Processing characteristics of stainless steel fasteners

It is well known that stainless steel is less machinable than medium carbon steel. With the development of the equipment manufacturing industry, stainless steel fasteners are increasingly used in all walks of life. The processing and manufacturing technology of stainless steel fasteners is gradually becoming more mature. Each enterprise should select the appropriate blade material when processing stainless steel according to its actual needs, and the cutting amount should be used to achieve the best cost performance.

1, the choice of tool materials

The processing tools for stainless steel fasteners should be reasonably selected. According to the cutting characteristics of stainless steel fasteners, the tool material is required to have good heat resistance, wear resistance, and small affinity with stainless steel. High-speed steel material tools are currently used in machining stainless steel fasteners, often using carbide tools. YG-type hard alloys are often used in the processing of stainless steel fasteners. The toughness of YG-type hard alloys is good. Large front angles can be used, and the cutting edges can be sharpened to make the cutting light and the chips and tools are not easy to produce. Bonding, more suitable for processing stainless steel fasteners. This type of advantage of YG-based alloys is especially important when roughing and cutting with vibration. In addition, the thermal conductivity of YG alloys is nearly twice as high as that of high speed steel and twice as high as that of YT alloys. Therefore, YG alloys are widely used in the cutting of stainless steel fasteners, especially in the machining of rough turning tools, cutting knives, and reaming drills. For a long time, NG6, YG8N, YW2 and other common grades of hard alloys are generally used as tool materials for stainless steel fasteners, but they cannot achieve a smooth surface; new grades of carbide 813, 767, 640, 798 are used. YM051, YM10, YS2T, YD15, FK235 and other cutting stainless steel fasteners can obtain better results.

2, the choice of tool parameters

In addition to selecting the right tool material, the stainless steel fasteners must be selected to the appropriate tool geometry. The rake angle (γo): The hardness and strength of stainless steel fasteners are not high, but the plasticity and toughness are good, the heat strength is high, and the chips are not easily cut off during cutting. On the premise of ensuring that the knife has sufficient strength, a large rake angle should be used, which not only reduces the plastic deformation of the metal to be cut, but also reduces the cutting force and the cutting temperature, and at the same time reduces the depth of the hardened layer. The front angle of turning various stainless steel fasteners is approximately 12° to 30°. For martensitic stainless steel fasteners (such as 20Cr13), the rake angle can be larger, for austenite and austenite + ferrite Stainless steel fasteners, the front angle should be a small value. For stainless steel fasteners with low hardness after quenching and tempering or quenching and tempering, a larger rake angle may be adopted; for smaller diameter or thin-walled parts, a larger rake angle is preferred.

3, the choice of cutting amount

The amount of cutting has a great influence on the work hardening, cutting force and cutting heat when processing stainless steel fasteners, especially the durability of the tool. Whether the selected cutting amount is reasonable or not will directly affect the cutting effect. Table 1 below shows the selection of the cutting amount for the thread and the drilling, expanding and reaming when the tool material is high speed steel.

Table 1 Cutting amount when threading and drilling, expanding and reaming

4, the conclusion

Due to the poor machinability of stainless steel fasteners, there is a higher requirement for the cooling, lubrication, penetration and cleaning performance of the cutting fluid. Therefore, when processing stainless steel fasteners, a cooling device must be used to make the cutting process The cutting coolant nozzle is aligned with the cutting zone to take away the cutting heat and improve the cutting conditions. It is best to use high-pressure spray cooling and other cooling methods to significantly improve the cutting performance.