Seamless Pipe Piercing Process Parameter Optimization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for manufacturing seamless tubes using piercing and rolling processes often result in internal surface flaws and thickness deviations, particularly in the top portion of the hollow shell, due to issues with rotary forging and shear deformation during the transient region of piercing, leading to increased manufacturing costs and reduced quality.
Innovation Solution
The process involves using a piercer with cone-shaped skew rolls and grooved disk rolls, optimizing the ratios of roll diameters and angles, and controlling the rotational frequency to suppress rotary forging and shear deformation, ensuring the square root of the product of the rotational frequency and outer diameter reduction ratio is within specific limits, thereby stabilizing billet gripping and reducing defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional piercing and rolling methods are used, then the manufacturing process can be completed, but internal surface flaws and thickness deviations occur in the top portion of the hollow shell
Solution Approach 1:
The invention optimizes multiple process parameters including the ratio of gorge portion diameter to billet outer diameter (D1/d between 0.03-0.07), the ratio of grooved portion diameter to billet outer diameter (D2/d between 0.06-0.12), the inlet face angle (θ1 between 2.0°-4.0°), and the outlet face angle (θ2 between 6.0°-10.0°). These parameter changes control the deformation characteristics during piercing to eliminate internal surface flaws and thickness deviations.
Solution Approach 2:
The invention introduces dynamic control of the rotational frequency of the billet during piercing. By controlling the square root of the product of rotational frequency and outer diameter reduction ratio to be within specific limits, the method dynamically adjusts the rotary forging effect to prevent internal surface flaws while maintaining process efficiency.
2Reliability
If the rotational frequency and roll diameter ratios are not optimized, then the piercing process is simpler, but rotary forging and shear deformation cause defects in the hollow shell
Solution Approach 1:
The invention establishes specific ranges for multiple parameters: D1/d ratio (0.03-0.07), D2/d ratio (0.06-0.12), D2/D1 ratio (0.15-0.30), inlet face angle θ1 (2.0°-4.0°), and outlet face angle θ2 (6.0°-10.0°). By optimizing these parameters, the method achieves reliable quality consistency while managing the complexity through systematic parameter control.
Solution Approach 2:
The invention implements control based on the relationship between rotational frequency and outer diameter reduction ratio. By monitoring and controlling the square root of their product within specific limits, the system provides feedback control to maintain quality consistency and prevent defects during the piercing process.
3Productivity
If expansion ratio is increased to improve productivity, then more material can be processed, but outer diameter increase at the bottom portion of hollow shell occurs
Solution Approach 1:
The invention optimizes the D2/d ratio (grooved portion diameter to billet outer diameter) to be between 0.06-0.12 and controls the expansion ratio to be at least 1.15. These parameter changes enable increased productivity through higher expansion ratios while suppressing outer diameter increase at the bottom portion of the hollow shell through proper roll geometry design.
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
This approach effectively prevents internal surface flaws and thickness deviations across the entire length of the seamless tube, enhancing yield and productivity by maintaining a consistent quality from the top to the bottom portion of the hollow shell.
Implementation Method 1
a billet is advanced while being spirally rotated by the drive rotation of the main rolls
Implementation Method 2
piercing a billet in a piercer (a skew rolling mill) to produce a hollow shell
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A high quality hollow shell in which the occurrence of internal surface flaws caused by the rotary forging effect and/or shear deformation is prevented by suppressing the rotary forging frequency and shear deformation in a transient region at the stage of billet gripping and a worsening of thickness deviations in the top portion of the hollow shell is also prevented is reliably produced with preventing miss-rolling such as incomplete billet gripping and troubles in bottom withdrawal and an increase in the outer diameter of the hollow shell in the bottom portion. A billet is pierced while being rotated and advanced to produce a hollow shell, from which a seamless tube is finally manufactured, using a pair of skew rolls, a pair of disk rolls, and a plug under such conditions that each of the ratio (Dg/d) of the diameter Dg of the gorge portion of the skew rolls and the outer diameter d of the billet, the ratio (Dd/d) of the diameter Dd of the groove bottom of the disk rolls and the outer diameter d of the billet, the ratio (Dd/Dg) of the diameter Dg and the diameter Dd, the inlet face angle θ1 of the skew rolls, and the square root of the product (Ns x Df)0.5 of the rotational frequency Ns of the billet in a transient (non-steady state) region when billet gripping and the reduction ratio Df of the outer diameter of the billet satisfies a prescribed equation.