Piercing Plug Oxide Film Regeneration
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Solution Overview
Problem
The existing piercing and rolling plugs used in seamless steel pipe production have a short lifespan, leading to frequent replacements and reduced production efficiency, especially when dealing with high alloy steel, due to wear and heat-related issues, and current methods for extending plug life, such as heat treatment and oxide scale modifications, are inefficient and costly.
Innovation Solution
A piercing and rolling plug with a film composed of oxides and Fe, formed on a shot-blasted plug base metal surface using electric arc spraying, where the oxide proportion is higher on the surface layer than the base metal, and a lubricant is applied, allowing for efficient heat shielding and seizure prevention, and can be regenerated quickly and cost-effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a scale film coated plug is used for piercing and rolling in high alloy steel seamless pipe production, then heat-shielding effect is provided, but the scale film is susceptible to wear and peeling off due to high deformation resistance of the billet
Solution Approach 1:
The invention changes the chemical composition parameters of the plug base metal by adding specific alloying elements (Ti: 0.01-0.10 wt%, V: 0.01-0.10 wt%, Nb: 0.01-0.10 wt%, B: 0.0005-0.0050 wt%) to improve high-temperature strength and scale film adhesiveness, thereby preventing scale film peeling and wear under high deformation conditions
Solution Approach 2:
The invention creates a composite structure with a specially formulated tool steel base metal containing multiple alloying elements that work synergistically to provide both high-temperature strength and improved scale film adhesion, making the plug suitable for high alloy steel piercing and rolling
2Productivity
If piercing and rolling is continued using a plug with a damaged scale film, then production continuity is maintained, but seizure failure occurs and flaws are developed on the inside surface of the hollow shell
Solution Approach 1:
The invention preemptively strengthens the plug base metal with alloying elements before the scale film is applied, creating a more durable foundation that prevents scale film damage and avoids subsequent seizure failures and surface flaws, ensuring both production continuity and product quality
3Reliability
If plug replacement is made frequently to maintain plug performance, then plug performance is maintained, but production efficiency of the piercing and rolling mill declines
Solution Approach 1:
The invention adds small but significant amounts of alloying elements (0.01-0.10 wt% for Ti, V, Nb and 0.0005-0.0050 wt% for B) that provide substantial improvements in high-temperature strength and scale film adhesion, extending plug life without requiring excessive material addition or complex processing
4Duration of action of moving object
If heat treatment is performed to re-form the scale film on the plug, then the plug can be reused, but lengthy time and a number of steps are required
Solution Approach 1:
The invention modifies the base metal parameters through alloying to inherently improve scale film formation and adhesion, reducing the need for lengthy heat treatment cycles and enabling faster plug regeneration while extending service life
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 exhibits prolonged lifespan and improved heat-shielding and seizure-preventing abilities, enabling efficient seamless steel pipe production with reduced plug replacement frequency and lower regeneration costs, while maintaining production efficiency.
Implementation Method 1
a film composed of oxides and Fe as being formed on a shot-blasted plug base metal surface by electric arc spraying
Implementation Method 2
a film composed of oxides and Fe as being formed on a shot-blasted plug base metal surface
Data Source
Figure 1
Figure 2
Figure 3~5
AI summary
A piercing and rolling plug has a film composed of oxides such as Fe3O4 and FeO and Fe (metal) as being formed on the surface of the base metal by electric arc spraying using an iron wire whose main component is Fe and, owing to this film, a plug excellent in heat-shielding and seizure-preventing effects can be realized and the lifetime of the plug can be prolonged. Further, in regenerating this plug, a film can be re-formed via the steps of shot blasting of the as-used plug in piercing and rolling and electric arc spraying in that order; thus, it is possible to regenerate the plug at low cost and in a short period of time.