Influence of Heat Input and Preheating on Microstructure and Mechanical Properties of Coarse Grain Heat-Affected Zone of Metal Arc Gas-Welded Pearlitic Rail Steel

Autor: Adnan Raza Khan, Hao Wang, Yu Shengfu
Rok vydání: 2019
Předmět:
Zdroj: Journal of Materials Engineering and Performance. 28:7676-7686
ISSN: 1544-1024
1059-9495
DOI: 10.1007/s11665-019-04486-1
Popis: Influence of varying heat input (0.66-1.43 kJ/mm) and different preheat temperatures (150-350 °C) on microstructure and mechanical properties of the coarse-grained heat-affected zone (CGHAZ) of MAG-welded pearlitic rail steel has been investigated. Results show that at low heat inputs (0.66-1.00 kJ/mm), microstructures are mainly composed of martensite, whereas high heat inputs (1.29-1.43 kJ/mm) have coarsened the grains and formed cracks. 1.16 kJ/mm of heat input is found optimum which has produced a crack-free surface with the least martensite. Afterward, by using the optimum heat input of 1.16 kJ/mm samples are welded at different preheat temperatures ranging from 150 to 350 °C, which has reduced the martensite and increased the pearlite, successively. Preheat temperatures of 250 °C are found optimum, where grain size and $$t_{{800 - 300\,^\circ {\text{C}}}}$$ cooling rate are 38.1 ± 9.8 μm and 3.1 °C/s, respectively. Furthermore, hardness is 659 ± 7 HV, tensile strength is 1349 ± 16 MPa, and toughness is 6.4 ± 0.5 J, respectively. Finally, the confocal scanning laser microscopy analysis, at optimum heat input of 1.16 kJ/cm and 250 °C of preheat temperature, is also presented. The entire study concludes that preheating is inevitable in MAG welding of pearlitic rail steel. 1.16 kJ/mm of heat input with 250 °C of preheating temperature is suitable in MAG welding of pearlitic rail steel where microstructure is composed of pearlite, ferrite, and sorbite having no martensite and no cracks.
Databáze: OpenAIRE
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