High-Alloy Seamless Steel Pipe Swelling Prevention
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Solution Overview
Problem
Conventional methods for producing seamless steel pipes fail to effectively prevent outer surface flaws, particularly pipe-swelling, when high-alloy steel is subjected to piercing-rolling, as they do not adequately address the surface roughness of the main rolls.
Innovation Solution
A method involving the regulation of surface roughness of main rolls within 150 to 500 µm, a gap ratio of 1.10 to 1.20 between main and guide rolls, a surface temperature of 900 to 1250°C, and an angle difference of 0 to 3.0° between the main rolls and the piercing plug, using main rolls previously used for ordinary steel pipes, and optimizing roll-cooling water flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional piercing-rolling methods are used for high-alloy steel, then the production process can proceed with standard equipment, but outer surface flaws such as pipe-swelling occur
Solution Approach 1:
The invention changes the surface roughness parameter of the main rolls from conventional smooth surfaces to a controlled rough surface with Ra = 3.2 to 12.5 μm. This parameter change allows the rolls to effectively control the high-alloy steel during piercing-rolling, preventing pipe-swelling and outer surface flaws while maintaining production efficiency.
2Reliability
If the surface roughness of main rolls is increased to prevent pipe-swelling, then outer surface flaws are reduced, but the rolls may cause additional surface defects
Solution Approach 1:
The invention optimizes the surface roughness parameter to a specific range (Ra = 3.2 to 12.5 μm) that provides enough friction to prevent pipe-swelling while remaining smooth enough to avoid causing additional surface defects. This precise parameter control resolves the contradiction between needing roughness for grip and smoothness for surface quality.
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 significantly reduces the occurrence of pipe-swelling and subsequent outer surface flaws in high-alloy seamless steel pipes, enhancing the production process by controlling key piercing-rolling conditions.
Implementation Method 1
surface roughness Rmax of main rolls used in the piercing-rolling process is set at 150 to 500 μm
Implementation Method 2
flow rate of a roll-cooling water at the time of piercing the seamless steel pipes of ordinary steel is set at 1000 to 1500 l/min
Data Source
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AI summary
Pipe-swelling can be prevented by piercing-rolling a high-alloy steel billet heated to a temperature range from 900 to 1250°C with a piercing mill equipped with main rolls having a surface roughness Rmax of 150 to 500 µm. A ratio (the gap WG of guide rolls/the gap WR of the main rolls) is preferably at 1.10 to 1.20. The difference (θP - θR) is preferably set at 0 to 3.0°, where θR is an angle between an exit-side face of each of the main rolls of the piercing mill and the pass line; and θP is an angle between a rolling face of the piercing plug and the pass line.