JP2543283B2 - Manufacturing method of ERW steel pipe with excellent roundness - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an electric resistance welded steel pipe having excellent pipe end and roundness of the pipe body.

[0002]

2. Description of the Related Art A conventional electric resistance welded pipe is formed by continuously forming a band steel using a roll having a hole shape and performing electric resistance welding, and then arranging a plurality of drawing stands for a fixed shape to form a perfect circle. Molding is performed to keep the shape close to. However, for example, Japanese Patent Application No. Sho 62
As shown in No. 157620, conventionally, since a method of forming a perfect circle with a hole type by drawing with two sets of upper and lower rolls is adopted, when giving a reduction (reduction), Horizontal side rolls with different 90-degree roll axis angles are placed in front of a pair of upper and lower squeeze rolls, and the pipes are deformed vertically in order to prevent flaws so that they do not come into contact with the roll flange at the initial stage of molding. , Drawing is performed.

However, such thin and high-strength steel pipes, especially steel pipes for propeller shafts, have a t / D (t: wall thickness,
In a thin-walled pipe having an outer diameter of 3% or less, the circularity of the pipe body is good, but the pipe end of the cut portion has an elliptical shape and the roundness is low, and the residual stress of the pipe is There is a problem that deformation occurs due to the uniform distribution.

[0004]

In the conventional forming method, the strain history applied to the steel pipe is controlled by setting the side rolls before draw forming, so that the roundness of the pipe end becomes close to that of the pipe body. It is necessary to perform such molding. However, with this method, it is necessary to set the side rolls arranged on the entrance side and change the hole shape of the side rolls in accordance with the material strength and t / D, which makes stable operation difficult. The present invention
The purpose of the present invention is to easily manufacture a thin-walled electric resistance welded steel pipe having high roundness at both ends of the pipe body.

[0005]

DISCLOSURE OF THE INVENTION To solve the above problems, the present inventors first analyzed the sizer molding in detail, and as a result, made it possible to increase the roundness of the pipe end with a steel pipe having a small t / D. The reason why it cannot be done is that in forming by shaping the steel pipe after welding using rolls, the deformation of uneven bending / unbending in the circumferential direction when forming in the axial direction of the steel pipe causes compression strain in the circumferential direction. I found out that it happens because it is added at the same time as the transformation. Further, it was found that the steel pipe is bent along the axial direction of the steel pipe of the roll, and the cause is that the number of roll divisions of the small diameter electric resistance welded steel pipe sizer standard machine is as small as two rolls.

[0006] That is, the gist of the present invention is that in the method of manufacturing the electric resistance welded steel pipe by continuously roll-forming the strip steel, in the sizer process for adjusting the size and shape,
The final stage sizer roll is divided into four or more, the bottom diameter of each roll is 3 times or more the diameter of the steel pipe, and the bottom diameter of each roll is equal, and the sizer roll is non-driving.
Longitudinal direction with a draw ratio of 0.05 to 0.5% or less
A method for producing an electric resistance welded steel pipe having excellent circularity, characterized in that the circumferential distribution of the residual stress in the direction and the circumferential direction of the steel pipe is made uniform .

[0007]

According to the present invention, the deformation of the pipe end caused by the non-uniform residual stress is easily prevented by uniformly imparting the axial bending / unbending deformation of the pipe in the circumferential direction. is there.

By using a multi-divided roll close to axially symmetric deformation so that the circumferential direction is uniformly formed at the final stage of sizer molding, the strain history is made uniform in the circumferential direction, and the circumferential residual stress is distributed in the circumferential direction. Can be made uniform, the difference in deformation between the pipe body and the pipe end can be reduced, and the roundness of the pipe end can be improved. As the number of divisions is large and the roll diameter Dr is large, the bending curvature in the longitudinal direction (having a distribution with the roll bottom diameter and the angle in the roll circumferential direction) is made uniform in the circumferential direction (Fig. 1), and residual stress after molding is reduced. The uniformity can be lowered and the roundness of the tube end can be improved. In addition, the roll is not driven, and the roll friction generated by the drive roll and the peripheral speed difference have little influence on the forming.

