Tapered Round Billet Geometry for Piercing Plug Protection
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Solution Overview
Problem
The Mannesmann process for producing seamless metal tubes often results in significant damage to piercing plugs, leading to reduced durability and potential flaws on the internal surface of the tubes due to mechanical impact during piercing-rolling.
Innovation Solution
A round billet with a tapered portion is used, which increases the contact area with the piercing plug, distributing stress and reducing mechanical impact, thereby minimizing damage and maintaining the protective coating on the plug.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a round billet with a hole is used in the Mannesmann process, then the piercing-rolling can be performed to produce seamless metal tubes, but significant damage occurs to the piercing plug due to mechanical impact
Solution Approach 1:
A tapered portion is formed in advance on the internal surface of the hole at the front end of the round billet, before the piercing-rolling process. This preliminary geometric modification distributes the mechanical impact stress during piercing-rolling, preventing concentration of force on the piercing plug and thereby reducing damage while maintaining production capability
Solution Approach 2:
The geometry of the hole in the round billet is modified by introducing a tapered portion with a specific angle (5-45 degrees). This parameter change in the billet structure alters the stress distribution pattern during piercing-rolling, reducing the mechanical impact on the piercing plug and improving its durability
2Productivity
If piercing-rolling is performed on a hollow round billet, then seamless metal tubes can be produced, but flaws are generated on the internal surface of the hollow shell due to piercing plug damage
Solution Approach 1:
The tapered portion is pre-formed on the internal surface of the hole before piercing-rolling. This preliminary action ensures that during the subsequent piercing-rolling process, the stress is distributed along the tapered surface, preventing piercing plug damage and avoiding the generation of flaws on the internal surface of the produced seamless metal tube
Solution Approach 2:
By changing the geometric parameters of the hole (introducing taper angle and tapered portion length), the stress distribution during piercing-rolling is optimized. This parameter modification prevents localized stress concentration that would cause piercing plug damage and subsequent internal surface flaws in the final product
Data Source
AI summary
Provided is a round billet capable of reducing damage on a piercing plug in a method of producing a seamless metal tube with a Mannesmann process. The round billet (5), for use in a seamless metal tube, to be produced into a seamless metal tube with a Mannesmann process includes a body having a hole (6) formed in an axial direction of the body. The hole (6) includes an aperture (6a) opening at least at one end face of the round billet (5), and a tapered portion (61) continued to the aperture (6a) and having a diameter gradually increasing toward the aperture (6a).