JPS623691B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing square steel pipes, and improves forming accuracy by accurately and easily dividing welded steel pipes produced by continuous roll forming into, for example, square pipes. This invention relates to a method for producing a significantly improved square steel pipe.

There are two methods for manufacturing square steel pipes (hereinafter simply referred to as square pipes) from round tubular materials: forming cut pipes into square pipes, or continuously forming pipes from steel strips. In some cases, the material is formed into a rectangular tube, but in both cases, a method is adopted in which a multi-stage driven rolling roll stand is installed and driven, and the material is passed through and formed.

The drive type rolling roll stand has the function of applying a thrust force to form the tube forward and to feed it forward, and has a configuration in which, for example, a pair of vertical rolls are rotationally driven by an electric motor or the like. For example, when this is used as a four-way rolling roll for a square tube, the upper and lower drive rolls and the left and right rolls are different in size, and the left and right side rolls have a smaller diameter, so it is difficult to make rolls with the same diameter. It was difficult. Therefore, during rolling, the upper and lower large-diameter drive rolls first come into contact and the tube begins to deform, and then the small-diameter side rolls come into contact with it, which should form the four corners of the square tube at the circumference of the tube material. The positioning of the division tends to be inaccurate, and it is extremely difficult to correct the division position in the next stage of rolling. If this dividing position is inaccurate, the lengths of each side of the square tube will be different, resulting in non-uniform corner radii and deformation during the rolling process.

In addition, the speed at each part on the circumferential surface of the drive roll, which is not a flat surface, is different and out of synchronization with the line speed, which tends to cause local slips and so-called overbends. It was not possible to increase the amount of rolling formed per rolling roll stand, and the number of stages of the stand was increasing.

This invention is a method for continuously forming welded steel pipes into square tubes using a continuous roll forming method, which produces square tubes with high forming accuracy, and furthermore produces square tubes with high forming accuracy in a group of rolling stands with a reduced number of rolling stands. This paper proposes a method for manufacturing pipes.

That is, the present invention provides a method of rolling a welded steel pipe formed into a pipe by a continuous roll forming method into a square steel pipe.
The forming line consists of a rolling roll stand and a multi-stage driven rolling roll stand installed in front of it, and the majority of the prescribed forming amount from welded round steel pipes to square pipes is
This method of manufacturing a square steel pipe is characterized in that forming is carried out using the above non-driven four-roll rolling stand, and then the remaining forming is carried out using a multi-stage driven rolling rolling stand to complete the forming.

The method of this invention will be explained below based on the drawings.

Here, the case of a square steel pipe will be explained. As shown in the process diagram in Fig. 1, a steel strip 1 is formed by a plurality of breakdown rolls and side rolls 2, passed through a fin pass roll 3, and immediately before a squeeze roll 4, welded using heat generated by electric resistance. The welded steel pipe 5 is then passed through the coolant, and then placed on the sizing roll stand 6.
It is formed into a square tube by a rolling roll stand group 7 according to the present invention, and then cut into a predetermined length by a traveling cutting machine 8.
Cut with.

In the rolling roll stand group 7, first of all, a Turks head stand 10 is arranged, which is configured to apply rolling force to a steel pipe from four directions: top, bottom, right and left, on an idler roll that does not have a driving force. A plurality of directional rolling roll stands 20 are arranged in a two-stage configuration here.

An example of the Turk's head stand 10 will be explained based on FIGS. 2 and 3. An L-shaped stand consisting of a support 12 and a horizontal base 13 is erected on a base 11 on the floor, and a corner is provided in the center. A U-shaped gripping member 14 with a hole 14a is fastened to the support column 12, and a bearing member 17 consisting of an L-shaped vertical plate 15 and a bottom plate 16 is placed on the diagonal lines of the four corners of the square hole 18a provided in the center. The fixed holding plate 18 is inserted into the groove of the gripping member 14 and fixed, and the idler roll 19 is pivotally supported between the L-shaped vertical plates 15 facing each other. 4 vertical and horizontal idler rolls 1
9 have the same dimensions, and the roll surfaces are formed so that the steel pipe can be rolled down from four directions to a predetermined shape.

On the other hand, the four-way rolling roll stand 20 is a normal drive-type rolling roll stand used for manufacturing square tubes, in which a pair of vertically opposing drive rolls 21 are pivotally supported between supports 22, and are rotationally driven by an electric motor 23. Since the structure is such that the workpiece is sent forward while being rolled down, the drive roll 21 has a larger diameter than the rolling rolls (not shown) that are horizontally opposed and are used to roll down the side surface of the pipe, as described above. is used.