The sizer roll of the present invention is divided into four or more parts. The reason is to improve the roll position and the accuracy of the pipe body, and it is easy to make it non-driving, and
This is because it is easy to make the rigidity of the housing that supports the roll uniform.

The reason for making the bottom diameter of the sizer roll more than three times the steel pipe diameter is that the difference in roll axial curvature when divided into four or more becomes smaller as the roll diameter becomes larger, and the roll bottom becomes smaller. This is because the larger the diameter, the higher the effect of making the residual stress uniform. Since the variation of the residual stress in the circumferential direction becomes almost uniform when the roll bottom diameter is three times the steel pipe diameter, the deformation of the pipe end is also reduced as shown in FIG.

As described above, according to the present invention, by making the sizer roll into four or more and the roll bottom diameter to be three times or more, an electric resistance welded steel pipe having a good roundness not only in the pipe body but also in the pipe end can be obtained. It is a thing.

Further, in order to make the residual stress uniform, it is necessary to give a reduction amount that erases the history in the sizer, and the reduction ratio is such that at least the entire circumference of the pipe is in the plastic region and the pipe before molding is Considering the shape irregularity, an appropriate reduction ratio is 0.05 to 0.5% as shown in FIG.

FIG. 4 shows an example of the construction of a concrete pipe forming apparatus. Reference numeral 1 is a steel pipe, 2 is a squeeze roll for welding, 3 is a vertical (side) roll, and 4 is a horizontal (upper and lower) roll. After arranging a plurality of horizontal and vertical sizer stands, a four-division non-drive sizer roll 5 is installed to complete the final shaping process.

[0014]

EXAMPLE As an example of the present invention, the outer diameter D = 75.0
(Mm) wall thickness t = 1.6 (mm), t / D = 2.1 (%)
The measurement result of the roundness measuring machine of the pipe end portion when the thin-walled electric resistance welded steel pipe of No. 3 was given a drawing amount of 0.1% at the final stage. When only the conventional horizontal roll and vertical two-roll method is used for drawing, the residual stress in the longitudinal direction is non-uniform in the circumferential direction, so that the pipe end deforms as shown in Fig. 5 and the perfect circle at the pipe end is generated. In contrast to the fact that the degree is not secured, it is apparent that the tube body and the tube end of the four-division roll have good roundness. Further, according to the method of the present invention, in addition to the conventional two rolls in which a plurality of vertical / horizontal rolls are combined and the four roll sizer only for vertical movement, the thin-wall electric resistance welded steel pipe with improved pipe end deformation is manufactured by incorporating it in the final stage. it can.

[0015]

EFFECT OF THE INVENTION The method of the present invention uses an existing pipe forming apparatus, and only by adding a stand at the final stage, in a thin-wall ERW steel pipe,
It is possible to easily manufacture a steel pipe having a high circularity over the entire length and a uniform residual stress distribution, and it is possible to bring industrially beneficial effects.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing the influence of the number of roll divisions and the bottom diameter on the present invention.

FIG. 2 is a diagram showing the influence of the number of roll divisions and the bottom diameter on the present invention.

FIG. 3 is a diagram showing the relationship between the circularity of the sizer diaphragm of the present invention, the tube body, and the tube end.

FIG. 4 is a configuration diagram of a pipe forming apparatus.

FIG. 5 is a comparison diagram of circularity shapes of steel pipes when a conventional two-roll and a four-roll method of the present invention are formed.

[Explanation of symbols]

 1 Steel Pipe 2 SQ Roll for Welding 3 Vertical (Side) Roll 4 Horizontal (Upper and Lower) Roll 5 4 Roll Non-Drive Roll of the Present Invention

Claims (1)

(57) [Claims] 1. A method for producing an electric resistance welded steel pipe by continuously roll-forming a band steel, wherein in a sizer process for adjusting the size and shape, the final sizer roll is divided into four or more parts, and the bottom diameter of each roll is adjusted. and more than three times the roll diameter of the steel pipe diameter and the bottom diameter of each roll was set to equal diameter, sizer
The roll is not driven, and the aperture is 0.05 to 0.5% or less.
Circumferential direction of steel pipe of residual stress in longitudinal and circumferential directions
A method for producing an electric resistance welded steel pipe having excellent circularity, which is characterized by making the direction distribution uniform .