For integrated CNC shear blades exceeding 3 meters in length, high alloy steels such as Cr12MoV, DC53, LD, and H13K are typically utilized. Because these blades demand exceptional precision in parallelism, perpendicularity, hole pitch tolerances, and hardness uniformity, the margin for heat-treatment distortion is incredibly slim.

To mitigate this, a two-stage preheating process is standard during the heating, soaking, and quenching cycles:

• Stage 1: Isothermal holding at 500°C.

• Stage 2: Temperature ramp-up to 850°C for the second preheat.

During the heating cycle, the material undergoes thermal expansion, by volumetric contraction upon reaching the phase transition point. Implementing a strict preheating regimen is therefore paramount to minimizing distortion, particularly in extra-long, single-piece blades.