Abstract: Using low-temperature Hi-B cold-rolled sheets with a thickness of 0.23 mm as raw materials, after decarburization annealing, the subsequent process was carried out by the post-inhibitor method with NH₃ as the nitriding gas. The effects of different nitriding temperatures on the microstructure and precipitates of the decarburized and nitrided Hi-B steel sheets were studied by means of optical microscopy, high-resolution transmission electron microscopy, scanning electron microscopy and energy dispersive spectrometry. The results show that under the nitriding conditions of 750 and 800 ℃, the average grain size of the microstructure remains basically unchanged compared with that of the decarburized sheet. However, after nitriding at 850 ℃, the average grain size increases from 23.09 to 26.19 μm. After nitriding treatment at 750 and 800 ℃, the precipitate type is amorphous Si₃N₄. But when the nitriding temperature rises to 850 ℃, microcrystalline regions appear in the amorphous Si₃N₄ precipitates.