JP2006075869A - O press die for uoe tube and method for manufacturing uoe tube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an O-press die having excellent wear resistance and impact resistance by hardening at least a part of the O-press die used in an O-working step of a UOE steel tube, and to provide a UOE steel tube manufacturing method having the O-working step using this die. <P>SOLUTION: The press die 100 which is used in the O-working step of a UOE steel tube manufacturing process has an upper die 10 and a lower die 20. The upper die 10 comprises a first part having the Shore hardness measured in compliance with JIS Z2246 being ≥46 and a second part having the Shore hardness being <46, and at least a top 15 of the upper die is included in the first part in the press die 100. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an O-press mold used in a UOE steel pipe manufacturing process, and a UOE steel pipe manufacturing method.

  The UOE steel pipe is a steel pipe mainly used for a line pipe for a pipeline for transportation of oil, natural gas and the like. The name is derived from a typical manufacturing process of UOE steel pipe, and the manufacturing process roughly includes about 20 processes. The first half of the UOE steel pipe manufacturing process consists of a process of cutting the steel sheet according to the dimensions of the steel pipe to be manufactured, a process of grinding the end of the steel sheet, a process of bending the end of the steel sheet, and U processing. The steel plate processed by this process, including the step of obtaining a pipe and the step of obtaining an open pipe by O processing, is then subjected to tack welding on a groove (usually X groove) previously applied to both ends of the steel plate. A product (steel pipe) is obtained through a process to be performed, a process in which submerged arc welding is performed, an expander process, a water pressure test process, an inspection process, and the like.

  When the U-shaped tube after U processing is O-processed by O-press molding, O-press dies each composed of a semicircular upper die and a lower die are usually used. The radii of the upper mold and the lower mold are substantially the same. In order to improve the roundness of the product (steel pipe) by adding a drawing process during O press molding, the ends of the upper mold and the lower mold are In general, about 0.5 inch (about 12.7 mm) is cut off from the end of a semicircle having two perfect circles.

  When U processing is performed on the U-shaped tube after U processing by using the above-mentioned mold, the mold, particularly the upper mold, is usually caused by friction between the edge of the U-shaped tube and the O-press mold. Seizure and wear occur within a range of less than 45 ° centered on the inner peripheral apex. It is known that this seizure and wear in the O-press mold progresses each time the number of presses is repeated, and when the number of presses is exceeded, the original shape of the upper mold that should be precisely semicircular is impaired. If an open pipe is manufactured using a mold whose original shape is damaged in this way, the edge of the U-shaped pipe is damaged, so the groove accuracy deteriorates, and the welding quality during tacking and submerged arc welding Decreases. Moreover, since the inner diameter of at least a part of the mold increases due to the above-described wear, it may cause a reduction in processing accuracy in drawing. This reduction in processing accuracy leads to deterioration of the shape of the pipe after O-pressing, and as a result, the roundness of the product (steel pipe) is reduced. Therefore, a technique for suppressing the wear of the O-press mold is desired. Yes.

Heretofore, several techniques have been disclosed regarding UOE steel pipe manufacturing methods. For example, Patent Document 1 discloses a mold for O press that can expand the range of the manufacturable diameter of a UOE steel pipe and a method for producing a UOE steel pipe using the same. Patent Document 2 discloses a method of manufacturing a UOE steel pipe that can improve the crushing strength when an external pressure is applied by performing heat treatment on the outer surface and the inner surface of the steel pipe after pipe expansion.
JP 2003-39115 A JP 2003-342639 A

  However, the techniques disclosed in Patent Document 1 and Patent Document 2 do not consider the wear of the O-press mold, and it is difficult to suppress the wear of the O-press mold. Even if the method is used, it is difficult to obtain a UOE steel pipe having excellent roundness.

  On the other hand, as a method for preventing the wear of the O-press mold, a method exemplified below can be examined. For example, there are a method in which the mold itself is hardened to improve the wear resistance, a method in which high-frequency quenching or hard metal plating such as chromium is applied to the entire surface of the mold. However, when the wear resistance of the O-press mold is improved by these methods, if the mold itself is too hard in the former method, the impact force when the U-shaped tube comes into contact with the O-press mold is reduced. As a result of the mold being unbearable, the mold may be cracked or damaged. On the other hand, if the entire surface of the mold is subjected to surface treatment by the latter method, it is difficult to finish the mold to the required dimensions due to large deformation during quenching by high-frequency quenching, and hard metals such as chromium When plating is performed, the plating peels off by sliding between the U-shaped tube edge and the mold surface, making it difficult to withstand practical use.

