Skew Rolling Layout for Seamless Tube End Shape Correction
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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 in hot rolling processes due to irregular shapes and sizes that cannot be adequately controlled.
Innovation Solution
A skew rolling apparatus is configured to correct the shape of non-steady-state portions by using a skew outside-diameter mill with specific roll gap and roll number configurations, ensuring the roll gap between outside-diameter rolling rolls satisfies certain conditions to reduce the outside diameter and maintain wall thickness, thereby preventing shape defects and facilitating smooth hot rolling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pierce rolling is performed with a skew rolling mill, then seamless pipe shells can be produced efficiently, but shape defects occur in non-steady-state portions at the front and back ends
Solution Approach 1:
The patent applies preliminary action by performing outside-diameter rolling in the skew rolling mill immediately after pierce rolling, while the pipe shell is still in the rolling mill and at appropriate temperature. This preliminary shaping action corrects the non-steady-state portions before the pipe shell leaves the rolling mill, preventing shape defects that would otherwise require subsequent corrective operations or cause insertion failures in hot rolling.
Solution Approach 2:
The patent applies local quality by selectively correcting only the non-steady-state portions at the front and back ends of the pipe shell through outside-diameter rolling, while leaving the steady-state middle portion unchanged. The roll gap is specifically controlled to affect only the end portions, applying different treatment to different parts of the same workpiece based on their specific needs.
2Productivity
If non-steady-state portions are not corrected, then production flow is maintained, but insertion failures occur in hot rolling processes
Solution Approach 1:
The patent performs outside-diameter rolling as a preliminary action immediately after pierce rolling, correcting the shape of non-steady-state portions before the pipe shell proceeds to hot rolling. This ensures that when hot rolling begins, all portions of the pipe shell have appropriate shapes for successful internal tool insertion, eliminating insertion failures without interrupting production flow.
Solution Approach 2:
The patent applies preliminary anti-action by preemptively correcting the shape defects in non-steady-state portions through outside-diameter rolling, counteracting the potential problem of insertion failure before it occurs in the hot rolling process. This preventive approach eliminates the harmful effect of shape defects before they can cause production interruptions.
3Manufacturing precision
If roll gap is reduced to correct outside diameter, then shape defects are prevented, but wall thickness may be compromised
Solution Approach 1:
The patent applies local quality by controlling the roll gap to affect only the non-steady-state portions at the ends of the pipe shell, while maintaining appropriate clearance for the steady-state middle portion. This localized rolling action corrects outside diameter accuracy at the ends without applying excessive compression that would reduce wall thickness in the main body of the pipe shell.
Solution Approach 2:
The patent applies partial action by performing outside-diameter rolling with specific roll gap settings that are sufficient to correct the shape of non-steady-state portions but controlled to avoid excessive compression. The roll gap is optimized to provide just enough reduction to achieve accurate outside diameter while maintaining adequate wall thickness, avoiding both insufficient and excessive rolling actions.
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
The solution effectively prevents shape defects in non-steady-state portions, allowing for successful insertion of internal tools and stable hot rolling processes, enhancing productivity and yield of seamless steel pipes by ensuring the inside diameters of non-steady-state portions match the steady-state portion dimensions.
Implementation Method 1
the roll gap between outside-diameter rolling rolls satisfies certain conditions to reduce the outside diameter
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
Figure 1(a)~1(b)
Figure 2(a)~3(c)
Figure 4
AI summary
Provided herein is 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 for pierce rolling; and a skew outside-diameter mill following the skew pierce rolling mill, the skew rolling apparatus satisfying the following formulae (1) and (2), 3×1.2PO+2G≤LS≤0.8BL 1.2PO+2G>DS≥DB+2G where LS is the distance (mm) between a rolling zone of pierce rolling rolls and a rolling zone of outside-diameter rolling rolls, DS is the roll gap between the outside-diameter rolling rolls, PO is the outside diameter (mm) of a plug, G is the gap (mm) between the plug and the pierce rolling rolls, BL is the length (mm) of a bar, and DB is the outside diameter (mm) of the bar.