Parameter optimization approaches for CNC turning of quenched steel

The parameter optimization approaches for CNC turning of quenched steel can start from aspects such as tool material, geometric parameters, cutting parameters, and cooling and lubrication. The following are specific strategies:

Tool material selection: Quenched steel has high hardness and high requirements for the wear resistance, impact resistance and high-temperature resistance of the tools. Cubic boron nitride (CBN) tools are the preferred choice. Their hardness is second only to diamond, and their heat resistance can reach 1400 ° C to 1500 ° C. They are suitable for semi-finishing and finishing of quenched steel. Coated cemented carbide tools are suitable for medium-hardness quenched steel. The TiAlN coating can effectively reduce the cutting temperature and perform stably under intermittent cutting conditions. After adding metal elements such as TiC to alumina, the hardness, flexural strength and heat resistance of ceramic cutting tools are all improved, making them suitable for turning, milling, boring and planing quenched steel.

Tool geometric parameter adjustment: The rake Angle should be selected as zero degrees or negative values, generally ranging from -10° to 0°. When the workpiece material has high hardness and intermittent cutting is required, a larger negative rake Angle should be chosen, such as -10° to -30°. If a positive rake Angle indexable blade is used, a larger negative chamfer should be ground to enhance the strength of the cutting edge. The relief Angle should be slightly larger than that of a common tool to reduce the friction of the rear tool face. Generally, it is taken as 8° to 10°. The main deflection Angle is set at 30° to 60°, and the secondary deflection Angle is set at 6° to 15° to enhance the strength of the tool tip and improve the heat dissipation conditions. When the edge inclination Angle is negative, the strength of the tool tip can be increased. However, if the negative value is too large, the F force will increase, causing vibration when the rigidity of the process system is poor. Therefore, it is generally taken as -5° to 0°, and -10° to -20° for intermittent cutting. The radius of the tool tip arc affects the strength of the tool tip and the roughness of the machined surface. Due to the rigidity of the process system, it is generally advisable to take 0.5 to 2mm.

Optimization of cutting parameters: The cutting speed should not be set too low or too high to maintain the durability of the cutting tool. The cutting speed of cemented carbide tools is generally 30 to 75 meters per minute, that of ceramic tools is 60 to 120 meters per minute, and that of cubic boron nitride tools is 100 to 200 meters per minute. When performing intermittent cutting or when the hardness of the workpiece material is too high, the cutting speed should be reduced, generally to about half of the minimum cutting speed. The cutting depth is generally selected based on the machining allowance and the rigidity of the process system, usually ranging from 0.1 to 3mm. The feed rate is generally 0.05 to 0.4mm/r. When the hardness of the workpiece material is high or intermittent cutting is carried out, the feed rate should be reduced to prevent chipping and tool breakage.

Cooling and lubrication: During the cutting of quenched steel, the cutting heat is difficult to be carried away by the chips, and the cutting temperature is high. Therefore, attention should be paid to cooling and lubrication. The coolant should have excellent heat transfer performance, chemical stability, lubricating performance and safety, capable of quickly removing the heat generated by the tool and workpiece, reducing tool wear and damage, and improving processing accuracy and efficiency. The nozzle should be directly facing the contact surface between the tool and the workpiece, evenly spraying the coolant on both the tool and the workpiece. The position and Angle should be appropriate to ensure that the coolant can cover the entire contact surface between the tool and the workpiece.