the gap between the upper and lower dies is a predetermined value G ₀ , and the horizontal dimension b is the predetermined gap between the upper and lower dies. When the value G ₀ is set, the horizontal distances of the virtual lines connecting the left and right inner surfaces of the upper die 2A and the left and right inner surfaces of the lower die 2B in the vertical direction. G ₀ is a predetermined gap between the upper and lower dies 2A and 2B, and is usually about 12.7 mm (1/2 inch).

  In this case, one insert liner 3 is attached to the master die 4, and the outer surface shape of the insert liner 3 attached to the master die 4 is made to correspond to the inner surface shape of the master die 4. When a plurality of insert liners 3 are mounted on the master die 4, the outer surface shape of the outermost insert liner 3 mounted on the master die 4 is as described above, and the inner layer insert is more than the outermost insert liner 3. The outer surface shape of the liner is made to correspond to the inner surface shape of the insert liner of the outer layer to be mounted.

As described above, an example mold according to the present invention is composed of upper and lower dies arranged on the upper and lower sides, and the inner surfaces of the upper and lower dies are notched in the upper half and the lower half of the horizontally long circle. When the upper and lower dies are in close contact with each other, the inner surfaces of the upper and lower dies are connected to each other without any level difference. _When it is set to ₀ , it becomes a horizontally long circular shape in which a longitudinal dimension a is a short axis and a horizontal dimension b is a long axis, with a part cut away.

  Next, a method for manufacturing a UOE steel pipe using the above-described exemplary mold according to the present invention will be described with reference to FIGS. FIG. 3 is a schematic diagram showing the manufacturing process of the UOE steel pipe when the above-described die according to the present invention is used and the gap G between the upper and lower dies is set to 0 at the time of O pressing. FIG. 4 is a schematic diagram showing the manufacturing process of the UOE steel pipe when the gap G of the upper die shown in FIG. 3 is opened.

3 and 4, (a) is when the O-press is at the lowest position, (b) is after joining of the opposite ends, (c) is after tube expansion, and 1 is an example of the mold according to the present invention. The formed O pipe before expansion, P indicates a UOE steel pipe after expansion. In the figure, 1S is a joint, and d _min and d _max are the minimum manufacturable outer diameter and the manufacturable maximum outer diameter when an example of the mold according to the present invention is used.

  In the UOE pipe manufacturing method according to the present invention, the UOE steel pipe is formed by bending a plate material having a predetermined width into a U shape, and then forming the UOE steel pipe with a mold whose inner surface is a part of a horizontally long circle. After that, the opposite end portions of the O tube are joined and expanded at a predetermined expansion rate for manufacturing. For example, when the gap between the upper and lower dies is 0, the circumference of the inner surface of the mold according to the present invention is the same as the circumference of a conventional true circular mold, and the O tube 1 is formed. Suppose that

The minimum manufacturable outer diameter d _min 'when using a conventional round die was determined by the gap G between the upper and lower dies becoming 0 and the lower die being in close contact during O-press. is there. On the other hand, in the case of using an example of the mold according to the present invention, the minimum manufacturable outer diameter d _min is the same as in the case of a conventional mold because the upper and lower dies are in close contact during O-press. However, in this case, when the mold of the example according to the present invention is used, the bending that occurs in the plate material when the upper and lower dies are in close contact with each other is slight, so that it does not remain after dedieing. Since it is possible to obtain a horizontally long O-tube 1 having the same outer peripheral length as that formed and having no bent portion, it is possible to correct the horizontally long circular shape by expanding the tube at a predetermined tube expansion rate thereafter. Thus, the outer diameter d _{min of the} product is the same d _min 'as before, and the product P of the UOE steel pipe having good mechanical properties, shape and dimensional accuracy can be obtained (see Fig. 3 (c)). .

