Skew Rolling Layout for Defect-Free Seamless Pipe Shell Ends
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Solution Overview
Problem
Pierce rolling with a skew rolling mill results in shape defects in non-steady-state portions at the front and back ends of seamless pipe shells, leading to insertion failures and reduced productivity due to unsatisfactory wall thickness and surface quality, which complicates the hot rolling process.
Innovation Solution
A skew rolling apparatus comprising a skew piercing mill and a skew outside-diameter mill, where the distance between rolling zones and roll gaps are optimized to satisfy specific formulas, ensuring the roll gap of the outside-diameter rolling rolls is between 84% to 99% of the steady-state portion's outside diameter, and including a drive unit and sensor for precise control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the non-steady-state portions are not properly shaped, then insertion failures of internal tools occur during hot rolling, but adding shaping processes increases device complexity
Solution Approach 1:
The patent combines the outside-diameter rolling function with the existing skew rolling mill used for pierce rolling. By integrating both functions into a single apparatus with appropriately positioned rolling rolls, the system achieves the shaping of non-steady-state portions without requiring a completely separate dedicated machine, thus limiting the increase in device complexity.
2Productivity
If outside-diameter rolling is performed to correct shape defects, then productivity improves, but the process requires precise control of roll gaps and distances
Solution Approach 1:
The patent establishes specific parameter ranges for the outside-diameter rolling process: the roll gap DS should be 84% to 99% of the outside diameter dO2 of the steady-state portion, and the distance LS between rolling zones should satisfy 3×(1.2PO+2G)≤LS≤0.8BL. These quantified parameters provide clear control targets that balance the need for shape correction with operational feasibility.
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
Prevents shape defects in non-steady-state portions, enabling successful insertion of internal tools and improving the productivity and yield of seamless steel pipes by ensuring accurate dimensions and surface quality.
Implementation Method 1
outside-diameter rolling is performed on the non-steady-state portions to provide satisfactory outside diameters and circular cross-sections
Implementation Method 2
barrel- or cone-shaped rolling rolls are positioned askew at an angle to the pass line, and are rotated to draw in a solid round billet between the rolls
Data Source
AI summary
A skew rolling apparatus with which shape defects in non-steady-state portions at the front and back ends of a seamless pipe shell can be prevented. The skew rolling apparatus includes a skew pierce rolling mill configured to pierce roll a steel material into a seamless pipe shell, and a skew outside-diameter mill following the skew piercing mill in a pass direction of the seamless pipe shell in the skew rolling apparatus. The skew rolling apparatus satisfies specified formulae.