Study on thickness effects of low carbon steel in rapid cooling process

Hot stamping is among the latest technology applied in sheet metal manufacturing. It is a combination of a forming and rapid cooling to produce stronger products with the creation of martensite inside the sheet metal components. To cope with a huge range of sheet metal that suitably used for hot forming process, this research investigates microstructure changes during the rapid cooling process of three different sheet metal thicknesses. The Low Carbon Steel specimens of 2, 4 and 6mm thick were heated in a furnace to austenite region before immediately quenched in water and normalized in air. During the process, cooling rates were measured with acquisition system. The quenched specimens were observed using metallurgical microscope. The results show that water quench produced martensite structures while air quench produced pearlite and ferrite structures. The 2mm specimen of water quench formed a higher percentage of martensite and compactly bonded structure compared to 4mm and 6 mm specimens’ structure. For the air quench, 2mm specimen formed finely dispersed pearlite and ferrite. However, the microstructure of 4mm and 6mm specimens’ shows coarse pearlite and ferrite with lower hardness surface