High-Alloy Seamless Pipe Inner Surface Flaw Suppression
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Solution Overview
Problem
The Mannesmann process for producing seamless metal pipes often results in inner surface flaws due to lamination defects, especially when working with high-alloy materials that have high deformation resistance, leading to increased work-induced heat and grain boundary melting.
Innovation Solution
A method involving heating a high-alloy billet with 20-30% Cr and 22-60% Ni, piercing-rolling it to form a hollow shell, cooling it, and then reheating before elongation-rolling to minimize temperature deviations and prevent scale formation, thereby reducing the likelihood of lamination defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the Mannesmann process is used to produce high-alloy seamless metal pipes, then manufacturing efficiency and capability to produce large diameter pipes are improved, but inner surface flaws due to lamination defects occur
Solution Approach 1:
The patent applies preliminary action by heating the hollow shell before elongation-rolling. This pre-heating step ensures the material is at optimal temperature prior to the high-deformation rolling process, preventing work-induced heat from causing grain boundary melting and lamination defects, while still allowing efficient production
2Ease of manufacture
If high-alloy billet with high deformation resistance is piercing-rolled, then seamless metal pipe is produced, but work-induced heat increases causing grain boundary melting and lamination defects
Solution Approach 1:
The patent applies periodic action by implementing intermittent heating cycles. The hollow shell is heated before elongation-rolling, then allowed to cool between processing stages. This periodic heating and cooling prevents cumulative work-induced heat buildup that would otherwise cause grain boundary melting and lamination defects
3Reliability
If the Ugine Sejournet process is used for high-alloy pipes, then lamination defects are reduced, but manufacturing efficiency decreases and large diameter pipe production becomes difficult
Solution Approach 1:
The patent applies parameter changes by modifying the temperature parameters during the Mannesmann process. By controlling and adjusting the heating temperature and timing before elongation-rolling, the process achieves the quality results of the Ugine Sejournet process while maintaining the high productivity and large diameter capability of the Mannesmann process
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 suppresses the occurrence of inner surface flaws by eliminating temperature deviations and enhancing oxidation resistance, ensuring the production of high-alloy seamless metal pipes with improved quality and reduced manufacturing costs.
Implementation Method 1
heating a high-alloy billet containing, by mass %, Cr: 20 to 30% and Ni: more than 22% and not more than 60% in a heating furnace
Implementation Method 2
piercing-rolling the heated high-alloy billet with a piercing machine to produce a hollow shell
Implementation Method 3
cooling the hollow shell and then reheating the hollow shell in the heating furnace
Implementation Method 4
reheating the hollow shell in the heating furnace; elongation-rolling the heated hollow shell with the piercing machine
Data Source
AI summary
A method of producing a seamless metal pipe, which can suppress the occurrence of inner surface flaws, is provided. A method of producing a seamless metal pipe according to an embodiment of the present invention includes the steps of: heating a high alloy billet BL containing, by mass %, Cr: 20 to 30% and Ni: more than 22% and not more than 60% in a heating furnace F1 (S2); piercing-rolling the high alloy billet BL heated in the heating furnace F1 with a piercing machine P1 to produce a hollow shell (S3); cooling the hollow shell and then reheating the hollow shell in the heating furnace F1 (S4); and elongation-rolling the heated hollow shell with the piercing machine P1 (S5).