JPS6138717A - Straightening method for welded steel pipes - Google Patents

Abstract

PURPOSE:To straighten the bend of a steel pipe caused by a molding effectively by providing a roll pair pressing a bead from the inside and outside of a pipe and by extending the bead of a welding part with rolling by a roll pair. CONSTITUTION:Rolling rolls 121, 122 of a bead part and each rolling reaction force receiving rolls 131, 132, 141, 142, 151, 152 are arranged at the prescribed position in a rolling work device. The rolls 121, 141 among each roll thereof are then driven and the necessary rolling of the bead part is performed over the whole length of a steel pipe 9 by a bead part rolling roll with moving the welding pipe 9. The bead part is extended in the longitudinal direction of the pipe by said rolling and as a result the lengths of the bead part being compressed by welding and of the other part are made uniform and the bend is straightened.

Description

Detailed Description of the Invention (Industrial Application Field) This invention is an arc welding w1 having a straight welded part.
The present invention relates to a method for correcting bends caused by welding of grass.

(Prior Art) Regarding the straightening of arc welded steel pipes having straight welded parts, a welded steel pipe produced by the UOE pipe manufacturing method will be described below as a representative example.

FIG. 1 is a process diagram showing the general manufacturing process of welded steel pipes using the UOEE pipe manufacturing method. In the figure, first, in the C milling process (1), forming is added to bend both sides of the steel plate, and then the next U
In the pressing process (2), this is further formed into a U-shape, and in the first O-pressing process (3), it is formed into a tubular shape in which both edges of the steel plate face each other and touch each other, and the tack is attached to both edges in the welding process (4). After tacking the parts, the inner welding process (5) and the outer welding process (
In step 6), the tack welding and main welding are performed from the inner and outer surfaces of the tube, respectively, and the tube is formed into a tube shape. However, the ill in this state has poor roundness and straightness due to errors in bending the steel plate and distortion due to thermal stress during welding of the inner and outer surfaces, so the tube is expanded in the next tube expansion step (7). Removal of residual stress, roundness,
After the straightness is corrected, the product is made into a product through an inspection step (8). Figure 2 is an explanatory diagram schematically showing the transition of the shape of the tube (9) in the longitudinal direction during the above manufacturing process. Or, a convex shape (hereinafter simply referred to as a convex shape) may become distorted near the weld after welding due to partial heating during welding due to arc welding and shrinkage during solidification of molten metal during welding. Shrinkage occurs, resulting in a concave shape (hereinafter simply referred to as a concave shape) with the seam as a reference, which deteriorates the straightness and the roundness due to this influence. Although such a shape can be corrected by expanding the tube, Normally, complete correction is possible; even after expansion, the tube usually remains convex (a) or concave (b).

The pipe expanding machine used in the pipe expansion process (7) usually has a member called a segment that is divided into multiple pieces in the circumferential direction attached to a pipe expansion head, and is inserted into the inside of the pipe to apply hydraulic pressure, etc. This method expands the segment concentrically to expand the tube, and the correction of the curvature by this method is due to the following reason.

The mechanical strength within the cross section of the pipe after welding is higher in the weld metal and the vicinity of the weld due to the quenching during welding than in other parts, and is approximately constant elsewhere. When such a tube is expanded, the outside diameter of the tube increases and this deformation causes the tube to shrink in the longitudinal and wall thickness directions, but since the mechanical strength of the welded part is υ higher than that of other tubes, the circumference due to expansion increases. The deformation in the direction is large in parts other than the welded part and small in the welded part, and the deformation in the longitudinal direction accompanying this deformation is also large in parts other than the welded part and small in the welded part. As a result, the length of the steel pipe when welded and the length of the portion other than the welded portion are approximately equalized, and the bending of the steel pipe caused by welding is reduced.

However, such correction of bends only indirectly reduces the bends through the process of deformation of the steel pipe due to pipe expansion, and the effect of straightening is small in terms of wood quality. Moreover, the mechanical strength of a steel pipe, which controls deformation in the circumferential and longitudinal directions, varies from steel to steel and within a steel pipe due to the rolling conditions of the steel plate used as the raw material, changes in heat input during welding, etc. The accuracy of straightening is also insufficient due to factors such as fluctuations in the deformation of the steel pipe during the process, and for this reason, it is difficult to maintain a stable straight shape even after expansion, as shown in Figure 2 above. It is something that cannot be done.

