1. The excessive amount of deoxidizer aluminum during melting can easily form aluminum nitride inclusions with the nitrogen in the steel, leading to brittle fracture of the casting.
2. Excessive use of boric acid during the construction of furnace lining leads to the formation of carbon boron compounds in the steel.
3. Excessive carbon content and other alloying elements exceeding the scale can also increase the brittleness of steel. For example, when using pig iron for carbonization, if the addition is not careful or calculated, harmful elements can be introduced.
4. The steel is severely overheated and the heat treatment operation is improper, resulting in coarse grains.