Due to the high hardness, brittleness, high strength and low thermal conductivity of quenched steel, the cutting force is large, the cutting temperature is high, the tool is easy to wear and there is a situation of cutting. Therefore, it is a common material that is difficult to cut, and corresponding measures must be taken in order to turn smoothly.
1. Selection of cutting tools for quenching steel processing
Selecting cutting tool materials with high hardness, high bending strength and good heat resistance is an important condition for turning quenched steel. As long as it is hard alloy, it can be used to turn quenched steel. The grades of cemented carbide with good cutting effect mainly include yt05, YS10, ys8, 600, 610, 726, 758, 767, 813, etc. hot pressed alumina or silicon nitride composite ceramics are also suitable for turning quenched steel because of their higher hardness and heat resistance than cemented carbide; Cubic boron nitride has very little affinity with iron group materials. It is the best tool material for high-speed semi finish turning and finish turning quenched steel.
2. Selection of geometric parameters for Turning Hardened Steel Tools
The geometric parameters of turning hardened steel tools should be comprehensively considered and selected according to the workpiece material, the performance of tool material and cutting conditions. Generally, when processing quenched steel, the main deflection angle is generally between 30 ° and 60 °. Generally, the quenching hardness is low and the rigidity of the process system is good, so a smaller main deflection angle can be selected. On the contrary, the main deflection angle can be appropriately increased. When the front angle is between 0 ° and 8 °, the higher the quenching hardness, the greater the front angle of the pair. When finishing, the front angle can be taken as 0 °. When turning quenched steel, the back angle should not be too large. Generally, it is better to take 3 ° to 5 °.
3. Selection of cutting parameters
When turning quenched steel, reasonable cutting parameters must be selected after selecting suitable tool materials and tool geometric parameters according to its machining performance and workpiece shape and hardness. In order to meet certain processing requirements, that is, select the blade material according to the processing performance of quenched steel.
Cutting quenched steel has high cutting resistance, high cutting temperature and low tool durability. Therefore, the cutting speed is usually lower than that of general steel under the same conditions. The cutting speed is generally between 40-100m/min, and the reasonable cutting speed decreases with the increase of workpiece hardness. When the hardness of the workpiece reaches above HRC65, the cutting speed of rough machining can be less than 30m/min, while the cutting speed of finishing machining with small cutting depth and tool feeding can be 100 m /min-120m / min. If cermet and cubic boron nitride are used for fine turning, the cutting speed can reach 120-200m / min.