Steel Pipe Press Die Geometry for Smaller Seam Gaps
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Solution Overview
Problem
Existing steel pipe forming techniques require high press forces, large-scale machinery, and result in seam gap portions that are difficult to weld due to excessive open amounts, leading to weld defects and misalignment, which can impair material characteristics and pipe roundness.
Innovation Solution
A press die and method that uses a pair of dies with arc portions and linear or small-curvature portions, where the arc centers align with the bending center and have central angles greater than 70 degrees, allowing for efficient formation of steel pipes with high roundness by minimizing seam gap portions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If traditional UOE forming techniques are used to press-bend steel plates into U or O shapes, then steel pipes can be formed, but high press force is required and large-scale press machines are needed
Solution Approach 1:
The press die is divided into multiple components including a punch with rounded ends, a punch support with support portions, and a die with specific geometry. This segmentation allows each component to perform a specific function in the forming process, distributing the press force requirements and enabling the use of smaller press machines while still achieving the desired O-shape formation with acceptable seam gap open amounts
Solution Approach 2:
The punch is designed with rounded ends and the punch support includes support portions that contact the plate material before the final pressing action. This preliminary action pre-bends the edge portions and provides support during forming, reducing the peak press force required and allowing smaller press machines to be used effectively
2Reliability
If the open amount of the seam gap portion is reduced to improve weldability, then welding quality improves, but the punch support width must be reduced which complicates the device design
Solution Approach 1:
The punch support includes support portions with specific local geometry designed to contact and support the plate material at critical locations during pressing. The support portions have widths and positions optimized to control the seam gap open amount locally, allowing the overall device to remain simple while achieving good weld quality through localized geometric features
Solution Approach 2:
The invention optimizes parameters such as the radius of the rounded punch ends, the width and position of the support portions, and the geometry of the die to achieve the desired balance between seam gap open amount and device simplicity. By carefully adjusting these geometric parameters, acceptable weld quality is achieved without requiring complex device modifications
3Ease of manufacture
If multiple three-point press bending operations are performed to form the O-shape, then the pipe can be formed, but the seam gap open amount becomes excessively large making welding difficult
Solution Approach 1:
The punch is designed with rounded ends rather than sharp edges, and the support portions have curved contact surfaces. This curvature distributes the pressing force more evenly across the plate material, preventing excessive localized deformation that would lead to large seam gap open amounts, while still allowing the O-shape to be formed through the pressing operations
Solution Approach 2:
The support portions act as intermediaries between the punch and the plate material during the pressing operation. They provide distributed support that controls the deformation pattern, preventing the seam gap from opening excessively while allowing the forming process to proceed. The support portions mediate the interaction between the pressing force and the plate material to achieve controlled deformation
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method enables efficient steel pipe formation with improved roundness and reduced seam gap portions, minimizing the need for large-scale machinery and reducing weld defects.
Implementation Method 1
the welded portion receives a force caused by springback to open the seam gap portion
Data Source
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AI summary
A press die for use in a steel pipe forming process of bending a plate material to form a preformed body having a U-shaped cross section, pressing the preformed body to form an open pipe, which is a tubular body having a seam gap portion in a longitudinal direction, and thereafter joining the seam gap portion to form a steel pipe. The press die includes a pair of dies. The preformed body is installed in one of the pair of dies such that the other die is opposed to a U-shaped open side of the preformed body, and the preformed body is pressed while the preformed body is held between the pair of dies. A surface of each die to be in contact with the preformed body has an arc portion having a diameter equal or substantially equal to an outer diameter of the steel pipe such that an arc center is located at a position coincident with a bending center of the die. The arc portion in each die has a central angle equal to or larger than 70 degrees, and a total angle of the central angles of the dies is smaller than 360 degrees.