Piercing Mill Plug Tapered Geometry Reduces Erosion
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Solution Overview
Problem
Plugs used in piercing mills for forming seamless pipes or tubes experience erosion due to heat and pressure, leading to reduced useful life and limitations in re-grinding for reuse, as existing designs either erode quickly or require excessive re-grinding allowances that shorten the plug length.
Innovation Solution
A plug design featuring a tip end portion with a gentler curved surface and a tapered portion with varying diameters, allowing for a gap formation between the billet and the plug, reducing heat transfer and erosion, while enabling reuse with a reduced re-grinding allowance by satisfying specific geometric expressions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the plug has a conventional shape with a columnar portion, then the gap allows heat dissipation and reduces erosion, but the re-grinding allowance becomes excessively large requiring excessive material removal
Solution Approach 1:
The invention changes the geometric parameters of the plug by introducing a tapered portion with gradually varying outer diameter instead of a fixed columnar shape. The outer diameter increases from the front end to the back end according to specific expressions (D1 at front end, D2 at back end where D2 > D1), allowing the gap to be maintained while reducing the re-grinding allowance to within 5-20mm.
Solution Approach 2:
The invention applies different geometric characteristics to different portions of the plug. The tip end portion maintains a semi-spherical shape for hole formation, while the tapered portion has a gradually increasing diameter to reduce heat transfer and erosion. This local differentiation allows each portion to optimize its function while solving the overall contradiction.
2Reliability
If the plug is frequently re-grinded to remove erosion, then the plug can be reused, but the overall plug length is reduced and useful life is limited
Solution Approach 1:
By changing the geometric parameters from a fixed columnar shape to a tapered shape with controlled diameter variation, the invention reduces the re-grinding allowance to 5-20mm per re-grinding cycle. This allows multiple re-grinding cycles before the plug length becomes insufficient, thereby extending the total useful life of the plug.
3Object-affected harmful factors
If the tip end portion has a gentler curve with larger radius of curvature, then the hole diameter increases and gap formation is improved, but the tip end portion length must be optimized
Solution Approach 1:
The invention optimizes the geometric parameters of the tip end portion by setting the radius of curvature R1 greater than the length L1 (R1 > L1), creating a gentler curve compared to conventional designs where R1 = L1. This parameter change increases the hole diameter formed in the billet and improves gap formation, thereby reducing heat transfer to the plug.
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 plug design effectively reduces erosion and extends the number of billets that can be pierced before erosion occurs, allowing for successful reuse with minimized re-grinding needs, as the gentler curve and tapered shape prevent contact and heat transfer, thereby prolonging the plug's operational life.
Implementation Method 1
less heat is transmitted from the billet to the plug 200
Implementation Method 2
the gap IS allows heat stored in the plug 200 to be dissipated
Data Source
Figure 1A~1B
Figure 2
Figure 3~4
AI summary
A plug has a tip end portion, a taper portion, and a middle portion. The surface of the tip end portion is a spherical surface whose radius of curvature is R1 and length is L1 that is shorter than R1. The outer diameter of the taper portion on the front end side is D1, and the outer diameter on the back end side is D2 that is larger than D1, and the length is L2. The plug satisfies Expression (1), Expression (2) if 0<L1/R1<0.5 and Expression (3) if 0.5≤L1/R1<1. The curve of the spherical surface of the tip end portion is gentler than that of the semi-spherical surface, and the diameter of a hole formed in a billet by the tip end portion is larger than that in the case of the semi-spherical surface. Therefore, the taper portion does not contact with the billet. 0.5D1<L1+L2≤2.5D1 1.0<D2/D1≤1.4 1.0<D2/D1<1.8-0.8L1/R1