Thin-Walled Steel Pipe Cooling Suppresses Quenching Bending
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Solution Overview
Problem
Thin-walled steel pipes with a low wall thickness to outer diameter ratio (t/D) of at most 0.07 often experience significant quenching-induced bending during quenching, which is a quality defect, and existing cooling methods either compromise manufacturing efficiency or are complex and ineffective in suppressing this bending.
Innovation Solution
A method of cooling thin-walled steel pipes where the inner surface is cooled by spraying water inside the pipe and the outer surface is cooled by a downward flow of water from two equally spaced locations, with the inner surface cooling initiated at least 7 seconds before outer surface cooling, ensuring the axial stress remains below the yield stress to prevent bending while maintaining manufacturing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If slow cooling is performed at the initial stage of cooling only the outer surface of the pipe, then quenching-induced bending is suppressed, but cooling time is necessarily elongated and manufacturing efficiency is decreased
Solution Approach 1:
The cooling process is segmented into two simultaneous operations: inner surface cooling and outer surface cooling. By dividing the cooling action into two parallel streams targeting different surfaces, the method achieves uniform cooling without the need for prolonged slow cooling of only the outer surface, thus suppressing bending while maintaining efficiency.
Solution Approach 2:
Inner surface cooling is started 7 seconds prior to outer surface cooling. This preliminary action on the inner surface creates a temperature gradient that counteracts the thermal stress caused by outer surface cooling, preventing quenching-induced bending while enabling faster overall cooling.
2Manufacturing precision
If water sprayed from nozzles is allowed to impinge on the outer surface of the pipe over substantially the entire length with varied spraying timing, then uniform cooling is achieved, but the structure and control of the apparatus become complicated
Solution Approach 1:
The cooling apparatus is segmented into two independent cooling systems: one for the inner surface and one for the outer surface. Each system operates with simple, fixed parameters (inner surface cooling starts 7 seconds earlier), eliminating the need for complex variable control mechanisms while achieving uniform cooling.
Solution Approach 2:
The method changes the timing parameter of cooling initiation rather than varying the spraying pattern or nozzle configuration. By simply adjusting when inner surface cooling starts relative to outer surface cooling, uniform cooling is achieved without complicating the apparatus structure.
3Productivity
If conventional quenching methods are used on thin-walled pipes with t/D ratio of at most 0.07, then cooling speed is maintained, but large amounts of quenching-induced bending occur which is considered a defect in quality
Solution Approach 1:
The quenching process is divided into simultaneous inner surface cooling and outer surface cooling operations. This segmentation allows rapid cooling to be maintained while the coordinated timing (inner surface cooling starting 7 seconds earlier) prevents thermal stress accumulation that causes bending in thin-walled pipes.
Solution Approach 2:
The method changes the timing parameter by initiating inner surface cooling 7 seconds before outer surface cooling. This parameter adjustment creates an optimal temperature gradient that suppresses quenching-induced bending while maintaining high cooling speeds suitable for thin-walled pipes with t/D ratio of at most 0.07.
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 effectively suppresses quenching-induced bending in thin-walled steel pipes without reducing manufacturing efficiency, improving the uniformity of cooling and mechanical properties, thereby enhancing the toughness of the steel pipes.
Implementation Method 1
cooling of the inner surface of the steel pipe is carried out by spraying cooling water inside the steel pipe
Implementation Method 2
cooling of the outer surface of the steel pipe is carried out by making cooling water flow downwards in a planar shape in the axial direction onto the outer surface
Implementation Method 3
the inner surface and outer surface of a horizontally-disposed steel pipe are cooled while rotating the steel pipe in its circumferential direction
Data Source
Figure 1
Figure 2(a)~2(b)
AI summary
A method of cooling a steel pipe which can effectively suppress quenching-induced bending which occurs when quenching a thin-walled steel pipe with a wall thickness/outer diameter ratio of at most 0.07 without decreasing the manufacturing efficiency of the steel pipe comprises cooling the inner surface of the steel pipe by spraying cooling water into the interior of a horizontally-disposed steel pipe 2 while rotating the pipe in its circumferential direction, and the outer surface is cooled by producing a downward flow of cooling water streams 5a and 5b in a planar shape from above onto the outer surface along the axial direction of the steel pipe 2. Cooling of the inner surface is started at least 7 seconds before cooling of the outer surface. Cooling of the outer surface is carried out by producing downward flow in a planar shape of cooling water 5a and 5b at two locations 4a and 4b at approximately equal distances from the uppermost portion of the steel pipe 2, and the flow rate of cooling water 5a which flows down at a location on the upstream side in the rotational direction of the steel pipe 2 is made larger than the flow rate of cooling water 5b which flows down at a location on the downstream side in the rotational direction.