After updating the quenching equipment with high control precision and high degree of automation, the quality and efficiency of locomotive gear production are expected to further increase. The dual-frequency quenching equipment needs to complete the verification of the subway and urban rail locomotive gears while promoting. Industry associations can strive to establish projects and organize relevant units to improve the basic research work of locomotive induction gears, such as the stress distribution of the hardened layer and the determination of fatigue strength.
China South Locomotive Group Qishuyan Locomotive & Rolling Vehicle Technology Research Institute Dai Dong Jin Guobao
The use of induction heating technology in the domestic locomotive industry originated in the 1960s. Locomotive induction hardened gears generally require a hardened layer with a depth of 2 to 4 mm and a hardness of 52 to 60 HRC. After 40 years of development, induction hardening locomotive gears are widely used in passenger and freight locomotives (DF, SS series, etc.) below 200km/h, as well as urban light rail and subway locomotives, and are used to replace imported locomotive gears.
I. Current status of locomotive gear induction heat treatment
1. Status of technology
All domestic manufacturers use medium frequency buried oil along the tooth profile quenching process. From the 1970s to the mid-1990s, the domestic locomotive induction gear manufacturers experienced the quenching process, the mass production of domestically produced locomotive gears of 120km/h or less, and the localization of imported locomotive gears, and the process was gradually stabilized. Since the mid-1990s, with the rapid development of the railway industry, the running speed of locomotives and the number of towing tons have increased year by year. The failure rate of induction gears has gradually increased during service life, which is manifested in the fact that the ends of the gears are not hardened at all ends. Bending fatigue cracks have occurred. After years of research and exploration, the relevant manufacturers have achieved hardening in the full tooth width range after adopting the new technology.
The speed of induction gears for locomotives has been increased from 80 to 100 km/h to 140 to 160 km/h, and the service life has increased from 400,000 km to over 1 million km.
2. Equipment status
(1) The machine tool equipment level of various domestic manufacturers is uneven, the first generation hydraulic lifting, infinite position, quenching transformer semi-submersible machine tool, the 1.5th generation hydraulic lifting, limited position, PLC control machine tool, and the second generation screw Stepper motor lifting and semi-CNC control machine tools coexist. The first-generation machine tool still dominates. Because the first-generation machine tool still uses the design of the late 1960s, the positioning accuracy is poor and the stability is poor. It can not meet the requirements of gear production, and must be updated. The second-generation hardening machine is only 1 Taiwan, put into use in 2004, basically meets the production requirements, but still fails to reach the technical level of the universal quenching machine at the same time.
(2) The power quenching power supply still uses the machine type intermediate frequency generator (group). A few manufacturers have tried the domestic thyristor intermediate frequency power supply, but due to poor reliability, it has not been promoted. The third generation all solid state IGBT intermediate frequency power supply is in the domestic locomotive. The gear induction heat treatment industry has not been used.
Second, the problem of induction heat treatment of locomotive gears
1. Basic research is seriously inadequate
(1) The design theory of the gears with a speed of 160km/h or less is more abundant, and for the speed of 160km/h or more, whether the locomotive can use the induction gear is still in a blank stage.
(2) The induction gear is not subjected to physical contact and bending fatigue strength test, so that the service life of the gear cannot be accurately estimated.
(3) The stress distribution in the hardened layer of the induction gear has not been studied in depth.
(4) Dual-frequency quenching of urban rail and metro locomotive induction gears with a modulus of less than 6mm is a development trend, but dual-frequency quenching is still in the research stage. Designers have many blind spots on the application range and service life of dual-frequency quenching gears. It can carry out the physical test verification of the test bench of the double-frequency hardened gear.
2. Equipment aging
(1) Induction hardening machine tools of domestic locomotive gear manufacturers are generally aging, and CNC CNC, screw servo motor precise travel, online real-time monitoring and other technologies have not been adopted. Many domestic induction equipment manufacturers still rely on the technical level of gear quenching machines 10 years ago.
(2) The intermediate frequency power supply is still a medium-frequency generator (group), and the all-solid-state IGBT intermediate frequency power supply has not been successfully used in the railway industry.
(3) Reheating and light cooling, ignoring the influence of cooling medium on quenching quality. At present, domestic locomotive induction gear manufacturers still use engine oil as the main quenching medium, and the hardness distribution of tooth surface is not ideal.
(4) Gear cold and hot processing is not enough, neglecting the influence of machining points such as chamfer size, shape and root roughness, tooth root arc shape on induction heating and final quality.
Third, the prospect of locomotive gear induction heat treatment
(1) After updating the quenching equipment with high control precision and high degree of automation, the production quality and efficiency of locomotive gears are expected to be further improved.
(2) The dual-frequency quenching equipment needs to complete the verification of the subway and urban rail locomotive gears while promoting.
(3) Industry associations can strive to establish projects and organize relevant units to improve the basic research work of locomotive induction gears, such as the stress distribution of the hardened layer and the determination of fatigue strength.
This article was issued by the "Mechanical Workers" (Hot Processing), the 11th issue of 2006, so stay tuned!
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