JPH033526B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fin pass for an electric resistance welded steel pipe in which a cylindrical strip is rolled down in the circumferential direction of the pipe by a plurality of fin pass rolls to finish form it into a blank pipe. This invention relates to a rolling reduction control method in roll forming.

Generally, electric resistance welded steel pipes are manufactured using manufacturing equipment based on cage roll forming, step roll forming, semi-cage roll forming, and the like.
That is, in the manufacturing equipment based on the cage roll forming method shown in FIGS. 1 and 2, for example, the strip plate 10 is formed by a breakdown roll 12 in the initial and middle stages of forming, an edge forming roll 14, an outside cage roll 16, and an inside roll. After being sequentially formed into a cylindrical shape on the cage roll 18, a random type first fine pass roll (1F) 20 and a second fine pass roll (2
F) 22, the third fin pass roll (3F) 24 sequentially rolls down the pipe in the circumferential direction, thereby stably forming the edge portion 10a, and finish forming the blank pipe 26 into a predetermined pipe shape and size. . The raw pipe 26 rolled down in the circumferential direction by the fin pass rolls 20, 22, and 24 is subjected to high-frequency heating at both seam edge portions 26a, and is upset-welded by the squeeze rolls 28 to become an electric resistance welded steel pipe 29. In addition,
In FIG. 1 and FIG. 2, 20a, 22a,
24a indicates the upper roll, 20b, 22b, 24
b indicates side roll, 20c, 22c, 24
c indicates the lower roll. Further, FIG. 3 shows the state of forming the raw tube by the first fin pass roll 20.

In the manufacturing process of the above-mentioned electric resistance welded steel pipe, the forming condition of both edges of the strip is extremely important, and if the edge forming is defective, this will lead to a decrease in the shape quality of the welded part and a decrease in material yield. In particular, the front and rear ends of the strip are unsteady regions of forming and the restraint applied to the strip is weak, making the strip easy to fluctuate, and the action of longitudinal tension is also reduced. This results in forming defects such as asymmetrical bending of both left and right edges and the generation of edge waves, which is a bigger problem than the material yield.

By the way, in the above-mentioned method for forming ERW steel pipes, the rolling conditions such as the amount of reduction and the distribution of the rolling reduction of the tandem type fine pass rolls have a very large influence on the formability of the strip edge. Depending on the selection of conditions, edge forming defects such as edge waves may occur, making stable welding with a squeeze roll difficult.

For this reason, selection of an appropriate fine pass reduction amount and appropriate reduction distribution that can stabilize edge forming has become an extremely important management element. Therefore, we conducted various experiments and research to examine the appropriate amount of reduction and distribution of reduction in the fine pass, and found that, in particular,
It has been recognized that the roll reduction distribution has a large effect on edge formability, and the appropriate fine pass forming conditions are to set the total roll reduction amount of the fine pass in the range of 0.5% to 1.5%, and to adjust the roll reduction distribution of the fine pass to the first fine pass roll. It has become clear that it is desirable to use a gradient reduction distribution for the first fine pass roll with strong reduction, in which the reduction amount is large and the reduction amounts of the other subsequent fine pass rolls are gradually reduced. The molding conditions have been adopted to stabilize edge molding.

However, when using the inclined reduction distribution conditions of the first fine-pass roll strong reduction die, although the edge forming in the steady part of the strip is extremely stable, the edge forming shape in the unsteady forming area of the leading and trailing ends of the strip is still This has not been improved, resulting in frequent forming defects due to edge waves, etc., and a decrease in material yield due to welding defects.

The present invention stabilizes the edge forming shape of the leading end and trailing end as unsteady forming areas of the strip plate, improves the quality of the welded part shape of the leading end and trailing end, and
Fin pass roll forming of ERW steel pipes that makes it possible to manufacture ERW steel pipes with high material yield and excellent welded part shape quality by stabilizing the edge forming of the middle part as the steady forming area of the strip. The purpose of the present invention is to provide a method for controlling the reduction in pressure.

