Stable hardness and good uniformity

Because BL transformation is a slow process, generally GCr15 steel takes 4h, GCr18Mo steel takes 5h, the ferrule is isothermal in nitrate for a long time, and the surface and core structure transformation is almost carried out at the same time, so the hardness is stable and uniformity is good. Generally, the hardness of GCr15 steel bl after quenching is 59~61hrc, and the uniformity is ≤ 1 HRC, unlike the problems of low hardness, soft spots, poor uniformity and so on when the ferrule wall thickness is slightly larger during quenching.