Effect of Preheating Temperature on the Mechanical and Fracture Properties of Welded Pearlitic Rail Steels

Heshmat A. Aglan, Sudan Ahmed, Kaushal R. Prayakarao, Mahmood Fateh

Federal Railroad Administration, Washington DC, USA.
Mechanical Engineering Department, Tuskegee University, Tuskegee, USA.

DOI: 10.4236/eng.2013.511101                

Abstract

The effect of preheating temperature on the mechanical and fracture behavior, hardness, and the microstructure of slot welded pearlitic rail steel were studied. Railhead sections with slots were preheated to 200℃, 300℃, 350℃ and 400℃ before gas metal arc filling to simulate defects repair. Another sample, welded at room temperature (RT) with no preheat, was studied in comparison. The parent rail steel has ultimate strength, yield strength and strain to failure of 1146 MPa, 717 MPa and 9.3%, respectively. Optimum values of these properties for the welded rail steels were found to be 1023 MPa, 655 MPa and 4.7%, respectively, for the 200℃ preheat temperature. On this basis, the optimum weld efficiency was found to be 89.2%. The average apparent fracture toughness K_I for the parent rail was 127 MPa.m^0.5, while that for the optimum welded joint (200℃ preheat) was 116.5 MPa.m^0.5. In addition, the average hardness values of the weld, fusion zone, and heat affected zone (HAZ) were 313.5, 332 and 313.6 HB, respectively, while that for parent rail steel was about 360 HB. Dominance of bainite and acicular ferrite phase in the weld microstructure was observed at 200℃ preheat.

Keywords

Preheat Temperature; Welded Rail Steels; Weld Microstructure; Welding Efficiency; Fracture Toughness

Conflicts of Interest

The authors declare no conflicts of interest.

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