Abstract
The heat input into the material during welding significantly affects the properties of high-strength steels in the near-weld zone. A zone of hardness decrease forms, which is called the soft zone. The width of the soft zone also depends on the cooling time t8/5. An investigation of the influence of welding parameters on the resulting properties of welded joints can be performed by thermal physical simulation. In this study, the effect of the cooling rate on the mechanical properties of the heat-affected zone of the steel S960MC with a thickness of 3 mm was investigated. Thermal physical simulation was performed on a Gleeble 3500. Three levels of cooling time were used, which were determined from the reference temperature cycle obtained by metal active gas welding (MAG). A tensile test, hardness measurement, impact test with fracture surface evaluation, and microstructural evaluation were performed to investigate the modified specimen thickness. The shortest time t8/5 = 7 s did not provide tensile and yield strength at the minimum required value. The absorbed energy after recalculation to the standard sample size of 10 × 10 mm was above the 27 J limit at −40 °C. The hardness profile also depended on the cooling rate and always had a softening zone.
Highlights
High-strength low-alloy (HSLA) steels provide design engineers with new opportunities in the design of mobile vehicles
inter-critical heat-affected zone (ICHAZ)—fine-grained area of the heat-affected zone (FGHAZ) transition area; (d) FGHAZ area; (e) microstructures of typical subzones of the HAZ that are formed in the S960MC steel due to different
The mainly focused on steels with awith thickness of 5 mm wherewhere it is easier to carry allout of the work mainly focused on steels a thickness of 5and mmmore, and more, it is easier to out carry all required tests
Summary
High-strength low-alloy (HSLA) steels provide design engineers with new opportunities in the design of mobile vehicles. Tempering processes occurring in the HAZ of welds involve a process similar to that when manufacturing the base material They include carbon rejection of the supersaturated martensite, the transformation of metastable carbides to stable ones, or the spheroidization of carbides. Sefcikova et al [18], Pisarski et al [19], and other authors [4,20,21] used this type of add-on material in their experiments They compared the results of the mechanical properties of welded joints, when applying undermatching and matching welding wire. In the case of the physical simulation of the welding process, the most common task is to investigate the loading of the material by the temperature cycle This is important due to its effect on the resulting structure and mechanical properties of the HAZ. The behavior of HLSA thin sheets when subjected to a welding cycle load is very interesting, but not featured in the literature so far
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