Numerical Simulation and Experimental Study of the Drawing Process for Phi508mm Equal Tee

Literature Overview

This paper, authored by Liu L. Min, Zhong Z. Ping, Xie Tan, and Yan H. Yan, was published in the Journal of Plasticity Engineering (Vol. 16, No. 5, 2009, pp. 15-20). The research originates from the Advanced Manufacturing Technology Research Center of the China Academy of Machinery Science and the Beijing Institute of Mechanical and Electrical Engineering. The study focuses on one of the most challenging aspects of large-diameter tee manufacturing: the drawing operation of the branch pipe during hot extrusion forming of X80 grade Phi508mm equal tees.

Core Technical Content

The formation of large-diameter tees via hot extrusion represents a well-recognized bottleneck in pipe fitting manufacturing. Among the various process steps involved, the drawing of the branch pipe constitutes the critical final forming operation that determines the dimensional accuracy, wall thickness uniformity, and overall structural integrity of the finished tee. The authors employed finite element numerical simulation to analyze the drawing passes and forming loads, and then validated the simulation results through physical experiments.

The key technical challenge lies in the fact that X80 steel, with its high yield strength of approximately 552 MPa and tensile strength of at least 620 MPa, presents significant forming difficulties. The Phi508mm diameter further amplifies the forming loads and complicates the thermal management during the drawing process. The number of drawing passes, the reduction rate per pass, and the die geometry all significantly influence the residual stress distribution and the risk of cracking.

Key Technical Parameters and Process Analysis

The numerical simulation revealed that the number of drawing passes directly affects the peak stress concentration at the root of the branch pipe. Too few passes result in excessive localized strain and potential cracking, while too many passes increase cycle time and energy consumption without proportional improvement in forming quality. The optimal pass arrangement was determined through iterative simulation, balancing forming load with dimensional accuracy.

Engineering Practice Integration

From a practical standpoint, this research addresses a real production bottleneck. In the oil and gas industry, large-diameter X80 tees are essential components for pipeline networks, and their manufacturing quality directly affects system reliability. The simulation-validated process parameters provide a reliable foundation for production planning. The experimental verification confirmed that the simulated forming loads and strain distributions matched the physical test results within acceptable tolerances.

The study also highlights the importance of die design in the drawing process. The die geometry must accommodate the material flow patterns predicted by the simulation, ensuring uniform wall thickness reduction without inducing excessive bending or buckling of the branch pipe wall.

Key Insights and Reflections

The most valuable aspect of this work is the systematic approach combining numerical simulation with experimental validation. In my decades of experience in pipe fitting manufacturing, I have observed that purely experimental approaches are costly and time-consuming for large-diameter fittings, while purely simulation-based approaches carry the risk of unverified assumptions. This hybrid methodology represents the mature engineering practice that should be adopted for similar large-scale forming problems.

One critical observation is that the simulation accurately predicted the forming load peaks, which directly informs the selection of press capacity. For a Phi508mm X80 tee, the drawing loads can reach several thousand tons, making equipment selection a critical decision. The study's findings provide quantitative data for this purpose.

Study Value and Outlook

This paper serves as a valuable reference for engineers involved in the design and optimization of large-diameter tee manufacturing processes. The methodology can be extended to other high-strength steel grades such as X100 or X120, which are increasingly used in high-pressure pipeline systems. Future work should address the microstructural evolution during the multi-pass drawing process and its impact on the final mechanical properties and toughness of the tee, particularly in the branch root region where strain concentration is most severe.