When the needle bearing is overheated, not only the surface quality of the workpiece is poor, but also the corrosion resistance of the workpiece is degraded. In the case of severe overheating, coarse grains are produced, and at the same time, the weight of the iron wire in the steel is increased, which tends to deteriorate the performance of the workpiece. When the imported bearings are overheated, the following protective measures are available:
1. Strictly control the forging heating temperature and heating and holding time of stainless steel box and flange parts to prevent the workpiece from overheating and causing coarse defects in the workpiece.
2. In the forging production, if the forging ratio is small, the final forging temperature is high, and the coarse-grained structure defects are also prone to occur. The forging ratio of the workpiece should be suitable and sufficient, and the final forging temperature is moderate.
3. The temperature of the imported bearing workpiece heat treatment solution should not be too high, the holding time should not be too long, the heating temperature should not be higher than 1150"C, and the holding time should be calculated as 1 l_5min/mm.
4. For the coarse workpiece with overheated structure, the method of forging and refining the grain can be used to eliminate the defect, prevent the orange peel surface defect when the workpiece is cold deformed, and improve the surface quality of the workpiece.