Pusher Mandrel Geometry for Seamless Pipe Wall Thickness Control
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Solution Overview
Problem
Seamless pipe manufacturing via pusher piercing and rolling often results in wall thickness deviation at the tip end due to eccentric rotation of the pusher mandrel, which is challenging to prevent given the irregular shape and size variations of the billet.
Innovation Solution
A pusher device is designed with specific geometric relationships between the pusher mandrel and billet cross-sectional areas, mandrel length, and cylinder shaft movement, ensuring ratios of 0.3 ≤ Sp/Sb ≤ 1.2 and Lc/Dc ≤ 45, along with a rounded tip end to reduce friction and eccentric rotation, thereby minimizing wall thickness deviation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pusher piercing and rolling is used to prevent defective biting, then biting stability is improved, but wall thickness deviation occurs at the tip end
Solution Approach 1:
The patent changes the geometric parameters of the pusher mandrel (cross-sectional area ratio Sp/Sb between 0.3-1.2, length Lp between 500-2000mm) to optimize its performance. By adjusting these parameters, the mandrel can effectively prevent eccentric rotation while maintaining stable biting, thus resolving the contradiction between biting stability and wall thickness uniformity
Solution Approach 2:
The tip end of the pusher mandrel is designed with a rounded shape (spheroidal curvature) instead of a sharp edge. This curved design reduces friction and contact stress during the piercing process, preventing the mandrel from eccentrically rotating and thereby maintaining uniform wall thickness at the tip end while preserving biting stability
2Manufacturing precision
If the shaft center of the billet is aligned with the shaft center of the pusher mandrel, then eccentric rotation is reduced, but alignment is difficult due to billet shape variations
Solution Approach 1:
The patent specifies optimal parameter ranges for the pusher mandrel (cross-sectional area ratio Sp/Sb between 0.3-1.2, length Lp between 500-2000mm) that make the system tolerant to minor misalignments. These parameter optimizations reduce the sensitivity to center alignment errors, allowing effective operation even when billet shape variations cause slight offset between centers
Solution Approach 2:
The rounded tip end design creates a larger contact area between the mandrel and billet, which helps self-align the centers during the pushing process. The curved surface distributes contact forces more evenly, reducing the tendency for eccentric rotation even when perfect center alignment is not achieved
Data Source
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AI summary
A pusher device 4 includes a cylinder device 30 and a pusher mandrel 34. The cylinder device 30 includes a cylinder shaft 32. The pusher mandrel 34 is attached to the tip end of the cylinder shaft 32. The tip end of the pusher mandrel 34 is abutted against the rear end of a billet 20. The cross sectional area Sp of the pusher mandrel 34 and the cross sectional area Sb of the billet 20 satisfy Expression (1). The length Lp of the pusher mandrel 34 and the cross sectional area Sp of the pusher mandrel 34 satisfy Expression (2). The moving distance Lc of the tip end of the cylinder shaft 32 during piercing and rolling and the outer diameter Dc of the cylinder shaft 32 satisfy Expression (3). Therefore, the pusher device 4 can restrain the wall thickness deviation of the tip end part of a produced hollow shell. 0.3≤Sp/Sb Lp/Sp≤1.2 Lc/Dc≤45