Measures to prevent quenching cracks from forming on motorcycle sprockets:
To prevent quenching cracks in motorcycle sprockets, improvements can be made in the following aspects: ① improving the quality of raw materials; ② Control the rough machining size of the gear to avoid the machining size falling within the range that is prone to cracking during salt water quenching; ③ Perform stress relief annealing on rough gear blanks after rough machining; ④ Adopt reasonable quenching and cooling methods, etc Due to the difficulty in making significant changes to the quality of motorcycle sprocket raw materials, equipment, processing routes, and heat treatment processes, PAG type quenching cooling media are used for quenching and cooling If the quenching hardness is too low (< 35HRC) or the hardness is severely uneven, the following two methods can be used to solve it on the production site: 1) Under the condition of unchanged heat treatment process parameters, the PAG type quenching cooling medium is replaced with salt water with a mass fraction of about 89% for quenching and cooling, and the heating temperature of the quenching gear (made of 45 steel) is strictly controlled [i.e. (820 ± 10) C]. After being heated to full heat, it is pre cooled to around 770C (the workpiece is slightly dark red) and then cooled in water. After cooling in water for 4-6 seconds, the speed is suitable to lift the motorcycle sprocket out of the water surface for air cooling, protecting the water outlet temperature of the motorcycle sprocket from exceeding 150C, and immediately tempering2) (45 steel motorcycle sprocket) is heated at a sub temperature quenching temperature [i.e. (770 ± 10) C], and the motorcycle sprocket is quenched and cooled after passing through the furnace. The water outlet temperature of the gear is also controlled (should be higher than 100, and its quenching hardness is generally greater than 52HRC), and tempering is carried out immediately
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