JPH08260B2 - Setting method of ERW tube cage roll - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for setting an electric resistance welded cage roll.

That is, when a strip-shaped steel plate is continuously formed to manufacture a tubular product, the cage roll is optimized to prevent buckling and twisting.

[Conventional technology]

For roll setting in ERW pipe manufacturing, downhill forming is used to gradually lower the height of the material for the breakdown in the initial stage of forming, and roll gap setting is used to adjust the reduction in the fin pass. However, for cage rolls, a uniform setting method has not been established due to the large degree of freedom in setting rolls and the large number of rolls. Generally, in forming with a cage roll, it is difficult to apply a tensile force in the longitudinal direction or a compressive force in the circumferential direction to the steel strip, so that bending deformation mainly occurs in the cross-sectional shape of the steel strip in the width direction. It is conceivable that the bending is distributed mainly on the entrance side, mainly on the exit side, or evenly distributed. In addition, as another view of bending distribution, the center of the steel strip is mainly bent at the entrance side, the edge of the steel strip is mainly bent at the exit side, the edge of the steel strip is mainly bent at the entrance side, and the Bending distribution such as bending the center of the steel strip is conceivable.For steel pipes to be formed, when the conditions such as various outer diameters and plate thickness are different, what kind of bending distribution is taken in the cage roll row. The issue is whether the best results can be obtained. Therefore, it is conceivable to determine the roll setting position of each cage roll pair in the cage roll row by repeating trial and error, but in this case, setting is difficult because the number of rolls is large.

As a conventional cage roll setting method, according to a report entitled “Outline of 26-inch ERW Steel Pipe Manufacturing Equipment” published on pages 39 to 43 of Ishikawajima Harima Technical Report 19-1 (1979), As shown in the figure, the cage roll 1 has the same deformation even if the outer diameter changes.
There is a setting method that allows you to simply slide on a straight line. This method has the following problems.

(A) When the pipe outer diameter changes, the length of the equipment does not change, so the total length of the cage roll row does not change, and the ratio of the pipe outer diameter to the cage roll row length is different, and the deformation cannot be considered similar. . Therefore, it is difficult to set the optimum setting that can be commonly used for both the pipe having a small outer diameter and the pipe having a large outer diameter in a range that can be manufactured by the manufacturing facility.

(B) When the wall thickness and strength are changed, the rigidity of the material and the progress of plastic deformation are changed, so the optimum roll setting position changes, but this roll setting method does not consider the effects of wall thickness and strength. Therefore, if the wall thicknesses are greatly different, or if the strengths of the materials are significantly different, it is difficult to make optimum settings that can be shared.

(C) A setting method that is particularly advantageous for preventing buckling, which is a problem when manufacturing a thin-walled tube, and is particularly effective for preventing twisting, which is a problem when manufacturing a thick-walled tube, is not clear. Therefore, in the conventional production of electric resistance welded pipes with roll setting, buckling in the production of pipes with a small wall thickness-outer diameter ratio (t / D) and twisting in the production of pipes with a large wall thickness-outer diameter ratio are prevented. I can't.

[Problems to be solved by the invention]

In the conventional technique, as a method of setting the cage roll, it is possible to prevent molding defects due to buckling in a thin material over a wide range of outer diameter, plate thickness, and strength range. There was no way to prevent molding failure. Therefore, over a wide range of outer diameters, plate thicknesses, and strengths, the cage rolls can be optimally set without any particular difficulty, and the occurrence of molding defects due to buckling of thin-walled materials and thickness There is a demand for the appearance of a method for optimally setting cage rolls that can prevent the occurrence of molding defects due to twist in meat material.

[Means for solving problems]

