Gears, the most basic way of transmitting kinetic power, are widely being used in various areas. In recent years, there have been amazing new development in modern industry: stronger, lighter, and more precise are required now more than in the past, due to innovation in power-transmission technology...
Gears, the most basic way of transmitting kinetic power, are widely being used in various areas. In recent years, there have been amazing new development in modern industry: stronger, lighter, and more precise are required now more than in the past, due to innovation in power-transmission technology and the energy conversation requirements. This study deals with the effect of effective case of the fatigue strength in SCM415 carburized spur gears. The test gears are heat-treated by three different methods. After normalizing for 1 hour at 930℃ then soaking, carburizing and homogenizing in endo converted gas type furnace. Last try to the Oil-quenching for 10 minutes at 850℃. In addition, we investigated the effect these heat-treatments had on hardness, metallography, and compression residual stress of the risk section of the teeth. After conducting on electro-hydraulic servo-controlled fatigue strength test to identify fatigue in the S-N curves, we investigated the effect of effective case depth on fatigue strength of the risk section of the teeth. The followings are the results of the this study. 1. The effective case depth was 0.72mm in S40CQ, 0.81mm in S50CQ and 0.97 mm in S66CQ on the risk section of the teeth and S40CQ and S50CQ increased in hardness from surface to 1mm depth but, S66CQ test gear showed a trend of decrease. 2. The warpage and transformation of span gage by heat-treatment were low 16-44%, 20-39% in S66CQ. 3. The fatigue strength was 1005 MPa in S66CQ, 850 MPa in S50CQ and 810 MPa in S40CQ and compared with S40CQ, S50CQ and S66CQ increased 18% and 24% in fatigue strength. 4. Estimated fatigue strength by the proposed formula of fatigue strength was 1074 MPa in S66CQ, 933 MPa in S50CQ and 810 MPa in S40CQ 5. S40CQ had a 5% difference, S50CQ and S66CQ had each of error value of between fatigue strength by the fatigue strength estimated formula and a result of fatigue test 3∼8%.
Gears, the most basic way of transmitting kinetic power, are widely being used in various areas. In recent years, there have been amazing new development in modern industry: stronger, lighter, and more precise are required now more than in the past, due to innovation in power-transmission technology and the energy conversation requirements. This study deals with the effect of effective case of the fatigue strength in SCM415 carburized spur gears. The test gears are heat-treated by three different methods. After normalizing for 1 hour at 930℃ then soaking, carburizing and homogenizing in endo converted gas type furnace. Last try to the Oil-quenching for 10 minutes at 850℃. In addition, we investigated the effect these heat-treatments had on hardness, metallography, and compression residual stress of the risk section of the teeth. After conducting on electro-hydraulic servo-controlled fatigue strength test to identify fatigue in the S-N curves, we investigated the effect of effective case depth on fatigue strength of the risk section of the teeth. The followings are the results of the this study. 1. The effective case depth was 0.72mm in S40CQ, 0.81mm in S50CQ and 0.97 mm in S66CQ on the risk section of the teeth and S40CQ and S50CQ increased in hardness from surface to 1mm depth but, S66CQ test gear showed a trend of decrease. 2. The warpage and transformation of span gage by heat-treatment were low 16-44%, 20-39% in S66CQ. 3. The fatigue strength was 1005 MPa in S66CQ, 850 MPa in S50CQ and 810 MPa in S40CQ and compared with S40CQ, S50CQ and S66CQ increased 18% and 24% in fatigue strength. 4. Estimated fatigue strength by the proposed formula of fatigue strength was 1074 MPa in S66CQ, 933 MPa in S50CQ and 810 MPa in S40CQ 5. S40CQ had a 5% difference, S50CQ and S66CQ had each of error value of between fatigue strength by the fatigue strength estimated formula and a result of fatigue test 3∼8%.
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