In order to achieve the above object, the present invention provides fins of an electric resistance welded steel pipe that are finished formed into a blank pipe by sequentially rolling down a cylindrical strip circle in the pipe circumferential direction with a plurality of fin pass rolls. In the rolling reduction control method in pass roll forming, for the tip and rear ends of the strip as unsteady forming areas, the rolling reduction amount of each fine pass roll is approximately equal to each other, and the rolling reduction is distributed evenly, and steady forming is performed. For the intermediate part of the strip plate as a zone, the rolling reduction amount of the first fine pass roll is relatively large, and the rolling reduction amount of the other succeeding fine pass rolls is gradually reduced, so that an inclined rolling distribution is adopted. This is what I did.

The present invention will be explained in detail below.

The present invention was made based on the results of numerous experiments and studies conducted by the inventors in order to obtain an appropriate range of fine pass reduction forming conditions without edge forming defects. In other words, we clarified the appropriate reduction distribution of the tandem type fin pass rolls at the front and rear ends of the strip, which are the unsteady forming region, and the middle part of the strip, which is the steady forming region. This is to dynamically change the distribution of the reduction in pressure and control the reduction.

The appropriate rolling reduction distribution condition range for tandem type fin pass rolls obtained as a result of experiments and research by the inventors is as follows.

First, the proper fin pass rolling reduction distribution conditions () that do not cause edge forming defects at the leading and trailing ends of the strip, which is an unsteady region of forming, are as shown by the shaded area in Figure 4A, for the first fin pass roll (1F). Reduction rate r ₁
(The rolling reduction ratio r _i of each stand is expressed as r _i =100l _o (l _i-1 /l _i ) using the outer circumference length l _i of the exit side of the i-th stand). The rolling reduction ratio r ₂ of the second fine pass roll (2F) and the third fine pass roll (3F),
r ₃ is within the range of 0.5 to 1.0, and r ₁ ≧ r ₂ ≧
It satisfies _r3 . That is, this fine pass appropriate rolling reduction distribution condition range () is a fine pass forming condition close to a substantially uniform rolling reduction distribution. In addition, the second
If the rolling reduction ratios r ₂ and r ₃ of the fine pass roll (2F) and the third fine pass roll (3F) deviate from the above-mentioned fine pass roll appropriate rolling reduction distribution condition range () and are in the region P exceeding 1.0. The occurrence of edge waves and buckling in the circumferential direction of the edges at the tip and rear end of the strip becomes significant, and there is a possibility that excessive thickening will occur at the edge of the raw pipe. In addition, the second fine pass roll (2F), the third fine pass roll (3F)
The area Q in which the rolling reduction ratios r ₂ and r ₃ of
In this case, the occurrence of edge waves at the tip and rear end of the band plate becomes noticeable, and there is a possibility that a defect in the shape of the tip flower occurs.

Next, as shown by the shaded area in FIG. 4B, the range of appropriate rolling reduction conditions for the fine pass in which edge forming failure does not occur in the middle part of the strip as the steady forming area of the strip is as shown by the shaded area in FIG. 4B. The rolling reduction ratio r ₂ of the second fine pass roll (2F) and the third fine pass roll (3F) when the rolling reduction ratio r ₁ of is 1,
r ₃ is within the range of r ₂ =0.1 to 0.5 and r ₃ =0 to 0.3, and satisfies r ₁ > r ₂ > r ₃ . In other words, this fine pass appropriate rolling reduction distribution condition range () is a first fine pass where the rolling reduction ratio of the first fine pass roll (1F) is the largest and the rolling reduction ratios of the other succeeding fine pass rolls are decreased in stages. This is the condition for forming the fin pass with a gradient reduction distribution under strong pressure of the fin pass roll. In addition, the rolling reduction ratio r ₂ of the second fine pass roll (2F) and the third fine pass roll (3F),
If r ₃ deviates from the above-mentioned fin path appropriate reduction distribution condition range () and is in the region R of FIG. This results in excessive thickening. In addition, when the reduction ratios r ₂ and r ₃ are in the region S of Fig. 4B, the occurrence of edge waves becomes noticeable, and the welding becomes unstable due to vertical fluctuations of the edges during welding, and the weld seam Twisting, etc. may occur.

