Three-Roll Inclined Rolling for Seamless Tube Wall Thickness Control
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Solution Overview
Problem
The existing two-roll-type inclined rolling mills used in the Mannesmann process face issues with Mannesmann fracture, leading to inner flaws, and outer flaws due to damage from disk rolls, limiting the production of seamless metal tubes with varying wall thicknesses without quality problems.
Innovation Solution
A three-roll-type inclined rolling mill is adapted with adjustable cross angles and convex entrance-side lateral surfaces, allowing for the production of seamless metal tubes with different wall thicknesses by changing the setup conditions, including the cross angle and roll opening, to prevent flaws and ensure efficient production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a two-roll-type inclined rolling mill is used for piercing rolling, then the production process can be carried out, but inner flaws occur due to Mannesmann fracture
Solution Approach 1:
The patent divides the rolling process into two distinct stages: piercing rolling using a two-roll-type inclined rolling mill to create the initial hollow shell, followed by elongating rolling using a three-roll-type inclined rolling mill to refine the wall thickness and eliminate defects. This segmentation allows each process to optimize for its specific function, resolving the quality issues caused by using a single rolling mill type for both operations.
Solution Approach 2:
The patent employs dynamic adjustment of rolling parameters including varying the feed angle, cross angle, and roll opening during the elongating rolling process. These dynamic adjustments enable precise control over material flow and stress distribution, preventing Mannesmann fracture and eliminating inner flaws while maintaining production efficiency.
2Productivity
If a two-roll-type inclined rolling mill with disk rolls is used, then piercing rolling can be performed, but outer flaws occur due to damage from disk rolls
Solution Approach 1:
The patent extracts and removes the problematic disk rolls from the piercing rolling process by using a plug instead. The plug is pushed through the center of the hollow shell during elongating rolling, eliminating the source of outer flaws caused by disk roll damage while maintaining the structural integrity and quality of the seamless metal tube.
Solution Approach 2:
The patent introduces a plug as an intermediary tool that replaces the harmful disk rolls. The plug serves as a mediator that performs the necessary function of creating the hollow shell without causing outer flaws, thereby resolving the quality issue while preserving productivity.
3Manufacturing precision
If the cross angle of inclined rolls is increased to produce thin-walled tubes, then thin-walled seamless metal tubes can be produced, but plug choking occurs
Solution Approach 1:
The patent employs dynamic adjustment of the cross angle during the elongating rolling process. The cross angle is varied according to the specific wall thickness requirements and production stage, enabling precise control over material flow and preventing both excessive wall thickness and plug choking. This dynamic parameter control resolves the contradiction between manufacturing precision and process stability.
Solution Approach 2:
The patent systematically changes multiple parameters including cross angle, feed angle, and roll opening during the elongating rolling process. These parameter changes are coordinated to achieve the desired wall thickness while maintaining smooth material flow and preventing plug choking, thereby resolving the contradiction between precision and ease of manufacture.
4Manufacturing precision
If the roll opening is adjusted to produce thick-walled tubes, then thick-walled seamless metal tubes can be produced, but material thrusting occurs
Solution Approach 1:
The patent uses dynamic adjustment of the roll opening and other rolling parameters during the elongating rolling process. The roll opening is systematically varied according to the target wall thickness and production stage, enabling precise control over material distribution while preventing material thrusting and maintaining process stability.
Solution Approach 2:
The patent implements coordinated changes in multiple parameters including roll opening, cross angle, and feed angle during elongating rolling. These parameter changes are designed to achieve the desired thick-walled tube dimensions while ensuring smooth material flow and preventing material thrusting, thereby resolving the contradiction between manufacturing precision and ease of manufacture.
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 method enables the production of both thin-walled and thick-walled seamless metal tubes without quality issues, making the three-roll-type inclined rolling mill practical for various seamless metal tube production, reducing material thrusting and plug choking, and maintaining production efficiency.
Implementation Method 1
The workpiece moves forward on the pass line while rolling around its own axis and is piercing-rolled by the inclined rolls and the plug
Implementation Method 2
the central portion of the rolling workpiece receives a compression stress, which acts in the direction in which the inclined rolls face each other
Implementation Method 3
Mannesmann fracture means a phenomenon that the central portion of a workpiece embrittles and fractures
Implementation Method 4
These stresses act repeatedly every quarter turn of the workpiece
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A method disclosed herewith is a method for producing a first seamless metal tube with a first wall thickness and a second seamless metal tube with a second wall thickness by using a three-roll-type inclined rolling mill, and the method includes a first inclination rolling step (#5), a setting changing step (#10), and a second inclination rolling step (#15). At the first inclination rolling step, a first workpiece is rolled by the inclined rolling mill. At the setting changing step, a setup condition of the inclined rolling mill is changed in a manner (a) or (b) as described below. At the second inclined rolling step, a second workpiece is rolled by the inclined rolling mill under the changed condition. (a) When the second wall thickness is smaller than the first wall thickness, the cross angle of each of the inclined rolls is made greater than the cross angle set for the first inclination rolling step. (b) When the second wall thickness is larger than the first wall thickness, the cross angle of each of the inclined rolls is made smaller than the cross angle set for the first inclination rolling step.