JPH01237025A - Method for correcting bend of steel tube - Google Patents

Abstract

PURPOSE:To manufacture a steel tube free from bend by dividing the steel tube into the former half and the latter half to expand the tube, first, computing a correcting target figure for the bend, comparing this value with the actual corrected value and confirming the result to correct the bend of the steel tube. CONSTITUTION:The bend is measured before the tube is expanded to compute a correction target figure alpha for the bend necessary to obtain the final state free from the bend. The former half corresponding to 1/2 of the length is expanded by a 1st tube expanding machine 10 and a 1st bend correction is performed by a correction roller 6 to confirm the quantity of partial bend of the steel tube 1. In this case, when a difference is found between an actual correction quantity and the target quantity alpha1, a control program for the correction roller is modified so that the final target figure alpha is attained by residual (n-1) tube expansions and the 2nd tube expansion is corrected by a new program. When this process is carried out every tube expansion the quantity alpha of reverse bend of the target figure can be corrected. In this way, the steel tube free from bend can be manufactured.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for straightening a bent steel pipe, and a method for straightening a steel pipe so that the axes of both ends of the pipe are aligned, without adversely affecting the roundness. It is used in the field of manufacturing large diameter pipes.

[Conventional technology]

Steel pipes manufactured by forming steel plates into a cylindrical shape using a press or the like and then welding them bend due to welding distortion. As a method for correcting such bends in steel pipes, Japanese Patent Laid-Open No. 62-97716 discloses a method of simultaneously applying a load in the direction of straightening the bends while expanding the pipe using a mechanical pipe expander and giving it plastic deformation. I proposed it. This method is
This is an excellent method for solving various problems.

However, when actually implementing this method to obtain a steel pipe without bending, the mechanical pipe expansion method, in which the entire length of the steel pipe is divided into parts and expanded several times, cannot be expanded at the same temperature. It is not possible to determine how much strain should be applied in the straightening direction to finally obtain a steel pipe without bending. As a result, there was a problem in that it was not easy to match the axes of both ends of the steel pipe.

[Problem to be solved by the invention]

In order to easily implement the technique disclosed in JP-A No. 62-97716, the present invention determines the optimum load to be applied to the straightening roller for each tube expansion operation. The object of the present invention is to provide a method for straightening the bending of a steel pipe to obtain an unbent steel pipe whose axes at both ends coincide with each other.

Moreover, the straightening device only needs to be attached to the second half of the pipe expanding machine, which is usually a pair of pipe expanding machines, and can be implemented with a small equipment cost.

[Means for Solving the Problems] The present invention provides a method for correcting a bend in a steel pipe when expanding a steel pipe having a bend in the length direction by dividing the pipe into a first half and a second half from the middle part. After completion of the process, the entire length of the steel pipe is measured for bending, (2) the target value for bend correction is calculated to match the axes of both ends of the steel pipe, and (3) during the latter half of the pipe expansion, a load is applied to match the target correction value. This method of straightening a steel pipe is characterized by straightening the steel pipe in addition to the straightening direction, and aligning the axes of both ends of the steel pipe.

In this case, it is preferable to set the bend correction target value for each pipe expansion position to correct the bend, and further compare the bend correction target value for each pipe expansion position with the actual value after correction,
By correcting the correction target value after the last correction so that this difference becomes zero after the final correction, reliable correction of the bend can be performed.

[Effect]

Fig. 1 shows a pipe expanding machine for steel pipe 1. After the steel pipe 1 has been expanded in the first half part A shown in Fig. 2 by the first pipe expanding machine IO, the second part B is expanded by the second pipe expanding machine 10. I do.

Pipe expander 10.11 consisting of two units as a pair as shown in Figure 1
A bend correction roller 6 is attached to the tube expander 11 which is in charge of the latter half of the pipe expansion machine 11, and as shown in FIGS. 2 and 5, a bend measurement sensor 7a is installed.

Attach 7b, 7c, correction amount measuring sensor, 8a, 8b.

First, half of the steel pipe l is expanded by the pipe expander 10, and then
It is carried into the tube expander II. Before starting the pipe expansion work, as shown in Fig. 2, bend measurement sensors 7 f7a, 7b,
7c) Measure the bend I of the steel pipe 1.

Figure 3 shows a schematic diagram of a steel pipe l whose bending amount α has been corrected, and the amount of correction is made during the pipe expansion process repeated n times so that the axes of both ends of the steel pipe coincide when viewed through the pipe. αl, α2, . . . α shown in FIG. This bending amount α is corrected by applying a correction roller.

[Example] Fig. 1 shows the installation situation of a bend correction device in a mechanical pipe expansion process. A tube expander head for expanding a steel pipe 1 consists of a cone 2, a segment 3, and a pull rod 4. As shown in the figure, the pipe expansion equipment usually consists of two pipe expansion machines 10 and 11, which are used to expand each half of the steel pipe.
It is also possible to expand the entire length of the steel pipe with just 1. The rollers 5 carry the steel pipe 1 into the pipe expanding machine, and further move the steel pipe by the length of one expansion for each expansion cycle. The correction roller 6 corrects the bend. The sensor 7 measures the bending of the steel pipe before it is expanded by the pipe expander 11. This sensor 7 can be of various types, such as a contact type or a non-contact type, and the number of measurement points is not limited to three.

