Die for bending-press forming

Abstract

[Problem] To propose a die for bending-press forming whereby the effects of bending moments are small and a high-roundness cylinder can be obtained. [Solution] In this die for bending-press forming, said die comprising a left / right pair of die blocks (1) that support a sheet material (S) at two points and a punch (2) that can move toward and away from the die blocks (1) and bends the sheet material (S) sandwiched between the die blocks (1) and the punch (2) by successively applying pressure thereto in the width direction thereof, the punch (2) comprises the following: a punch head (2a) that has a working surface (K) that directly contacts the sheet material (S) and applies pressure thereto so as to give the sheet material (S) a concave shape; and a punch support (2b) that is attached to the punch head (2a) so as to be held thereby and supports said punch head (2a). The center (O) of the working surface (K) of the punch head (2a) coincides with the central axis (q) of the punch support (2b), and the shape of said working surface (K) is a non-uniform circular arc, the radius thereof in the widthwise middle thereof being the maximum radius thereof.

Description

technical field [0001] The present invention relates to a method suitable for efficiently producing large-diameter and thick-walled steel pipes for use in, for example, line pipes and the like, by pressing a sheet material in sequence along its feeding direction by three-point bending press to perform bending processing. Dies for bending and stamping. Background technique [0002] As a technique for producing large-diameter and thick-walled steel pipes for use in line pipes and the like, so-called UOE forming techniques are widely used. After being press-formed into an O-shape, the ends are butt-jointed by welding to form a steel pipe, and the diameter is enlarged (so-called pipe expansion) in order to improve roundness. [0003] However, in the above-mentioned UOE forming technology, a high pressing pressure is required in the process of pressing a steel sheet to form a U-shape or an O-shape, so that a large pressing machine has to be used. [0004] Therefore, recently, w...

AI Technical Summary

Problems solved by technology

[0009] However, with this bending method, the number of times of processing increases, making it difficult to efficiently manufacture. As a countermeasure for this, for example, Patent Document 1 proposes a method in which, during press forming in the width direction of a steel sheet, At both end portions in the width direction of the steel plate and at a specified middle portion, straight portions of desired lengths are left, and the straight portions are bent to form arcuate portions, and the seam portions are welded. To form a semi-formed round steel pipe, after heating the whole of the semi-formed round steel pipe, make its forming surface pass between a plurality of semi-circular forming rollers corresponding to the final radius to perform thermoforming, thereby adjusting the shape

[0010] However, the method disclosed in the above-mentioned Patent Document 1 has the following problem: the molded body after press forming has a shape close to a quadrilateral, and it is necessary to separately provide a process for correcting the shape (heating process). volume will lead to a significant increase in manufacturing costs

However, since the rotation support is smaller than the width of the curved plate, there is a concern that a large surface pressure will act on this part, causing wear and deformation of the rotation support, and the rotation function may not be maintained in the early stage.

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