High-Cr Stainless Steel Pipe End Correction Seizure Prevention
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Solution Overview
Problem
Seizure flaws are generated on the inner surface of seamless pipes during pipe end correction due to the removal of the solid alkali soap lubricant film during the correction process, especially in high Cr stainless steels like martensitic and duplex stainless steels, which affects dimensional accuracy and corrosion resistance.
Innovation Solution
A pipe end correction method that applies a lubricant film, such as an alkali soap solution or paste, to the inner surface of the seamless pipe or the plug before correction, allowing the oxide scale to remain and reducing friction during the expansion process, followed by shotblasting and acid pickling to remove the oxide scale and lubricant after correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a solid alkali soap lubricant film is applied to the inner surface of the seamless pipe before pipe end correction, then friction during correction is reduced, but the lubricant film is removed during the correction process causing seizure flaws on the inner surface
Solution Approach 1:
Oxide scale is retained on the inner surface to serve as an intermediary layer between the plug and the pipe's inner surface during correction. This intermediary prevents direct contact and seizure while allowing the correction force to be transmitted effectively
Solution Approach 2:
The oxide scale is deliberately retained on the inner surface before the pipe end correction process begins. This preliminary condition preparation ensures that the scale is present to prevent seizure during the subsequent correction operation
2Reliability
If oxide scale is removed from the inner surface before pipe end correction, then corrosion resistance is improved, but friction during correction increases causing seizure flaws
Solution Approach 1:
The oxide scale is deliberately retained on the inner surface before the pipe end correction process begins. This preliminary condition preparation ensures that the scale is present to prevent seizure during the subsequent correction operation
Solution Approach 2:
The oxide scale serves a temporary protective function during correction, then is removed afterward through shotblasting and acid pickling. The scale is discarded after serving its purpose as a seizure prevention layer
3Ease of manufacture
If shotblasting and acid pickling are performed before pipe end correction, then the inner surface is cleaned, but the lubricant film cannot be maintained during correction
Solution Approach 1:
The oxide scale is deliberately retained on the inner surface before the pipe end correction process begins. This preliminary condition preparation ensures that the scale is present to prevent seizure during the subsequent correction operation
Solution Approach 2:
The oxide scale serves a temporary protective function during correction, then is removed afterward through shotblasting and acid pickling. The scale is discarded after serving its purpose as a seizure prevention layer
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
Prevents seizure flaws during pipe end correction and reduces processing load, ensuring accurate dimensional correction and maintaining corrosion resistance in high Cr stainless steel seamless pipes.
Implementation Method 1
applying lubricant at least either on the inner surface of the pipe end portion of the seamless pipe or on a surface of the plug, so as to form a lubricant film thereon
Implementation Method 2
shotblasting and acid pickling to remove the oxide scale and lubricant after correction
Implementation Method 3
shotblasting and acid pickling to remove the oxide scale and lubricant after correction
Data Source
Figure 1
Figure 2(a)~2(c)
Figure 3
AI summary
The pipe end correction method of a seamless pipe for correcting an inner diameter of pipe end of a seamless pipe made of a high Cr stainless steel containing 8 to 35 mass% Cr, and 0.1 to 10 mass% Ni includes: a pipe end correction step, following hot tube-making and heat treatment, of forcing a plug into the inside of pipe end portion of the seamless pipe for inner diameter correction so as to expand the pipe end portion while oxide scale remains accumulated on an inner surface of the pipe end portion of the seamless pipe, the oxide scale being generated during the tube-making or the heat treatment; and a lubricant film forming step, prior to the pipe end correction step, of applying lubricant at least either on the inner surface of the pipe end portion of the seamless pipe or on a surface of the plug so as to form a lubricant film thereon. This makes it possible to prevent seizure flaws from being generated on the inner surface of the pipe end portion in the case of producing the seamless pipe of the high Cr stainless steel.