Finite Element Simulation and Verification of Seamless Steel Pipe Tension Reduction at Baosteel

Literature Overview

This paper by Wang Chaofeng and colleagues, published in the Journal of Plasticity Engineering in 2018, presents a comprehensive finite element analysis of the tension reduction process for seamless steel pipes at Baoshan Steel Corporation. The authors, affiliated with Baosteel's Steel Pipe and Strip Division and Yanshan University's School of Mechanical Engineering, developed a three-dimensional thermo-mechanically coupled finite element model of a 14-stand tension reduction mill using MSC.Marc software. The study was supported by the National Natural Science Foundation of China (Grants 51374184 and U1560206). The model was validated against actual production data, and parametric studies were conducted to investigate the effects of friction coefficient and billet inlet temperature on the final pipe wall thickness.

Core Technical Content and Model Description

The tension reduction process is a critical step in seamless steel pipe production, where the pipe is simultaneously reduced in diameter and wall thickness by a series of rolling stands while being pulled through by a tensioning device. The 14-stand configuration used at Baosteel represents a modern, high-precision production line capable of producing pipes with tight dimensional tolerances.

The finite element model was built using MSC.Marc software and incorporated thermo-mechanical coupling to account for the interaction between thermal and mechanical phenomena during the rolling process. The model captured the following key aspects:

The simulation results showed good agreement with measured wall thickness and temperature data, confirming the reliability of the model. One of the most interesting findings was that the wall thickness does not monotonically decrease or increase during the tension reduction process; instead, it exhibits a complex variation pattern as the pipe passes through each stand.

Thermo-Mechanical Analysis Results

The simulation revealed several important characteristics of the tension reduction process:

• The wall thickness variation through the 14 stands is non-monotonic, with alternating increases and decreases depending on the rolling geometry and tension conditions at each stand.
• The outer surface of the finished pipe is cooler than the inner surface, indicating a radial temperature gradient across the wall thickness. This gradient is caused by the contact between the outer surface and the cooler rolling rolls, while the inner surface is insulated from direct contact cooling.
• The strain field shows complex deformation patterns that vary with the rolling geometry and the tension applied at each stand.

The parametric study investigated the effects of two key variables:

1. Friction coefficient: Higher friction between the pipe and rolls increases the rolling force and affects the wall thickness reduction pattern. The study found that the friction coefficient has a significant influence on the final wall thickness distribution.
2. Billet inlet temperature: Higher inlet temperatures reduce the flow stress of the material, affecting the rolling forces and the deformation behavior. The study established clear relationships between inlet temperature and final wall thickness.

Engineering Practice Implications

The findings from this study have direct practical applications for optimizing the tension reduction process:

1. The non-monotonic wall thickness variation means that process parameter adjustments must be made stand by stand, rather than assuming a uniform reduction pattern.
2. The radial temperature gradient should be considered when predicting mechanical properties and dimensional accuracy of the finished pipe, as the inner and outer surfaces may have different microstructures.
3. Friction coefficient control through roll surface condition and lubrication is a critical lever for achieving target wall thickness specifications.
4. Inlet temperature control is essential for consistent production quality, and the parametric relationships established in the study can be used for process optimization.
5. The validated finite element model can serve as a virtual prototyping tool for evaluating process changes before implementing them on the production line.

Study Insights and Reflections

This paper demonstrates the value of finite element modeling in understanding and optimizing complex metal forming processes. The thermo-mechanically coupled approach is essential for accurately predicting the behavior of the tension reduction process, as thermal and mechanical phenomena are strongly coupled. The validation against production data is a critical step that confirms the model's predictive capability. The finding that wall thickness does not vary monotonically is particularly important, as it challenges the common assumption of uniform reduction and highlights the complexity of multi-stand rolling processes. The parametric study provides actionable insights for process engineers, showing how friction coefficient and inlet temperature can be adjusted to achieve target specifications. The model can also be extended to include material flow stress models that account for temperature and strain rate effects, further improving its predictive accuracy. Overall, this study represents a mature application of computational methods to steel pipe manufacturing and provides a framework for similar analyses in other forming processes.