FIG. 5 is a partial vertical sectional view of the steel pipe I during expansion. steel pipe l
is conveyed by rollers 5 and expanded by tube expanders 11 (2, 3, 4), and its bends are corrected by straightening rollers 6. The bending sensors 8 (8a, 8b) shown in Fig. 5 measure the amount of partial bending of the steel pipe 1, and confirm the actual amount of correction compared to the amount of correction required for each pipe expansion operation. It is.

Next, the method for correcting bending according to the present invention will be explained.

First, the steel pipe 1 is expanded by half of its length by the first pipe expanding machine 1O in the conventional manner, and one of the purposes of the pipe expansion work is to improve the shape of the steel pipe, that is, to improve its true roundness and straightness.

However, this expansion does not necessarily make the steel pipe into a perfect shape; for example, the straightness of the pipe is affected by a number of factors, such as fluctuations in the wall thickness of the steel pipe, warping due to welding, and the setting of the pipe expander. It leaves some bends.

After the steel pipe 1 has been expanded by the first tube expander IO, it is carried into the tube expander 11 of the tube 2, and the remaining half is expanded. Before that, the bending condition of the entire steel pipe is measured as shown in Fig. 2.

From this measurement result, as shown in Figure 3, when the entire steel pipe is finally passed through, it is found that there is no bending, that is, the amount of reverse bending α required to align the axes of both ends of the steel pipe.
seek. Furthermore, in order to achieve this reverse bending amount α most appropriately among the tube expansion operations performed n times by tube expansion filling, as shown in FIG. 4, correction lαl is performed during each tube expansion operation.

...Determine αn.

When the second pipe expander 11 starts the actual pipe expansion work, for example, 1
In the first tube expansion, the correction roller 6 is operated to correct the amount α1, but when the first tube expansion is completed, the sensor 8 (8a) shown in FIG.

Note the amount actually corrected by 8b).

If there is a difference between the actually corrected amount and the target amount αl, the correction roller control program is set so that the final target value α amount is corrected by the remaining (n-1) tube expansion operations. After the correction, the second pipe expansion work is started and the correction work is performed using a new program. By performing such work every n times of pipe expansion work, the reverse bending amount α of the target value is reliably corrected. Can be done.

Of course, such control of the amount of straightening is based on the bending state of the steel pipe obtained from the bending measurement results and the number of times the steel pipe will be expanded. This is done by an automatic control device that has a program that automatically calculates the amount, taking into consideration the effect that the amount of correction has on the bending of the entire steel pipe and the effect that the amount of n-th correction has, which is very different.

However, depending on the level of straightness required of the steel pipe, the amount of correction α1 for each pipe expansion determined to obtain the reverse bending amount α determined by the sensor 7
. The pipe can also be expanded without being corrected by the sensor 8 (8a, 8b).

In addition, when expanding the entire steel pipe with one pipe expanding machine, it is sufficient to omit the first pipe expanding machine 10 in FIG. The method of the present invention can be applied in exactly the same way as for pipe expansion using a pipe expander.

〔Effect of the invention〕

By the method of the present invention, the axes of both ends of the steel pipe are aligned, and the steel pipe 1
You can get a timeless steel pipe as seen through a book.

Such steel pipes have properties that are important for practical use and in agriculture, and slight bends in the middle of the steel pipe are not a problem, as is the case when laying pipelines to transport oil and gas. The present invention is extremely effective when manufacturing a steel pipe that requires no bending as a whole because of the convenience of connecting the steel pipes one after another.

In addition, the method of the present invention can be effectively carried out using only one of the two pipe expanding machines that are normally used as a pair, and since the straightening operation is performed at the same timing as the pipe expanding, special It can be carried out without increasing equipment costs or labor costs, such as not requiring an increase in man-hours.

[Brief explanation of the drawing]

Fig. 1 is a layout diagram of a mechanical pipe expansion device to which the method of the present invention is applied, Fig. 2 is an explanatory diagram showing a method for measuring bending of steel pipes,
FIG. 3 is a schematic diagram showing the state of the steel pipe after straightening the bend according to the present invention, and FIG. 4 shows the straightening Iαl at each tube expansion to obtain the final bending correction amount α. α2. . . . An explanatory diagram of α0, and FIG. 5 is a partial vertical sectional view of a steel pipe showing a bend straightening process. l...Steel pipe 2...Pipe expander cone 3...Pipe expander segment 4...Pipe expander pull rod 5...Steel pipe conveyance roller 6...Bending correction roller 7 (7a, 7b, 7c) -Bending measurement sensor 8
(8a, 8b) - Correction amount measurement sensor 10.11...
・Pipe expansion machine

Claims (1)

[Scope of Claims] 1. A method for straightening a bend in a steel pipe when expanding a steel pipe having a bend in the length direction by dividing it into a first half and a second half from the middle part, which includes measuring the bend in the entire length of the steel pipe after completing the first half of the pipe expansion. Calculate the bend correction target value to align the axes of both ends of the steel pipe, and during the latter half of the pipe expansion, apply a load that matches the bend correction target value in the bend correction direction of the steel pipe to correct the bend, A method for straightening bends in steel pipes, which is characterized by matching the hearts. 2. A method for correcting bends in steel pipes, which corrects bends by setting the bend correction target value according to claim 1 for each pipe expansion position. 3. Bent correction of a steel pipe according to claim 2, which compares the bend correction target value for each pipe expansion position and the actual value after correction, and corrects the correction target value after the correction so that this difference becomes zero by the last bend correction. Method.