Ultra-acoustic induction heating quenching of thin-walled gears

Jiangsu Taizhou Machinery Factory (225300) Lu Jilong Jiangsu Taihang Electric Co., Ltd. (225300) Yan Wenjian 20, normal modulus m=2.5t0 surface for gear machining positioning surface. The thinnest part of the ring gear is only 4.375mm, so the rooting strength is taken into account, and the penetration hardening phenomenon including the ring gear occurs during induction heating quenching, which makes it difficult to process the subsequent keyway. In order to solve this problem, we redesigned the gear core, and the well carried out the process comparison test to solve the problem satisfactorily.
The heat treatment technology requires that the heat treatment technical requirement is that the tooth blank is normalized to 179~229HB, and the precision cutting is followed by high frequency induction heating quenching to the hardness of 48-55HRC, the root hardened layer depth > equipment power 100kW; quenching, number of turns 3 Hey. The gap between the inductor and the gear is reduced from 3mm to about 2mm, which increases the coupling between the inductor and the gear, and increases the speed of induction heating.
Changed to a cone, the cone induction heating device schematic size is smaller than the gear cone hole h core 2, the inductor 3, the workpiece 0.6~0.8mm, so that the sense of the 4 insulating rubber board should be heated as the gear can be approximated as a solid body In order to reduce the inward velocity of the temperature layer during induction heating, and at the same time prevent the inner hole from shrinking after the gear is quenched and “bite” the heart rod. The heart stick and the quenching machine are insulated by a rubber board to prevent the gear from hitting the ring during heating and causing spark burn. The specific heating device is as shown.
The thin-wall gear quenching process parameters are heated by full-tooth simultaneous heating. The induction heating speed is controlled by adjusting the input power of the heating power source, that is, by adjusting the anode voltage, the anode current, and the gate current to control the specific power obtained when the gear is induction-heated. The induction heating quenching process parameters are shown in Table 1.
Table 1 gear single-piece induction heating quenching process parameters X art anode voltage anode current / A gate current heating time cooling method water spray cooling, water out of the injection: 2 for each process.
After the test and analysis of the gears, the test was carried out by sectioning. The results are shown in Table 2, and the test sites are shown. It can be seen from Table 2 that the process 1 has a large input power, the specific power is obtained when the gear is heated, and the heating speed is fast, so that the root temperature difference between the tooth tip and the tooth test portion is large, when the tooth tip reaches the heating quenching temperature. The root temperature is low and the quenching hardness is insufficient. The heating rate of Process 2 is slightly reduced, but it is still faster. Process 4 seems to be more satisfactory, but when the keyway is machined to near tolerance, the hardened layer is deeper, the tool advances hard, and the process 3 hardens the case, and the keyway is easy to process.
Table 2 Thin S gear single piece test quenching results X art tooth gallery hardness HRC gum and heart hardness HRC One note: Point B is near the meshing line.
The design of the cooling medium circulation line of induction hardening machine is 0,56mm, and the surface quenching structure is fine martensite + residual rhyme.
According to the test results of single piece, we carried out batch test quenching (60 pieces) according to process 3, and randomly selected 6 pieces, the hardness of the tooth top was 57 ~ 58HRC, the hardness of the involute part of the tooth profile was 5657HRC, and the depth of the root hardened layer was 0. 50~0.60mm, the hardness of the other gear teeth is 57 ~ 59HRC, all the gears are inserted smoothly, meeting the design requirements.
Only, the process is reliable, the quality of the children is stable, and the r design requirements are met. Practice has proved that it is feasible to use the cone mandrel and the appropriate inductor to achieve hardening along the groove by the optimization of the heat treatment process parameters, while avoiding hardening of the ring gear. The cooling of the induction and quenching process of Nanjing Automobile Semi-axle Factory is not only important for the equipment, tooling itself, but also for quenching X parts. The former mainly determines the service life of the equipment tooling, while the latter determines the intrinsic quality of the quenched workpiece. The equipment tooling cooling is generally carried out with clean water, and the quenching cooling is selected according to the process requirements, the material of the workpiece, the hardness and depth of the hardened layer, etc., and the quenching medium commonly used in addition to water is sodium chloride and polyvinyl alcohol. , an aqueous solution such as an emulsion. Due to the different cooling effects, different cooling medium requirements must be considered when considering the cooling pipeline. In addition, factors such as pressure and flow rate on the pipeline must be considered. The left picture shows the structure of the circulating cooling circuit of the 8000Hz medium frequency induction hardening machine.
When the cooling medium is consistent with the quenching medium (clean water): close the valve 4, open the valves 3, 6, and open the B booster pump and the D pump.
When the cooling medium is inconsistent with the quenching medium: close the valves 3, 6, open the valve 4, open the B, C booster pump and E, D pump D valve 5, 7 to adjust the cooling water pressure flow, after the valve 5 A time relay controlled solenoid valve is connected to the microcomputer.
1 is a water replenishment valve, and a water storage (liquid) pool structure is used in the pipeline to precipitate impurities in the cooling medium.
In order to ensure the circulation of the cooling water (liquid), the pump is used for reflux.
In order to ensure the quenching cooling pressure, the ZW series self-priming booster pump is used and a 0~.6MPa pressure gauge is arranged in the pipeline.
For the continuous working cooling tank, a cooling tower system or a special quenching liquid circulation cooling system (with heat exchanger) may be installed, and the control (upper page) is cooled in the oil to obtain the martensite structure. Therefore, the water cooling time is too short, resulting in a shallow hardening layer and insufficient hardness of the tread. If the water cooling time is too long, the edge of the contour will be easily cracked. Due to the different seasons and water temperatures, the water cooling time can be appropriately adjusted according to the actual situation and the diameter of the wheel.
After tempering, the hardness of the wheel tread reached 370390HB, and the finished car reached the 360370HB after 45mm of unilateral side. The hardness decreased gradually, and the hardness of the core was also improved. The surface metallographic structure is tempered sorbite, the surface hardness of the wheel is 340-380HB. The original process can be completely replaced by quenching and tempering process, and the operation is simple, which not only improves the production efficiency, but also ensures the quality of the wheel. The wheels treated by this process have been used by users to a good extent.

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