Steel composition design and production process features

Normalizing is a heat treatment in which steel is heated to austenitizing temperature and then cooled (mainly air-cooled). Normalizing improves the coarse grains and uneven microstructure of steel and parts subjected to high-temperature hot processing (rolling, forging), thereby improving machinability and preventing grain coarsening during carburizing of cold forged parts. There are many methods of annealing, the main purpose of which is to soften the material. For example, if normalizing is not air-cooled but slow-cooled, the steel can be further softened. This heat treatment is called full annealing. In addition, there is spheroidizing annealing, which is heating hypoeutectoid steel to the austenite-ferrite two-phase region or heating hypereutectoid steel to the austenite-cementite two-phase region and then slowly cooling. After spheroidizing annealing, the microstructure of the steel becomes a mixed structure of ferrite and spheroidal carbides, and the hardness is greatly reduced, so it is used as a softening treatment method for cold forging and wire drawing. When the hot-rolled steel contains hard bainite that is difficult to cut, the steel can be heated to below the two-phase temperature and then air-cooled after being kept warm. This is called low-temperature annealing.

I would like to discuss the requirements for steel bars, pipes, wires, and similar materials used in component manufacturing. These materials should facilitate easy processing during production while maintaining structural integrity throughout hardening heat treatment to enhance component strength. Various processing methods are employed to shape these materials, including hot forging, cold forging, wire drawing, and cutting. In recent years, there has been a noticeable shift towards cold forging techniques, which are characterized by lower CO2 emissions and higher yield charges. However, it is important to note that cold forging requires a larger forming load compared to hot forging. To mitigate the load on cold forging dies, workpieces are often annealed prior to the cold forging process. To optimize this process, the implementation of steel softening technology—eliminating the need for pre-cold forging annealing—has proven beneficial. The primary methods employed in the production of softened steel are controlled rolling and controlled cooling. By adjusting the steel composition and carefully managing the rolling and cooling processes, we can significantly enhance the softening effect of the steel. To achieve effective softening, the final rolling temperature of the steel should be reduced, followed by a controlled slow cooling process. This can be accomplished by using a heat preservation cover on the cooling belt of the rolled material. The combination of low-temperature rolling and slow cooling results in a microstructure consisting of soft ferrite and pearlite, while also inhibiting the formation of hard bainite structures. Importantly, the pearlite itself exhibits softer characteristics. Moreover, low-temperature rolling helps to prevent recrystallization and grain growth during processing. Thus, the fine austenite structure produced during rolling is effectively transformed into ferrite through the cooling process. I believe that the adoption of this steel softening technology would greatly enhance our manufacturing efficiency and product quality. I look forward to your thoughts on this matter.