Optimization of Resistance Upset Butt Welding Parameters of Steel Rebars: A Study on Mechanical Properties and Microstructure

Document Type : Original Articles

Authors

Hoda Mirseifi ¹

Hamed Ghohani Arab ²

Mahmood Sharifitabar ³

¹ Civil Engineering Department, University of Sistan and Baluchestan, Zahedan, Iran

² University of Sistan and Baluchestan,, Civil Engineering Department,, Zahedan,, Iran

³ Materials Engineering Department, Hakim Sabzevari University, Sabzevar, Iran

10.22067/jmme.2025.92300.1192

Abstract

This study investigates the effect of resistance upset butt welding (RUBW) process parameters on the joining of steel bars with different diameters. The conducted evaluations included microstructure, ultimate tensile strength (UTS), elongation, and localized hardness of the welded specimens. Parameter optimization was performed using Central Composite Design (CCD) and Particle Swarm Optimization (PSO) algorithms. The maximum ultimate tensile strength of 628 MPa and an elongation of 25% were achieved under optimal conditions for an 18-mm-diameter rebar, a welding current of 8460 A, and a welding pressure of 1.64 MPa. Analysis of variance showed that the quadratic model provided accurate predictions for ultimate tensile strength, while the linear model was accurate for elongation. The PSO algorithm was used to determine the optimal input parameters, and its results were compared with those from the CCD method. The JMatPro software was used to analyze the phase types and compared with experimental observations. The results showed that the joint interface contained needle-shaped ferrite grains and the heat affected zone exhibited a coarse-grained ferrite-pearlite microstructure.

Keywords

Solid-state welding

Design of experiments

Optimal Response

Hardness distribution

Variance analysis

Subjects

• Welding

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