By the way, the fine pass total rolling reduction rate under the fine pass proper rolling reduction distribution conditions according to the present invention is as follows:
As a result of experiments and research, it has been found that setting the content in the range of 0.5 to 1.5% is satisfactory.

Figure 5 shows the tip and rear ends of the strip, which is an unsteady forming area under the fine pass rolling distribution conditions, from a series of experiments and research conducted to obtain the fine pass appropriate rolling reduction distribution condition ranges () and () in the present invention. and the edge wave steepness (d/l _s ) at the middle part of the strip, which is the steady forming area (as shown in Figure 6, the value obtained by dividing the edge wave depth d by the edge wave span l _s ). The following is an example of the influence that can have. In Fig. 5, the mark △ indicates the result when forming is carried out under the fine pass rolling reduction distribution conditions shown in L1 of Fig. _4A . It is confirmed that the edge wave is small and the edge forming is stable. On the other hand, the circle mark in Figure 5 is the result when forming is performed under the fine pass reduction distribution conditions shown in L2 in Figure _4B , and the edge waves in the steady section of the strip are extremely small and the forming is stable. However, it is recognized that the edge waves at the leading and trailing ends of the strip are large and the forming is unstable. In addition, a detailed investigation into the effect of edge wave steepness (d/l _s ) on weld quality revealed that the steepness (d/l _s ) was 20×
It is recognized that there is no problem if it is less than 10 ^-4 .

From the above results, forming is performed under the appropriate rolling distribution conditions () at the leading and trailing ends of the strip, which are the unsteady forming region, and under the proper rolling distribution conditions () at the middle section of the strip, which is the steady forming region. Once formed, it is clear that the edge forming of the strip is extremely stable. In other words, at each position of the tip, steady portion, and rear end of the strip, the fine pass reduction distribution is
By changing the appropriate reduction distribution conditions () and () shown in the figure, it is possible to significantly improve the edge forming defects of the strip, resulting in an ERW steel pipe with excellent weld quality and shape. It becomes possible to manufacture the same, and it also becomes possible to improve the material yield.

Next, specific implementation procedures according to the present invention will be explained.

FIG. 7 is an explanatory diagram showing the fin pass roll reduction control method in the present invention. First, before threading the strip, the rolling of the tandem type fin pass roll is carried out at the fourth
The rolling distribution is set to the appropriate rolling distribution condition range () shown in Figure A, and then the strip is inserted and forming is performed. In the range of the unsteady forming area A at the tip of the strip, forming is performed with the reduction distribution within the appropriate reduction distribution condition range (), and after passing point X at the tip of the strip, the steady forming area S
In the forming, the rolling reduction of the tandem type fine pass rolls is changed to the rolling reduction distribution within the proper rolling distribution condition range () shown in FIG. 4B, and forming is performed under the rolling reduction distribution conditions. From point Y at the rear end of the strip, that is, in the unsteady forming area B, the rolling distribution is changed again to the proper rolling distribution condition range (), and forming is performed under the rolling distribution condition. by the way,
The ranges of the unsteady forming regions A and B are determined in advance based on the outer diameter of the tube, the plate thickness, the strength of the material, etc. In addition, changing the rolling reduction distribution of the fine pass rolls at points X and Y actually requires some time to change the rolling reduction, as shown by broken lines a-b and c-d in FIG. Although the conditions may deviate from the appropriate rolling reduction distribution condition range (), (), since the molding is for a short time, no molding defects occur.

