| Crankshaft is one key component which often used in equipment, and its main function to transmit, in this paper, the crankshaft of JB36-400press which fractured was researched. The flywheel and the connecting rod were connected by crankshaft of press, during the working process, and the rotational movement of the flywheel was changed to the reciprocation of the connecting rod by the crankshaft. The load of crankshaft of JB36-400press is4000KN, is one of the large forging machine. Crankshaft is one key component of the press, it was borne the impact load during the running. The crankshaft was occurred failure frequently within the scope of the service life of the press, the failure mostly were the crankshaft cracked. This type of press is the main product for Yangzhou metal forming machine tool co., LTD. The fracture failure of crankshaft had serious impact on the enterprise. In order to avoid the failure phenomenon, this paper aimed at the crankshaft fracture failure, analyzed the crankshaft fracture, optimized the structure of crankshaft and the heat treatment process parameters, strengthened the mechanical properties of the crankshaft and improved the service life of press.The crankshaft fracture morphology was researched, according to the shell ridge on the macroscopic cross section and the fracture microstructure characteristics of judgment for the fatigue fracture of crankshaft fracture types. The analysis experimental results show that main reasons of fatigue fracture were the surface induction hardening were uniformed^caused the quenching microstructure uneven, tempered sorbite of matrix was uneven and the stress concentration. Depending on the causes of fracture failure, optimized the structure and the heat treatment process of the crankshaft, the3D-deform was used to determine the crankshaft decarburization depth. Simulated the load force of crankshaft with the ANSYS analysis software, got the crankshaft stress contours. Simulation results show that the stress of the crankshaft fillet area was the largest, stress value was4.998×108Pa, there was the dangerous place of crankshaft, consistent with the actual fracture of crankshaft position. The crankshaft neck and shoulder radius were changed from20mm to22mm, the simulation results show that the maximum stress value was4.4745×108Pa, the stress was reduced by1.01%.The quenching and tempering treatment and surface induction hardening were optimized, the temperature of quenching and tempering treatment was860℃, and the tempering temperature was300℃, The (hardness was increased by8.7%. Surface induction quenching process parameters were optimized, The experimental results show that the surface quenching microstructures were uniform, without the micro cracks, the average surface hardness was53.98HRC, tempering temperature decreased to300℃, the average surface hardness value was51.43HRC, conformed to the requirements of the hardness, at the same time reduce the quenching stress, avoided to produce quenching crack.Fatigue resistance and wear resistance were enhanced by surface strengthening technology, in this paper, surface induction hardening and shot peening were researched, and tested the changing of hardness, residual stress and wear properties. The test results show that the hardness of strengthened layer was improved, and the average hardness value of surface induction hardening was49.23HRC, the average hardness value of shot peening was51.33HRC, it was improved4.26%. The value of surface compressive residual stress was370.05MPa, and the value of shot peening was497.19MPa, it was improved24.97%. The wear resistance was increased and the wear weightlessness was reduced after shot peening then surface induction hardening. The combination technique should be used to raise the ability of crankshaft against fatigue failure and make the crankshaft lift longer. |
PDF Full Text Request