On the other hand, the maximum manufacturable outer diameter d _max ′ when a conventional true circular mold is used is that when the gap G between the upper and lower dies is excessively opened during O pressing, the O tube 1 becomes too long. As described above, buckling occurs, the side portion of the O-tube 1 is bent and the shape is deteriorated (see FIG. 4D). On the other hand, when an example die according to the present invention is used, the maximum manufacturable outer diameter d _max of the UOE steel pipe is the same as that when a conventional true circular die is used during O-pressing. In this case, when an example of the mold according to the present invention is used, the inner surface of the mold is horizontally long, so that the gap G is rounded during O-press. Since the plate material is deformed so that it protrudes in a clean curved shape, the gap G between the upper and lower dies can be widened compared to the conventional mold without causing buckling in the plate material. Since the O-tube 1 has a longer outer peripheral length than that of the mold and the vertical length without a bent portion does not become excessive, the shape can be corrected by expanding the tube at a predetermined expansion rate thereafter. The outer diameter d _{max of the} product is larger than the conventional maximum outer diameter d ′ _max In addition, the mechanical properties, shape and dimensional accuracy of the product P of the UOE steel pipe can be improved (see FIG. 4C).

Thus, in the manufacturing method of the UOE steel pipe using the example die according to the present invention, it is possible to suppress the occurrence of buckling during O-press and form an O-tube having a good shape without a bent portion. Therefore, even if the pipe is expanded at a normal expansion ratio, a product with good mechanical properties, shape and dimensional accuracy can be obtained, and the range of the manufacturable outer diameter of the UOE steel pipe can be expanded.
In addition, when a pipe expansion rate exceeds a normal range, since the problem that elongation becomes small tends to generate | occur | produce especially among the mechanical properties of a UOE steel pipe, a pipe expansion rate is made into a normal range. The pipe expansion rate varies depending on the outer diameter, thickness, material, and the like of the UOE steel pipe, but can be 0.5 to 1.5%, for example. Here, in the mold according to an example of the present invention, when the gap between the upper and lower dies is set to a predetermined value G ₀ , the horizontal dimension b / vertical dimension a of the oblong circle exceeds 1.00. It is preferably 0.5 or less, more preferably more than 1.00 and 1.02 or less.

  If the horizontal dimension b / longitudinal dimension a of the oblong circle exceeds 1.05, the O pipe becomes too long at the O-press due to the outer diameter and thickness of the UOE steel pipe, and the normal expansion This is because even if the pipe is expanded at a rate, the dimensional accuracy such as the roundness of the product may be out of the allowable range. When the horizontal dimension b / longitudinal dimension a of the oblong circle is 1.00, it is a case of a conventional mold having an inner surface of a perfect circle, and as described above, manufacture of a UOE steel pipe from an example mold according to the present invention. The range of possible outer diameter is narrow.

  On the other hand, when the horizontal dimension b / longitudinal dimension a of the oblong circle is less than 1.00, the O pipe becomes too long in the vicinity of the gap due to the outer diameter and wall thickness of the UOE steel pipe during O-pressing. This is because a bent portion is generated, and the dimensional accuracy such as the roundness of the product may be out of the allowable range even if the tube is expanded at a normal expansion rate. The horizontal dimension b / vertical dimension a of the oblong circle is more preferably more than 1.00 and 1.02 or less, because the dimensional accuracy such as roundness of the product can be further improved.

  Next, a mold according to a reference example will be described. An example mold according to the reference example has one die as an existing die and the other as a new die so that the mold production cost can be halved. It consists of an upper die and a lower die. The inner surface of one of the upper and lower dies has a shape obtained by partially cutting the upper half or the lower half of the horizontally long circle, and the other inner surface of the upper and lower dies is the upper half or the lower half of a true circle. The upper and lower dies are connected to each other without a step when the upper and lower dies are brought into close contact with each other. Since the other structure is the same structure as the above-described mold according to the present invention, the description thereof is omitted.

  In FIG. 5A, the upper die 2A is an existing die, the lower die 2B is a new die, the inner surface of the upper die 2A is partially cut out of the upper half of a true circle, and the lower die Although the inner surface of 2B is shown as a mold in which the lower half of the horizontally long circle is partially cut away, the upper die 2A is a new die, the lower die 2B is an existing die, and the inner surface of the upper die 2A is horizontally long. Alternatively, the upper half of the circle may be partially cut out, and the inner surface of the lower die 2B may be a mold that is cut out of the lower half of the true circle.