Note that, in the case of the 4-roll type fin pass roll 20 shown in FIG.
Three or more rolls of 0b (at least the upper roll in the case of a two-roll type fine pass roll) are controlled by a hydraulic reduction control mechanism or an electric reduction control mechanism to control the upper roll and both rollers so that a predetermined reduction amount is achieved during forming. The side roll (in the case of a two-roll type fin pass roll, the upper roll) is dynamically moved to make it possible to change the amount of reduction of the fin pass.

In addition, when changing the setting position of the fine pass rolls, coordinates are managed for the arbitrary reference points of each rolling reduction control roll, and in order to apply a prescribed rolling reduction, the coordinate points to which the reference points of these rolls should be moved must be calculated in advance. , the amount and direction of movement of each roll that allows the reference point of each roll to be moved to the coordinate point may be calculated, and each roll may be moved in accordance with the calculation result. Furthermore, if a control mechanism is provided that measures each roll gap of the fin pass roll and makes the measured value a predetermined value, it is possible to improve the accuracy of the dynamic reduction control of the fin pass according to the present invention.

According to the present invention, for example, the wall thickness t/outer diameter D, which has conventionally caused a problem of generation of edge waves, is 1%.
It is also possible to stably manufacture front and rear high-strength, thin-walled electric resistance welded steel pipes.

Further, the present invention is not limited to the electric resistance welded steel pipe manufacturing equipment using the cage roll forming method, but is similarly applicable to fin pass roll forming using manufacturing equipment such as the step roll forming method or the semi-cage roll method.

As described above, the rolling reduction control method in fine pass roll forming of an ERW steel pipe according to the present invention is based on the rolling reduction amount of each fine pass roll for the tip and rear ends of the strip as unsteady forming regions. The rolling reduction is distributed evenly so that they are approximately equal to each other, and the rolling reduction amount of the first fine pass roll is relatively large for the middle part of the strip serving as a steady forming area, and the rolling reduction amount of the other succeeding fine pass rolls is set relatively large. This is a gradient reduction distribution that decreases stepwise. Therefore, according to the present invention, the edge forming shape of the leading and trailing ends as an unsteady forming area of the strip is stabilized, the shape quality of the welded part at the leading and trailing ends is improved, and the shape forming of the strip is improved. It is also possible to stabilize the edge forming in the middle part as a region, and it becomes possible to stably manufacture an electric resistance welded steel pipe with a high material yield and excellent welded part shape quality.

[Brief explanation of the drawing]

Fig. 1 is a plan view showing the process of forming an ERW steel pipe using the cage roll method, Fig. 2 is a side view of Fig. 1, Fig. 3 is an enlarged sectional view taken along line - in Fig. 2, 4. Figures A and B are diagrams showing the fine pass appropriate reduction distribution condition ranges () and () according to the present invention;
The figure is a diagram showing the influence of the fin pass reduction distribution on the generation of edge waves at each forming position in the longitudinal direction of the strip, Figure 6 is a schematic diagram showing the edge wave evaluation method, and Figure 7 is the fin pass according to the present invention. It is a schematic diagram which shows the roll reduction distribution control method. DESCRIPTION OF SYMBOLS 10... Band plate, 10a... Band plate edge part, 20... First fin pass roll (1F), 22... Second fin pass roll (2F), 24... Third fin pass roll (3F), 26... Base pipe.

Claims (1)

[Claims] 1 In a roll-down control method in fine-pass roll forming of an ERW steel pipe, in which a cylindrical strip is sequentially rolled down in the tube circumferential direction by a plurality of fine-pass rolls to form a blank pipe, an unsteady For the tip and rear ends of the strip, which serve as the forming area, the rolling reduction of each fin pass roll is distributed evenly so that they are approximately equal to each other, and for the middle part of the strip, which serves as the steady forming area, Fin pass roll forming of an ERW steel pipe characterized in that the rolling reduction amount of the first fine pass roll is relatively large and the rolling reduction amount of the other succeeding fine pass rolls is gradually reduced. Rolling down control method.