Seamless Pipe Piercing Plug Tip Draft Control
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Solution Overview
Problem
Existing methods for manufacturing seamless steel pipes often result in inner surface defects and wall thickness irregularities due to the rotary forging effect and shear deformation, leading to reduced piercing efficiency and operational issues like rolling interruptions, especially when dealing with materials like continuously casting materials.
Innovation Solution
The method involves setting the plug tip draft to 0.04 or below, controlling the root of the product of the gorge draft and the number of billet revolutions to prevent inner surface defects, and using a pusher to increase billet advancement velocity in the unsteady region, ensuring stable piercing-rolling and maintaining high piercing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the plug tip draft is reduced to suppress the rotary forging effect, then inner surface defects are prevented, but piercing efficiency decreases
Solution Approach 1:
The invention changes the plug tip draft parameter to a specific range (0.02 to 0.04) to optimize the balance between suppressing rotary forging effect and maintaining piercing efficiency. This parameter optimization allows the process to prevent inner surface defects while avoiding excessive reduction in piercing efficiency
Solution Approach 2:
The invention introduces dynamic control of the pusher to actively manage billet advancement velocity during piercing. By controlling the pusher to maintain billet advancement velocity at not lower than 80% of roll gorge peripheral velocity, the system dynamically compensates for the reduced piercing efficiency caused by lower plug tip draft, thereby maintaining acceptable productivity while preventing defects
2Object-affected harmful factors
If the plug tip draft is reduced, then rotary forging effect is suppressed, but wall thickness irregularities increase
Solution Approach 1:
The invention optimizes the plug tip draft parameter within a narrow range (0.02 to 0.04) to achieve the right balance. This specific parameter setting suppresses the rotary forging effect sufficiently to prevent inner surface defects while maintaining enough contact pressure to control wall thickness uniformity within acceptable limits (not higher than 10%)
Solution Approach 2:
The invention implements feedback control through monitoring wall thickness during the piercing process. By measuring actual wall thickness and comparing it against target values, the system can adjust process parameters in real-time to compensate for variations caused by reduced plug tip draft, thereby maintaining manufacturing precision
3Object-affected harmful factors
If piercing efficiency decreases, then billet advancement velocity reduces, but rolling interruptions occur
Solution Approach 1:
The invention introduces dynamic control of the pusher mechanism to actively maintain billet advancement velocity at not lower than 80% of the roll gorge peripheral velocity. This dynamic compensation prevents rolling interruptions that would otherwise occur due to the reduced piercing efficiency caused by lower plug tip draft
Solution Approach 2:
The pusher acts as an intermediary device between the billet and the rolling system. By actively pushing the billet forward to maintain adequate advancement velocity, the pusher mediates between the reduced piercing efficiency and the requirement for continuous stable rolling, preventing interruptions while allowing the use of lower plug tip draft values
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 effectively reduces inner surface defects and wall thickness irregularities while maintaining high piercing efficiency, preventing rolling interruptions and ensuring high-quality seamless pipes production.
Implementation Method 1
a rotary forging effect (Mannesmann effect) is exerted on the central portion of the billet during the period until the billet arrives at the tip of the piercing plug
Implementation Method 2
the billet undergoes piercing-rolling by the pair of inclined rolls and the plug to form a hollow raw pipe
Implementation Method 3
a pair of inclined rolls... gripped by the pair of inclined rolls... the billet advances while the rolls rotate it
Data Source
Figure 1
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Figure 4~5
AI summary
An object of the invention is to provide a technology of manufacturing seamless pipes excellent in quality features with high productivity. Thus is provided a method of manufacturing seamless pipes by carrying out piercing-rolling using a piercer provided with a pair of inclined rolls which method is characterized in that it has the following features (a) to (d): Feature (a): That the piercing-rolling is carried out under conditions such that the plug tip draft (TDFT) is not higher than 0.04 or the root of the product of the plug tip draft (TDFT) and the number of billet revolutions (N), namely (TDFT x N)0.5, is not greater than 0.4. Feature (b): That the positions of the inclined rolls are selected so that the gorge draft (GDFT) indicating the ratio of the roll gap (Rg) which is minimal in the gorge section between the inclined rolls to the billet outside diameter (Bd) may satisfy the relations defined by the formula (1) given below. Feature (c) : That the piercing-rolling is carried out using a plug having a shape satisfying the relations defined by the formula (2) given below. Feature (d): That the billet is pushed by the pusher at least in the unsteady region of the piercing-rolling. -0.01053×EL+0.8768≤GDFT≤-0.1765×EL+0.9717 -0.95×TDFT×N0.5+1.4≤L2/d2≤-1.4×TDFT×N0.5+3.15 In the above formulas, TDFT is 1 - (d1/Bd), where d1: minimum roll-to-roll distance (mm) at the plug tip position and Bd: billet outside diameter (mm), and N = (Ld x EL)/(0.5 x n x Bd x tanβ), where Ld: projected contact length (mm) from the billet gripped point to the plug tip, EL: piercing ratio, β: roll feed angle, L2: rolling section length (mm) of the plug, and d2: outside diameter (mm) of the plug at the boundary position between the rolling section and reeling section thereof.