  As shown in FIG. 5A, the reason why it is preferable to use the upper die 2A as the existing die and the lower die 2B as the new die is compared to the case of newly forming the upper die 2A that needs to be made of a hard material. This is because it is cheaper and more economical to make a new lower die 2B that can be made of a softer material than the upper die 2A. The lower die 2B can be made softer than the upper die 2A because, as shown in FIG. 5 (b), when the O die is pressed, the upper die 2A comes into contact with the end of the steel plate bent in a U shape. It is easy to get wrinkles and the use conditions are severe, but the use conditions are relatively loose because the bent portion of the steel plate bent in a U shape comes into contact with the lower die.

  In FIGS. 5A and 5C, the upper die 2A in which the insert liner 31 is mounted on the inner surface of the master die 4 is an existing die. Further, in the mold according to the reference example, when the upper and lower dies 2A and 2B are brought into close contact with each other, the inner surface of the die having a shape obtained by partially cutting away the upper half or the lower half of the horizontally long circular shape is conventional. One of the upper and lower dies 2 </ b> A and 2 </ b> B is newly made so as to be connected to the inner surface of the die without any step. Therefore, when the circumference of the inner surface of the mold according to the reference example is compared with a conventional mold having a true circular inner surface, the upper and lower dies 2A and 2B are brought into close contact with each other, as is apparent from FIG. Sometimes, the circumference of the inner surface of the mold according to the reference example is shorter than the circumference of the inner surface of the conventional mold.

  That is, when manufacturing a UOE steel pipe having a small outer diameter by closely contacting the upper and lower dies 2 </ b> A and 2 </ b> B during O-press using the mold according to the reference example, when using the mold according to the reference example Since the outer peripheral length of the O tube is shorter than the outer peripheral length of the O tube obtained by a conventional mold and can suppress buckling, it is possible to form an O tube having a good shape without a bent portion. Even if the pipe is expanded with a range of expansion ratios, it is possible to obtain a product having a smaller outer diameter and better mechanical properties, shape and dimensional accuracy than when a conventional mold is used. On the other hand, when a UOE steel pipe having a large outer diameter is manufactured by opening a gap between the upper and lower dies 2A and 2B using the mold according to the reference example and O-pressing, the occurrence of buckling is suppressed. Because it is possible to form an O-tube with a good shape without a bent portion, the outer diameter is larger than when a conventional mold is used, and the mechanical properties and shape are expanded even when the tube is expanded at a normal expansion rate.・ Products with good dimensional accuracy can be obtained.

Here, in the case of the mold according to the reference example, as in the case of the mold of the present invention, on the, in the case where the lower die 2A, the gap between 2B the predetermined value G _0, upper, lower die 2A 2B, the lateral dimension b / longitudinal dimension a of the oblong circle on the inner surface of either one is preferably more than 1.00 and 1.05 or less, and more than 1.00 and 1.02 or less. Further preferred. Since the reason for limiting in this way is the same as in the case of the mold of the present invention, description thereof is omitted.

In the above description, the inner surface of the master die 4 used for the upper and lower dies 2A, 2B is a horizontally long circle corresponding to the outer surface of the insert liner 3, but an existing master die having an inner surface of a true circle is used. You can also. In that case, as shown in FIG. 6 (a) or (b). Incidentally, in FIG. 6 (a) or (b), D ₀ is the diameter of the inner surface of the existing master die 4, a ', b', the vertical dimension of each mold inner surface, a transverse dimension.

That is, as shown in FIG. 6 (a), in order to configure the insert liner 3 to be attached to the master die 4 one above the other and to correspond to the outside diameter dimension set in stages, the existing master Since the inner surface of the die 4 is a circle having a diameter D ₀ , the outer surface of the insert liner 3 is made to have a circular shape corresponding to the inner surface of the master die 4, and the inner surface of the insert liner 3 is made into a horizontally long oval shape.

At that time, the required number of insert liners 3 is prepared in correspondence with the manufacture of UOE steel pipes having outer diameters set in stages. Alternatively, as shown in FIG. 6B, since the inner surface of the existing master die 4 is a circle having a diameter D ₀ , the outermost insert liner 3 to be mounted on the inner surface of the master die 4 has an outer surface that is the master die. When the UOE steel pipe whose outer diameter is smaller than that of the insert liner 3 is manufactured, both the inner and outer surfaces of the insert liner 3 are formed into a horizontally long oval shape. It is good also as a structure which mounts UOE steel pipe of the manufacturing outer diameter set in steps, in order.

