Effects of Reduction and Temperature on Residual Stress Distribution During Sizing of Seamless Steel Tubes

Literature Identification and Technical Background

This paper by Li Lianjin (Tianjin Mechanical Engineering Institute) and Hu Guangda (University of Science and Technology Beijing), published in the Journal of Plasticity Engineering (ISSN 1007-2012, Vol. 14, Issue 5, 2007, pp. 111-115), addresses a fundamental aspect of seamless steel tube manufacturing: the sizing (finishing) process. Funded by the Tianjin Natural Science Key Fund (043804011), this work investigates how the sizing reduction amount and processing temperature influence the residual stress distribution in the finished tube. The classification TG335.71 confirms the focus on metal forming processes.

Core Technical Analysis

The sizing process serves as the final production step in seamless tube manufacturing, responsible for achieving precise dimensional tolerances and geometric accuracy. The paper establishes that sizing not only corrects dimensional and ovality errors introduced during prior rolling and heat treatment operations but also significantly influences the mechanical properties of the finished tube through the residual stress field it creates.

Metal Flow During Sizing

The authors analyze the metal flow patterns during the sizing operation. During sizing, the tube is forced through a die with a reduction in cross-sectional area, causing:

Radial compressive deformation of the tube wall
Circumferential elongation due to material flow
Axial material displacement dependent on the die geometry and friction conditions
Differential deformation between the outer and inner surfaces of the tube wall

The residual stress distribution resulting from this deformation pattern is characterized by compressive stresses on the outer surface and tensile stresses on the inner surface, with the magnitude and gradient depending on the specific process parameters.

Influence of Reduction Amount

The sizing reduction amount is identified as a primary control variable. The following relationships are established:

Reduction Amount	Residual Stress Magnitude	Dimensional Accuracy	Material Deformation
Low (< 2%)	Low residual stress	May not meet tolerance	Insufficient correction
Moderate (2-5%)	Moderate residual stress	Good dimensional accuracy	Optimal balance
High (> 5%)	High residual stress	Excellent accuracy	Risk of cracking

The paper demonstrates that increasing the reduction amount increases the magnitude of residual stresses throughout the tube wall thickness. However, there exists an optimal range where dimensional requirements are met without generating excessive residual stresses that could impair mechanical performance.

Influence of Processing Temperature

Temperature is the second critical parameter investigated. The study reveals that:

Higher processing temperatures reduce the flow stress of the material, allowing greater deformation with lower applied forces
Elevated temperatures promote stress relaxation through dynamic recovery and recrystallization mechanisms
The residual stress distribution becomes more uniform at higher temperatures due to reduced strain hardening effects
However, excessively high temperatures may lead to grain coarsening and reduced mechanical properties

The optimal temperature window balances the need for dimensional correction against the risk of excessive thermal softening and potential microstructural degradation.

Engineering Practice Implications

For seamless tube manufacturers, this research provides critical guidance for process parameter optimization. The following practical recommendations emerge:

Process windows should be established based on tube diameter, wall thickness, and material grade
Residual stress levels should be monitored using magnetic flux leakage or X-ray diffraction methods
The sizing reduction should be calculated based on the maximum permissible ovality from prior operations
Temperature control during sizing should target the austenite region for carbon steel tubes to maximize stress relaxation

The residual stress state directly affects downstream performance, including fatigue life, resistance to stress corrosion cracking, and dimensional stability during subsequent service conditions. Tubes with uncontrolled residual stresses may exhibit premature failure in high-cycle fatigue applications or experience dimensional instability during heat treatment operations.

Key Questions and Reflections

The paper raises an important question: how should residual stress targets be set for specific end-use applications? A tube destined for pressure vessel service may have different residual stress requirements than one intended for structural applications. The connection between residual stress patterns and long-term service performance warrants further investigation, particularly in the context of modern high-performance steel grades where the balance between strength and toughness is critical.

Study Insights and Outlook

This work represents a significant contribution to the understanding of the sizing process in seamless tube manufacturing. The systematic investigation of reduction amount and temperature effects provides a theoretical basis for process optimization. For engineers in our field, the key takeaway is that the sizing process is not merely a dimensional correction step but a critical process that shapes the residual stress field and consequently the mechanical performance of the finished product. Future work should integrate these findings with finite element simulations that account for temperature-dependent material properties and complex die geometries to further refine process windows for modern high-strength tube grades.