JPH0147248B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to the creation of a U-press tool for the UOE steel pipe manufacturing process, which improves the workability of subsequent O-pressing, tacking, etc. when performing U-press bending in the UOE steel pipe manufacturing process. The purpose is to make welding pre-treatments such as cleaning and drying of the welded part easy and complete, and to improve the quality of the product obtained by main welding.

As one of the methods for manufacturing steel pipes, it is well known that the UOE method is particularly suitable for obtaining large steel pipes. That is, this method involves bending the ends of the raw steel plate, then U-press bending, and then O-press bending.
However, conventional steel pipe manufacturing using this method has various problems regarding U-press bending, and it is not easy to obtain the desired steel pipe smoothly and appropriately. If the U bending radius of the lid is extremely small, the O
Seam part 1 during handling of raw pipe 10 after pressing
0a will overlap, and the cleaning and drying of the seam portion 10a will be incomplete, and during the subsequent tacking work, the seam portions 10a, 10a must be pushed out from inside the pipe and tacking must be carried out while correcting the lapping state. This significantly impedes work efficiency and results in inferior quality. Even if this U-bending radius does not wrap by the O-press as described above, if it is smaller than the appropriate range, the O-press will bring them into close contact as shown in Figure 1b. Since pre-welding treatments such as cleaning and drying of the seam portion are incomplete, defects such as plowholes and slag entrainment are likely to occur in the weld portion. On the other hand, if the U-bending radius is large, as shown in Figure 1c, excessive spring back will occur after O-pressing, and excessive force will be required to butt the seams during tacking, and the shape will not be properly shaped. It is difficult to correct the clamp, and especially if it is excessive, the spring back force will cause the material 10 to stick tightly to the O-press die 11 as shown in Fig. 1d, making it difficult to take out the material after O-pressing. This becomes difficult, and furthermore, it becomes difficult to carry it into the O-press die 11. Of course, troubles during temporary attachment cannot be avoided.

The present invention has been devised after repeated studies in view of the above-mentioned circumstances, and by making the above-mentioned U-curve press tool specific, the above-mentioned disadvantages can be effectively overcome and preferred. We succeeded in accurately obtaining product steel pipes with excellent workability and quality. That is, an example of such a U press forming mechanism is as shown in FIG.
Brake rolls 5, 5 supporting the material plate 10 are disposed oppositely on both sides of the lower part of the frame, and a saddle plate 4 supported by a link mechanism 3 is provided between these brake rolls 5, 5, and a cylinder 2 is mounted on the saddle plate 4. The process is shown in FIG. 3 by disposing a punch 1 which is pushed and pressed down by the punch 1, and pressing the material plate 10 carried by the carrying means 6 onto the brake rolls 5, 5 with the punch 1. As shown step by step, the raw steel plate 8 is rolled down toward the saddle plate 4, and while the both sides of the raw steel plate 8 are supported by the brake rolls 5, 5, the middle part of the raw steel plate 8 is rolled down together with the saddle plate 4, and then punched. 1 passes through the line of the brake rolls 5, 5 and is pushed down, thereby bending the raw steel plate into a U shape, and then pushes the brake rolls 5, 5 inward to bend both ends of the raw steel plate 8 inward. It is molded by overpressing. By the way, in such U-bending forming, the degree of overpressing shown in Figure 3d is determined by considering the amount of springback of the steel plate, and this amount of springback is directly proportional to the strength of the material and its It is inversely proportional to the plate thickness, and as the plate thickness increases, the spring back amount decreases, so even if the same shape is to be obtained, it is necessary to change the pressing conditions depending on the strength and plate thickness. The inventors have also confirmed that the U press tool has a large influence in this case,
If the bending radius of the press tool is large, the spring back will also be large.Furthermore, it is constrained by the press limit, and the maximum bending angle, that is, the joining angle range of the material plate to the circumferential surface of the punch 1, is d in Fig. 3.
As shown in Figure 2, the maximum springback angle is approximately 230°, and therefore, in order to form a U-shape, it was confirmed that the tool shape must be determined so that the springback amount is 50° or less. That is, regarding the calculation of this amount of spring back, the following equation () is shown, for example, in Mechanical Engineering Handbook 17-58.