  By the way, in the present invention, the upper limit of the gap G between the upper and lower dies is preferably set to 50 mm in order not to cause a bent portion during O-pressing. In the above description, as the inner surface shape of the mold, an ellipse having a minor axis of dimension a and a major axis of dimension b is referred to as a laterally long circle, but the inner surface of the mold according to the present invention is a laterally long circular shape having a smooth curve. If it is. Of the oblong circles, the oblong ellipse that is easy to mathematically express and is easy to manufacture a mold is the most accurate form as a preferred embodiment of the present invention.

  Moreover, there is no problem even if the present invention is applied using a material other than steel instead of the UOE steel pipe that appears as an example in the above description.

  (Example 1) A steel plate having a predetermined width is bent into a U-shape, and then formed by an O press to form an O tube. Then, opposite ends of the O tube are joined and expanded at a predetermined expansion rate. A UOE tube was manufactured. At that time, in the invention example, as shown in FIG. 1, the inner surfaces of the upper and lower dies are formed by notching the upper half and the lower half of the horizontally long ellipse, and the upper and lower dies. Is used, an O-press mold configured so that the inner surfaces of the upper and lower dies are connected without a step, and the gap G between the upper and lower dies is set to 0 to 44 mm. As a result, the lateral dimension b / longitudinal dimension a of the horizontally long ellipse is 1.01 (the lateral dimension b is 603 mm and the longitudinal dimension a is 597 mm). Since the roundness of the product after expansion was within ± 1% and a UOE steel pipe having a product outer diameter of 597.5 to 625.5 mm could be manufactured, the range of manufacturable outer diameter was 28 mm. .

  The tube expansion rate was fixed at 0.95%, and the thickness t was 9.5 mm, and the length was 12 m APIX65 (API standard) UOE steel pipe. The roundness of the product of the UOE steel pipe was defined as (outer diameter vertical dimension−outer diameter horizontal dimension) / product outer diameter d (target) × 100 [%] within one product. Here, the length and width in the UOE steel pipe product correspond to the length and width when the O tube is formed by O press.

  On the other hand, in the conventional example, a UOE steel pipe is manufactured by using an O-press die having an inner surface with a diameter of 600 mm and a gap G between the upper and lower dies of 0 to 38 mm, and other conditions are the same as in the invention example. It was. In the conventional example, it is possible to manufacture a UOE steel pipe in which a bent portion does not occur during O-press, the roundness of the expanded product is within ± 1%, and the outer diameter of the product is 597.5 to 621.5 mm. Therefore, the range of the manufacturable outer diameter was 24 mm.

From this, it can be seen that according to the present invention, the range of product outer diameters that can be manufactured compared to the conventional example can be expanded.
(Reference Example) A steel plate having a predetermined width is bent into a U-shape, and then formed by an O press to form an O tube. Then, opposite ends of the O tube are joined, and the tube is expanded at a predetermined expansion rate. A UOE tube was manufactured. At that time, in the reference example, at the time of O press, as shown in FIG. 5A, the inner surface of the upper die has a shape obtained by cutting out only a part of the upper half of the true circle, and the inner surface of the lower die is a horizontally long ellipse. An O-press mold having a shape in which only a part of the lower half of the shape was cut out was used, and the gap G between the upper and lower dies was set to 0 to 41 mm. The horizontal dimension b / vertical dimension a of the horizontally long ellipse was 1.01 (horizontal dimension b was 603 mm, vertical dimension a was 597 mm), and the diameter D of the perfect circle was 603 mm, the same as the horizontal dimension b.

  As a result, in the case of the reference example, a bent portion does not occur during O-pressing, the roundness of the product after tube expansion is within ± 1%, and the outer diameter of the product is 599.0 to 625.5 mm. Since the steel pipe could be manufactured, the range of the manufacturable outer diameter was 26.5 mm. The tube expansion rate was fixed at 0.95%, and the thickness t was 9.5 mm, and the length was 12 m APIX65 (API standard) UOE steel pipe. The roundness of the product of the UOE steel pipe was defined as (outer diameter vertical dimension−outer diameter horizontal dimension) / product outer diameter d (target) × 100 [%] within one product. Here, the length and width in the UOE steel pipe product correspond to the length and width when the O tube is formed by O press.

