Research On Technology Of Steel GCr15 Quenching Tempering For Locomotive Diesel Fuel Injection Pump

The thesis examines quenching tempering process of different original microstructure of steel GCr15. The results show that the carbide inhomogeneity exceeded criterion will be aggravated the sensitivity of overheating quenching tempering microstructure. The grades of carbide spheroidizing, network, band and eliquation must be strictly controlled otherwise the overheating microstructure will arise in area of C, Cr depletion when austenitizing, causing coarse grain and mixed grain size, acicular or coarse acicular martensite instead of hide acicular martensite, formation of troostite in area C, Cr enrichment. It is still strong that overheating sensitivity of steel GCr15 that has reached the specification through normalizing and spheroidizing annealing. Though the inhomogeneity of steel GCr15 has satisfied requirement by second normalizing and spheroidizing annealing, its overheating sensitivity is still greater than that has passed in first examination. The existence of areas C, Cr depletion or enrichment in the steel that carbide reached specification through the second treatment has not be improved effectively, inheriting partly to spheroidizied microstructure, resulting in increment of austenitizing overheating sensitivity. So that it is necessary to lower quenching temperature suitably. The quenching process should be adjusted and the range of effective quenching temperature should be established according to the different original microstructure of the steel GCr15. The quenching process of parts sleeve and fuel let-out valve seat should be adjusted on the basis of steel GCr15 original microstructure situation. The quenching temperatures is of 845 - 860℃for the original material that the carbide inhomogeneity met the specification, and of 845 - 860℃for that the carbide met the specification through the second treatment. Moreover, The quenching temperature, temperature error and temperature uniform should be controlled strictly. It is indicated that quenching tempering microstructure has been fined and controlled in the range of specification through quenching process adjustment.