Abstract

Photovoltaic mounting structures operate in harsh environments, demanding high strength and elongation. However, a strength–graded product series within the same composition is lacking. Through Ti microalloying and heat treatment, we developed steels with strengths of 500–800 MPa and studied annealing effects at 640–740 °C. Scanning Electron Microscope (SEM) shows ferrite and cementite: with increasing temperature, ferrite changes from elongated to equiaxed via recovery and recrystallization, while cementite remains finely dispersed along grain boundaries. Transmission Electron Microscope (TEM) reveals TiC precipitates, which decrease in number but increase in size at higher temperatures. Grain refinement strengthening, dislocation strengthening, and precipitation strengthening are the primary strengthening mechanisms, contributing 91.2% and 94.4% to the yield strength after annealing at 640 °C and 720 °C, respectively. Within a wide annealing temperature range, the tensile strength fully covers the 550–650–750–800 MPa grades, with the corresponding elongation fluctuating between 12.4% and 25.3%, achieving a good strength–ductility balance. In summary, simply adding a single Ti element and adjusting the annealing temperature allows for the production of test steels with strengths ranging from 500 to 800 MPa and matched elongation. This approach not only reduces costs but also provides experimental evidence for the process development of a series of new steels for photovoltaic mounting brackets.

Keywords