  Therefore, the present invention provides an O-press mold having excellent wear resistance and impact resistance, which is used in the O machining process of UOE steel pipe, and manufacturing a UOE steel pipe having an O machining process using this mold. It is an object to provide a method.

  The present invention will be described below. In order to facilitate understanding of the present invention, reference numerals in the accompanying drawings are appended in parentheses, but the present invention is not limited to the illustrated embodiment.

The invention according to claim 1 is a press die (100) comprising an upper die (10) and a lower die (20) used in the O processing step of the UOE steel pipe manufacturing process,
The upper mold (10) has a first portion having a Shore hardness of 46 or more measured according to JIS Z2246,
A second portion having a Shore hardness of less than 46,
The press die (100) is characterized in that at least the apex (15) of the upper die is included in the first part.

  According to invention of Claim 1, it becomes possible to provide the press die (100) excellent in abrasion resistance and impact resistance.

  The invention according to claim 2 is the press die (100) according to claim 1, wherein the first portion is in a range smaller than 45 ° centered on the top of the upper die. To do.

  According to the second aspect of the present invention, a range smaller than 45 ° centering on the apex (15) of the upper mold (the end of the U-shaped tube after the general U processing is the upper mold of the O-press mold) The hardness of the part in contact with the inner surface of the mold and the end part in which the end portion should slide on the inner surface of the upper mold during O-press processing is 46 or more in Shore hardness. By using an O-press mold (100) having a Shore hardness of less than 46, it is excellent in wear resistance and impact resistance and can be suitably used in the O processing step of a normal UOE steel pipe. A mold (100) can be provided.

Invention of Claim 3 is a manufacturing method of UOE steel pipe,
A first step (S4) of processing a steel plate having an end bent into a U-shape;
The hardness of a steel sheet processed into a U shape in a range smaller than 45 ° centered on the top of the upper mold is 46 or more in Shore hardness measured in accordance with JIS Z2246. A second step (S5) of processing into an O shape using a press die characterized by having a Shore hardness of less than 46;
The above-mentioned problem is to be solved by a method for manufacturing a UOE steel pipe, characterized in that

  According to the invention described in claim 3, the manufacturing process of the UOE steel pipe includes an O processing step of performing O press molding using an O press mold having excellent wear resistance and impact resistance. It becomes possible to provide the manufacturing method of the UOE steel pipe which can obtain the UOE steel pipe which has circularity.

  According to the UOE steel pipe press die and the UOE steel pipe manufacturing method of the present invention, it is possible to obtain an O press die excellent in wear resistance and impact resistance, as well as a UOE steel pipe having excellent roundness. It becomes possible to provide the manufacturing method of the UOE steel pipe which can manufacture.

Hereinafter, the present invention will be described based on embodiments shown in the drawings.
FIG. 1 is a front view showing an embodiment of a press die according to the present invention. The press die 100 of the present invention includes an upper die 10 and a lower die 20, and the upper die 10 has a hardness in a range A smaller than 45 ° centered on the apex portion 15, which is JIS Z2246 ( 2000) is a Shore hardness measured in accordance with 2000) (hereinafter, simply referred to as “Shore hardness”) of 46 or more, and the hardness of the portion other than the above range A is less than 46 in Shore hardness. It has become. On the other hand, since the lower mold 20 is not worn by the edge of the U-shaped tube processed by the U processing process, it is possible to use a mold similar to the conventional one.

  The shapes of the upper mold 10 and the lower mold 20 of the mold 100 are the same or substantially the same, and the inner diameter R of the mold 100 varies depending on the product dimensions of the steel pipe (pipe) to be manufactured. Further, although the upper mold 10 and the lower mold 20 are semicircular, since the O machining process includes drawing, the edge portions 11 and 12 of the upper mold 10 and the edge portions 21 and 22 of the lower mold 20 are the same. Alternatively, from the dimension line (shown as a one-dot chain line in FIG. 1) that becomes a perfect circle when the upper mold 10 and the lower mold 20 having substantially the same shape are brought into contact with each other, the cutting amount B (0.5 inch (about 12 inches)) is obtained. .7 mm)) are cut off one by one.

