Pilger Rolling Tube Surface Quality via Mandrel Taper Optimization
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Solution Overview
Problem
The cold rolling process for metal tubes by pilger rolling faces challenges in achieving high dimensional accuracy and surface quality, particularly in preventing oval appearances and minute concave/convex irregularities on the inside surface, which deteriorate the signal-to-noise ratio in inner coil eddy current testing, and existing solutions require new equipment or increase manufacturing costs.
Innovation Solution
Optimizing the side relief rate of roll-dies, mandrel tapers, and feed rate to set the side relief rate between 0.5% to 1.5%, taper θ1 in the primary deformation zone to 0.25 degree or less, and taper θ2 in the final size reduction zone to 0.1 degree or less, while ensuring the feed rate is between 1.0 to 2.5 mm, to maintain a high S/N ratio without requiring new equipment or increasing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional pilger rolling is used with standard side relief rate and mandrel taper, then the process is simple and cost-effective, but the tube inside surface develops oval appearances and minute concave/convex irregularities that reduce dimensional accuracy and surface quality
Solution Approach 1:
The patent applies parameter changes by optimizing the side relief rate to 0.5-1.5% and mandrel tapers to θ1≤0.25° and θ2≤0.1°, which directly improves dimensional accuracy and surface quality without requiring new equipment or complex process changes
Solution Approach 2:
The patent uses partial action by applying minimal side relief (0.5-1.5%) rather than excessive relief, which is sufficient to prevent oval appearances and maintain surface quality while avoiding over-correction that could introduce other defects
2Productivity
If feed rate is increased to improve productivity, then production efficiency increases, but dimensional accuracy and surface quality deteriorate
Solution Approach 1:
The patent optimizes the feed rate parameter to balance productivity and manufacturing precision, achieving the best compromise between production efficiency and dimensional accuracy/surface quality in the cold rolling 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 ensures excellent dimensional accuracy and surface quality, achieving a sufficiently high S/N ratio in inner coil eddy current testing for metal tubes without increasing manufacturing costs or reducing product yield, making it suitable for steam generator tubes in Nuclear Power Plants.
Implementation Method 1
the tube radius reducing and wall thinning in succession undergo... between the primary deformation zone 11a in the roll caliber 11 of roll-dies 10 and the primary deformation zone 21 of the mandrel 20, the tube radius reducing and wall thinning are provided
Data Source
AI summary
In the cold rolling process by pilger rolling that holds a mandrel between each of paired roll-dies, by optimizing the side relief rate SR and the mandrel factors like the taper θ1 in the primary deformation zone of the mandrel and the taper θ2 in the final size reduction zone thereof, and the feed rate F of the workpiece material, and at the same time by properly adjusting the relationship between the side relief rate SR and the feed rate F, the dimension-related shape characteristics (near-perfect round shape) of the tube inside surface after the final finishing rolling process by pilger rolling can be ascertained to thereby ensure excellent surface property without requiring a new apparatus, and further without causing the decrease of the product yield and/or the increase of the manufacturing costs. Thus, this can be widely applied for producing steam generator tubes which exhibits high S/N ratio in the inner coil eddy current testing.