Research On Structure Property And Surface Stress Of New-type Crane Brake Wheel

Brake wheel is an important part in crane. However, heave loading usually leads to cracks especially for the large tonnage crane, which would induce accidents. In order to increase the operation life of the brake wheel, it should be necessary to study it’s microstructure, property, and stress distribution of the new alloy.Paper mainly includes the following aspects:1. Improvements of thermal fatigue resistance and comprehensive mechanical properties by additives.2. Comparisons of microstructure and mechanical property between ZG340A、ZG340B and ZG35CrMnSi by different heat treatment process.3. Effects of the residual stress for cracks on the surface of the brake wheel.The results indicate that:For all the new alloy mentioned above, the performance requirements could be satisfied by heat treatment process, especially for ZG340A and ZG35CrMnSi. For ZG340A, normalizing temperature is870℃, tempering temperature is550℃. For ZG35CrMnS, quenching temperature is860℃, tempering temperature is600℃Normalizing and tempering could reduce the surface defects, slag inclusion and oxide etc. for ZG340A. Moreover, the microstructure characteristic would be beneficial for alleviating the stress concentration at the crack tip and preventing crack propagation. Due to the migration of Ni, Cr and other elements in the form of oxide residue on the wear surface, the wear could soon move into steady state at about500℃. And benefited from the lubricant power originated from the alloy matrix, it has good anti-wear property.35CrMnSi has high fracture toughness and high temperature strength. And it’s main wear mechanism is micro spalling which is well distributed. The alloy also has good anti-wear property.Results indicate that the surface residual stress is small and well distributed(the measured value is less than62.2MPa). Furthermore, machining and extrusion could release the stress. So it could be confirmed that surface residual stress is not the main factor for the cracks. And further study shows that the alloy composition, metallurgical quality, heat treatment process and cycle changed contact force play import role.