Piercer Plug Hardness Gradient to Resist Deformation and Cracking
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Solution Overview
Problem
Piercer plugs used in the production of seamless steel pipes face issues with deformation and cracking, particularly at the tip portion, due to wear and tear, leading to reduced lifespan and increased manufacturing costs from complex processes and material inconsistencies.
Innovation Solution
A piercer plug design where the tip and trunk portions are made of the same material, with the tip being harder and the cylindrical portion having higher toughness, and a coating applied to prevent deformation and cracking, allowing for a longer lifespan by optimizing heat treatment to maintain austenite transformation temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the tip portion is made harder to reduce deformation, then the deformation resistance is improved, but the toughness decreases leading to cracking
Solution Approach 1:
The piercer plug employs local quality by making the tip portion harder than the trunk portion. The tip portion is subjected to heat treatment to achieve a hardness of 58 HRC or higher, while the trunk portion maintains a lower hardness of 48-55 HRC. This gradient structure allows the tip to resist deformation during piercing while the trunk retains sufficient toughness to prevent cracking, resolving the contradiction between deformation resistance and cracking resistance.
Solution Approach 2:
The invention applies parameter changes through controlled heat treatment processes. The tip portion is heated to an austenite transformation temperature of 800-950°C and held for 5-30 minutes, then rapidly cooled to achieve high hardness. The trunk portion undergoes different heat treatment parameters (heating to 700-800°C and holding for 10-60 minutes), resulting in different microstructures and hardness values that optimize both deformation resistance and cracking prevention.
2Reliability
If different materials are used for tip and trunk portions to optimize performance, then the deformation and cracking resistance are improved, but the manufacturing complexity increases
Solution Approach 1:
The invention applies homogeneity by using the same material composition (SCM440 steel) for both the tip and trunk portions of the piercer plug. This eliminates the need for separate material selection, casting, or joining processes that would be required if different materials were used. The uniform material base simplifies manufacturing while the differential heat treatment creates the necessary property gradients for optimal performance.
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 solution extends the life of the piercer plug by reducing deformation and cracking, enabling more rounds of piercing/rolling with reduced wear and tear, while maintaining piercing efficiency and preventing peeling of the coating.
Implementation Method 1
heating the piercer plug such that a temperature of the tip portion is not lower than an austenite transformation temperature
Data Source
AI summary
A piercer plug with increased life and a method of manufacturing it are provided. The piercer plug 1 includes a tip portion 2 and a trunk portion 3 made of the same material as the tip portion 2 and continuous to the tip portion 2. The trunk portion 3 includes a cylindrical portion 5 having a hole used for attaching a bar. The tip portion 2 is harder than the cylindrical portion 5.