Aluminum as grain refiner
Aluminum reduces grain growth in steels by forming fine nitrides that prevent the growth of larger crystals. This leads to a finer structure and increases the strength and toughness of the weld.
Physicochemical mechanism of action
Aluminum reacts with steel in hot environments to form fine nitrides. These nitrides have a low crystal size and block the uncontrolled growth of larger crystals, preventing grain growth during hot forming or welding.
Metallurgical relevance & risks in welding
Too high aluminum content can cause fusion issues and an increased risk of hot cracking. However, the finer structure improves the strength and toughness of the weld, increasing the component's service life and reliability.
Workshop practice & action guidelines
Add aluminum to the weld pool or as a spray. A typical content is 0.1–0.3% in steel. Make sure the aluminum content is not too high to avoid fusion problems. Achieve optimal grain refinement through controlled cooling and correct selection of aluminum content.