The Heavy Oil Burning Nozzle Made By 18CrNi8 Heat-treatment Process Study

Based on some enterprises in the production of heavy oil burning diesel engine 18CrNi8 nozzle quality unstable problem, research the nozzle failure situations, the manufacture, use and technical requirements according to the specific design of the nozzle index, studied 18CrNi8 materials of Marine heavy oil burning labor the carburizing, quenching and cooling and tempering process, analyzing the test results are discussed, get the following main results: 1. Marine heavy oil combustion labor.this is suitable for using vacuum carburizing process, carburizing temperature is 920 ℃, pulse number for 8 ~ 10 pulse, the surface carbon concentration of 1.0% C, the largest carbon concentration is 1.1% C, the lowest carbon concentration of 0.8% C. According to the technology of carburizing, after quenching surface hardness can reach 730 HV, more gentle hardness gradient, depth of carburizing layer conform to technical requirements. 2. The nozzle can use the high pressure gas quenching after carburizing, vacuum oil quenching, multi-purpose furnace oil quenching of three methods for quenching, nozzle seat surface hardness can reach above 720 HV. 18CrNi8 Marine heavy oil burning nozzle by 845 ℃ for 10 bar high pressure nitrogen quenching hardness gradient than with 835 ℃ oil quenching slightly flat. 3. The diameter of hole by vacuum oil quenching treatment is swollen up, large 0.01mm-0.03 mm. The diameter of hole in the parts with high pressure gas quenching trend is swollen, swollen slightly less than vacuum oil quenching, between the 0-0.025 mm.Vacuum oil quenching treatment of 18CrNi8 nozzle diameter reduction amount between 0.05 0.08 mm, high pressure nitrogen quenching amount of narrow between 0.05 0.06 mm. The quenching way make the length of the nozzle has a tendency to shorten, on the seat surface quenching way to beat the effects of a volume change value. Nozzle after high pressure gas quenching deformation of inner diameter, outside diameter is less than the oil quenching. 4. The marine diesel engine burning heavy oil 18CrNi8 nozzle adopts direct quenching after carburizing process, after-80 ℃ deep cooling residual austenite can reach 20%; The secondary heating quenching then through- 80 ℃ ~-120 ℃ after deep cooling residual austenite content can be below 10%. Deep cooling treatment temperature should be controlled within the- 120 ℃, time in 1 ~ 2 hours. 5. Marine heavy oil burning 18CrNi8 nozzle after quenching tempering temperature is controlled in 180-200 ℃, the hardness and microstructure after the tempering temperature conform to technical requirements. After dealing with the tempering of stabilizing temperature setting is about 120 ~ 150 ℃, the time should be in more than 10 hours. 6. Marine heavy oil combustion of 18 Cr Ni8 nozzle into the research of this article are carburizing, quenching and tempering heat treatment process and stabilization process, working condition of diesel engine bench test and simulation is carried on the experiment, the results show that the injection nozzle state is normal, atomization effect is good, there is no abnormal condition. Will be made according to the process of Marine heavy oil burning 18CrNi8 nozzle batch as couple, for the use of user installed, the user feedback information shows that the nozzle generally stable quality, reliable performance, good use, to achieve a good level.