Next, the process of rolling a steel pipe into a square pipe will be explained.
After the steel pipe formed by the continuous roll forming method leaves the squeeze roll 4, it is cooled with a coolant and then rolled in a sizing roll stand 6 to improve the roundness. With the driving force that feeds the subsequent steel strip in the process of forming,
Sent to Turksheadstand.

As mentioned above, the Turks head stand 10 has the following features:
Since idler rolls are used, a large amount of reduction can be achieved, and the fed steel pipe is rolled into a square tube shape at once, completing the reduction of about half of the total amount of square tube forming. That is, the division positions on the circumference of the steel pipe that should be the four corners of the square pipe are determined at once, and the accuracy of pipe cross-section division is improved.

In the case of the conventional method, if the division positioning is performed by successively rolling down with multi-stage driven four-way rolling rolls, the radius of each corner becomes uneven and deformation tends to occur due to the above-mentioned reasons, and the shape accuracy of the square tube tends to deteriorate. was likely to decrease. On the other hand, in the present invention, in the Turk's head stand 10 installed immediately after the sizing roll stand 6, idler rolls with the same shape are used for the four rolls, so the diameters of each roll in the horizontal and vertical directions are different. There is no difference in rolling timing based on

Further, since the rolling rolls are not flat, the line speed only partially matches the line speed, but since the idler rolls are not driven, they can easily be synchronized. However, in the case of driven rolls, since they have their own driving speed, a difference between the line speed and the line speed is likely to occur, so-called statesking motion occurs, and welding during pipe manufacturing due to disturbances in the line speed becomes impossible. This sometimes caused problems such as instability. Therefore, in the case of the conventional drive type, it was necessary to provide a separate drive motor for each roll stand and adjust the speed of each roll in order to minimize slips. On the other hand, according to this invention, since most of the forming is done by the Turk's head, it is possible to use more linear rolls for the driving rolls in the latter stage, there is no standing motion, and the driving electric motor Also, one common machine can drive multiple rolls, in this case two rolls.

Therefore, it is possible to form the tube at once with a large reduction amount without causing problems due to the driven rolls, and to improve the accuracy of dividing the tube cross section.

Next, the rectangular tubular steel pipe exiting the Turk's head stand 10 enters a four-way rolling roll stand 20, where it is given a driving force by drive rolls while being rolled and formed. Here, two-stage four-way rolling roll stand 2
0, it is finished into a square tube of a predetermined shape. As mentioned above, most of the forming can be completed in the Turk's head stand 10, so there is no need to increase the number of stages of the driven four-way rolling roll stand, problems caused by the driven rolls are reduced, and the rolling stand group can be It can be configured with less.

In addition, the propulsion force for the square tube is smoothly applied by the roll group of the continuous roll forming process described above and the driven four-way rolling roll stand 20, so that problems in rolling forming due to insufficient propulsive force do not occur.

As described in detail above, the method for manufacturing a square tube according to the present invention is a rolling process in which a Turk's head with a simple configuration is first placed in the process of successively manufacturing a round tube from a strip steel and then a square tube. This is an excellent method for manufacturing square tubes that can easily improve forming accuracy by using a group of roll stands.

[Brief explanation of the drawing]

FIG. 1 is a process diagram for explaining the manufacturing method according to the present invention, FIGS. 2 and 3 are explanatory diagrams of a Turk's headstand, FIG. 2 is a front view, and FIG. 3 is a side view. In the figure, 1... Steel strip, 6... Sizing roll stand, 7... Rolling roll stand group, 10...
Turkshead, 11... base, 12... pillar,
13... Horizontal table, 14... Gripping member, 17... Bearing member, 18... Holding plate, 19... Idler roll, 20... Rolling roll stand, 21... Drive roll, 22... Support column, 23...Electric motor.

Claims (1)

[Scope of Claims] 1. A method of rolling a welded steel pipe formed into a pipe by continuous roll forming into a square steel pipe,
The forming line consists of a non-driven 4-roll rolling stand installed in front of the sizing roll stand, and a multi-stage driven rolling roll stand installed in front of it, which performs prescribed forming from welded round steel pipes to square pipes. Most of the amount
A method for manufacturing a square steel pipe, characterized in that the above-mentioned process is carried out using the non-driven 4-roll rolling stand, and then the remaining forming is carried out using a multi-stage driven rolling roll stand to complete the forming.