The Influence of Finishing Rolling Temperature and Cooling Conditions of Rolled Products
Rolling is the commonest forming process used to produce high quality and large quantities of rolled products. As one of the most important process parameters, the finishing rolling temperature has great influence on the properties and quality of rolled products. The change of rolling temperature will significantly affect the microstructure and mechanical properties of the rolled products. Therefore, it is necessary to take effective measures to control the finishing rolling temperature during the rolling process in order to obtain a desired quality and mechanical properties of the rolled products.
Cooling conditions and cooling rate after rolling are also important process parameters to determine the microstructure and properties of rolled products. The cooling rate determines the austenite transformation temperature during cooling, which will affect the grain size and size of the ferrite portion, as well as the rate at which the secondary phases are formed. Both the finishing rolling temperature and the cooling conditions and cooling rate after rolling must be accounted for in order to obtain a desired microstructure and properties of the rolled product.
The objective of this paper is to investigate the influence of finishing rolling temperature and cooling conditions of rolled products on the mechanical properties. Hot rolled 304 stainless steel plates with different finishing rolling temperature and different cooling conditions were prepared and tested for their mechanical properties, including hardness, elongation, and impact energy. An Optical Emission Spectroscopy (OES) was used to analyze the microstructure of the plate.
The results showed that the hardness of the plate increased with increasing finishing rolling temperature, indicating that the higher finishing rolling temperature can strengthen the rolled product by enhancing its work hardening ability. It was also found that the hardness of the plate decreased with increasing cooling rate from secondary cooling water, indicating that a faster cooling rate could reduce the hardness through quenching effect.
The investigations into the OES analysis revealed that the structure of the rolled product was greatly influenced by the finishing rolling temperature and cooling conditions. It was found that both the size and the amount of ferrite phase in the plate decreased with increasing finishing rolling temperature, suggesting that the increase of the finishing rolling temperature decreased the amount of ferrite phase in the plate. The OES also revealed that a faster cooling rate resulted in a lower ferrite phase size.
The study also found that the impact energy of the 304 stainless steel plate decreased with increasing finishing rolling temperature, indicating that a higher finishing rolling temperature would reduce the impact energy due to the decrease of the ferrite phase. It was also found that the impact energy increased with increasing cooling rate from secondary cooling water, indicating that the faster cooling rate could increase the impact energy through tempering and refining.
In conclusion, the finishing rolling temperature has a significant influence on the microstructure and mechanical properties of the rolled products. The higher finishing rolling temperature causes the decrease of the ferrite phase in the plate and thus leads to a decrease in the impact energy of the plate. The faster cooling rate after rolling can increase the impact energy by refining and tempering the microstructure of the plate. Therefore, it is important to appropriately control the finishing rolling temperature and cooling conditions in order to obtain a desired microstructure and mechanical properties of the rolled product.
