Abstract: Microalloyed Nb has an important influence on the microstructure and hardness of tinned substrate. Even trace Nb can affect the recrystallization of metals, and the annealing temperature needs to be increased to meet the hardness requirements of the material. Compared with Nb-free steel, the tin-plated substrate containing trace niobium is mainly fiber-like at 570 ℃. There are only a very small amount of ferrite grains. 30%-40% of the microstructure are recrystallized at 600 ℃, and the recrystallization process is basically completed at 630 ℃. The annealing temperature is increased by about 30 ℃.