Mandrel Mill Segmentation for Seamless Pipe Production Efficiency
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Solution Overview
Problem
The production efficiency of seamless metal pipes is hindered by the need for frequent roll exchanges in piercing and mandrel mills, which decreases the operating ratio of manufacturing lines and overall efficiency.
Innovation Solution
A manufacturing method and apparatus that differentiate between preceding-stage and succeeding-stage stand groups in a mandrel mill, allowing for selective contact between the hollow shell and mandrel bar to optimize rolling processes, reducing the frequency of roll exchanges and enhancing production efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the frequency for exchanging rolls is increased to adapt to different steel grades and sizes, then the versatility of the manufacturing line is improved, but the operating ratio of the manufacturing line is decreased
Solution Approach 1:
The mandrel mill is divided into a preceding-stage stand group and a succeeding-stage stand group, each with specific functions. The preceding-stage stands perform outer diameter reduction without mandrel bar contact, while succeeding-stage stands perform thickness reduction with mandrel bar contact. This segmentation allows each group to be optimized for specific operations, reducing the need for complete roll exchanges when changing production parameters.
Solution Approach 2:
The patent implements dynamic control of the mandrel bar insertion and extraction timing based on the rolling stage. The mandrel bar is inserted before succeeding-stage rolling and extracted after preceding-stage rolling. This dynamic adjustment of mandrel bar presence allows the system to adapt to different steel grades and sizes without requiring physical roll exchanges, thereby maintaining high operating ratios.
2Productivity
If the elongation ratio in mandrel mill is increased to improve production efficiency, then the productivity is improved, but the device complexity is increased
Solution Approach 1:
By dividing the mandrel mill into preceding-stage and succeeding-stage stand groups with distinct functions, the system achieves high elongation ratios through coordinated operation of multiple stands. The preceding-stage stands prepare the hollow shell by outer diameter reduction, while succeeding-stage stands complete the elongation with mandrel bar contact, enabling high productivity without requiring overly complex individual stand configurations.
Solution Approach 2:
The patent ensures continuous elongation action through the coordinated operation of preceding-stage and succeeding-stage stands. The mandrel bar is maintained in the hollow shell throughout the succeeding-stage rolling process, ensuring continuous useful action for thickness reduction and elongation. This continuity maximizes productivity while keeping device complexity manageable through systematic coordination rather than complex individual components.
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 increases production efficiency by maintaining a higher operating ratio of manufacturing lines, allowing for more efficient processing and reduced roll exchange frequencies, thereby improving the overall production capacity and dimensional accuracy of seamless metal pipes.
Implementation Method 1
The hollow shell into which the mandrel bar is inserted is elongated by a mandrel mill
Implementation Method 2
The elongated hollow shell is heated as needed and is reduction-rolled by a sizing mill or a stretch reducing mill
Data Source
AI summary
A manufacturing method of a seamless metal pipe includes determining whether a preceding-stage stand group is used in outer diameter reduction or in thickness reduction of a hollow shell; and performing elongating on the hollow shell, into which a mandrel bar is inserted, based on the determination. In addition, in the elongating, when the preceding-stage stand group is used in the outer diameter reduction, the hollow shell is rolled in a state where an inner surface of the hollow shell does not come into contact with the mandrel bar in the preceding-stage stand group, and the hollow shell is rolled in a state where the inner surface of the hollow shell comes into contact with the mandrel bar in the succeeding-stage stand group.