A high-temperature bearing is made of Cr4Mo4V steel. Since Cr4Mo4V steel is very sensitive to heating temperature, mixed crystals and coarse grain defects are prone to occur during quenching and heating, which adversely affects product quality and performance. However, for high-temperature military bearing products with high production requirements, it is found that there are more mixed crystals in vacuum furnace production, and the product performance is reduced or even unqualified. In view of the defects caused by traditional heat treatment of Cr4Mo4V steel high-temperature bearings, medium-frequency induction heating power is used for heat treatment, and the production effect is good.
In the past, high-temperature bearings used a salt bath furnace heating and quenching process. Because the products were prone to corrosion pitting and the scrap rate reached more than 80%, this process was eliminated. After adopting the vacuum heat treatment process, the product quality is good, with a pass rate of 95%. However, mixed crystals and grain coarsening occurred during production, making some of the product's performance unqualified. Production tests show that using medium frequency induction heating power for 1100°C quenching heating and 550°C tempering can ensure normal grain size (grain size is 8), the hardness after tempering is about 62-63HRC, and the workpiece performance meets the technical requirements.
The process improvements and measures to prevent mixed crystals and grain coarsening during quenching and heating of Cr4Mo4V steel bearings at high temperatures are as follows:
(1) Select the appropriate quenching temperature and tempering temperature. The performance of the workpiece after tempering meets the technical requirements. The grain size after quenching is level 8 and the hardness after tempering is 62-63HRC.
(2) The quenching heating speed should be above 30°C/min to ensure that the quenching grain size is around level 8.
Numerous tests have proven that Cr4Mo4V steel high-temperature bearings use medium-frequency induction heating power for heat treatment, which avoids cracks, mixed crystals and coarse grain defects caused by traditional heat treatment. What's better, the service life is greatly improved, and the aesthetics is also greatly increased. It meets the production needs and is suitable for large-scale production in large quantities.
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GS-ZP-1200