Δθ=Mρ/EIθ () Here, Δθ: Spring back angle θ as shown in Fig. 4: Initial bending angle M: Bending moment at initial bending E: Elastic modulus I: Second moment of area, which is the surface of the material If the thickness is t and the length is l, then = lt ³ /12 ρ : Radius of the neutral plane during bending Note that M in formula () is approximately assumed to be a rigid plastic body. Therefore, as shown in FIG. 5, it is calculated as follows, where l is the length.

M=l・∫ ^t ₀ σyy・dy=σy・t ²・l/4 Therefore, Δθ=1/E σy・t ²・l/4 12/lt ³・P・θ=3
Since σy/E・ρ/t・θ, the maximum bending angle during U press is θmax=230°, so in order to form a U shape, Δθ should be 50° or less. There is a need.

By the way, the thickness range of UOE steel pipes is generally 6 to 50.
mm, and its strength is 30-70Kg/yield stress.
mm, and its outer diameter is 400 to 1500 mmφ, so it corresponds to this. As for the range of U bending radius,
Since it is sufficient to examine the range of approximately 150 to 700 mm, the results of the examination using the following equation () can be summarized as shown in FIG. 6.

Δθ=3・σy/E・ρ/t・θ () Here θ: 230°E: 21000Kg/mm ² σy: 30~70Kg/mm ² t: 6.4~50mm ρ: 150~700mm That is, this Figure 6 A diagonal line corresponding to the bending radius ρ was found at the bottom, a perpendicular line was drawn upward from the intersection of the diagonal line and the strength of the material plate σy, and the springback angle was found from the intersection with the diagonal line of the plate thickness t. However, when bending with a single radius, as in this case, it is clear that considerable restrictions occur in the thin to medium thickness range due to the relationship with the springback limit angle of 50°.

In order to make a U steel plate that can be loaded into an O press machine, the distance between the width d at the upper end of the U steel plate and the width D of the die forming surface is 1/2 (D-d), as shown in Fig. 7. Must be a value of 20mm.

However, in the past, over-pressing was done taking into account the amount of springback of the steel plate, and the width of the opening end was within the width range of the die forming surface in order to make a U steel plate that could be loaded into an O-press machine. has been thoroughly studied and formed with a punch that meets these purposes, but the punch has a diameter of 1 to 1 for a single outer diameter size, regardless of the thickness or strength of the steel plate.
Therefore, in order to bend and form high-strength, thin-walled steel plates, the radius must naturally be small, and in this case, the U-bending radius is generally small. There is a strong tendency for the seam to wrap during O-pressing, or at least for the seam to stick together, making it difficult to perform a preferable welding pretreatment.
Welding defects are inevitable, and tacking and other operations must be complicated. Therefore, the present inventors first
After examining the appropriate range for the seam spacing due to spring back after pressing, we found that it is 5 to 30 mm.
At this level, good tacking efficiency can be obtained, and since the seam portion can be properly cleaned and dried, excellent quality of the welded portion can be obtained. However, when we further examine the U-forming shape to obtain such an appropriate springback amount of 5 to 30 mm after O-pressing, we find that the above-mentioned disadvantages due to the inappropriate U-bending shape (lap or close contact at the seam), Difficulty in matching the seam due to excessive spring back or difficulty in taking out from the O-press die, etc.)
It depends on the average radius R after spring back in the range of 90 to 120 degrees, and when the O-press die radius and the radius of this part match, it is possible to obtain the best raw pipe after O-press. It has been confirmed through many experiments that the permissible range is approximately ±25 mm. Although this allowable range can be further expanded depending on the O press conditions, it is appropriate to keep it within ±25 mm in order to realize economical and efficient operation.