(Object of the Invention) In view of the above-mentioned circumstances, the present invention provides a method for straightening welded steel sheaths that can effectively and stably straighten bends in steel pipes caused by welding in the production of arc-welded steel pipes having a nucleated welded part. This is what we are trying to provide.

(Structure of the Invention) That is, in the manufacturing process of an arc-welded steel pipe having a nucleated weld, a pair of rolls that clamp the bead portion from the inside and outside of the pipe are provided, and the bead of the weld portion is rolled by the pair of rolls. The gist of this invention is a method for straightening a steel pipe, which is characterized by straightening a bend in a steel pipe caused by welding by stretching the inside.

For example, in the manufacturing process of arc-welded steel pipes using the above-mentioned UOE pipe manufacturing method, the curved shape of the pipe after welding becomes concave as shown in Figure 2 due to shrinkage of the weld, and the shape of this bead is As shown in the cross-sectional view of FIG. 3, the pipe (9) has a raised and durable shape (10/) from the inner and outer surfaces. If this embossed ridge shape (10/Xl0J) is flattened by rolling according to the method of the present invention, the bead portion αη
The shrinkage of the bead caused by stretching and welding returns to its original length, making the length of each section of the steel pipe uniform, and the bends can be straightened. If the tube after whitening correction is expanded as usual, it is possible to stably obtain a tube with good straightness as well as υ roundness.

Note that the present invention is not particularly limited in its scope of application, and can be applied to any straight seam arc welded steel pipe regardless of the manufacturing method. In the sense that it effectively contributes to roundness defects caused by Its application is significant.

FIG. 4 is a cross-sectional view showing an example of an apparatus for implementing the method of the present invention.

In the figure, (9) is the welded w4 pipe, αη is the bead part (
12/) (122) is a bead part rolling roll; (12/)
) is an upper roll equipped with a rolling down mechanism (not shown), (
12a) is the lower roll. (18/) (18 pieces), (
14 / The rolling reaction force receiver installed as shown in the figure is a roll.
/X14/X15/) is an outer roll supported by a support mechanism (not shown), and (18xX14aX152) is an inner roll.

aQ is the rolling roll (12, 2) on the inner surface of the tube and the rolling reaction force receiver are low IL/(13 pieces) (14 pieces) (15 pieces)
This is a roll support device that can support and move in the axial direction within a tube.

Note that the rolling reaction force on the inner surface of the tube due to rolling by the bead rolls is transmitted to the outer surface of the tube through the entire tube wall, so in order to prevent deformation of the tube wall due to this rolling reaction force, the rolling reaction force receiver is The contact length of the rolls (1B/ ) OB, 2), (14/XI), (15/X15) with the tube is different from that of the bead rolling roll (12/X12.2) and that of the straw. It is necessary to keep a large size for the straightening of the welded steel pipe according to the present invention using the apparatus shown in FIG. 4 as described below.

That is, this rolling processing device has a bead part rolling roll (1
21) (122) and each rolling reaction force receiver is a roll (187
)(18,2)(14/ )(14 x 151 x 152
) is placed at the predetermined position shown in Fig. 4, and the rollers (12/) and (14/) are driven to move the steel pipe at an appropriate speed, and then the entire length of the pipe is rolled by the bead rolling rolls. The required rolling of the bead portion is performed over a period of time. By this rolling, the bead portion is stretched in the longitudinal direction of the tube, and as a result, the lengths of the bead portion and other portions that have shrunk due to welding are equalized, and curvature is corrected.

Further, according to the method of the present invention, by adjusting the amount of reduction of the bead rolling roll in response to changes in the shape of the wI pipe after welding and changes in the shape of the pipe depending on the outside diameter or wall thickness of the pipe, it is possible to accurately It is possible to stably obtain good straightness by correcting curvature.

Next, an example in which the straightening method of the present invention is applied to a welded steel pipe manufacturing process using the UOE pipe manufacturing method will be described.

FIG. 5 is a process diagram showing an example of the manufacturing process of the above-mentioned UOE method. Figure 5 shows the outer welding process (6) and the tube expansion process (6) in the same UOE manufacturing process as shown in Figure 1 above.
This is an example in which a bead rolling process αη based on the present invention is provided between the process and 7). That is, the welded steel pipe that has exited the outer surface welding step (6) is straightened of curvature in the bead rolling step ση. Once the bends have been corrected in this way and the steel pipe has achieved a high level of straightness, it is sent to the pipe expansion process (7), where the straightness and roundness are corrected by pipe expansion, compared to the conventional method. This makes it possible to obtain a welded W4 pipe with extremely high dimensional accuracy.

