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1. The piston rod is subjected to alternating loads during normal use, φ 50mm × There is a sealing device at 770mm that rubs its surface back and forth, so it requires high hardness and wear resistance.
Made of 38CrMoALA material, φ 50mm × After quenching and tempering treatment and surface nitriding, the 770mm part has a core hardness of 28-32HRC, a surface nitriding layer depth of 0.2-0.3mm, and a surface hardness of 62-65HRC. This gives it both toughness and good wear resistance.
2. The structure is relatively simple, but with a large aspect ratio, it belongs to the slender shaft type component and has poor rigidity. In order to ensure machining accuracy, rough and fine turning should be separated during turning, and both rough and fine turning should use a tool holder to reduce the deformation of the workpiece during processing. When processing threads at both ends, a holder should be used.
3. When selecting the positioning reference, in order to ensure the coaxiality tolerance of the components and the mutual position accuracy of each part, all processing processes adopt two central hole positioning, in accordance with the principle of unified reference.
4. When grinding the outer circular surface, the workpiece is prone to deformation of the tool and elasticity, which affects the accuracy of the piston rod. Therefore, during processing, the hole should be polished and kept clean, with appropriate tightness between the hole and the top and good lubrication. General selection of grinding wheel: abrasive white alumina (WA), particle size 60 #, hardness medium soft or medium to ceramic bonding agent. In addition, the width of the grinding wheel should be narrow to reduce radial grinding force. During processing, attention should be paid to the selection of grinding amount and the grinding depth should be small.
5. During grinding φ 50mm × When the outer circle is 770mm and the taper is 1:20, the two processes need to be carried out separately. When grinding a 1:20 taper, the test piece must be ground first, and only after passing the inspection can the workpiece be officially ground. 1: The inspection of the 20 cone surface is carried out using a standard 1:20 ring gauge for color coating, and the contact surface should not be less than 80%.
6. In order to ensure the stability of the machining accuracy of the piston rod, manual straightening is not allowed throughout the entire machining process.
7. During nitriding treatment, threaded parts, etc., should be protected with protective devices.