The present invention has been invented in order to meet the above-mentioned demand, and its gist is a cage roll pair in which two cage rolls are symmetrically set between a breakdown roll row and a fin pass roll row. In a roll forming line for arranging a plurality of pairs as a cage roll row, and using the cage roll row to roll-form a steel strip, at the entrance side of the cage roll row as indicated by reference numeral 2 in FIG. 1 (a). A cross-sectional shape in the width direction of the steel strip which is symmetrical to the left and right, and reference numeral 3 in Fig. 1 (a).
The widthwise cross-sectional shape of the steel strip, which is also symmetrical on the exit side, and the outer diameter, wall thickness, and material strength of the steel pipe to be formed, as shown in Fig. Determine the deformed shape of the symmetrical steel strip,
Each cage roll pair is shown in FIG. 1 (b) along the deformed shape.
When setting at the required setting angle θ as shown in, the tangent line of the deformed shape and the generatrix of the cage roll match, and
Among the conditions that the forming reaction force by the cage rolls effectively works, the center position of the cross-sectional shape in the width direction of the symmetrical steel strip at each cage roll pair position obtained from the deformed shape, and the width direction A method for setting the electric resistance welded cage roll, characterized in that the set angle θ is set by selecting one that minimizes the moment arm determined by the direction of the forming reaction force determined from the tangential direction of the cage roll with respect to the cross-sectional shape. It is in.

Generally, in the breakdown used in the former stage of cage roll row formation and in the fin pass used in the latter stage of forming, the forming shape is mainly determined by the roll hole type, but in the cage, the contact area between the material and the roll is the circumference of the material. However, it is difficult to obtain the cross-sectional shape like the roll hole type. However, in order to accurately obtain the deformed shape in order to obtain the optimum setting value in the cage, it is necessary to determine the roll setting position by performing a calculation or an experiment to bend the plate in the cage three-dimensionally with each cage roll. .

Based on the actual conditions described above, the present inventors arrived at the present invention by the inventors of the present invention in the cross-sectional shape in the width direction of the steel strip on the entrance side of the cage roll row (breakdown shape in the former stage of cage molding). Similarly, the cross-sectional shape of the steel strip on the exit side in the width direction (fin-pass shape at the latter stage of cage molding) and the outer diameter, wall thickness, and material strength of the steel pipe to be molded are used for the entire length of the cage roll row using the interpolation function. It is based on the finding that even if the deformed shape of the steel strip is determined, the difference between the deformed shape and the actual deformed shape by the above-mentioned calculation or experiment is small.

In each of FIGS. 2 (a), (b) and (c), the alternate long and short dash line, the broken line and the solid line correspond to n = 2, 4 and 6,
Interpolated deformed shapes (B), (W) and (H)
In addition, the symbols ◯, Δ and □ also show the actually measured deformed shapes corresponding to n = 2, 4 and 6, respectively. That is, since it is difficult to measure the entire deformed shape, the opening width B, the total width W, the total height H, the entrance side of the cage roll row shown in FIGS. The B, W, and H obtained from the interpolated shape based on the deformed shape on the exit side were compared. That is, FIGS. 2 (a), (b), and (c) compare the actually measured shape and the interpolated shape in the cage, with the cage entry side stand as the base point of the distance in the hand length direction. In the figure, n of 2,
4 and 6 show the shape parameters described later, and it can be seen that the deformed shape used for roll setting (interpolated shape) and the actual deformed shape match with sufficient accuracy even if the shape parameters are changed. . Therefore, the present invention does not determine the set value of the cage roll so as to optimize the deformed shape by calculating or experimentally obtaining the deformed shape by changing the setting position of the cage roll, and vice versa. Deformation shape inside the cage is the widthwise cross-sectional shape of the symmetrical steel strip on the inlet side of the cage roll row, the symmetrical widthwise cross-sectional shape of the steel strip on the outlet side, and the steel pipe to be formed. The outer diameter, the wall thickness and the material strength of the cage rolls are used to determine the deformed shape of the symmetrical steel strip over the entire length of the cage roll row, and each cage roll pair is formed in accordance with the deformed shape. It is said that the setting angle should be set. However, regarding the optimum setting of each cage roll pair, in setting each cage roll at a required setting angle along the deformed shape determined by the interpolation function, in the present invention, in the present invention, the tangent line of the deformed shape is set. And the cage roll generatrix, and the condition that the forming reaction force by the cage roll effectively acts, the width of the symmetrical steel strip at each cage roll pair position obtained from the deformed shape From the direction center of the cross-section shape (the center of gravity of the line figure when the cross-section shape of the symmetrical steel strip is regarded as one line figure) position and the tangential direction of the cage roll to the cross-section shape It is characterized in that the setting angle is set by selecting a member that minimizes the moment arm that is determined by the direction of the forming reaction force that is set.
The technical significance of this characteristic configuration will be described later.