Regarding the reason for the above relationship, see O
The degree of influence on whether the seam portions 10a, 10a described above can be closed or opened after pressing is greater as the distance from the seam portion 10a increases. If the angle between the two parts is dθ, and the distance from each part to the seam part 10a is l, then the amount of displacement of the seam part can be expressed as l·dθ, and part B,
The degree of influence is greatest in the order of C and D. Therefore, it is clear that in such a U steel plate subjected to O-pressing, the condition of portions B, C, or D that are distant from the seam portion 10a has a decisive influence on the condition between the seam portions 10a and 10a after O-pressing. . Furthermore, the deformation process of the U steel plate during this O-pressing is as shown in Fig. 9, and while the part shown in Fig. 8 described above only undergoes deformation that conforms to the O-pressing die surface, the upper part ( During the O-press deformation process, the seam part side is sequentially bent to a radius γ smaller than the radius D/2 and then bent back to the die radius D/2 as shown in Fig. 10, and the entire die is bent. Therefore, the same result will be obtained regardless of the shape of the part near the seam, as long as it is not extremely smaller than the small radius γ bent in the O-pressing process.

Next, when considering the U press bending radius ds where the BC section in Figure 8 is the die radius after the O press, as shown in Figure 11a, ds = ρ' (θ - Δθ) = ρ・θ =ρ'(1-3σyρ/E・t)θ=ρθ Therefore, 1/ρ'=1/ρ-3σy/E・t (). If the O-press die radius is D/2, as shown in Figures 11b and 12, D/2 = ρ' + t/2, and therefore ρ = D/2 - t/2, If the U press punch radius is R, then ρ-t/2=R, so ρ=R+t/2 From the above formula, 1/D/2-t/2=1/R+D/2-3σy/Et(
) becomes. From this formula (), R was derived from ()
It is a formula.

R=1/1/D/2-t/2+3σy/Et-t/2(
) However, D: O press die diameter mm, t: steel plate thickness mm, σy: steel plate strength Kg/mm ² , E: steel plate elastic coefficient Kg/mm ² . However, in the present invention, as mentioned above, it has been decided that a range of ±25 mm is allowed from the viewpoint of economy and operational efficiency, so a radius of R±25 mm is used for the center of the bottom of the U press tool. As an example, the calculation results for an O press die radius (D/2) of 503 mm are shown in Figure 13, and the radius of punch 1, which is a V press tool, varies greatly depending on the plate thickness and strength. That is clear.

Therefore, we considered a U-press tool (punch) that takes into account the amount of spring back of the steel plate as described above, over-presses it, creates a U-steel plate that can be loaded into an O-press machine, and also satisfies the relationships described above. As a result, in a simple circular press tool with a radius as shown in Fig. 14, it is difficult to use an appropriate U-shaped steel plate due to the constraint due to the springback limit shown in Fig. 6 when using a thin-walled high-strength material. It is impossible to press-form it, and the seam portions 10a and 10a have a widened opening shape, which means that they cannot be loaded into an O-press machine.
Also, assuming that a U-shaped steel plate is possible, since the width d of the U-shaped steel plate and the diameter D of the O-press die are equal, as shown in Fig. 15, the required The minimum value of the clearance 1/2 (D-d) = 20 mm (minimum) cannot be obtained, making charging difficult or impossible. Therefore, in the present invention, as shown in FIG.
The radius (Rmm) in the angle range θ at a is R = 1/1/D/2-t/2+3σy/Et-t/2±25, where D: O press die diameter mm, t: steel plate thickness mm, σy: Strength of the steel plate Kg/mm ² , E: Elastic coefficient Kg/mm ² of the steel plate, where θ is 100 to 150° at the center of the bottom, and the tool 1 is continuous with the bottom 1a. The radius of curvature at both sides 1b, 1b is set to a radius _R1 smaller than the above radius R,
Based on the results of practical studies, the value of R ₁ is set to be in the range of R ₁ = 0.3R to 0.9R, and furthermore, such a radius
The angular range θ ₁ on both sides of the tool that takes R ₁ is 40° or more, and by using such a specific U press tool, it is possible to create an O press that satisfies all of the above requirements and is always preferable. A U-press steel plate for forming can be obtained appropriately. The above R ₁ is 0.9R
If it is larger than this, the same disadvantages as in the circular press tool shown in FIG. 14 will be recognized, and if it is less than 0.3R, it will be difficult to obtain a preferable U-press steel plate. The angle range θ ₁ on both sides of the tool with radius R ₁ is
The reason why the angle is set at 40° or more is because if the angle is less than 40°, it may become difficult to pull out the tool 1 after forming with the U press.

