As the core transmission component of pump equipment, steel pump shaft has extremely high requirements for precision, strength and wear resistance. CNC machining technology can achieve efficient and accurate mass production. The following is a complete manufacturing tutorial for CNC manufacturing steel pump shaft.
1. Material preparation and pretreatment
Preferably choose 45# high-quality carbon structural steel or 40Cr alloy structural steel. These two materials can meet the mechanical performance requirements of pump shaft after heat treatment. The raw materials need to be straightened, and the curvature is controlled within 0.05mm/m by using a hydraulic straightening machine. Then the rough turning is carried out, and 8-10mm machining allowance is reserved according to the size of the finished product. At the same time, the process ejector hole is drilled in the center of the two end faces to provide a positioning reference for subsequent external cylindrical processing.
2. CNC lathe rough processing
Select CNC lathe equipped with carbide external cylindrical turning tool. When writing the rough machining program, the layered cutting method is used: first turn the outer circle to φ55mm (reserve 5mm finishing allowance), then process the keyway step, and control the verticality of the step end face within 0.03mm. During the machining process, it is necessary to stop and check the workpiece temperature every 300mm cutting length. If it exceeds 60℃, it needs to be cooled with emulsion; the feed speed is set to 80-100mm/min, and the spindle speed is maintained at 800r/min to avoid deformation of the workpiece due to excessive cutting force.
3. Heat treatment strengthening
The workpiece after rough machining needs to be tempered: heat the workpiece to 850℃ (45# steel) or 860℃ (40Cr steel), keep it warm for 2 hours, then oil quench it, and then temper it at 500℃ for 3 hours. The final hardness needs to reach 220-250HBW. After heat treatment, aging treatment is required to eliminate internal stress. The workpiece is placed naturally for 48 hours, or kept warm in a 120℃ oven for 6 hours.
4. CNC lathe finishing
Replace with a precision CNC lathe (positioning accuracy 0.01mm), and the tool is replaced with a ceramic CBN blade to improve the surface quality. The finishing adopts the "one clamp and one top" clamping method, and the tailstock ejector pin applies a top force of 0.2-0.3MPa. The key processing parts include:
Matching shaft neck: dimensional accuracy must reach IT6 level (φ50h6), surface roughness Ra1.6μm;
Seal ring groove: groove width tolerance is controlled at ±0.02mm, and the parallelism between the groove bottom and the axis is ≤0.015mm;
Axle end thread: Use G76 thread cutting cycle to process M20×1.5 fine thread, and the tooth angle error does not exceed 1°.
5. CNC milling machine keyway processing
Transfer to CNC milling machine, use high-speed steel keyway milling cutter (φ12mm) to process the transmission keyway. Through the workpiece outer circle positioning, the layered milling method is adopted: first mill to a groove depth of 8mm (reserve 0.5mm margin), and then use a carbide milling cutter to fine mill to 10mm, ensuring the groove width tolerance H9, symmetry ≤0.02mm. After processing, the keyway and the journal clearance need to be checked with a go and no-go gauge.
6. Precision grinding and surface treatment
The final process uses cylindrical grinder for final processing, grinding the outer circle to φ50h5, and the roundness is controlled within 0.005mm. For the journal mating surface, polishing is required, using a wool wheel with chromium oxide polishing paste to increase the surface roughness to Ra0.8μm. The non-matching surface can be blackened to enhance the rust resistance.
7. Quality Inspection
Use a three-coordinate measuring machine to inspect key dimensions: the journal diameter error is ≤±0.008mm, and the full-length straightness is ≤0.01mm. Use magnetic flaw detection to check surface cracks to ensure that there are no defects exceeding 0.2mm. 10% of the workpieces are randomly inspected for torque testing. The 45# steel pump shaft needs to withstand a rated torque of ≥300N・m without plastic deformation.
During CNC manufacturing of steel pump shaft, special attention should be paid: the positioning reference surface should be cleaned before each clamping of the workpiece to avoid iron filings affecting the accuracy; during mass production, the tool compensation value should be calibrated every 2 hours to ensure dimensional stability. With this process solution, mass production of steel pump shafts with a pass rate of more than 98% can be achieved. If you need CNC machining of steel pump shaft services, contact us for a quote.