In the production of railway and rolling mill bearings, because of the large size and heavy weight of the rolling mill, the M-structure is brittle in the quenching of the steel. In order to obtain the high hardness after quenching, the strong cooling measures are often adopted, resulting in quenching microcracks. BL structure is much better than M organization toughness, while the surface of the formation of up to -400 ~ -500MPa compressive stress, greatly reducing the tendency of quenching crack; grinding in the surface stress to offset part of the grinding stress, the overall stress level Down, greatly reducing the grinding cracks.