(Effect of the invention) Next, the present invention will be explained in detail with reference to examples.

Using various steel plates with various wall thicknesses and plate widths, which are plain steel with a tensile strength of 50τ and a material return, the pipes are expanded in the manufacturing process of welded steel pipes using the conventional UOE pipe manufacturing method shown in Figure 1. A large number of test tubes (conventional example) with different outer diameters and wall thicknesses were obtained by mechanically expanding the tubes at a rate of 1%.

In addition, using the same material as above and using the TJOE pipe manufacturing method that incorporates the straightening method of the present invention shown in Fig. 5, the pipe can be expanded at a pipe expansion rate of 1% in the same manner as straightening the curved area by rolling the bead. ,
A large number of test tubes (examples of the present invention) with different outer diameters and wall thicknesses were obtained.

The roundness and curved edges of the above conventional example and the present invention example were investigated, and the relationship between roundness and wall thickness is shown in the graph of FIG.
The relationship between the diameter and the outer diameter is shown in the graph of FIG. As shown in Figure 8, roundness is defined as the outer diameter passing through the bead αη (
3) and the difference between this and the outer diameter in the 90 degree direction (A-B'
), and the bend is at 12 of the tube (9) as shown in Figure 9.
The amount of bending per m length (δ) is shown. Also, in FIGS. 6, 7, and 7, the circle indicates the conventional example, and the X indicates the example of the present invention.

Regarding the throughness and roundness shown in FIG. 6, regardless of the wall thickness, the example of the present invention always shows a higher level of performance than the conventional example, and the throughput shown in FIG. Regarding bending, the examples of the present invention always recorded a higher level of performance than the conventional examples, regardless of the size of the outer diameter.

As is clear from the above explanation, according to the method of the present invention, the bending of the pipe is corrected by rolling the bead portion with rolling rolls without substantially affecting the cross-sectional shape of the pipe. When the method of the present invention is applied to the manufacturing process of welded steel pipes that involves the pipe expansion process, it is possible to accurately respond to changes in shape and consistently obtain a high level of straightness. In combination with pipe expansion and straightening, it is possible to manufacture welded steel pipes with extremely good straightness and roundness.Therefore, the present invention greatly contributes to improving the dimensional accuracy of arc-welded steel pipes having neat welded parts. It is.

[Brief explanation of the drawing]

Figure 1 is a process diagram showing an example of the manufacturing process of welded steel pipes using the conventional UOE pipe manufacturing method, Figure 2 is an explanatory diagram schematically showing the shape of the base pipe for each process in the UOE pipe manufacturing method, The figure is a cross-sectional view showing the shape of a bead in a pipe welded part by arc bath welding.
Fig. 4 is an explanatory diagram showing an example of a device for carrying out the straightening method of the present invention, and is a cross-sectional view, and Fig. 5 is a welded steel pipe manufactured by the UOE pipe manufacturing method in which the method of the present invention is incorporated into a part of the process. A process diagram showing an example of the process, Figure 6 is a graph showing the relationship between roundness and wall thickness, Figure 7 is a graph showing the relationship between bending and outer diameter,
FIG. 8 is an explanatory diagram of a method for measuring roundness, and FIG. 9 is an explanatory diagram of a method for measuring curvature. 1: C press process, 2: U press process, 3: O press process, 4: Welding process for tacking, 5: Internal welding process, 6: External welding process, 7: Pipe expansion process, 8: Inspection process, 9: tube, lO
: Protrusion, l■: Bead part, 12/12.2 : Bead part rolling roll, ■311B2.14/14mm 15/15
．． 2: Rolling reaction force receiver is a roll, 16: Roll support device,
17: Bead part rolling process I; ＼ Sea i)-

Claims (1)

[Claims] (1) In the manufacturing process of arc-welded steel pipes with straight welds, a pair of rolls is provided that clamps the bead from the inside and outside of the pipe, and the pair of rolls rolls the bead of the weld and stretches the bead. A method for straightening steel pipes, which comprises straightening bends in steel pipes caused by welding.