FIGS. 3 (a) and 3 (b) are explanatory diagrams showing an example of a deformed shape interpolating method in a cage and an example of a function used for the interpolating according to the width direction cross-sectional shape of the steel strip on the cage entrance side and the cage exit side,
FIG. 6A specifically shows an example of the interpolation method of the deformed shape. In the widthwise cross-sectional shape of the steel strip on the cage entrance side and the widthwise cross-sectional shape of the steel strip on the cage exit side, the spatial locus between corresponding positions in the widthwise direction is interpolated by an interpolation function. As an example of the interpolation function, F (x) ＝ sin (π / 2 ・ [x / L] ⁿ ) (1) x: Distance from the cage entrance L: Total length of cage n: Shape parameter explain. Figure 3 points corresponding cage entry side in the width direction as shown in _{(a) (X 1, Y} 1, Z 1) and the cage outlet side of the point _{(X 2, Y 2, Z} 2) Equation (1 ) Is interpolated by the interpolation function.

For example, Y can be determined by Y (X) = Y ₁ + F (x) · (Y ₂ −Y ₁ ) (2). Further, as shown in FIG. 3 (b), when the shape parameter included in the interpolation function changes, the deformation is evenly performed in the cage (when n is small as 1 to 2) or the latter half of the cage. Is mainly deformed (when n is large like 4 to 6)
You can change the pattern of deformation as you do. In addition to the form of the interpolation function shown in equation (1), G (x) = (x / L) ⁿ [(x / L-1) ^m +1] x: distance from the cage entrance L: cage The total length n, m of: can be interpolated by polynomial ones such as shape parameters and those used in other forms of trigonometric functions.

In order to give such a deformed shape in the cage, the outer diameter, wall thickness, strength, etc. of the steel pipe must be taken into consideration. This is because in cage rolls in the formation of electric resistance welded pipes, the forming is mainly performed by bending, so the progress of bending and forming is governed by the outer diameter and wall thickness that affect bending rigidity, and
When the bending progresses, the strength goes beyond the deformation in the elastic range to enter the plastic deformation, and the degree of the plastic deformation varies depending on the strength. Therefore, the strength also becomes a factor controlling the deformation in the cage roll. Therefore, when setting the cage rolls, it is necessary to consider how the deformation should proceed optimally depending on the outer diameter, the wall thickness, the strength, etc., and set a large number of rolls. The optimum setting condition of the cage roll can be obtained by determining the shape parameter n of the formula (1) by calculation or experiment so as to have an optimum value in consideration of the outer diameter, the wall thickness, and the strength.

n = f (D, t, σY) (3) n: shape parameter D: outer diameter t: wall thickness σY: material strength, and a constant table of optimum values depending on outer diameter, wall thickness and strength, or
By having the function of Expression (3), the roll is set. The value of the shape parameter should be selected so that buckling does not occur, especially for thin-walled materials. Rather, in order to suppress the torsional moment based on the molding reaction force difference in the cage roll pair to be small, the tangent line of the deformed shape and the generatrix of the cage roll coincide with each other, and
Among the conditions that the forming reaction force by the cage roll effectively acts, the center position of the widthwise cross-sectional shape of the symmetrical steel strip in the cage roll pair position and the cage roll with respect to the widthwise cross-sectional shape It is necessary to determine the set angle of each cage roll pair by selecting the one that minimizes the moment arm that is determined by the direction (normal direction) of the forming reaction force that is determined from the tangential direction of.

By the way, inside the cage, unlike the breakdown before the forming and the fin pass after the forming, the material restraint by the roll is small, so it is easy to generate a twist. Therefore, it is necessary to reduce the twisting moment in order to prevent twisting in the cage. The torsion moment is determined by the difference between the left and right forming reaction forces times the moment arm. Among these, the difference between the left and right forming reaction forces is due to the variation of the raw material of the material, the difference between the left and right in the former stage of forming, etc., but each cage roll pair is set by the setting method using the above interpolation function. When setting at the required set angle, in order to prevent the deformed shape of the steel strip on the exit side of the cage roll row from losing the left-right symmetry and causing the twist so as to deviate from the cage roll pair, A position that minimizes the moment arm determined by the center position of the widthwise cross-sectional shape of the steel strip at the position and the direction of the forming reaction force (normal direction) determined from the tangential direction of the cage roll with respect to the widthwise cross-sectional shape. By selecting and setting the set angle of the cage roll pair, even if the reaction force difference in the cage roll pair becomes large, the value of the twisting moment based on this can be kept small. Become a result, it has become an advantageous setting for the twist.

