Billet Rear-End Groove Geometry for Cleaner Seamless Pipe Piercing
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Solution Overview
Problem
Current methods for producing seamless metal pipes using piercing machines struggle to effectively suppress burrs and internal defects, particularly when using alloy steel with low deformability, and may introduce defects during the elongation rolling process.
Innovation Solution
A method involving a piercing machine with skew rolls and a plug, where a billet is prepared with a hole having specific groove dimensions (groove width, height, and depth) to minimize burr formation and internal defects, by forming four grooves in a cross shape at the billet's rear end, satisfying the ratios 0.12 ≤ D/B ≤ 0.25, 0.10 ≤ H/B ≤ 0.20, and 0.05 ≤ L1/B < 0.10, which aids in absorbing the contact portion and reducing defect generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a hole with grooves is formed in the rear end of the billet to suppress burrs, then burr generation is reduced, but internal defects may arise at the inner surface of the hollow shell
Solution Approach 1:
The invention optimizes specific parameters of the grooves including groove depth (0.05 ≤ L1/B < 0.10), groove width (0.12 ≤ D/B ≤ 0.25), and groove height (0.10 ≤ H/B ≤ 0.20) to achieve the right balance between burr suppression and preventing internal defects. This parameter optimization allows the grooves to absorb excess material effectively while maintaining structural integrity during piercing-rolling
Solution Approach 2:
The invention applies grooves with specific dimensional characteristics at the localized region where burrs form (the rear end center of the billet). The grooves are positioned and dimensioned to affect only the local material flow and burr formation area, while the rest of the billet maintains its original properties for overall structural integrity
2Strength
If alloy steel with low deformability is used to maintain strength and corrosion resistance, then material performance is improved, but burr suppression becomes more difficult
Solution Approach 1:
The grooves are pre-formed in the alloy steel billet before piercing-rolling to anticipate and prevent burr formation. The preliminary groove structure prepares the material by creating pathways for excess material flow, compensating for the low deformability characteristics of alloy steel and preventing burr generation during the subsequent rolling process
Data Source
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AI summary
A method for producing a seamless metal pipe includes the steps of: preparing a billet (2) having a diameter (B); heating the billet (2); forming, in a center part of a rear end of the heated billet (2), a hole (7) including four grooves (8) extending in an axial direction of the billet (2), the grooves each having a groove width (D) satisfying Formula (1), a groove height (H) satisfying Formula (2), and a groove depth (L1) satisfying Formula (3); and subjecting the billet (2) provided with the hole (7) to piercing-rolling from a front end thereof by means of a piercing machine. By this means, the generation of burrs and internal defects at the rear end of a hollow shell after piercing-rolling can be suppressed. 0.12≤D/B≤0.25 0.10≤H/B≤0.20 0.05≤L1/B<0.10