Here, as a material of the upper mold 10 and the lower mold 20, spheroidal graphite cast iron (hereinafter referred to as “FCD”) is selected based on experience from the balance between wear resistance and impact resistance. Many of them can be rolled materials or other materials.
Moreover, about the method of raising the hardness in the said range A to 46 or more by Shore hardness, the range which raises hardness is limited locally, and this range A is the metal mold | die 100 whole. Since it is smaller than the area, any method can be applied as long as it is a method of increasing hardness such as quenching.

  FIG. 2 is a front view showing a conventional O-press mold 200, and FIG. 3 is a view of the vicinity of the apex of the O-press upper mold 30 when the U-shaped tube 50 is O-processed by the conventional O-press mold 200. It is a front view which shows an abrasion form. When the U-shaped tube 50 is O-processed, the edge portions 51 and 52 of the U-shaped tube slide on the inner surface of the O-press upper mold 30. If the edge portions 51 and 52 of the U-shaped tube are located within the wear range A and arranged as shown in FIG. 3, the wear of the upper mold 30 becomes intense, and the inner diameters of the wear portions 31 and 32 of the upper mold are increased. Is larger than other parts that are not worn. Since the upper mold 30 is deformed by such wear (amount of wear C), the roundness of the UOE pipe that has undergone O processing by the deformed upper mold 30 is lowered. Therefore, in the press die 100 of the present invention, the wear in the upper die 10 is reduced by setting the hardness in the range A of the upper die 10 to 46 or more in Shore hardness. According to the manufacturing method of a UOE steel pipe having a process of performing O processing using the press mold 100 of the present invention including the upper mold 10, it becomes possible to obtain a UOE steel pipe having excellent roundness.

FIG. 4 is a flowchart showing only main steps in an embodiment that can be adopted by the method for manufacturing a UOE steel pipe of the present invention. In the UOE steel pipe manufacturing method of the present invention, first, the steel sheet is cut according to the dimensions of the steel pipe to be manufactured (step S1). The steel plate cut in step S1 is cut at its end (step S2), and the cut steel plate is subsequently subjected to bending (C processing) at its end (step S3). The steel plate that has been subjected to the C processing in step S3 is processed into a U shape (U processing) (step S4), and then the shape is processed into an O shape (O processing) (step S5). The steel plate that has been subjected to O processing in step S5 is then welded at the end by tack welding (step S6), and then the end is completely welded by submerged arc welding (step S7). The steel sheet becomes a steel pipe by the submerged arc welding in step S7, and then the residual stress is removed by the pipe expanding process (step S8), and the UOE steel pipe is manufactured through the hydraulic pressure test (step S9) and the inspection (step S10).
The UOE steel pipe manufacturing method of the present invention is characterized in that the O pipe mold 100 is used to process the steel pipe in the O processing of step S5. By adopting the manufacturing method using the O-press mold 100 of the present invention, it becomes possible to obtain a UOE steel pipe having excellent roundness.

Examples of the present invention and comparative examples are shown below.
Table 1 shows the evaluation of wear resistance and impact resistance using press dies for manufacturing 28 inch (about 711 mm) outer diameter UOE steel pipes used in Examples and Comparative Examples of the present invention, and these dies. The evaluation results are also shown. The lower mold used in the examples and comparative examples of the present invention was made of the same material as the upper mold of Comparative Example 1.

The evaluation of wear resistance in Table 1 uses the wear amount C in FIG. 3, that is, the amount deformed from the original mold radius by wear, the allowable limit of this wear amount is 3 mm or less, and the number of O-presses is 5000 times. The case where the number was less than the allowable limit was evaluated as x, the case where the number of times was 5000 times or more and less than 10,000 times exceeding the limit, and the case where the number of times exceeded 10,000 but still within the allowable range. On the other hand, the impact resistance is evaluated based on the presence or absence of cracks or breakage of the mold itself. When the mold breaks or breaks 10,000 times or before the wear amount exceeds the allowable limit, x is cracked in the mold itself. The case where there was neither damage nor damage was judged as “good”.
The results of the abrasion resistance evaluation are shown in FIG.

Example 1
As for the hardness of the upper mold used in this example, the hardness in the wear range A was Shore hardness HS48, and the hardness in the region other than the range A was HS40. On the other hand, the material of the upper mold of this example was FCD700, and the hardness in the range was improved by quenching the wear range A.
The mold of this example had an abrasion amount C that was within an allowable limit even after the number of presses of 10,000 times, and was excellent in wear resistance, was free from cracking and breakage, and was excellent in impact resistance.