  On the other hand, in the conventional example, a UOE steel pipe is manufactured using an O-press mold in which the inner surfaces of the upper and lower dies have a perfect circle shape with a diameter D of 603 mm, and the gap G between the upper and lower dies is 0 to 38 mm. The conditions were the same as in the reference example. In the conventional example, it is possible to manufacture a UOE steel pipe in which a bent portion does not occur during O-press, the roundness of the expanded product is within ± 1%, and the outer diameter of the product is 600.5 to 625.0 mm. Therefore, the range of the manufacturable outer diameter was 24.5 mm.

Thus, according to the reference example, it can be seen that the range of product outer diameters that can be manufactured can be expanded as compared with the conventional example.
(Example 2) A steel sheet having a predetermined width is bent into a U-shape, and then formed by an O press to form an O tube. Then, opposite ends of the O tube are joined and expanded at a predetermined expansion rate. An APIX65 (API standard) UOE tube having a product outer diameter d of 609.6 mm, a wall thickness t of 9.5 mm, and a length of 12 m was manufactured.

  At that time, in the example of the invention, at the time of O-press, as shown in FIG. 1, the inner surfaces of the upper and lower dies are formed by notching the upper half and the lower half of the horizontally long circle, and the upper and lower dies. Was used, an O-press mold configured such that the inner surfaces of the upper and lower dies were connected without a step was used, and the gap G between the upper and lower dies was set to 12.7 mm. The horizontal dimension b / vertical dimension a of the ellipse was 1.01 to 1.05 at a 0.01 pitch, and the tube expansion ratio was constant at 0.95%. The average diameter ((a + b) / 2) was 600 mm in order to match the conventional diameter.

The conventional example uses an O-press mold having an inner surface with a diameter of 600 mm, the upper and lower die gap G is 12.7 mm, and other conditions are the same as those of the invention example. FIG. 7 shows the roundness of the product (after tube expansion). The roundness of the UOE steel pipe product was the same as in Example 1.
From this result, the upper and lower die gap G is set to 12.7 mm using an O-press mold in which the inner surface of the upper and lower dies has an elliptical shape with a horizontal dimension b / vertical dimension a exceeding 1.02 and 1.05 or less. In the case of the invention examples described above, the roundness of the product may not be within a very good range of ± 1%, but the roundness of the product is within an allowable range that is not problematic in practice. I understand that.

  Moreover, the upper and lower die gap G was set to 12.7 mm by using an O-press mold in which the inner surface of the upper and lower dies had an elliptical shape with a horizontal dimension b / vertical dimension a exceeding 1.00 and not more than 1.02. In the case of the invention example, it can be seen that the roundness of the product can be within a very good range of ± 1%, as in the case of the round shape of the conventional example.

1 O tube 1A, 1B Bending part 2A, 2B Upper and lower dies 3, 31 Insert liner (insert die)
4 Master die G, G ₀ , G ₁ upper and lower gaps D ₀ , D inner diameter A, A ′ center a, a ′ longitudinal dimension b, b ′ lateral dimension d _min , d ′ _min for each mold Manufacturable minimum outer diameter _dmax , d' _max Maximum manufacturable outer diameter for each mold 1S Joint P UOE steel pipe (product)
50 Buckling prevention stopper

Claims (3)

The upper and lower die inner surfaces are horizontally long so that the inner surface of the upper and lower dies is horizontally oblong when the gap between the upper and lower dies is a predetermined value. The upper half and the lower half are partly cut out, and when the upper and lower dies are in close contact, the inner surfaces of the upper and lower dies are connected to each other without any step. UOE pipe O-press mold. 2. The horizontal dimension b / vertical dimension a of the horizontally long circle when the gap between the upper and lower dies is set to a predetermined value is set to be more than 1.00 and 1.05 or less. Mold for O-press of UOE pipe. A plate material having a predetermined width is bent into a U-shape, and then formed into an O tube by using an O-press mold, and then the opposite end portions of the O tube are joined and expanded at a predetermined tube expansion rate. In the manufacturing method of the UOE pipe | tube which manufactures a pipe | tube, the metal mold | die for O presses of Claim 1 or 2 is used as said metal mold | die for O presses, The manufacturing method of the UOE pipe | tube characterized by the above-mentioned.

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