According to the present invention as explained above, UOE
U-bending followed by O in the steel pipe manufacturing process
It is possible to precisely obtain a state in which pretreatment for press forming, subsequent tack bonding, or actual welding can be carried out smoothly and appropriately.Therefore, the desired steel pipe can be manufactured efficiently and smoothly, and its welding process can be carried out efficiently and smoothly. It is an invention that can sufficiently improve the quality of parts and other properties, and has great industrial effects.

[Brief explanation of drawings]

The drawings show the technical contents of the present invention, and FIG. 1 is an explanatory diagram summarizing the inconvenient conditions in O-pressing and the subsequent pipe-making process based on inappropriate U-bending radius, and FIG. The figure is a front view showing an overview of the U-press forming mechanism, Fig. 3 is an explanatory diagram showing the step-by-step process of forming a raw steel plate by this U-press forming mechanism, and Fig. 4 shows the relationship between springback angles. An explanatory diagram, FIG. 5 is an explanatory diagram of the bending moment M during initial bending in the calculation formula,
Figure 6 is a diagram summarizing the relationship between bending radius, material plate strength, thickness and springback angle for practical UOE steel pipes, and Figure 7 is a U-shaped tube that can be loaded into an O-press machine. Figure 8 is an explanatory diagram showing the relationship between steel plates. Figure 8 is an explanatory diagram showing the relationship of the influence of each part of the U-shaped steel plate during O-forming. Figure 9 summarizes the deformation process of the U-shaped steel plate during O-press forming. Figure 10 is an explanatory diagram of the U-press bending radius where the bottom of the U-shaped steel plate after U-press becomes the die radius for O-press, Figures 11a, b, and 12 are the radii before and after springback. Figure 13 shows the relationship between the angle and the O press die radius and the U press tool radius.
A diagram summarizing the relationship between plate thickness and material steel plate strength, Fig. 14 is an explanatory diagram of a simple circular U-press tool, and Fig. 15 shows the disadvantageous relationship when the U-shaped steel plate width and O-press die diameter are equal. FIG. 16 is an explanatory diagram showing a cross-sectional view of the configuration of the U press tool according to the present invention. In these drawings, 1 is a punch which is a U press tool, 1a is its bottom, 1b is its both sides, 2 is a cylinder of the U press tool, 3 is a link mechanism, 4 is a saddle plate, 5 is a brake roll, and 8 is a Material steel plate, 10 is the raw pipe after O press, 1
0a indicates the seam portion, and 11 indicates an O-press die.

Claims (1)

[Claims] 1. The range of 100 to 150 degrees at the center of the bottom of the tool used in the U-forming process to obtain steel pipes by bending a steel plate by the UOE method is a radius (Rmm) determined by the following formula. A UOE steel pipe characterized in that the radius at both sides of the tool continuous to the center of the bottom is 0.30 to 0.90 of the radius of the center of the bottom, and the angular range of the radius is 40° or more. U press tool for manufacturing process. R=1/1/D/2-t/2+3σy/Et-t/2±25 However, D: O press die diameter mm, t: Steel plate thickness mm, σy: Steel plate strength Kg/mm ² , E: Indicates the elastic coefficient Kg/mm ² of the steel plate.