Medium frequency induction heating equipment has been widely used in forging, extrusion, hot rolling, pre shearing heating of various kinds of metal materials, as well as the whole tempering, annealing, tempering and other heat treatment fields due to its high thermal efficiency, uniform heating, low material burning loss rate and accurate control of heating temperature.
Induction heating equipment is applied to the manufacturing process of gearbox gear of automobile:
1. Working conditions
Transmission gear is an important part of the engine such as automobile, tractor, etc. it is used to change the speed ratio of engine crankshaft and transmission shaft, and often shift gears to make the root of the gear impacted. It is required that the gearbox gear has high bending strength, contact fatigue strength and good wear resistance, and the center part has enough strength and impact toughness. Therefore, the tooth surface works under high impact load and alternating load, so it is wear fast. In the process of working, the power is transmitted through the contact of the tooth surface. During the relative motion of the two tooth surfaces, both rolling and sliding are found, and there are large pressure stress and friction force
2. Machining process
The blank quality of gearbox gear is very important. Usually, forging is adopted. The strip structure of steel must be controlled so that it can not exceed grade 3. The processing process is as follows: blank forming - pre processing all cutting, carburizing (or carbonitriding), final heat treatment, shot peening (sand) and finishing
(1) Preheating treatment of blank
The CrMnTi steel gearbox gear needs low surface roughness and good machinability, which makes the chip of the teeth curl and the load of the machine tool is reduced and the life of the tool is prolonged. After normalizing, the hardness should be between 179^217hbs, and the evenly distributed pearlite + ferrite is obtained, which ensures the above requirements. The normalizing process temperature is 950~970 degrees C, after air cooling or blow drying, spray cooling. If the hardness is low, the water cooling and air cooling can be adopted.
(2) Carburizing
The carburizing temperature of gear is selected in Ω 20, considering the carburizing speed and deformation in the carburizing process ˆ The time of carbon insulation depends on the required depth of carburizing layer between 940 ℃ and the actual attempt is to add twice the required depth of carburizing layer and double the grinding amount of gear. Therefore, the carburizing time should be selected reasonably in the actual process.
(3) Final heat treatment technology of gear carburization
After the final heat treatment, the gear gets high hardness, high strength surface layer and good toughness center.
(4) Some problems to be noticed
The following conditions cannot be quenched directly after carburization, but the method of one-time heating quenching + low temperature tempering is required to ensure the technical requirements of gear
① For heat treatment, the gears with different conditions are limited to the gears that cannot be quenched directly.
② For gears that need to be turned after carburizing