(Example 2)
As for the hardness of the upper mold used in this example, the hardness in the wear range A was Shore hardness HS62, and the hardness in the region other than the range A was HS41. On the other hand, the material of the upper mold of this example was FCD700, and the hardness in the range was improved by quenching the wear range A.
The mold of this example has a wear amount C of about 0.5 mm even after 10000 presses and is extremely excellent in wear resistance, and is free of cracks and breakage and excellent in impact resistance. It was.

(Comparative Example 1)
As for the hardness of the upper mold used in this comparative example, the Shore hardness of the entire range was HS40. Therefore, the hardness of the wear range A does not satisfy the conditions of the present invention, but the hardness in a region other than the range A satisfies the conditions of the present invention. On the other hand, the material of the upper mold of this comparative example was FCD700.
The mold of this comparative example did not crack or break after the number of presses of 5000, but exceeded the allowable limit of the wear amount and was inferior in wear resistance. Therefore, it was obtained that the upper mold of this comparative example had insufficient performance in terms of wear resistance.

(Comparative Example 2)
As for the hardness of the upper mold used in this comparative example, the Shore hardness of the entire range was HS47. Therefore, the hardness of the wear range A satisfies the conditions of the present invention, but the hardness in the region other than the range A does not satisfy the conditions of the present invention. On the other hand, the material of the upper mold of this comparative example was FCD700, and the entire upper mold was hardened to improve the hardness of the entire mold.
The mold of this comparative example was cracked after 1000 presses. Therefore, when the hardness of the entire upper mold was Shore 46 or higher, the impact resistance was inferior, so that it was difficult to put to practical use.

(Comparative Example 3)
As for the hardness of the upper mold used in this comparative example, the Shore hardness of the entire range was HS35. The hardness in the wear range A did not satisfy the conditions of the present invention, but the hardness in the region other than the above range A satisfied the conditions of the present invention. On the other hand, the material of the upper mold of this comparative example was FCD500.
The mold of this comparative example greatly exceeded the allowable limit of the wear amount by 3000 times of pressing. On the other hand, there was no occurrence of cracking or breakage, and the impact resistance was excellent. Therefore, when the upper mold was soft, the impact resistance was excellent, but the wear resistance was inferior.

(Comparative Example 4)
The hardness of the upper mold used in this comparative example was HS45 in hardness in the wear range A with Shore hardness, and the hardness of the part other than the range A was HS40 in Shore hardness. Therefore, the hardness of the wear range A does not satisfy the conditions of the present invention, but the hardness in a region other than the range A satisfies the conditions of the present invention. On the other hand, the material of the upper mold of this comparative example was FCD700, and the hardness in the range was improved by applying a quenching treatment to the wear range A.
The mold of this comparative example exceeded the allowable limit of the wear amount by the number of presses of 8000 times, but had no impact and cracking and was excellent in impact resistance. Therefore, when the hardness of the wear range A is less than HS46 in Shore hardness, the result is that the mold is insufficient in terms of wear resistance.

  From the results of the above Examples and Comparative Examples, the hardness of the wear range A is 46 or more in Shore hardness, and the hardness of other parts is less than 46 in Shore hardness (Example 1 and Example 2). It was found that a press die having excellent wear resistance and impact resistance can be obtained.

It is a figure which shows the embodiment example of the press die of this invention. It is a figure which shows the conventional O press metal mold | die. It is a figure which shows the O press upper die top vicinity. It is a flowchart of the manufacturing method of a UOE steel pipe. It is a figure which shows a wear resistance test result.

Explanation of symbols

10 Upper mold 20 Lower mold 15 Vertex 50 U-shaped pipe 100 O press mold

Claims (3)

A press die having an upper die and a lower die used in the O processing step of the UOE steel pipe manufacturing process,
The upper mold has a first portion having a Shore hardness of 46 or more measured according to JIS Z2246,
A second portion having a Shore hardness of less than 46,
The press die, wherein at least a vertex of the upper die is included in the first part. 2. The press die according to claim 1, wherein the first portion is in a range smaller than 45 ° centered on the top of the upper die. A method for manufacturing a UOE steel pipe,
A first step of processing a steel plate having an end bent into a U shape;
The steel sheet processed into the U shape,
Hardness in a range smaller than 45 ° centered on the top of the upper mold is 46 or more in Shore hardness measured in accordance with JIS Z2246, and hardness other than the above range is less than 46 in Shore Shore hardness. A press die, characterized in that
And a second step of processing into an O shape using a UOE steel pipe.

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