Cold-Drawn Tube Surface Roughness Control
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Solution Overview
Problem
The production of longer-length, small-diameter heat-transfer tubes for steam generators in nuclear power facilities faces challenges with scoring and chattering vibration during cold drawing, particularly in Ni-based alloy Inconel tubes, where existing methods fail to consistently prevent these issues.
Innovation Solution
A blank tube made of a Ni-based alloy with a controlled inner surface roughness, between 0.10 μm and 0.50 μm, treated using blasting with zirconium oxide grains or pickling with fluoronitric acid, is used for cold drawing, ensuring optimal lubrication and reducing friction-related defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a chemically treated lubricating film is formed on the inner and outer surfaces of the blank tube, then the lubrication effect is improved, but the treatment requires huge man-hours and expensive chemicals, resulting in high operation costs
Solution Approach 1:
The patent replaces expensive chemical treatments with a simple oil application method. The oil lubricating film, while potentially less durable than chemical films, provides sufficient lubrication for the drawing process at a fraction of the cost, eliminating the need for expensive chemicals and complex treatment procedures
Solution Approach 2:
The patent changes the lubrication approach from chemical film formation to physical oil film application. By adjusting the parameters of oil viscosity, application pressure, and film thickness, the patent achieves effective lubrication without the high costs associated with chemical treatments
2Reliability
If a chemically treated lubricating film is formed on the inner and outer surfaces of the blank tube, then the lubrication effect is improved, but the processing time and complexity increase significantly
Solution Approach 1:
The patent replaces complex chemical treatment processes with a simple oil application method. The oil lubricating film, while potentially less durable than chemical films, provides sufficient lubrication for the drawing process at a fraction of the complexity, eliminating the need for expensive chemicals and complex treatment procedures
Solution Approach 2:
The patent extracts the essential lubrication function from the complex chemical treatment process and isolates it into a simple oil application step. This extraction removes the unnecessary complexity of chemical reactions, rinsing, and drying steps, leaving only the critical lubrication function
3Productivity
If an oil lubricating film is used instead of chemically treated film, then the cost and processing simplicity are improved, but the lubrication effectiveness may be insufficient for Ni-based alloys
Solution Approach 1:
The patent optimizes the parameters of the oil lubricating film, including viscosity, pressure, and application timing, to ensure sufficient lubrication effectiveness for Ni-based alloys during the drawing process
Solution Approach 2:
The patent introduces a high-pressure oil lubrication system as an intermediary between the tool and the workpiece. This high-pressure oil system acts as a mediator that ensures adequate lubrication reaches the contact surfaces, overcoming the insufficient lubrication that would occur with conventional oil application methods
4Ease of manufacture
If the inner surface roughness is not controlled, then the manufacturing process is simpler, but scoring and chattering vibration occur during cold drawing
Solution Approach 1:
The patent applies a preliminary surface treatment to the blank tube before the drawing process. This pre-treatment prepares the surface with appropriate roughness characteristics that will prevent scoring and chattering vibration during subsequent drawing operations, ensuring surface quality without adding complex manufacturing steps
Solution Approach 2:
The patent optimizes the surface roughness parameter of the blank tube to a specific range that prevents scoring and chattering vibration. By controlling the roughness parameter within optimal limits, the patent achieves both ease of manufacture and high 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
The controlled surface roughness effectively prevents scoring and chattering vibration, resulting in higher quality tubes with improved surface finish and reduced defects, suitable for high-pressure lubrication drawing methods.
Implementation Method 1
the inner surface of which before drawing has an inner surface roughness Ra satisfying the below-described Formula (i)... treated using blasting with zirconium oxide grains
Implementation Method 2
treated using blasting with zirconium oxide grains or pickling with fluoronitric acid
Implementation Method 3
a drawing process in which an oil lubricating film is formed on a surface of the workpiece... high-pressure lubrication drawing methods
Data Source
Figure 1~2
AI summary
Disclosed is a blank tube for cold drawing which is used for the production of a longer-length, small-diameter tube such as a heat-transfer tube for as steam generator in nuclear power facilities, in which the blank tube will not cause scoring and chattering vibration in a drawing process; and a method for producing the blank tube; as well as a method for producing a cold drawn tube which is obtained through cold drawing of the blank tube. The average surface roughness Ra (ANSI B46.1) of the inner surface of blank tube before drawing satisfies the condition: 0.10 µm Ra ≤ 1.00 µm in the case of a blank tube for cold drawing for use in an oil-lubricated drawing. In particular, the surface roughness Ra satisfies the condition: 0.10 µm ≤ Ra ≤ 0.50 µm in the case of a blank tube for use in a high-pressure lubrication drawing, and which is made of an austenitic alloy for use in a heat-transfer tube for a steam generator.