On the other hand, for the moment arm, in the cage setting method described above, the cross-sectional shape in the width direction of the symmetrical steel strip at the position of each cage roll pair can be obtained, so the material obtained from the deformed shape at the position of the cage roll can be obtained. It is possible to obtain the moment arm of the twisting moment determined by the center position of the figure and the direction (normal direction) of the forming reaction force determined from the tangential direction of the cage roll with respect to the cross-sectional shape in the width direction.

Fig. 4 shows the cross-sectional shape and cage roll position in the cage determined by the shape of the cage on the inlet side and the shape of the cage on the outlet side, and the direction of the reaction force determined by the tangential direction of the material and the roll (see the figure). The moment arm can be geometrically obtained from the normal direction (indicated by the arrow) and the position of the center of gravity. FIG. 4 (a) shows a cage roll setting in which the roll setting angle θ is large and the moment arm is long. In such a setting, twisting is likely to occur as described above. Also, the fourth
FIG. 6B shows a setting in which the roll setting angle θ is small and the moment arm is short. With such a setting, twisting is unlikely to occur as described above. Therefore, in order to prevent twisting, according to the present invention, the widthwise cross-sectional shape of the symmetrical steel strip on the inlet side of the cage roll row and the laterally-symmetrical widthwise sectional shape of the steel strip on the outlet side are also provided. Determining the symmetrical deformation shape of the steel strip over the entire length of the cage roll row by using the interpolation function from the outer diameter, wall thickness and material strength of the steel pipe to be formed, and according to the deformation shape, When setting the cage roll pair at a required set angle, the tangent line of the deformed shape and the generatrix of the cage roll match, and among the conditions that the molding reaction force by the cage roll effectively acts,
By the center position of the widthwise cross-sectional shape of the symmetrical steel strip at each cage roll pair position obtained from the deformed shape, and the direction of the molding reaction force determined from the tangential direction of the cage roll with respect to the widthwise cross-sectional shape By selecting the one that minimizes the moment arm to be determined and setting the set angle, it is possible to reliably prevent the twist that causes defective molding.

〔Example〕

 Next, examples of the present invention will be described.

FIG. 5 shows a roll forming apparatus used in the examples, in which four rows of breakdowns are used in the initial stage of forming, cage roll rows 1 are used in the middle stage of forming, and fin pass roll rows 5 are used in the latter stage of forming. As a thin-walled material forming example, a plate thickness of 0.8 mm and an outer diameter of 7
Molding was performed using a steel plate of 6.3 mm (t / D = 1%). FIG. 6 (a) shows the relationship between the roll setting parameter and the amount of buckling generated at the edge of the thin-walled tube. The degree of buckling of the edge portion is evaluated by using the buckling pitch (p) and the buckling wave height (h) shown in FIG.
h / p). Under these molding conditions, the shape parameter (3) of the interpolation function (1) was changed to 2 to 6 for molding. Buckling does not occur in the roll setting of the shape parameter n of 2 to 4, but buckling occurs in the roll setting of the shape parameter n of 6, and the steepness of the buckling of the edge portion becomes large. Therefore, it is understood that the shape parameter should be set to 2 to 4 under this molding condition.
It can be seen that the effect of preventing the edge buckling is great if the deformed shape is determined in consideration of the wall thickness, the outer diameter, and the strength from the shape on the cage entrance side and the shape on the cage exit side by the setting method of the present invention.

As an example of forming a thick material, an example of forming a steel pipe having a plate thickness of 8 mm and an outer diameter of 76.3 mm (plate thickness / outer diameter ratio t / D = 10%) is shown. FIG. 7 shows an example in which the roll setting angle is changed and the size of the moment arm is changed to three levels of large, medium and small. Specifically, the moment arm indicated by the symbol □ in FIG. The large setting is an example in which the roll setting angle is gradually changed from 19 ° on the cage inlet side to 28 ° on the cage outlet side, and in this case, the material is kept on the outlet side of the second stage of the cage. The arrows indicate that the car was so twisted that it was impossible to enter the next cage. Similarly, the setting in the moment arm indicated by the symbol △ is an example in which the roll setting angle is gradually changed from 13 ° on the cage entrance side to 24 ° on the cage exit side. The arrow shows that the twist angle of the material gradually increased to about 30 ° and progressed to the 10th stage of the cage as it progressed, but it was twisted significantly before entering the fin path and could not enter the fin path. Similarly, the setting of the small moment arm indicated by the symbol ○ is an example in which the roll setting angle is gradually changed from 5 ° on the cage entrance side to 25 ° on the cage exit side. Even in the step position,
The twist angle of the material was suppressed to within 10 °, indicating that the material was able to enter the fin pass roll without any trouble. As described above, when the moment arm is set to be small, twisting does not occur, but when the moment arm is set to be large, twisting occurs. It can be understood that the effect of preventing the twist by the cage roll setting method of the present invention is great.

〔The invention's effect〕

By adopting the method of the present invention, it is possible to prevent edge buckling even when molding a wide range of outer diameters, wall thicknesses, and strengths,
In addition, twisting can be prevented and the molded shape can be made stable and good. Further, along with that, the excellent effect that the quality of the welded portion can be stably improved is also exhibited.

[Brief description of drawings]

FIG. 1 (a) is an explanatory view showing a cage setting method according to the present invention, FIG. 1 (b) is an explanatory sectional view of a part of FIG. 1 (a), and FIGS. 2 (a), (b) and (c) are cages. Explanatory drawing showing that the deformed shape predicted from the cross-sectional shape of the steel strip on the inlet side and the outlet side (line in the figure) and the actually measured deformed shape (symbol in the figure) are in good agreement. ) And (e) are the measured dimensions of the shape of the cross section in the width direction of the steel strip on the inlet side and the outlet side of the cage roll row, respectively, for shape comparison with those shown in (a), (b), and (c) above. Explanatory views, FIGS. 3 (a) and 3 (b) are for an interpolating method and an interpolating method of a deformed shape in a cage depending on the cross-sectional shape of the steel strip on the cage entrance side and the cross-sectional shape of the steel strip on the cage exit side. FIGS. 4 (a) and 4 (b) are explanatory views showing examples of functions to be used. FIG. 5 is an explanatory view showing a method for obtaining a moment arm and a method for determining a roll set angle, FIG. 5 is an explanatory view of a roll forming apparatus used for carrying out the present invention, and FIG. 6 is an example of a thin material, FIG. 6A is an explanatory diagram showing that buckling can be prevented. FIG. 6A shows the relationship between the roll setting parameter and the size of buckling generated in the edge portion of the thin-walled tube, and FIG. p) and the height (h) of the buckling wave are shown, and the steepness (λ = h / p) can be calculated by measuring these (p) and (h). FIG. 7 is an embodiment of thick material, and is an explanatory view that twisting can be prevented, and FIG. 8 is an explanatory view showing an example of a conventional cage setting method.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takehisa Nagao 5-3 Tokai-cho, Tokai-shi, Aichi Nippon Steel Co., Ltd. Shikikaisha Nagoya Works (56) References The Journal of the Japan Society for Plasticity Processing Volume 27 Issue 306 874-881, Vol. 23, No. 259, p. 792 ~ 798

Claims (1)

[Claims] 1. A plurality of cage roll pairs formed by symmetrically setting two cage rolls between a breakdown roll row and a fin-pass roll row are arranged as a cage roll row, and the cage rolls are arranged. In a roll forming line that roll-forms steel strips using rows, the widthwise cross-sectional shape of the symmetrical strips on the inlet side of the cage roll row and the cross-sectional shape of the strips on the exit side And the outer diameter, wall thickness and material strength of the steel pipe to be formed, determine the symmetrical deformation shape of the steel strip over the entire length of the cage roll row using the interpolation function.
A condition that the tangent line of the deformed shape and the generatrix of the cage roll coincide with each other when the cage roll pair is set at a required set angle along the deformed shape, and that the molding reaction force of the cage roll effectively acts. Satisfying the conditions, the center position of the widthwise sectional shape of the symmetrical steel strip at each cage roll pair position obtained from the deformed shape, and the molding determined from the tangential direction of the cage roll with respect to the widthwise sectional shape. A method for setting an electric resistance welded cage roll, characterized in that the set angle is set by selecting one that minimizes a moment arm that is determined by the direction of the reaction force.